GroupDIY

Project Specific Discussions => Dynamic Processors => Topic started by: mnats on August 23, 2016, 04:40:22 PM

Title: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on August 23, 2016, 04:40:22 PM
(http://mnats.net/images/fetrack/rev_a_top_open_high_three_quarters_small.jpg) (http://mnats.net/fetrack/rev_a_top_open_high_three_quarters.jpg)

You can see more about it at Hairball Audio (http://hairballaudio.com/). Build guide is at Hairball's blog site (http://www.hairballaudio.com/blog/resources/category/build-guides). Some background information and documentation can be found on my FET/RACK page (http://mnats.net/fetrack.html).

Problems with this build? Read the 1176 FAQ (http://mnats.net/1176_FAQ.html).

Please post any questions not answered by the FAQ above or the extensive information at Hairball Audio's site (http://hairballaudio.com/) to this thread. Please do not start new threads just for your particular issue with the FET/RACK as these will not be monitored by Mike or myself. Please keep any commercial discussion confined to the White Market Thread (http://groupdiy.com/index.php?topic=28923.0)

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on August 25, 2016, 07:23:05 AM
Thanks Mike & Mnats for helping us out to get our hands on some great sounding gear!

I just have a small quick question which I am a bit worried about.

I'm kind of a noob in electronics and I'm trying to nail down everything properly on the first go for my build.

I just finished building my power supply and was checking the ground resistance.
Mike states on his blog that you need to have a ground reference close to 0.2 Ω and anything above 1 Ω is danger.
I'm getting a reading of 0.8 to 0.9 Ω. I'm not sure why it is that high. Is this an alright ground to start plugging in my 1176?
What can I do to decrease the resistance?

EDIT (NEW QUESTION):
I turned on my unit to test out the readings as stated in the build guide.
After about 5 sec from power up a quick tiny line of smoke passed by.
I didn't catch from which component it came from as I was a bit worried about the capacitor blowing up as mentioned in the guide.

I proceeded to do the readings of the -10V diode and +30V zener diode and they were reading correctly.
I then turned off the unit and tested the two 1k resistors. they were ranging around 900 and 950 ohms.
The 75 resistor was ranging properly at almost exactly 75 ohms.

Should I be worried even if everything is reading correctly?

I would also like to mention that when I first turned on the power supply, there was a small weird noise at the IEC that lasted like 3 sec before the smoke.

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 25, 2016, 09:43:40 AM
I just finished building my power supply and was checking the ground resistance.
Mike states on his blog that you need to have a ground reference close to 0.2 Ω and anything above 1 Ω is danger.
I'm getting a reading of 0.8 to 0.9 Ω. I'm not sure why it is that high. Is this an alright ground to start plugging in my 1176?
What can I do to decrease the resistance?

Hard to say, but there is a chance that resistance is from you meter probes. You could touch your probes together (not touching your build) and see what the resistance reading is in just the probes.  Subtract that number from the number your getting when you measure the FET rack ground.

EDIT (NEW QUESTION):
I turned on my unit to test out the readings as stated in the build guide.
After about 5 sec from power up a quick tiny line of smoke passed by.
I didn't catch from which component it came from as I was a bit worried about the capacitor blowing up as mentioned in the guide.

That's not a cap failing.  That would be huge event that would stink up your room.

I proceeded to do the readings of the -10V diode and +30V zener diode and they were reading correctly.
I then turned off the unit and tested the two 1k resistors. they were ranging around 900 and 950 ohms.
The 75 resistor was ranging properly at almost exactly 75 ohms.

Should I be worried even if everything is reading correctly?

I would also like to mention that when I first turned on the power supply, there was a small weird noise at the IEC that lasted like 3 sec before the smoke.

Thanks!

Readings were good, that's good.

You can't really test resistors on the board without considering what's around them.  Those resistors are in series so they shouldn't be interacting with one another however there may be other considerations like the caps and diodes around them. If you're worried about those resistors you can de-solder and lift one leg and then measure.  I suspect they'll read fine.

Make sure your voltage select switch is set correctly.

Not sure about the smoke but it sounds like you're working ok. I little high pitched noise on power-up is normal if I recall correctly. Probably the power transformer. If you had anything really wrong the fuse would blow.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on August 25, 2016, 09:54:32 AM
I just finished building my power supply and was checking the ground resistance.
Mike states on his blog that you need to have a ground reference close to 0.2 Ω and anything above 1 Ω is danger.
I'm getting a reading of 0.8 to 0.9 Ω. I'm not sure why it is that high. Is this an alright ground to start plugging in my 1176?
What can I do to decrease the resistance?

Hard to say, but there is a chance that resistance is from you meter probes. You could touch your probes together (not touching your build) and see what the resistance reading is in just the probes.  Subtract that number from the number your getting when you measure the FET rack ground.

EDIT (NEW QUESTION):
I turned on my unit to test out the readings as stated in the build guide.
After about 5 sec from power up a quick tiny line of smoke passed by.
I didn't catch from which component it came from as I was a bit worried about the capacitor blowing up as mentioned in the guide.

That's not a cap failing.  That would be huge event that would stink up your room.

I proceeded to do the readings of the -10V diode and +30V zener diode and they were reading correctly.
I then turned off the unit and tested the two 1k resistors. they were ranging around 900 and 950 ohms.
The 75 resistor was ranging properly at almost exactly 75 ohms.

Should I be worried even if everything is reading correctly?

I would also like to mention that when I first turned on the power supply, there was a small weird noise at the IEC that lasted like 3 sec before the smoke.

Thanks!

Readings were good, that's good.

You can't really test resistors on the board without considering what's around them.  Those resistors are in series so they shouldn't be interacting with one another however there may be other considerations like the caps and diodes around them. If you're worried about those resistors you can de-solder and lift one leg and then measure.  I suspect they'll read fine.

Make sure your voltage select switch is set correctly.

Not sure about the smoke but it sounds like you're working ok. I little high pitched noise on power-up is normal if I recall correctly. Probably the power transformer. If you had anything really wrong the fuse would blow.

Mike

Thanks a lot for the great detailed and fast replies Mike!

I will proceed with the soldering of the signal pre-amp section.

Cheers!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Harpo on August 25, 2016, 02:17:21 PM
I proceeded to do the readings of the -10V diode and +30V zener diode...
Both are zeners  ;) (the 1N4740 for the -10VDC rail obviously with wrong symbol for CR9 in the schematic), but if you placed the correct part with correct orientation, all should be fine.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on August 25, 2016, 04:09:34 PM
(the 1N4740 for the -10VDC rail obviously with wrong symbol for CR9 in the schematic)
Thanks for pointing this out. I will fix the documentation. *edit - zener symbol fixed as well as some resistor quantity errors on the Rev D doc.*
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 02, 2016, 08:36:13 PM
Quick question about Q12 & Q13 transistors.

Is it necessary for them to touch on their flat surface?

If so, can anybody explain why? I am quite curious.

I'm having a hard time getting them to touch perfectly!

Thanks.

EDIT: Nevermind...  Answer: "THERMAL COUPLING"

But if someone has some tips on how to get them flat touching on each other, that would be great!

*Picture Below*
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 03, 2016, 11:49:19 AM
This is as close as I could get them...

Any help or recommendation would be much appreciated.

FRONT SIDE
(https://s18.postimg.org/r2zyonjc9/Transistor_Side_1.jpg)

BACK SIDE
(https://s14.postimg.org/xf7j8uoyp/Transistor_Side_2.jpg)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on September 05, 2016, 12:29:21 AM
This is as close as I could get them...

Any help or recommendation would be much appreciated.
If I'm understanding correctly you want to know how to get two transistors to contact each other after they are soldered in place. In my experience it is best to bind them together - either temporarily or permanently - before soldering them. Otherwise the three leads create a stable tripod that inhibits their movement.

However there is no compelling reason why they need to touch in this application. It just helps the stability of the circuit if they are near, otherwise thermal variations cause the needle to drift in GR mode.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on September 05, 2016, 01:02:29 AM
Dang it!

How am I ever supposed to finish remodeling my house with all this cool stuff to build?!

Also, the stereo linking option looks more solid than the original red versions. How well do the two compression circuits track with the new linking version? I may have to replace the ones in my stereo Rev D that I build some time ago.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 05, 2016, 08:33:04 AM
This is as close as I could get them...

Any help or recommendation would be much appreciated.
If I'm understanding correctly you want to know how to get two transistors to contact each other after they are soldered in place. In my experience it is best to bind them together - either temporarily or permanently - before soldering them. Otherwise the three leads create a stable tripod that inhibits their movement.

However there is no compelling reason why they need to touch in this application. It just helps the stability of the circuit if they are near, otherwise thermal variations cause the needle to drift in GR mode.

Hey Mnats, Thanks for the reply.

Yea I want them to stay in contact to prevent any mishaps in the latter stages.

Would you say using duct tape to couple them together is a safe way to do this?
If not, what material would you recommend to couple them properly together?

But from what I understand, the way I have them placed will do just fine I suppose, correct?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on September 05, 2016, 10:45:00 AM
You could do how the the transistors on Hairball's 990. They use shrink tubing to keep them right next to each other. or you could just apply some thermal paste.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 05, 2016, 10:49:52 AM
But from what I understand, the way I have them placed will do just fine I suppose, correct?

Looks fine to me!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 05, 2016, 10:57:29 AM
Dang it!

How am I ever supposed to finish remodeling my house with all this cool stuff to build?!

Also, the stereo linking option looks more solid than the original red versions. How well do the two compression circuits track with the new linking version? I may have to replace the ones in my stereo Rev D that I build some time ago.

Thanks!

Paul

Hi Paul,

It's the same linking, adapted from the MC77. It's just set up to be integrated easier.

It tracks well however, since the linking is preformed before the side chain, all of the side chain component tolerences are brought into play. So you need to tweak the att/rel and output on each unit a little once your stereo material is set up.

The kits come with the traditional UREI RCA link which is post side chain and tracks well. However, it does slow your attack time and you'll need stereo FETs or a UA link box.

Both have pros and cons.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on September 06, 2016, 12:11:33 AM
Mike,

Thanks for the info.

I think that if it's pretty close, it will be more than sufficient for the material that this was designed for, or at least how I use mine.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 08, 2016, 02:51:35 PM
Is this ruined?

I suppose there is no way to fix this right?  :'(

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 08, 2016, 03:47:42 PM
I checked continuity from the RED point to both GREEN points using the Diode function on my DMM.

It was reading 1V when not touching, and 0V when touching either points.

Does this mean the scratched trace is not damaged and will function properly?

How can I cover it up/fix the scratched part?

Thanks.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 08, 2016, 03:54:08 PM
I don't really see anything too bad.

Check the continuity with the Ω setting.  When you touch each end of the trace, is the reading less than 1Ω?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 08, 2016, 04:05:43 PM
I don't really see anything too bad.

Check the continuity with the Ω setting.  When you touch each end of the trace, is the reading less than 1Ω?

Mike

Hey Mike,

I'm getting a reading between 0.7 to 0.8 Ω, that's a good thing I suppose?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 08, 2016, 04:07:28 PM
I don't really see anything too bad.

Check the continuity with the Ω setting.  When you touch each end of the trace, is the reading less than 1Ω?

Mike

Hey Mike,

I'm getting a reading between 0.7 to 0.8 Ω, that's a good thing I suppose?

Yup...most of that resistance is probably in your leads.  You should be good.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 08, 2016, 04:11:07 PM
I don't really see anything too bad.

Check the continuity with the Ω setting.  When you touch each end of the trace, is the reading less than 1Ω?

Mike

Hey Mike,

I'm getting a reading between 0.7 to 0.8 Ω, that's a good thing I suppose?

Yup...most of that resistance is probably in your leads.  You should be good.

Sweet! Thanks for the awesome help!

Gonna need to purchase a new slimmer screw driver -_-

I scratched the trace while screwing the silver pans because my current screw driver is a fat one...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 08, 2016, 04:13:15 PM
I don't really see anything too bad.

Check the continuity with the Ω setting.  When you touch each end of the trace, is the reading less than 1Ω?

Mike

Hey Mike,

I'm getting a reading between 0.7 to 0.8 Ω, that's a good thing I suppose?

Yup...most of that resistance is probably in your leads.  You should be good.

Sweet! Thanks for the awesome help!

Gonna need to purchase a new slimmer screw driver -_-

I scratched the trace while screwing the silver pans because my current screw driver is a fat one...

Most likely just scratched the solder mask over the trace. Old school gear doesn't generally even have solder mask.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 13, 2016, 06:01:50 PM
Hey Guys,

So I just finished calibrating my Hairball 1176 Rev D and gave it a test run by compressing a Bass D.I.

I noticed something weird...

When I had a ratio of 20:1, the GR meter was reading around -3 to -5 db reduction.

When I had a ration of 4:1, the GR meter was reading -10db to -20db + of reduction.

Even when I would switch between both ratios, I noticed the 20:1's output was louder than the 4:1's output.

They both had the exact same settings as I was A/B-ing them during the process.

My Ratio Buttons are properly soldered to the ratio PCB and the PCB is aligned with the front panel ratio texts.

I'm not sure why my 4:1 ratio is behaving like a 20:1 ratio and vice versa...

Some pictures to help out:

4:1 Ratio
(https://s12.postimg.org/ao8nlz8yx/4_to_1_Ratio.jpg) (https://postimg.org/image/ao8nlz8yx/)

20:1 Ratio
(https://s12.postimg.org/e94j57dih/20_to_1_Ratio.jpg) (https://postimg.org/image/e94j57dih/)

DAW Waveforms
(https://s12.postimg.org/rek1bb7e1/DAW_Waveforms.jpg) (https://postimg.org/image/rek1bb7e1/)

PCB | Buttons
(https://s12.postimg.org/53w6bca3t/PCB_Buttons.jpg) (https://postimg.org/image/53w6bca3t/)

I also noticed that my T-Pad makes a crackling noise to the signal every time I rotate between Negative Infinity to 18 db, anything above doesn't add mechanical noise.

I don't mind the noise as I never ride compression on analog gear, but it would be nice to fix it anyway so it feels clean and tidy.

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2016, 07:29:23 PM
Hey Guys,

So I just finished calibrating my Hairball 1176 Rev D and gave it a test run by compressing a Bass D.I.

I noticed something weird...

When I had a ratio of 20:1, the GR meter was reading around -3 to -5 db reduction.

When I had a ration of 4:1, the GR meter was reading -10db to -20db + of reduction.

Even when I would switch between both ratios, I noticed the 20:1's output was louder than the 4:1's output.

They both had the exact same settings as I was A/B-ing them during the process.

My Ratio Buttons are properly soldered to the ratio PCB and the PCB is aligned with the front panel ratio texts.

I'm not sure why my 4:1 ratio is behaving like a 20:1 ratio and vice versa...

Some pictures to help out:

4:1 Ratio
(https://s12.postimg.org/ao8nlz8yx/4_to_1_Ratio.jpg) (https://postimg.org/image/ao8nlz8yx/)

20:1 Ratio
(https://s12.postimg.org/e94j57dih/20_to_1_Ratio.jpg) (https://postimg.org/image/e94j57dih/)

DAW Waveforms
(https://s12.postimg.org/rek1bb7e1/DAW_Waveforms.jpg) (https://postimg.org/image/rek1bb7e1/)

PCB | Buttons
(https://s12.postimg.org/53w6bca3t/PCB_Buttons.jpg) (https://postimg.org/image/53w6bca3t/)

I also noticed that my T-Pad makes a crackling noise to the signal every time I rotate between Negative Infinity to 18 db, anything above doesn't add mechanical noise.

I don't mind the noise as I never ride compression on analog gear, but it would be nice to fix it anyway so it feels clean and tidy.

Thanks!

The 1176 threshold lowers as you move down the ratios. So the 4:1 threshold is way lower than the 20:1 ratio, so you'll see more OVERALL compression at 4:1.  Ratio is a totally different thing that has nothing to do with a single point compression.  Checkout the UREI manual for more info. However, your unit is working as expected.

We use the BI T-Pads because they tend not to suffer from end of track noise like other pots.  Sounds like maybe you have some EOT noise. It's really hard to get rid of in these Tpads because to Tpad sits before the amp stages so any little noise in the pot get's amplified.  We can send you another one if you like to see if you get any better results, but keep in mind the desoldering can be a little tricky.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 13, 2016, 07:49:24 PM
Hey Guys,

So I just finished calibrating my Hairball 1176 Rev D and gave it a test run by compressing a Bass D.I.

I noticed something weird...

When I had a ratio of 20:1, the GR meter was reading around -3 to -5 db reduction.

When I had a ration of 4:1, the GR meter was reading -10db to -20db + of reduction.

Even when I would switch between both ratios, I noticed the 20:1's output was louder than the 4:1's output.

They both had the exact same settings as I was A/B-ing them during the process.

My Ratio Buttons are properly soldered to the ratio PCB and the PCB is aligned with the front panel ratio texts.

I'm not sure why my 4:1 ratio is behaving like a 20:1 ratio and vice versa...

Some pictures to help out:

4:1 Ratio
(https://s12.postimg.org/ao8nlz8yx/4_to_1_Ratio.jpg) (https://postimg.org/image/ao8nlz8yx/)

20:1 Ratio
(https://s12.postimg.org/e94j57dih/20_to_1_Ratio.jpg) (https://postimg.org/image/e94j57dih/)

DAW Waveforms
(https://s12.postimg.org/rek1bb7e1/DAW_Waveforms.jpg) (https://postimg.org/image/rek1bb7e1/)

PCB | Buttons
(https://s12.postimg.org/53w6bca3t/PCB_Buttons.jpg) (https://postimg.org/image/53w6bca3t/)

I also noticed that my T-Pad makes a crackling noise to the signal every time I rotate between Negative Infinity to 18 db, anything above doesn't add mechanical noise.

I don't mind the noise as I never ride compression on analog gear, but it would be nice to fix it anyway so it feels clean and tidy.

Thanks!

The 1176 threshold lowers as you move down the ratios. So the 4:1 threshold is way lower than the 20:1 ratio, so you'll see more OVERALL compression at 4:1.  Ratio is a totally different thing that has nothing to do with a single point compression.  Checkout the UREI manual for more info. However, your unit is working as expected.

We use the BI T-Pads because they tend not to suffer from end of track noise like other pots.  Sounds like maybe you have some EOT noise. It's really hard to get rid of in these Tpads because to Tpad sits before the amp stages so any little noise in the pot get's amplified.  We can send you another one if you like to see if you get any better results, but keep in mind the desoldering can be a little tricky.

Mike

Cheers Mike!

You always have the most informative answers.

I would love to get another t-pad if that would be possible!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2016, 07:51:09 PM
Send me an email to the "[email protected]" address for the t-pad.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: twentys7ven on September 13, 2016, 10:16:27 PM
Hi guys,

I posted a couple of days ago in the Rev A thread but figured I'd ask here too, I'm currently working on my second FET/Rack kit and it appears I've run into some trouble. I'm able to complete the Q bias calibration but I'm unable to complete step 2 as my VU meter won't budge no matter what I do, it stays all the way to the left. Any ideas of where potential trouble could be? I'm relatively new to DIY so I'm unsure how to check the voltages against the schematic or if that would even help narrow it down.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2016, 10:20:09 PM
Hi guys,

I posted a couple of days ago in the Rev A thread but figured I'd ask here too, I'm currently working on my second FET/Rack kit and it appears I've run into some trouble. I'm able to complete the Q bias calibration but I'm unable to complete step 2 as my VU meter won't budge no matter what I do, it stays all the way to the left. Any ideas of where potential trouble could be? I'm relatively new to DIY so I'm unsure how to check the voltages against the schematic or if that would even help narrow it down.

which version of the PCB do you have? I want to keep things in the proper thread. Let me know and I'll answer in the appropriate thread.

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: twentys7ven on September 13, 2016, 10:30:01 PM
which version of the PCB do you have? I want to keep things in the proper thread. Let me know and I'll answer in the appropriate thread.

Thanks!

v1.12 I believe, from the most recent batch of Rev As that got sent out about a month ago.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2016, 10:37:06 PM
which version of the PCB do you have? I want to keep things in the proper thread. Let me know and I'll answer in the appropriate thread.

Thanks!

v1.12 I believe, from the most recent batch of Rev As that got sent out about a month ago.

Then this is the correct thread.

Does the meter work in +4 or +8? 

Get a good signal going through it...like at least 0dbu (0.775VAC) on the output.  Does the meter react in +8 or +4?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 14, 2016, 05:21:18 PM
Hey Mike,

When i purchased my rev d kit, i also ordered with it the orange drop caps.

If i were to replace the film caps with the drops, would I then have to re-calibrate my 1176?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 14, 2016, 05:42:13 PM
Hey Mike,

When i purchased my rev d kit, i also ordered with it the orange drop caps.

If i were to replace the film caps with the drops, would I then have to re-calibrate my 1176?

Nope.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: twentys7ven on September 14, 2016, 11:57:59 PM
Then this is the correct thread.

Does the meter work in +4 or +8? 

Get a good signal going through it...like at least 0dbu (0.775VAC) on the output.  Does the meter react in +8 or +4?

Nope, not at all. Just fed it a signal and the meter won't budge at all regardless of how loud of a signal is passed through or what the meter is set to display.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 15, 2016, 11:01:42 AM
Then this is the correct thread.

Does the meter work in +4 or +8? 

Get a good signal going through it...like at least 0dbu (0.775VAC) on the output.  Does the meter react in +8 or +4?

Nope, not at all. Just fed it a signal and the meter won't budge at all regardless of how loud of a signal is passed through or what the meter is set to display.

Hmmmm. Sounds like a damaged meter maybe. You have the signal wire harness on there? (Metal Spades).
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 15, 2016, 11:37:25 AM
Hi

This is my first time here. I've just completed building 2 Rev As and I'm having a bit of trouble with the Q bias calibration.
Before I go on, I've re-verified all components correctly placed, DC voltages correct, calibration parameters set per the Q bias instructions on the site, exact same problem on both units.

Here's what I've got-
1K signal reads 0dbu (0.775VAC) at the input and that signal reaches the primary of the input transformer->
with the input knob at 24, the signal after the tranny reads 0.120 VAC at TP1 and the signal voltage tracks with the knob from 0-0.360VAC which seems correct->
but there are 0.0 volts on the Q1 side of R5 (27Kohm).

The signal drops to zero volts after R5.
Henceforth, there is no signal anywhere down the chain and my calibration stops there.

I've tested Q1 and it has many mega ohms across it on both units, solder joints and component values all good.

I'm obviously missing something. Any help would be much obliged.

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 15, 2016, 11:41:56 AM
Hi

This is my first time here. I've just completed building 2 Rev As and I'm having a bit of trouble with the Q bias calibration.
Before I go on, I've re-verified all components correctly placed, DC voltages correct, calibration parameters set per the Q bias instructions on the site, exact same problem on both units.

Here's what I've got-
1K signal reads 0dbu (0.775VAC) at the input and that signal reaches the primary of the input transformer->
with the input knob at 24, the signal after the tranny reads 0.120 VAC at TP1 and the signal voltage tracks with the knob from 0-0.360VAC which seems correct->
but there are 0.0 volts on the Q1 side of R5 (27Kohm).

The signal drops to zero volts after R5.
Henceforth, there is no signal anywhere down the chain and my calibration stops there.

I've tested Q1 and it has many mega ohms across it on both units, solder joints and component values all good.

I'm obviously missing something. Any help would be much obliged.

Short somewhere around Q1 I would say. What happens if you remove Q1? Then can you get signal to the output?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 15, 2016, 11:56:00 AM
I've not tried that yet. Will pull it later today and let you know what I find.
Thanks for the quickness...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: twentys7ven on September 15, 2016, 02:02:00 PM
Then this is the correct thread.

Does the meter work in +4 or +8? 

Get a good signal going through it...like at least 0dbu (0.775VAC) on the output.  Does the meter react in +8 or +4?

Nope, not at all. Just fed it a signal and the meter won't budge at all regardless of how loud of a signal is passed through or what the meter is set to display.

Hmmmm. Sounds like a damaged meter maybe. You have the signal wire harness on there? (Metal Spades).

If those are the terminals underneath the meter then yep.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 15, 2016, 08:15:38 PM
K.
Removed Q1. And yes, the signal now makes it to the gate of Q2.
But it stops there because there is no DC voltage on the power rail to Q2 and Q3.
There are however, 30 VDC on both sides of R17.

I guess there is a short somewhere around Q2 or Q3 or both or dang.
I'm confused.  Kids calling.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 16, 2016, 01:21:05 AM
Alright, I got the first one calibrated. R17 was missing a pad so no power on the rails downstream of it.

Fixed that and on to my second Rev As problems.
Again, can't perform the Q bias calibration this time because R59 produces no change in output signal when adjusted. It stays at its full output regardless of how many ccw turns. Verified components and reflowed joints. No change.

Thanks for the help.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 16, 2016, 03:18:09 PM
Hope I didn't make it sound like I was out of the woods. 
Searched the other threads but kinda got lost.
I could still use some help with the Q bias trim pot problem.
Anybody out there?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 18, 2016, 09:35:42 AM
OK. Negative DC voltage is getting all the way to R7, which has a small drop across it, but not to the gate of Q1/R6.
Pulling Q1 and looking for ground...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 19, 2016, 12:21:24 AM
Then this is the correct thread.

Does the meter work in +4 or +8? 

Get a good signal going through it...like at least 0dbu (0.775VAC) on the output.  Does the meter react in +8 or +4?

Nope, not at all. Just fed it a signal and the meter won't budge at all regardless of how loud of a signal is passed through or what the meter is set to display.

Hmmmm. Sounds like a damaged meter maybe. You have the signal wire harness on there? (Metal Spades).

If those are the terminals underneath the meter then yep.

Send us an email.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 19, 2016, 12:24:25 AM
OK. Negative DC voltage is getting all the way to R7, which has a small drop across it, but not to the gate of Q1/R6.
Pulling Q1 and looking for ground...

Does this one have output with Q1 in, but no output with Q1 out?

If so, you have a bad Q1.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 19, 2016, 01:09:24 AM
Q1 is good and I got the Q bias set. Just had to fix a couple solder pads/traces.
I set the null too after a pad fix as well.

Now I'm stuck on the tracking adjust procedure-
On step 4 turning up the input only gets me 1vac  at the output (attack off)
Also turning the compression on and of yields no change in output voltage. There is no compression  happening.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 19, 2016, 03:40:37 PM
Q1 is good and I got the Q bias set. Just had to fix a couple solder pads/traces.
I set the null too after a pad fix as well.

Now I'm stuck on the tracking adjust procedure-
On step 4 turning up the input only gets me 1vac  at the output (attack off)
Also turning the compression on and of yields no change in output voltage. There is no compression  happening.

With the new wiring, really the only issue can be solder, component mix up, or killing a semi on installation.  I'd go through the side chain (GR amp) and ratio board touching up anything that looks weird.  There is some PAD21/22 measurement stuff in these threads. If you still have issues after touching up the PCB or can't find the pad 22/21 stuff, let me know.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 20, 2016, 02:04:42 PM
Revision A question via email:

 
Quote
I calibrated one last night and everything went great. When I started the second one, the q bias didn't seem to change the voltage at the output xlr. However I noticed when I adjusted the q bias the meter would change. Also the output control changed the voltage at the output xlr. Any suggestions on where I should begin searching? I checked all solder points and components.

Seems like the qbias is probably working but the Q1 FET isn't responding to it. You might want to check solder joints on Q1. Possible it's dead too.

If you can, without damaging the pads, try swapping Q1 and Q11. If you can set the qbias and the meter stops reacting...the Q11 (currently your Q1) is dead.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seb121314 on September 20, 2016, 03:47:22 PM
Hi,
i have a pair of these in revision D and i have the active stereo link in it. I have a problem to make them work in stereo, the one who receive the signal from the link have more gain reduction then the one who send. i try changing the cable and re calibrate the two but nothing changed.it's pretty problematic when i do parallel compression the stereo image change due to the difference of GR.
bye the way these are really cool product and fun to build !
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 20, 2016, 09:22:39 PM
Hi,
i have a pair of these in revision D and i have the active stereo link in it. I have a problem to make them work in stereo, the one who receive the signal from the link have more gain reduction then the one who send. i try changing the cable and re calibrate the two but nothing changed.it's pretty problematic when i do parallel compression the stereo image change due to the difference of GR.
bye the way these are really cool product and fun to build !

Hi,

This is addressed in the link build guide.

The linking happens before the side chain, so all of the tolerance difference in the attack pots and release pots change things.

Read the bottom of this page:
http://www.hairballaudio.com/blog/resources/build-guides/fetrack-newbractive-link

You need to tweak the four controls slightly for perfect imaging.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seb121314 on September 20, 2016, 09:47:29 PM
oh okay sorry i didin't read that part i will try this thanks !
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jettison on September 21, 2016, 02:24:43 PM
Got it.
The trace from C17 to the junction of R36, R37, and Q7 was open so the GR amp wasn't getting signal from the output of the preamp.
Fixed that and all is well. Both my units are cal'ed and ready to go. 
T'was fun except for the few pads that needed help.

Thanks man
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 23, 2016, 08:43:07 PM
I know this isn't really an issue to post about and I know I am going to sound like a mega noob but, I was curious as to what the roles of capacitors C1, C7, C8, and C10 are?

If anybody can give a brief explanation as to how each of them affects the rest of the audio circuit would be great.

I can't find anything on the web that gives an explanation of what a capacitor does in an audio unit (aside from the caps in the power supply acting as reservoir caps to maintain current *correct me if im wrong*)

I will be trying out the orange drops soon for my rev. D so I figured it would be nice if I could understand what each capacitors is doing to the signal.

But just curious about the those specific ones i named earlier.

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 23, 2016, 11:36:02 PM
I know this isn't really an issue to post about and I know I am going to sound like a mega noob but, I was curious as to what the roles of capacitors C1, C7, C8, and C10 are?

If anybody can give a brief explanation as to how each of them affects the rest of the audio circuit would be great.

I can't find anything on the web that gives an explanation of what a capacitor does in an audio unit (aside from the caps in the power supply acting as reservoir caps to maintain current *correct me if im wrong*)

I will be trying out the orange drops soon for my rev. D so I figured it would be nice if I could understand what each capacitors is doing to the signal.

But just curious about the those specific ones i named earlier.

Thanks!

They are coupling caps. The connect two sections of the circuit together and block unwanted DC from one section from moving to the next. Since they are in series with the signal and the audio passes through them they have noticeable impact on the sound.

Deeper:
http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 24, 2016, 08:14:06 AM
I know this isn't really an issue to post about and I know I am going to sound like a mega noob but, I was curious as to what the roles of capacitors C1, C7, C8, and C10 are?

If anybody can give a brief explanation as to how each of them affects the rest of the audio circuit would be great.

I can't find anything on the web that gives an explanation of what a capacitor does in an audio unit (aside from the caps in the power supply acting as reservoir caps to maintain current *correct me if im wrong*)

I will be trying out the orange drops soon for my rev. D so I figured it would be nice if I could understand what each capacitors is doing to the signal.

But just curious about the those specific ones i named earlier.

Thanks!

They are coupling caps. The connect two sections of the circuit together and block unwanted DC from one section from moving to the next. Since they are in series with the signal and the audio passes through them they have noticeable impact on the sound.

Deeper:
http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html

Mike

Cheers Mike!

Btw I got the T-pad, haven't installed it yet though.

Thanks for the awesome service!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 24, 2016, 05:53:18 PM
Hey guys,
Finished my 1176 Rev D build and am having trouble with the q bias calibration. I have everything set as recommended but turning R59 from max (CW) to its minimum only results in a -.5 Db change. Has anyone had/dealt with this problem before?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 25, 2016, 01:46:35 AM
Hey guys,
Finished my 1176 Rev D build and am having trouble with the q bias calibration. I have everything set as recommended but turning R59 from max (CW) to its minimum only results in a -.5 Db change. Has anyone had/dealt with this problem before?

What is the DC V range at pad 18 and then pad 7 (using chasis as common) as you rotate the Qbias?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 25, 2016, 03:00:39 PM
Hey guys,
Finished my 1176 Rev D build and am having trouble with the q bias calibration. I have everything set as recommended but turning R59 from max (CW) to its minimum only results in a -.5 Db change. Has anyone had/dealt with this problem before?

What is the DC V range at pad 18 and then pad 7 (using chasis as common) as you rotate the Qbias?

Mike

At pad 18 it reads 0 to -73.4 VDC and at pad 7 it's reading -1 to -71.8 VDC. 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 25, 2016, 11:24:37 PM
What is the DC V range at pad 18 and then pad 7 (using chasis as common) as you rotate the Qbias?

Mike


At pad 18 it reads 0 to -73.4 VDC and at pad 7 it's reading -1 to -71.8 VDC.

That'a not really possible.  Try gain and check your meter. Should be 0 to a couple volts negative.

You have -10VDC at that power supply test point right?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 26, 2016, 04:41:32 AM
That'a not really possible.  Try gain and check your meter. Should be 0 to a couple volts negative.

You have -10VDC at that power supply test point right?

So I have the DMM set to the 2V setting and pad 18 is reading 0 to -.092 and pad 7 is reading 0 to -.089.  Am I still far off?   Where is the power supply test point? This is all new to me. My Lola build was assemble and record.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on September 26, 2016, 01:14:45 PM
So I have the DMM set to the 2V setting and pad 18 is reading 0 to -.092 and pad 7 is reading 0 to -.089.  Am I still far off?   Where is the power supply test point? This is all new to me. My Lola build was assemble and record.

I think he's talking about the Diode CR9, turn your unit on and measure it in DC and see if you get -10VDC./

Check the build guide and scroll down to the bottom to see how to test it

Link: http://www.hairballaudio.com/blog/resources/build-guides/fetrack-v2-build-and-calibration-guide

Wait for Mikes response though, that might not be it. Just tryin to help!

Good Luck
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 26, 2016, 01:20:07 PM
So I have the DMM set to the 2V setting and pad 18 is reading 0 to -.092 and pad 7 is reading 0 to -.089.  Am I still far off?   Where is the power supply test point? This is all new to me. My Lola build was assemble and record.

Your pad 18 is all messed up. It's too low. should be 0 to about -2.5 VDC.

Check the value of R35 (10K) and R60 (3.9K). Are they the right value? Re-flow those joints.

What is your DCV on each side of R35 and then each side of R60. Always using chassis for common.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 26, 2016, 01:26:55 PM
I think he's talking about the Diode CR9, turn your unit on and measure it in DC and see if you get -10VDC./

Check the build guide and scroll down to the bottom to see how to test it

Link: http://www.hairballaudio.com/blog/resources/build-guides/fetrack-v2-build-and-calibration-guide

Wait for Mikes response though, that might not be it. Just tryin to help!

Good Luck

Yes also check your -10V test point as described in the guide.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 26, 2016, 02:53:01 PM
Your pad 18 is all messed up. It's too low. should be 0 to about -2.5 VDC.

Check the value of R35 (10K) and R60 (3.9K). Are they the right value? Re-flow those joints.

What is your DCV on each side of R35 and then each side of R60. Always using chassis for common.

Mike

Remounted R35 and R60.  R35 is reading -9.85V and -0.0V. R60 is reading -0.0V and -.08V. I assumed that my meter was just a little off at the power supply test point but should it be exactly 10V or should I be rounding up as I have been from -9.85V?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 26, 2016, 03:24:50 PM
Remounted R35 and R60.  R35 is reading -9.85V and -0.0V. R60 is reading -0.0V and -.08V. I assumed that my meter was just a little off at the power supply test point but should it be exactly 10V or should I be rounding up as I have been from -9.85V?

Your problem is around R35. You should have the -9.85(ish) on one side and something around -2.5 on the other. I doubt the resistor is dead, that rarely happens, but who knows. Look for a dead pad on R35. Measure it's resistance in place...what do you get. It may not read 10K and that's fine...just tell me what you get.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 26, 2016, 04:18:12 PM
Your problem is around R35. You should have the -9.85(ish) on one side and something around -2.5 on the other. I doubt the resistor is dead, that rarely happens, but who knows. Look for a dead pad on R35. Measure it's resistance in place...what do you get. It may not read 10K and that's fine...just tell me what you get.

Mike

It's reading -39.1K
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 26, 2016, 04:28:39 PM
It's reading -39.1K

Resistance is not a (-) value. You just measure the resistance across the resistor. A lead on each leg with the meter set to ohms. You should probably be getting between 1-2KΩ.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 26, 2016, 05:04:05 PM
Resistance is not a (-) value. You just measure the resistance across the resistor. A lead on each leg with the meter set to ohms. You should probably be getting between 1-2KΩ.

Mike

It's still reading at 39,1  I'm going to check all of my components again and I'll get back to you.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on September 29, 2016, 06:32:59 PM
I'm a new user to the forum- so I am unsure of the general protocol for throwing a hail mary.

After purchasing the Hairball 1176 rev A, and building it, I have run into a strange issue. After a clean (o what I would describe as a clean) build over the last week, I reached the point of first power on. After running all tests according to the build guides, the VU meter lit up, and with GR engaged pin to the right. After 10 minutes, the need began to slowly fall, and the light would no longer remain lit. Now there is nothing registering on the VU meter.

Are there specific areas/readings I should be looking for along the various test points? I scoured what I could from the forums, but all I can find is a spread sheet that asks me to measure the pins for all of the diodes.

While I am not new to building electronics, this is my first large scale project aside from amps and pedals. Any assistance would be appreciated!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 29, 2016, 09:41:42 PM
I'm a new user to the forum- so I am unsure of the general protocol for throwing a hail mary.

After purchasing the Hairball 1176 rev A, and building it, I have run into a strange issue. After a clean (o what I would describe as a clean) build over the last week, I reached the point of first power on. After running all tests according to the build guides, the VU meter lit up, and with GR engaged pin to the right. After 10 minutes, the need began to slowly fall, and the light would no longer remain lit. Now there is nothing registering on the VU meter.

Are there specific areas/readings I should be looking for along the various test points? I scoured what I could from the forums, but all I can find is a spread sheet that asks me to measure the pins for all of the diodes.

While I am not new to building electronics, this is my first large scale project aside from amps and pedals. Any assistance would be appreciated!

Hi...you're following the right protocol.

Did your fuse blow?

If you power up the unit and test the +30VDC and -10VDC rail as described in the guide, what do you get?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 29, 2016, 09:43:55 PM
It's still reading at 39,1  I'm going to check all of my components again and I'll get back to you.

For some stupid reason, R63 had a  270K resistor instead of 1.5K. Replaced it and bam! Step 1 done. The rest are pretty tricky. I doubt you've heard the last from me. Hahaha. Thanks Mike for all of your help!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 29, 2016, 09:51:46 PM
Actually here's a quick question. I misread C2 and C13 and had them mixed up. While removing the cap that was 27pF it broke. I ordered one on Amazon. It doesn't look the same but it's 27pF/50V. Is that ok?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 29, 2016, 09:54:43 PM
Actually here's a quick question. I misread C2 and C13 and had them mixed up. While removing the cap that was 27pF it broke. I ordered one on Amazon. It doesn't look the same but it's 27pF/50V. Is that ok?

Yup.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 30, 2016, 03:38:28 AM
Anddddddd sure enough... The lowest I can get the VDC across R74 is .31. Any suggestions on this one?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 30, 2016, 10:54:14 AM
Anddddddd sure enough... The lowest I can get the VDC across R74 is .31. Any suggestions on this one?

Start by going through all of your component values in the meter section and touching up and suspect soldering.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 30, 2016, 07:51:46 PM
Start by going through all of your component values in the meter section and touching up and suspect soldering.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on September 30, 2016, 07:53:44 PM

I've checked and resoldered. I feel like the more I work on it the worse it's getting though. Do you see any spot I should be concerned about?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 02, 2016, 02:22:21 AM
I've checked and resoldered. I feel like the more I work on it the worse it's getting though. Do you see any spot I should be concerned about?

Bueller...? Bueller...? My soldering is... Anyone? Anyone?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 02, 2016, 03:35:50 AM
New idea. Can someone PLEASE post a picture of a fully functional Rev D PCB that I may compare to. I had some left over resistors that I had to install from the interactive map. I'd just like to see if I possibly have an extra resistor somewhere or not. Can't find a pic of the new Rev D anywhere though. Thanks.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: StudioJakubka on October 02, 2016, 03:39:27 PM
Your problem is around R35. You should have the -9.85(ish) on one side and something around -2.5 on the other. I doubt the resistor is dead, that rarely happens, but who knows. Look for a dead pad on R35. Measure it's resistance in place...what do you get. It may not read 10K and that's fine...just tell me what you get.

Mike

Hi Mike, -9.85VDC and -2.5VDC on R35, rev A? I am way off then.
Is there anywhere Rev A typical voltages? Or voltages on measuring points on the new PCB?
Thanks.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 02, 2016, 05:59:56 PM
Hi Mike, -9.85VDC and -2.5VDC on R35, rev A? I am way off then.
Is there anywhere Rev A typical voltages? Or voltages on measuring points on the new PCB?
Thanks.

Wait you have a Rev A? Is it the new version that just came out? PCB is V1.12?

What is your DC at pad 18 again?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 02, 2016, 06:06:30 PM
New idea. Can someone PLEASE post a picture of a fully functional Rev D PCB that I may compare to. I had some left over resistors that I had to install from the interactive map. I'd just like to see if I possibly have an extra resistor somewhere or not. Can't find a pic of the new Rev D anywhere though. Thanks.

Visual comparison is mostly useless. It's a circuit issue. Soldering seems good, but I can't really tell, again pictures rarely help.

1) The QBias is set right?
2) Now you're stuck at null adjust right?
3) You have the jumper in the correct location?
4) You've verified the component values agains the Rev D map? Remember in the guide there is a link for helping read color codes.
5) Look at the GR Meter Driver section here (older schematic but mostly accurate):
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf
How do those DC voltages measure.
6)make sure you didn't mix up the 100Ω and 2K square trimmers.

Mike

PS: Also remember we have flat rate repair if that interests you.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 02, 2016, 08:21:15 PM
Visual comparison is mostly useless. It's a circuit issue. Soldering seems good, but I can't really tell, again pictures rarely help.

1) The QBias is set right?
2) Now you're stuck at null adjust right?
3) You have the jumper in the correct location?
4) You've verified the component values agains the Rev D map? Remember in the guide there is a link for helping read color codes.
5) Look at the GR Meter Driver section here (older schematic but mostly accurate):
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf
How do those DC voltages measure.
6)make sure you didn't mix up the 100Ω and 2K square trimmers.

I'm going to check all of that when I get home but more than likely I'll be mailing it off to you tomorrow. Maybe I'll have better luck with my other Rev D and 2x Rev A's. Thanks Mike

Mike

PS: Also remember we have flat rate repair if that interests you.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 02, 2016, 08:25:10 PM


In my years of experience in working on these it's usually something silly like a bad joint that doesn't look all the bad. Either way, if you do send it in, we'll send you a full report on what was wrong.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 02, 2016, 10:18:52 PM
In my years of experience in working on these it's usually something silly like a bad joint that doesn't look all the bad. Either way, if you do send it in, we'll send you a full report on what was wrong.

Mike

It's Murphy's Law. If I keep trying to fix it, I'll never figure it out and if I send it to you, I would've figured it out in the time it takes for shipping. Haha. I just want to use this glorious thing at this point! One more attempt at solder joints tonight then off to you tomorrow if no results.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 03, 2016, 01:09:57 PM
It's Murphy's Law. If I keep trying to fix it, I'll never figure it out and if I send it to you, I would've figured it out in the time it takes for shipping. Haha. I just want to use this glorious thing at this point! One more attempt at solder joints tonight then off to you tomorrow if no results.

Andddddd I had two of the pots switched around. Lets hope that was the last problem. Thanks again, Mike!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 03, 2016, 04:33:55 PM
Andddddd I had two of the pots switched around. Lets hope that was the last problem. Thanks again, Mike!

I found a replacement 2k pot but it's 3296 instead of 3396. Will that still work?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 03, 2016, 04:55:17 PM
As a follow-up to my request for help (and hopefully continue on with calibration and building a mate) here is what was discovered:

Yes, it was the fuse, and two more of them just to get the rail readings. (which eventually were 30.4 /-9.7)

The issue is the main power supply cable length to the PCB (well at least that is what I am going to assume right now, because the unit has been powered up now for about 3 hours). The cable length was about a mil too short on one of the connectors when it was plugged into the pcb, and was causing one of the leads to pull out. This is probably why it was solid when I had things loosely put together. once I un-braided a loop or two it seems to have enough play to allow for a solid connection.

thanks again.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2016, 05:03:51 PM
As a follow-up to my request for help (and hopefully continue on with calibration and building a mate) here is what was discovered:

Yes, it was the fuse, and two more of them just to get the rail readings. (which eventually were 30.4 /-9.7)

The issue is the main power supply cable length to the PCB (well at least that is what I am going to assume right now, because the unit has been powered up now for about 3 hours). The cable length was about a mil too short on one of the connectors when it was plugged into the pcb, and was causing one of the leads to pull out. This is probably why it was solid when I had things loosely put together. once I un-braided a loop or two it seems to have enough play to allow for a solid connection.

thanks again.

Ah makes sense.

We have since discovered this issue ourselves and have stopped braiding those wires. Sorry for the hassle!

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 03, 2016, 10:53:37 PM
As I was checking CR8 with my meter it popped and sparked. I seriously can't catch a break. I'm assuming this means I need a new one. I searched Mouser for a 30v DC zener diode and nothing similar looking came up. Where can I get a replacement pronto? Also, I tried to carry on after this happened. Got to step 3 of calibration and couldn't get the attack knob to cause the 10db drop. Are these two things linked? I'm gaining a whole new respect for you guys through this build...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2016, 11:09:06 PM
As I was checking CR8 with my meter it popped and sparked. I seriously can't catch a break. I'm assuming this means I need a new one. I searched Mouser for a 30v DC zener diode and nothing similar looking came up. Where can I get a replacement pronto?

Sounds like you shorted it.  We can sell one to you or Newark has them.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 03, 2016, 11:10:40 PM
Sounds like you shorted it.  We can sell one to you or Newark has them.

How do I go about getting that from you? I'd like to order it and have it rush shipped asap.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2016, 11:20:16 PM
How do I go about getting that from you? I'd like to order it and have it rush shipped asap.

Email us. We don't usually ship on Tuesdays but I can get it out.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2016, 11:23:17 PM
Email us. We don't usually ship on Tuesdays but I can get it out.

Is it even damaged?  To you get 30V ish at the 30v test point?  If so its fine.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2016, 11:30:19 PM
Both of your issues so far were caused by misplaced components. I suspect more of that first.

If you're not getting a 10dB drop either:

1) Your Qbias isn't set right
2) You have a misplaced component in the "GR Control Amp" section (including the ratio PCB)
3) You're doing the calibration step wrong.

I'd start by going through all those "GR Control Amp" parts including the ratio PCB. Having a 470Ω, 47K, or 470K resistor swapped will ruin your time.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on October 04, 2016, 11:20:16 PM
Both of your issues so far were caused by misplaced components. I suspect more of that first.

If you're not getting a 10dB drop either:

1) Your Qbias isn't set right
2) You have a misplaced component in the "GR Control Amp" section (including the ratio PCB)
3) You're doing the calibration step wrong.

I'd start by going through all those "GR Control Amp" parts including the ratio PCB. Having a 470Ω, 47K, or 470K resistor swapped will ruin your time.

Mike

I accept defeat and am going to surrender my build to you geniuses. Hopefully you can tell me what I did wrong for the next time :(
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 04, 2016, 11:23:14 PM
I accept defeat and am going to surrender my build to you geniuses. Hopefully you can tell me what I did wrong for the next time :(

Send us an email. We'll figure it out.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: StudioJakubka on October 09, 2016, 11:44:23 AM
Wait you have a Rev A? Is it the new version that just came out? PCB is V1.12?

What is your DC at pad 18 again?

Mike

Yes, Rev A 1.12, 4 weeks old.

Vladimir
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 09, 2016, 11:50:26 AM
Yes, Rev A 1.12, 4 weeks old.

Vladimir

So what's your DC at pad 18 when you rotate the qbias pot?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: StudioJakubka on October 09, 2016, 11:58:28 AM
So what's your DC at pad 18 when you rotate the qbias pot?

it goes from -1.764 to -1.016, Other points are:

1   0
7   -1.407
15   0
18   -1.744
19   -1.404
21   -5.98
22   0
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 09, 2016, 12:19:14 PM
it goes from -1.764 to -1.016, Other points are:

1   0
7   -1.407
15   0
18   -1.744
19   -1.404
21   -5.98
22   0

Don't worry about the other stuff. Those other points may not even have DC or are relevant. It just confuses the fact finding process.

What is your DC on either side of R60?

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: StudioJakubka on October 09, 2016, 12:27:08 PM
Don't worry about the other stuff. Those other points may not even have DC or are relevant. It just confuses the fact finding process.

What is your DC on either side of R60?

R60 -1.014, -1.015
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 09, 2016, 12:43:41 PM
R60 -1.014, -1.015

that should be -1ish and -1.5ish on either side of R60.  You should be seeing around -1 to -1.7ish at pad 18 with rotation of the bias.

Are you sure R60 and R83 are the correct value of resistor? Triple check. If they are reflow those and the trimmer joints.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 09, 2016, 02:34:21 PM
Well, an update, to what I thought was going to be my last post here.

The unit continues to blow fuses, to the level that I went to a 400mA slow blow so that I could even test anything, or attempt a calibration. After trying to calibrate even the q-bias (which I was getting a reading on the xor out only while turning the output dial) the unit bricked. Now I am getting voltages half of what they should be, regardless of the situation.

Refloated the soldering, checked all connections, etc. etc. At this point I am about to erase it in concrete and throw it in the river.

Any ideas?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 09, 2016, 03:10:21 PM
Well, an update, to what I thought was going to be my last post here.

The unit continues to blow fuses, to the level that I went to a 400mA slow blow so that I could even test anything, or attempt a calibration. After trying to calibrate even the q-bias (which I was getting a reading on the xor out only while turning the output dial) the unit bricked. Now I am getting voltages half of what they should be, regardless of the situation.

Refloated the soldering, checked all connections, etc. etc. At this point I am about to erase it in concrete and throw it in the river.

Any ideas?

Where are you located? You should use a 200mA slo blo for 240 regions and a 400mA for 120 regions.  Never increase the fuse,  if they are blowing at the correct level, something is wrong.

Did you build and test the power supply before stuffing the rest of the PCB as shown in the guide? Did it test fine then?

Don't toss it in the river,  we offer flat rate build repair.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 09, 2016, 05:06:59 PM
...Saved from the river.


Everything on the power side tests out fine (as stated before). I am at the recommended fuse level and following the calibration steps. I am sending 0.775 in, and I am registering nothing on the output test points. In fact, the only voltage showing are when the output dial is turned. Are there sectional test points? Something that could be glaringly obvious?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on October 09, 2016, 06:42:07 PM
I have judti finished REV A. And this time I am getting into troubles. It seems that none of the q-bias and tracking trims are working. With Null trim I was able to set voltage in between TP 10/11 to 0,002V. Unit compresses but I am not able to adjust VU tracking. I have checked all the leads which seems fine.
I have measured following voltages acros the board:

PSU: 30.63/-9.78
TP 7, 19 =-9.53V
TP 15, 17, 22=0V
TP 18, 21=-9.78

At the R60 ( -9.7/-9.72)
At the R35 (25.79/30.52)

It is beyond my experience to see where I should look at.

Thanks a lot

Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on October 09, 2016, 11:32:53 PM
Mike!

The new kits are awesome! I was able to build two Rev A's in about the same time it used to take me to build one! And the new chassis is very sexy, very professional looking. I got both of them built up and calibrated without any issue.

The only I have to figure out is the active stereo link. Disconnected both units seen to performing as they should. With the active link engaged, they are about 4-5 dB off on the metering, and this tracks when either compressor's input controls are adjusted (yes, I have checked to make sure one is send and the either is receive). I also confirmed this discrepancy by metering the XLR outputs. I had calibrated both units twice just make sure I didn't make a mistake there, so I guess I just have to see if there is swapped component on the active link card, unless there is something else I don't know about or if there is a super secret procedure I am not aware for setting both compressors for stereo linking.

Again, awesome work. I look forward to doing more of these.

Thanks!

Paul


Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on October 10, 2016, 06:35:07 AM
Are there sectional test points? Something that could be glaringly obvious?
Have you read the FAQ linked from the first post? Blowing fuses suggests excessive current draw. It may be able to be traced by finding which points show the greatest deviation from the typical voltages at various test points on the schematic that matches your revision.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 10, 2016, 11:24:15 AM
I had overlooked this! My apologies.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 10, 2016, 07:13:18 PM
...Saved from the river.


Everything on the power side tests out fine (as stated before). I am at the recommended fuse level and following the calibration steps. I am sending 0.775 in, and I am registering nothing on the output test points. In fact, the only voltage showing are when the output dial is turned. Are there sectional test points? Something that could be glaringly obvious?

You're signal is most likely not making it through the two pre and line amp stages. 

Set the input and output at 12 o'clock. GR turned off. 20:1. Release full CW. Feed a 0.775VAC 1K signal at the input. Qbias full CW. Which ever end of the qbias gives you the largest signal at TP 15.

What is your VAC (using chassis as common) at TP:

-TP 1
-TP 15
-TP 17
-OUT +

AC for each.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 10, 2016, 07:15:23 PM
Mike!

The new kits are awesome! I was able to build two Rev A's in about the same time it used to take me to build one! And the new chassis is very sexy, very professional looking. I got both of them built up and calibrated without any issue.

The only I have to figure out is the active stereo link. Disconnected both units seen to performing as they should. With the active link engaged, they are about 4-5 dB off on the metering, and this tracks when either compressor's input controls are adjusted (yes, I have checked to make sure one is send and the either is receive). I also confirmed this discrepancy by metering the XLR outputs. I had calibrated both units twice just make sure I didn't make a mistake there, so I guess I just have to see if there is swapped component on the active link card, unless there is something else I don't know about or if there is a super secret procedure I am not aware for setting both compressors for stereo linking.

Again, awesome work. I look forward to doing more of these.

Thanks!

Paul


Thanks!

Paul

Thanks! MNATS and I worked hard on it.

Read the last section of the active link build guide.  About adjusting the in/out/attack for proper tracking.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 10, 2016, 07:18:44 PM
I have judti finished REV A. And this time I am getting into troubles. It seems that none of the q-bias and tracking trims are working. With Null trim I was able to set voltage in between TP 10/11 to 0,002V. Unit compresses but I am not able to adjust VU tracking. I have checked all the leads which seems fine.
I have measured following voltages acros the board:

PSU: 30.63/-9.78
TP 7, 19 =-9.53V
TP 15, 17, 22=0V
TP 18, 21=-9.78

At the R60 ( -9.7/-9.72)
At the R35 (25.79/30.52)

It is beyond my experience to see where I should look at.

Thanks a lot

Jan

Voltages are meaningless unless you specify AC or DC.

First things first.  Get the Qbias calibration working.  All the calibration steps must be completed in order and each one must been done correctly before moving on.

Read my response to ebenchristensen 2 posts above. Same steps for you.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on October 10, 2016, 07:41:36 PM
Thanks! MNATS and I worked hard on it.

Read the last section of the active link build guide.  About adjusting the in/out/attack for proper tracking.

Mike

Reading? Who has time for that?

I thought it somewhere easy to find. I have been suffering from an epic bout of laziness since I got home from the road.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on October 10, 2016, 08:03:11 PM
Thanks! MNATS and I worked hard on it.

Read the last section of the active link build guide.  About adjusting the in/out/attack for proper tracking.

Mike

One last question. Maybe...

Is the 4-5dB difference that I am seeing on the output as described in the last part of the Active Link guide within the range one would typically see? Also, there is a slight difference between where the input knobs need to be set for there to be similar (not linked) gain reduction when using a 1kHz tone. I take that is probably due to the tolerance range of the potentiometers.

One thing I would probably recommend and I will do myself next time is use multi turn trimmers for bias and null adjustments, as the single turns make it hard if you really want to be precise (less than 1 mV). I know it's not necessary to be that accurate, but if you're slightly OCD like me, you'll want to have the finer level of control when making adjustments. And if you plan on traveling with them as I do, I think the adjustments will stay in place better when the unit is moved around in a road case.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 10, 2016, 08:11:51 PM
One last question. Maybe...

Is the 4-5dB difference that I am seeing on the output as described in the last part of the Active Link guide within the range one would typically see? Also, there is a slight difference between where the input knobs need to be set for there to be similar (not linked) gain reduction when using a 1kHz tone. I take that is probably due to the tolerance range of the potentiometers.

One thing I would probably recommend and I will do myself next time is use multi turn trimmers for bias and null adjustments, as the single turns make it hard if you really want to be precise (less than 1 mV). I know it's not necessary to be that accurate, but if you're slightly OCD like me, you'll want to have the finer level of control when making adjustments. And if you plan on traveling with them as I do, I think the adjustments will stay in place better when the unit is moved around in a road case.

Thanks!

Paul

Right, all the pots are 20% tolerance parts, which is pretty significant.  You could confirm the units are working correctly by testing the max output. Send like a -30dbu signal (0.025 VAC) and with GR off set the in/out to max.  You should see like 40-45db of gain.

There are definitely pros and cons to the multi-turns. Single turns are a lot easier for newer builders to grasp.  But yes harder to dial in perfect.

Thanks!

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on October 10, 2016, 08:39:26 PM
Thanks for confirming that for me.

I'm definitely getting tons of gain, much more than I could use. Cranked all the way open with a 1 kHz tone, I can really make the output transformers sing.

Thanks again for yours and MNAT's awesome work. Looking forward to your next projects.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 10, 2016, 08:58:58 PM
Thanks for confirming that for me.

I'm definitely getting tons of gain, much more than I could use. Cranked all the way open with a 1 kHz tone, I can really make the output transformers sing.

Thanks again for yours and MNAT's awesome work. Looking forward to your next projects.

Thanks!

Paul

One thing about the trimmers and moving the units.  You can always put a dab of locktite where the trimmer meets the trimmer body to hold it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: [email protected] on October 11, 2016, 02:37:26 PM
Hi -

My first FET Rack build.  Quick question I noticed instead of two 200pF Blue Caps, I have 220pF caps instead. Are those okay to use in place for C3 and C6 on the REV D?  Or do I need to fill out a missing order form?

Thanks

Elisa
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 11, 2016, 03:05:33 PM
Hi -

My first FET Rack build.  Quick question I noticed instead of two 200pF Blue Caps, I have 220pF caps instead. Are those okay to use in place for C3 and C6 on the REV D?  Or do I need to fill out a missing order form?

Thanks

Elisa

Hi Elisa,

That was a deviation we made at Hairball.

200pF used to be a more standard value. They have become harder and harder to fine and when you do they are expensive and in low stock. We moved to the more standard 220pF.

As MNATs has stated the original used a mica 220pF there is you want to hunt a couple down. Honestly I don't think it would make any difference.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on October 12, 2016, 12:44:29 AM
Mike,

Just wanted to report that Active Stereo link works very well in my tests with program material. Using just tone is not a great indicator of whether or not it is functioning properly. Both compressors seemed to track the same and it definitely sounded like both sides were being compressed equally.

My one question is, since the new PCBs don't have holes drilled on all four corners, how you would recommend mounting directly to a different chassis for stereo builds? I guess one could rig up some sort of support for the side that does not have mounting holes. That was the one of the first things I thought of when building the units.

Again, the new rack compressor kits are killer!  I'll post some notes a little later that may be helpful for people building these units. Or it may not be helpful.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 12, 2016, 01:02:12 AM
Mike,

Just wanted to report that Active Stereo link works very well in my tests with program material. Using just tone is not a great indicator of whether or not it is functioning properly. Both compressors seemed to track the same and it definitely sounded like both sides were being compressed equally.

My one question is, since the new PCBs don't have holes drilled on all four corners, how you would recommend mounting directly to a different chassis for stereo builds? I guess one could rig up some sort of support for the side that does not have mounting holes. That was the one of the first things I thought of when building the units.

Again, the new rack compressor kits are killer!  I'll post some notes a little later that may be helpful for people building these units. Or it may not be helpful.

Thanks!

Paul

That's funny, I had the same issue in testing.  I can't believe I forgot to mention it earlier.  Ya the sine wave just tracks poorly, I suspect it may be a phase issue in the summing amp but who knows.  I pulled my hair out over it for a few days until I used actually program material and got much better results. I like it too.

For stereo builds we're still recommending the older boards for now. However, as you've mentioned, with a little ingenuity you could get these working in a dual build.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RR25 on October 12, 2016, 07:25:41 AM
Hi Mike and everyone else,

I have just built a Rev A (new version) and everything seemed to be going pretty well until calibration step 3.

The power supply test results were +30.13V DC and -9.18V DC, I was able to get the 1dB drop during Q bias calibration and I was measuring 0.00V DC across TP10 / TP11 for the null adjust step.

Unfortunately when I try to put the unit into compression to complete the meter tracking adjustment I am only able to achieve 0.4dB of gain reduction.
The only thing I can see is that might be an issue is that my voltages for Q2 and Q3 are low. (all other transistor voltages are very close to spec)

Q2.
G - 0.66V DC
S - 2.04V DC
D - 2.09V DC

Q3
G - 1.55V DC
S - 2.10V DC
D - 20.5V DC

Any help would be much appreciated.

Cheers,
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 12, 2016, 03:11:33 PM
1776 rev A v1.12

Conditions:
Sending 0.775VAC into input XLR
W/ GR meter in "off" position
qBias pot in any rotation does not change voltages.
TP1:0.000VAC
TP15:0.007VAC
TP17:0.000
Out+:0.016VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 12, 2016, 03:14:31 PM
1776 rev A v1.12

Conditions:
Sending 0.775VAC into input XLR
W/ GR meter in "off" position
qBias pot in any rotation does not change voltages.
TP1:0.000VAC
TP15:0.007VAC
TP17:0.000
Out+:0.016VAC

What's your VAC at the input transformer pin 1?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 12, 2016, 03:18:40 PM
Hi Mike and everyone else,

I have just built a Rev A (new version) and everything seemed to be going pretty well until calibration step 3.

The power supply test results were +30.13V DC and -9.18V DC, I was able to get the 1dB drop during Q bias calibration and I was measuring 0.00V DC across TP10 / TP11 for the null adjust step.

Unfortunately when I try to put the unit into compression to complete the meter tracking adjustment I am only able to achieve 0.4dB of gain reduction.
The only thing I can see is that might be an issue is that my voltages for Q2 and Q3 are low. (all other transistor voltages are very close to spec)

Q2.
G - 0.66V DC
S - 2.04V DC
D - 2.09V DC

Q3
G - 1.55V DC
S - 2.10V DC
D - 20.5V DC

Any help would be much appreciated.

Cheers,

Try this:

Input/output: Mid Way
release/attack: full CW
Ratio: 20
Meter: GR

Feed and confirm a 0.775VAC 1K signal measuring between input XLR + and -.

No measure these TPs using chassis as your common.

TP22 - Measure for AC for all ratios and list them.
TP21 - Measure for DC for all ratios and list them.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 12, 2016, 03:27:24 PM
same conditions as stated above

 input trans pin 1 is 0.006VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 12, 2016, 03:30:41 PM
same conditions as stated above

 input trans pin 1 is 0.006VAC

Carefully remove Q1. Do you get VAC at any of those TPs with Q1 removed?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on October 12, 2016, 04:12:09 PM
Hi Mike and everyone else,

I have just built a Rev A (new version) and everything seemed to be going pretty well until calibration step 3.

The power supply test results were +30.13V DC and -9.18V DC, I was able to get the 1dB drop during Q bias calibration and I was measuring 0.00V DC across TP10 / TP11 for the null adjust step.

Unfortunately when I try to put the unit into compression to complete the meter tracking adjustment I am only able to achieve 0.4dB of gain reduction.
The only thing I can see is that might be an issue is that my voltages for Q2 and Q3 are low. (all other transistor voltages are very close to spec)

Q2.
G - 0.66V DC
S - 2.04V DC
D - 2.09V DC

Q3
G - 1.55V DC
S - 2.10V DC
D - 20.5V DC

Any help would be much appreciated.

Cheers,

You wrote Rev A but those voltages correlate much closer to voltages on the Rev D. Keep in mind that Q3 on the Rev A is a bipolar transistor and so has a base, emitter and collector. In any case, if those voltages are being accurately measured it suggests that the signal preamp isn't working properly. But you also said that you were able to calibrate for a 1 dB drop.

Do your output levels seem right (very hot)? Are you measuring your input level on the test points provided behind the XLR on the main PCB (this ensures the measurement points are under load)? Are you using pins 2 and 3 as the input, rather than connecting one lead to ground?

If those voltages are accurate it would be worth checking components around those transistors for value, shorts, poor joints etc.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 12, 2016, 04:13:00 PM
Same conditions as above, removing Q1 completely.

TP-1:   0.000VAC
TP-15: 0.000VAC
TP-17: 0.000VAC
Out+:  0.002(+/-)0.001VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 12, 2016, 07:12:27 PM
Same conditions as above, removing Q1 completely.

TP-1:   0.000VAC
TP-15: 0.000VAC
TP-17: 0.000VAC
Out+:  0.002(+/-)0.001VAC

Your signal is dying like immediately after the input.

So you have 0.775 VAC between input + and -, but nothing between input tx pin 1 or pin 4 and the chassis???

Is your tpad fully soldered?  Check all 9 tpad solder pads carefully.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 13, 2016, 11:43:22 AM
For clarification: Fet Rack A v1.12

I'm uncertain what you met by tpad (though I have found that in the older revision builds). Sorry for the hassle, but could you please clarify?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 13, 2016, 11:48:37 AM
For clarification: Fet Rack A v1.12

I'm uncertain what you met by tpad (though I have found that in the older revision builds). Sorry for the hassle, but could you please clarify?

The 3 deck input pot.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 13, 2016, 12:08:40 PM
re-floated all the soldering, and followed the testing conditions with .775 in etc etc and still showing zeros.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 13, 2016, 12:37:12 PM
re-floated all the soldering, and followed the testing conditions with .775 in etc etc and still showing zeros.

Reflow the input XLR.

Then with 0.775 VAC at the input (between 2+3). Measure for AC (chassis as common) for all 9 pins on the T-Pad.


7 8 9
4 5 6
1 2 3
output pot this way->
SHAFT/Front Panel HERE
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 13, 2016, 01:07:51 PM
      7                  8                9   
(0.764)    (0.766)    (0.762)
     4                   5                6
(0.006)    (0.766)     (0.766)
     1                   2                 3
(0.768)    (0.766)     (0.769)

             (front of Unit)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on October 13, 2016, 03:33:21 PM
Voltages are meaningless unless you specify AC or DC.

First things first.  Get the Qbias calibration working.  All the calibration steps must be completed in order and each one must been done correctly before moving on.

Read my response to ebenchristensen 2 posts above. Same steps for you.

Mike



Thanks Mike,
It was just poor soldering jobs on two pads. I should have looked closer at first time.  You made great job first with kits and here as well.  I read everything and it helped me a bit to understand whats going in there.
Thanks
Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 13, 2016, 04:53:47 PM
      7                  8                9   
(0.764)    (0.766)    (0.762)
     4                   5                6
(0.006)    (0.766)     (0.766)
     1                   2                 3
(0.768)    (0.766)     (0.769)

             (front of Unit)

And your input is mid way? Doesn't make any sense.

Can you safely remove your input transformer?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 14, 2016, 10:27:44 AM
Conditions:
0.775 VAC measured at (+) & (-) XLR input
Ratio: 20 /Metter "Off"
Input dial half way / Output dial halfway
Attack off (full CCW) / Release full CW

Pad VAC measurements are as follow:

      7                  8                9   
(0.205)    (0.207)    (0.033)
     4                   5                6
(0.001)    (0.207)     (0.188)
     1                   2                 3
(0.219)    (0.207)     (0.782)

             (front of Unit) >Output knob


At this point I feel like I'm taking crazy pills, as this isn't one I reported yesterday.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 14, 2016, 10:35:12 AM
Conditions:
0.775 VAC measured at (+) & (-) XLR input
Ratio: 20 /Metter "Off"
Input dial half way / Output dial halfway
Attack off (full CCW) / Release full CW

Pad VAC measurements are as follow:

      7                  8                9   
(0.205)    (0.207)    (0.033)
     4                   5                6
(0.001)    (0.207)     (0.188)
     1                   2                 3
(0.219)    (0.207)     (0.782)

             (front of Unit) >Output knob


At this point I feel like I'm taking crazy pills, as this isn't one I reported yesterday.

What about input tx pin 4?  That's on the ame side as pin 1...at the opposite end of the row.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ebenchristensen on October 14, 2016, 10:43:57 AM
Getting

0.032 VAC


Q1 is still removed (per your recommendation ) btw
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 14, 2016, 10:51:27 AM
Getting

0.032 VAC


Q1 is still removed (per your recommendation ) btw

Do you have all 3 L-Brackets installed on the back panel? Fully screwed in, tightened?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 14, 2016, 11:04:26 AM
If I had to guess based on this. Either your T-Pad is bad (very rare) or your input tx is bad (kinda rare).  Make sure all of the solder joints on those two parts look good. Look for any lifted pads or damaged traces on either of those parts. Make sure all 3 l-brackets are secured to the PCB and enclosure (one of those supplies common to the PCB).

If you're still having an issue, measure the input primary and secondary coils with your DMM Ω setting. You can do this in the PCB with no signal, unit powered off. MAKE SURE the input pot is mid way.

The pins are like this:

1          8
2          7
3          6
4          5

What is the Ω between:

1 and 4
5 and 8
1 and 6
4 and 6
5 and 6
8 and 6

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RR25 on October 15, 2016, 03:20:08 AM
Try this:

Input/output: Mid Way
release/attack: full CW
Ratio: 20
Meter: GR

Feed and confirm a 0.775VAC 1K signal measuring between input XLR + and -.

No measure these TPs using chassis as your common.

TP22 - Measure for AC for all ratios and list them.
TP21 - Measure for DC for all ratios and list them.

Mike

Hi Mike,

I have measured the DC voltage at TP21 and the AC voltage at TP22 for all ratios with a 0.775V AC signal (measured at input XLR + and -)

These are my results (settings as stated above and using chassis as common):

TP21
4:1 = -1.502V DC
8:1 = -2.333V DC
12:1 = -3.167V DC
20:1 = -5.825V DC

TP22
4:1 = 0.006V AC
8:1 = 0.013V AC
12:1 = 0.021V AC
20:1 = 0.039V AC

Thanks again for all the help.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 16, 2016, 12:06:45 PM
Ok, I just finished the build of 2 Rev A kits paying a lot of attention to get everything right in the first place, but it seems both units have a/some problems in different spots:

The +30VDC and -10VDC from the power supply measure correctly on both units.

#1:
I fail at the first calibration step for the Q gain. There is signal coming through the unit, but it seems way too low in level. Sending in [email protected] 0dBu results in about -15dBu at the output XLR with input and output pots at 24,  GR off and 20:1 selected. If I crank the output pot all the way, I get just about 0dBu at the output and the only way to get it to +11dBu is to turn both input and output up all the way. I suspect I am losing 6 or 12dB of signal somewhere along the way. Where should I look, or what points to check along to way to find the problem area?

#2:
The first time I powered it on, the output level started to rise over the course of 10 to 20 seconds from about 0 to over 20dBu when I quickly switched it off again. Now the GR meter is just pegged from the beginning when I switch the unit on, even with no input signal going in and on 20:1 and with GR turned off. I noticed that touching/measuring the gate on Q11 brings the meter down but it goes back up all the way as soon as I let go.

I did notice that R17 in the kits was 4.7k but on the Rev A 1.2.5 Voltage sheet it is specified as 8.2k but that might not have anything to do with those issues.

Many thanks for your help!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 16, 2016, 12:31:28 PM
@RR25
Your TP22 is real low. What is your V AC at pad 15 under the same conditions?

@mixmasta
#1 Does adjusting the Qbias to either extreme change the output?

#2 Contact with the gate at Q1/11 just sends the unit into extreme gain reduction. Have you tried calibrating it yet? Make sure all of the L-Brackets are secured on both units. One of them ties the PCB ground to the chassis ground and is needed for proper operation.

R17 value is not the issue. The new value is correct.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 16, 2016, 01:24:38 PM
@mixmasta
#1 Does adjusting the Qbias to either extreme change the output?

#2 Contact with the gate at Q1/11 just sends the unit into extreme gain reduction. Have you tried calibrating it yet? Make sure all of the L-Brackets are secured on both units. One of them ties the PCB ground to the chassis ground and is needed for proper operation.

R17 value is not the issue. The new value is correct.

Mike

Hi Mike,

Thank you for the quick replies!

#1: No, output stays around -15.6dBu over the whole range of the Q Bias trim

#2: Just tried calibrating it, and it seems fine! I must have been panicky about the +20dB output level in relation to what I got with the first unit.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 16, 2016, 01:38:53 PM
For the low output unit, I would start by going over all of your resistors and visually checking the values.

Looks for anything out of place in comparison to the working unit. Look for any suspect solder joints.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 17, 2016, 10:38:54 AM
For the low output unit, I would start by going over all of your resistors and visually checking the values.

Looks for anything out of place in comparison to the working unit. Look for any suspect solder joints.

Mike

I compared all the resistors and the color codes are the same. Also had a look at the bottom side and it does look clean, no shorts or forgotten solder pads that I noticed. Did touch up a couple of solder joints but it did not make a difference in the levels coming through the unit. Also checked the transistors and small film caps to make sure I didn't mix up something there.

I got 0.775VAC at the input but don't know what the values should be later on as I haven't fully figured out the schematic yet. But I compared some points that I could identify being in the audio path between the 2 units, and levels seem to be down throughout the unit.

With input/output at 24, 20:1 and GR off, on the functioning unit #2 one I got:
TP15: 3.746 VAC
TP17: 0.6 VAC
at R8: 0.087 VAC
at R5: 0.086 VAC

The values for #1 were:
TP15: 0.5 VAC
TP17: 0.15 VAC
R8: 0.012 VAC
R5: 0.011 VAC

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: CBarx on October 17, 2016, 05:46:53 PM
Ok, so I hate to have to come here for this, but here we go.  I've got 6 Rev A v1.12s on the bench being built right now.  I just wrapped up two of them and began calibration.  Unit one started showing issues immediately.  Upon power up, the meter never moved from left position.  I attempted step one of calibration to find that I could not get the output to push beyond 1.04VAC. 

So being unable to progress beyond step one, I hooked the other completed unit up to the oscillator and immediately noticed a much hotter signal.  THAT unit calibrated just fine all the way through. 

So back to unit one.  After some reading and (most likely unnecessarily) reflowing some solder joints, I'm here with the same problem.  Strangely enough, even though I tested the power supply voltages of all PCBs before populating the rest of the components (All voltages checked out fine THEN), I'm now seeing that the left lead of CR9 is giving me a reading of -1.5mVDC.  The 30VDC test point check out fine.  I'm at a loss here.  I've gone over components and can't find any mistakes, and I populated all 6 boards at the same time, so if there was an issue with one, there'd be an issue with all of them.  Any help here would be greatly appreciated. 

CB
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on October 17, 2016, 08:32:51 PM
Strangely enough, even though I tested the power supply voltages of all PCBs before populating the rest of the components (All voltages checked out fine THEN), I'm now seeing that the left lead of CR9 is giving me a reading of -1.5mVDC.  The 30VDC test point check out fine.  I'm at a loss here.  I've gone over components and can't find any mistakes, and I populated all 6 boards at the same time, so if there was an issue with one, there'd be an issue with all of them.  Any help here would be greatly appreciated. 
If power supply voltages were correct before populating the rest of the board then something must be dragging the -10 v supply down. Set your multimeter to measure resistance and measure between the anode of CR9 and ground. Remove CN3 and try again to see if your ratio circuit is causing an issue.

If the resistance is still low after you have removed CN3 then start checking the GR Meter Driver circuit for shorts or incorrect component values. If the resistance jumps higher after removing CN3 then check your ratio circuit for same.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 17, 2016, 10:46:34 PM
I compared all the resistors and the color codes are the same. Also had a look at the bottom side and it does look clean, no shorts or forgotten solder pads that I noticed. Did touch up a couple of solder joints but it did not make a difference in the levels coming through the unit. Also checked the transistors and small film caps to make sure I didn't mix up something there.

I got 0.775VAC at the input but don't know what the values should be later on as I haven't fully figured out the schematic yet. But I compared some points that I could identify being in the audio path between the 2 units, and levels seem to be down throughout the unit.

With input/output at 24, 20:1 and GR off, on the functioning unit #2 one I got:
TP15: 3.746 VAC
TP17: 0.6 VAC
at R8: 0.087 VAC
at R5: 0.086 VAC

The values for #1 were:
TP15: 0.5 VAC
TP17: 0.15 VAC
R8: 0.012 VAC
R5: 0.011 VAC

The low voltage at TP15 indicates something is bad in the first gain section. Does removing the Q1 FET help get voltage at 15?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 18, 2016, 06:56:44 AM
The low voltage at TP15 indicates something is bad in the first gain section. Does removing the Q1 FET help get voltage at 15?

Yes, when I take it out I get +3.9VAC at TP15 and +18dBu at the output. Does that indicate a bad Q1 or something else in that gain stage?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RR25 on October 19, 2016, 10:38:18 AM
@RR25
Your TP22 is real low. What is your V AC at pad 15 under the same conditions?

Mike

Hi Mike, I have tested TP15 and I got a reading of 0.072V AC (0.775V AC at input test points, referencing the chassis, Input and output = mid, 20:1, meter = GR, attack and release = CW)

Thanks for the help Mike,
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 19, 2016, 05:22:52 PM
Hi Mike, I have tested TP15 and I got a reading of 0.072V AC (0.775V AC at input test points, referencing the chassis, Input and output = mid, 20:1, meter = GR, attack and release = CW)

Thanks for the help Mike,

This is with GR bypassed? You have something wrong in your first stage labeled "signal preamp".

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 19, 2016, 05:27:13 PM
Yes, when I take it out I get +3.9VAC at TP15 and +18dBu at the output. Does that indicate a bad Q1 or something else in that gain stage?

It indicates a bad FET or bad qbias circuit.

With the FET out, what is your DC at the GATE pad of Q1 as you rotate the qbias from end to end.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 20, 2016, 07:16:33 AM
It indicates a bad FET or bad qbias circuit.

With the FET out, what is your DC at the GATE pad of Q1 as you rotate the qbias from end to end.

Mike

I have 0VDC at the gate of Q1 for the whole trim range, it must be the Q Bias circuit then.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 20, 2016, 12:06:50 PM
I have 0VDC at the gate of Q1 for the whole trim range, it must be the Q Bias circuit then.

Ya on the rev A that should have something (roughly) like -0.5 to -1.5 VDC.

What is your DC range at pad 18 rotating the pot?

Make sure R60, R83, and the trimmer R59 are all the correct value and properly soldered.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on October 20, 2016, 07:15:31 PM
Hi Mike, I have tested TP15 and I got a reading of 0.072V AC (0.775V AC at input test points, referencing the chassis, Input and output = mid, 20:1, meter = GR, attack and release = CW)

Thanks for the help Mike,

This is with GR bypassed? You have something wrong in your first stage labeled "signal preamp".

Mike
As mentioned in my earlier reply regarding your issue, Mike's analysis agrees with mine. If you are building an "A" then your transistor voltages are wrong; check all components in that stage for value, soldering, shorts etc.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 12:06:44 AM
Hey Mike , 

I Finished the Build on my second REV A , and things seem to go smooth untill i tried to CAL it.

The R59 Q Bias would not Drop the 1 db or down to 2.44V on the  ,  but the  meter on the REV A would drop all the way down as I adjusted.   

I check around and  looked for anyhing out of place or any cold solders , But all seemed fine .   The last thing I check was the sound of the output .  With a 1K tone @ 0 db Passing through  , the output of the unit was distorted even with the output pot all the way down. 

what could I have messed up this time haha .

let me know if you need more info

thanks for the support

-Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:12:12 AM
Hey Mike , 

I Finished the Build on my second REV A , and things seem to go smooth untill i tried to CAL it.

The R59 Q Bias would not Drop the 1 db or down to 2.44V on the  ,  but the  meter on the REV A would drop all the way down as I adjusted.   

I check around and  looked for anyhing out of place or any cold solders , But all seemed fine .   The last thing I check was the sound of the output .  With a 1K tone @ 0 db Passing through  , the output of the unit was distorted even with the output pot all the way down. 

what could I have messed up this time haha .

let me know if you need more info

thanks for the support

-Chris

Calibration has to be done in order. If you can't get the qbias set, you need to stop there and figure that out before moving on.

What is your DC at PAD 18 at each extreme of the qbias pot?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 12:23:48 AM
Calibration has to be done in order. If you can't get the qbias set, you need to stop there and figure that out before moving on.

What is your DC at PAD 18 at each extreme of the qbias pot?

Mike

Looks Like -1.5 with the Q bias cranked .

Also , I noticed Q6 is Getting Pretty hot , Is that normal ?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:32:37 AM
Looks Like -1.5 with the Q bias cranked .

Also , I noticed Q6 is Getting Pretty hot , Is that normal ?

Need the range.  High and low.

Yes Q6 will burn your hand off. Keep the heat sink on it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 12:42:05 AM
Need the range.  High and low.

Yes Q6 will burn your hand off. Keep the heat sink on it.
At q bias all the way up it is -1.5VDC , half way Down is read -.532VDC
Then it's at O.1 vdc all the way down .
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:47:26 AM
At q bias all the way up it is -1.5VDC , half way Down is read -.532VDC
Then it's at O.1 vdc all the way down .

Seems good.

So when you walk through the calibration steps, starting with the trimmer maxed to -1.5 as you roll towards zero it won't drop the 1db?

You have the new V1.12 Rev A PCB?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 12:53:02 AM
Seems good.

So when you walk through the calibration steps, starting with the trimmer maxed to -1.5 as you roll towards zero it won't drop the 1db?

You have the new V1.12 Rev A PCB?

Mike

Yes it is the new PCB.  I bought two of the kits second hand , un-built.

No, it will not drop . But the meter in the unit drops as I turn down the Q bias , but nothing like how the first one I built . There is no sudden drop .
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 01:01:07 AM
Yes it is the new PCB.  I bought two of the kits second hand , un-built.

No, it will not drop . But the meter in the unit drops as I turn down the Q bias , but nothing like how the first one I built . There is no sudden drop .

And you're in bypass right?

(this is my last post before bed, I'll check back in the AM).

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 01:03:35 AM
And you're in bypass right?

(this is my last post before bed, I'll check back in the AM).

Mike



Yes , it's in by-pass

I'm hitting the hay as well .  I'll bug you tomorrow haha.
  Thanks again
-Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 09:04:15 AM
Ya on the rev A that should have something (roughly) like -0.5 to -1.5 VDC.

What is your DC range at pad 18 rotating the pot?

Make sure R60, R83, and the trimmer R59 are all the correct value and properly soldered.

Mike

At pad 18, I get -1.78VDC to about -1.03VDC for the q bias trimmer range.

Checked the resistors and trimmer and they look correct and solder pads are fine.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 09:54:19 AM
At pad 18, I get -1.78VDC to about -1.03VDC for the q bias trimmer range.

Checked the resistors and trimmer and they look correct and solder pads are fine.

Yes ,

At TP18 I also Get  -1.784 VDC to -1.02 VDC

( this is all with No Signal, and the Q bias all the way up )

TP19 -1.56 VDC
TP21 -6.04 VDC ?? on my other Rev a its around -1.54 VDC
TP22  0.02
TP7 -1.56 VDC
TP17 0.0
TP15 0.0
TP1 0.0
TP10 12.56
TP11 12.38

ALSO , with It  in Bypass , if i Adjust the release , The front meter drops ?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 11:21:36 AM
Yes ,

At TP18 I also Get  -1.784 VDC to -1.02 VDC

( this is all with No Signal, and the Q bias all the way up )

TP19 -1.56 VDC
TP21 -6.04 VDC ?? on my other Rev a its around -1.54 VDC
TP22  0.02
TP7 -1.56 VDC
TP17 0.0
TP15 0.0
TP1 0.0
TP10 12.56
TP11 12.38

ALSO , with It  in Bypass , if i Adjust the release , The front meter drops ?

What's your AC V at TP15 with a 1K 0dB signal w/ GR OFF and input/output midway? What is it at the output XLR pin 2?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 11:25:08 AM
At pad 18, I get -1.78VDC to about -1.03VDC for the q bias trimmer range.

Checked the resistors and trimmer and they look correct and solder pads are fine.

But you still have a constant 0 DC V at the gate of Q1?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 11:33:53 AM
What's your AC V at TP15 with a 1K 0dB signal w/ GR OFF and input/output midway? What is it at the output XLR pin 2?

Mike

looks like 16.5 V AC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 11:46:13 AM
But you still have a constant 0 DC V at the gate of Q1?

Yes, I just checked again, 0 DC at the Q1 gate no matter where the q bias trim is.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 11:50:48 AM
looks like 16.5 V AC

Where? At pad 15 or the output?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 11:54:26 AM
Yes, I just checked again, 0 DC at the Q1 gate no matter where the q bias trim is.

Examine your release pot. Is it soldered well? Are and of the three legs broken off the body?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 11:55:42 AM
Where? At pad 15 or the output?

At TP15 I get 4.8 V AC , and the pin 2 on the out put i get 16.5 V AC

Thanks again for the support
-C
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:01:36 PM
At TP15 I get 4.8 V AC , and the pin 2 on the out put i get 16.5 V AC

Thanks again for the support
-C

Pin 2 seems super hot. What is it measuring between out + and out -?

You have 0.775 VAC between between in + and in -?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 12:06:21 PM
Pin 2 seems super hot. What is it measuring between out + and out -?

You have 0.775 VAC between between in + and in -?

Mike

Yeah , it seems really hot .  and I do have 0.775 at the Input .
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:18:35 PM
Yeah , it seems really hot .  and I do have 0.775 at the Input .

You should have about 2.5 VAC at 15 (using the enclosure as common) and 7.5VAC (20ish dB) between the output + and - if I recall. That's with no GR and the pots midway assuming you have the in/out max position aligned to "0" on the front panel and then set them to "24" for measurement.  0.775 AC V at the input is between + and - input...not the enclosure.

If all that is correct and you're still that hot then you have something off in the signal line or signal preamp. Probably the first one. Visually read and check all of the R values.  Check the schematic w/ voltages in those sections.

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Voltatages are always checked using the enclosure as your reference (black probe) except when measuring the input/output AC level. That is always done between input/output +/- also known as pin 2 and pin 3.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 12:28:04 PM
You should have about 2.5 VAC at 15 (using the enclosure as common) and 7.5VAC (20ish dB) between the output + and - if I recall. That's with no GR and the pots midway assuming you have the in/out max position aligned to "0" on the front panel and then set them to "24" for measurement.  0.775 AC V at the input is between + and - input...not the enclosure.

If all that is correct and you're still that hot then you have something off in the signal line or signal preamp. Probably the first one. Visually read and check all of the R values.  Check the schematic w/ voltages in those sections.

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Voltatages are always checked using the enclosure as your reference (black probe) except when measuring the input/output AC level. That is always done between input/output +/- also known as pin 2 and pin 3.

Mike


With everything set correct on the front panel and  .775 V ac across the input ,  I am getting 4.8 VAC at tp 15.

I am going to go through the line amp and pre amp now.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 12:32:22 PM
Examine your release pot. Is it soldered well? Are and of the three legs broken off the body?

Mike

Legs and solder pads of the release pot seem fine. However, the pot itself feels a bit scratchy compared to the other pots. Measuring the resistance between the bottom and middle leg (the way its mounted) gives me a resistance of 0R at both extremes, going rapidly up to around 180k to 230k around the middle of the turn range. This is with the unit powered off and its hard to read as the auto range of my DMM is jumping quite a bit.

It seems to be connected all right, but is there a way to check if it's operating right while its soldered in?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:33:54 PM

With everything set correct on the front panel and  .775 V ac across the input ,  I am getting 4.8 VAC at tp 15.

I am going to go through the line amp and pre amp now.

I have to work on an A shortly...I confirm that should be closer to 2.75 VAC in a few.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 12:42:29 PM
You should have about 2.5 VAC at 15 (using the enclosure as common) and 7.5VAC (20ish dB) between the output + and - if I recall. That's with no GR and the pots midway assuming you have the in/out max position aligned to "0" on the front panel and then set them to "24" for measurement.  0.775 AC V at the input is between + and - input...not the enclosure.

If all that is correct and you're still that hot then you have something off in the signal line or signal preamp. Probably the first one. Visually read and check all of the R values.  Check the schematic w/ voltages in those sections.

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf


Voltatages are always checked using the enclosure as your reference (black probe) except when measuring the input/output AC level. That is always done between input/output +/- also known as pin 2 and pin 3.

Mike

All the votages look good  except for Q3  . where i should be getting 13.74V , I am getting 15.6V, and  where i should be seeing 6.13V , I am getting 6.9V.

does that sound like that could be the reason for the high output/ issue ?

-Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:52:45 PM
Just to clarify. In GR OFF mode, your Rev A FET/RACK is basically a 45dB mic pre that looks like this:

Input Attenuator->input Transformer->Signal Preamp->Output Pot->Signal Line Amp->Output Transformer.

TP15 sits at the end of the signal preamp before the output pot and output +/- are at the end of the chain.

Here are my measurements:
With Q1 calibrated:
TP15: 3.2 VAC
Output +/-: 7.00 VAC

With Q1 out of circuit (removed or qbias more than -1.5 VDC):
TP15: 3.6 VAC
Output +/-: 8.00 VAC

All of that is normal. If you're getting 4.8 VAC at TP15 that is too hot. Like an extra 3.5dB and when that hits the next stage that hotness as going to get even hotter.

Really examine that first stage.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 12:55:27 PM
All the votages look good  except for Q3  . where i should be getting 13.74V , I am getting 15.6V, and  where i should be seeing 6.13V , I am getting 6.9V.

does that sound like that could be the reason for the high output/ issue ?

-Chris

I don't think that's it. IIRC the value of R13 was change in the version which would account for the voltage difference. It would not be causing your issue. I'd say you could try difference FETs but it seems like you either have a gain issue or a measurement issue.  I'm kinda stumped.  Did you say this is your only unit?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 01:06:33 PM
I don't think that's it. IIRC the value of R13 was change in the version which would account for the voltage difference. It would not be causing your issue. I'd say you could try difference FETs but it seems like you either have a gain issue or a measurement issue.  I'm kinda stumped.  Did you say this is your only unit?

I have two REV A , the first one tests normal and sounds great .  I have a good multi meter , and Im am positive that my 1k tone is at .775

I went through the  signal pre amp and  signal line amp and all the voltages look good , and everything is in the right spot . I am pretty stumped as well .

-c
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 01:12:36 PM
Legs and solder pads of the release pot seem fine. However, the pot itself feels a bit scratchy compared to the other pots. Measuring the resistance between the bottom and middle leg (the way its mounted) gives me a resistance of 0R at both extremes, going rapidly up to around 180k to 230k around the middle of the turn range. This is with the unit powered off and its hard to read as the auto range of my DMM is jumping quite a bit.

It seems to be connected all right, but is there a way to check if it's operating right while its soldered in?

One thing  , I am getting .775 at the Input test points, but if I adjust the input pot  it changes a bit ...then ,  if I un plug the XLR and test just the XLR , I get  .968 v. 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 01:19:20 PM
One thing  , I am getting .775 at the Input test points, but if I adjust the input pot  it changes a bit ...then ,  if I un plug the XLR and test just the XLR , I get  .968 v.

The input pot rotation will change the input level at the XLR a little. In a perfect world, its load is constant, but in reality it's not. So the fluctuations in load change the input level, that's normal.

Are you saying you have .968 VAC at the input with no signal attached? That doesn't seem right.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 01:20:26 PM
Just to clarify. In GR OFF mode, your Rev A FET/RACK is basically a 45dB mic pre that looks like this:

Input Attenuator->input Transformer->Signal Preamp->Output Pot->Signal Line Amp->Output Transformer.

TP15 sits at the end of the signal preamp before the output pot and output +/- are at the end of the chain.

Here are my measurements:
With Q1 calibrated:
TP15: 3.2 VAC
Output +/-: 7.00 VAC

With Q1 out of circuit (removed or qbias more than -1.5 VDC):
TP15: 3.6 VAC
Output +/-: 8.00 VAC

All of that is normal. If you're getting 4.8 VAC at TP15 that is too hot. Like an extra 3.5dB and when that hits the next stage that hotness as going to get even hotter.

Really examine that first stage.

Mike
Hmm... at TP15 im still getting  5 V, and a out put of 16 V..

Totally stumped
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 01:24:22 PM
The input pot rotation will change the input level at the XLR a little. In a perfect world, its load is constant, but in reality it's not. So the fluctuations in load change the input level, that's normal.

Are you saying you have .968 VAC at the input with no signal attached? That doesn't seem right.

Mike


No, my bad . im getting  .968 from the Signal source not plugged into the the Rev a .
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 01:35:21 PM

No, my bad . im getting  .968 from the Signal source not plugged into the the Rev a .


Also At TP 21 I am getting -5.8 VDC , but on my working Rev A its -0.756 VDC.

Not sure what happing there
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 01:50:07 PM

Also At TP 21 I am getting -5.8 VDC , but on my working Rev A its -0.756 VDC.

Not sure what happing there

Same ratio setting?  That - DC value is controlled by the ratio selected.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 01:55:36 PM
Same ratio setting?  That - DC value is controlled by the ratio selected.

Mike

AHH,  yeah , the ratio was not the same .. Its totally normal there .  But Im still having that Gain issue..  ugh .
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 01:58:01 PM
Legs and solder pads of the release pot seem fine. However, the pot itself feels a bit scratchy compared to the other pots. Measuring the resistance between the bottom and middle leg (the way its mounted) gives me a resistance of 0R at both extremes, going rapidly up to around 180k to 230k around the middle of the turn range. This is with the unit powered off and its hard to read as the auto range of my DMM is jumping quite a bit.

It seems to be connected all right, but is there a way to check if it's operating right while its soldered in?

Let's start with why the bias is dying between the TP18 and the Q1 gate.

Set you TP18 voltage for the most negative. What is that value?

Then measure the pins for DC at CN10 list them here starting from closest to the front panel back:

1:
2:
3:
4:
5:
6:

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 02:04:43 PM
AHH,  yeah , the ratio was not the same .. Its totally normal there .  But Im still having that Gain issue..  ugh .

Ya I mean you could try different FETs. We'll send you a new pair, but I still think your unit is too hot, and that's what is causing the issue. I could be wrong. Email us if you want different FETs.

TP22 (under the big orange cap by the output) has low Ω to the enclosure when in bypass mode? Like less than an ohm?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 02:16:03 PM
Ya I mean you could try different FETs. We'll send you a new pair, but I still think your unit is too hot, and that's what is causing the issue. I could be wrong. Email us if you want different FETs.

TP22 (under the big orange cap by the output) has low Ω to the enclosure when in bypass mode? Like less than an ohm?

Mike

Hey Thank man, I might email  you guys for  for Those  FETs  , I can not find anything that would be cause the super high out up , I have gone through it multiple time s, but nothing stands out .

and yes , TP22 read about 0.0 to 0.1  ohms.

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 02:23:18 PM
Hey Thank man, I might email  you guys for  for Those  FETs  , I can not find anything that would be cause the super high out up , I have gone through it multiple time s, but nothing stands out .

and yes , TP22 read about 0.0 to 0.1  ohms.

Ya thing is the Q1 FET cannot add gain, only take away.  That's why I don't think they are the issue.

We're happy to send some though. Of course you can always send it in for repair.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 02:25:57 PM
Maybe replace Q2 and Q3 as well.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 02:31:50 PM
Let's start with why the bias is dying between the TP18 and the Q1 gate.

Set you TP18 voltage for the most negative. What is that value?

Then measure the pins for DC at CN10 list them here starting from closest to the front panel back:

I get -1.78VDC at TP18 with the q bias fully CW.

At CN10, I have:
1: -1.78 VDC
2: 0
3: 0
4: 0
5: 0
6: 0

This is with GR off. If I turn it on, I got some fluctuating voltages as 4 and 5.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 02:42:45 PM
I get -1.78VDC at TP18 with the q bias fully CW.

At CN10, I have:
1: -1.78 VDC
2: 0
3: 0
4: 0
5: 0
6: 0

This is with GR off. If I turn it on, I got some fluctuating voltages as 4 and 5.

Ya you should have DC at 1, 2, and 3. (actually 4,5, 6...pin 6 is closest to face plate, I'm named them backwards in the first post).

What's your DC at PAD 21 in 20:1 ratio?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 02:59:55 PM
What's your DC at PAD 21 in 20:1 ratio?

-6.04VDC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 03:05:34 PM
That connector that connects the attack/release to the main PCB.  Check all those pads/solder joints and connections.

We're close.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 03:29:26 PM
That connector that connects the attack/release to the main PCB.  Check all those pads/solder joints and connections.

We're close.

CN10 and CN12 seem good, conducting fine from the main board to the attack/release board. Is there a direct connection from TP21 to that connector?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 03:57:38 PM
Maybe replace Q2 and Q3 as well.


UPDATE !

It was Q1 .. I was lucky enough to have  extra 2N5457's that I had order from Studio electronics of Burbank for our 4 Vintage D and E lots .

So , I replaces Q1 and Q11  , and its working great !

thanks again for all your help, You guys have A LOT of patience ! haha thanks again.

-Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 04:03:41 PM

UPDATE !

It was Q1 .. I was lucky enough to have  extra 2N5457's that I had order from Studio electronics of Burbank for our 4 Vintage D and E lots .

So , I replaces Q1 and Q11  , and its working great !

thanks again for all your help, You guys have A LOT of patience ! haha thanks again.

-Chris

Well damn!

There you go.  Glad you got it sorted.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 04:05:54 PM
CN10 and CN12 seem good, conducting fine from the main board to the attack/release board. Is there a direct connection from TP21 to that connector?

What is your DC at each of the 3 release Pads?

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 04:13:45 PM
What is your DC at each of the 3 release Pads?

From top to bottom:
1: -1.78VDC
2: 0 to -1.78VDC depending on release
3: 0 VDC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 04:26:52 PM
From top to bottom:
1: -1.78VDC
2: 0 to -1.78VDC depending on release
3: 0 VDC

That ain't right. R57 is the correct value?

I think your release pot is messed up. Can you remove it and test it?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 04:56:38 PM
That ain't right. R57 is the correct value?

I think your release pot is messed up. Can you remove it and test it?

R57 is 270k and the release pot says 5Meg on it.

I just removed it and it measures from 0 to 4.9M between middle and outside pins. With that removed I could also measure R57 and it really is 270k.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 04:59:09 PM
R57 is 270k and the release pot says 5Meg on it.

I just removed it and it measures from 0 to 4.9M between middle and outside pins. With that removed I could also measure R57 and it really is 270k.

Hmmmmm.  What about between both outside pins? About 5M?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 21, 2016, 05:06:41 PM
Hmmmmm.  What about between both outside pins? About 5M?

Mike

Yes, also 4.9M on my meter
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 05:15:50 PM
Yes, also 4.9M on my meter

I'll have to look at the schematic this weekend.  Something is happening right below.

You have the proper DC at 18 and you have no DC after the release.  It should be on the other side of the release.  Your PAD 21 is fine.

On the side of the release with no voltage...what is the resistance to ground?  Maybe there is a short there killing the DC.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 06:23:28 PM
It continues ...  UGH.

This Rev A is still not right . I might Have to send it in .  Its still WAY to hot at the out put.

I can not figure out why at all.


It got to be something in the Line amp or preamp but, I cant find it

-Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 21, 2016, 06:54:44 PM
It continues ...  UGH.

This Rev A is still not right . I might Have to send it in .  Its still WAY to hot at the out put.

I can not figure out why at all.


It got to be something in the Line amp or preamp but, I cant find it

-Chris

Ya I figured.

I really think your Signal Preamp is too hot which will only be made worse in the Line Amp.

If you're sure all of the Signal Preamp resistors/caps are correct, you could try replacing Q2 and Q3.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ccommon on October 21, 2016, 07:29:10 PM
Ya I figured.

I really think your Signal Preamp is too hot which will only be made worse in the Line Amp.

If you're sure all of the Signal Preamp resistors/caps are correct, you could try replacing Q2 and Q3.

Mike

Yup .. I think I'll order those to be on the safe side.

It was odd the kit was  Missing  all 4x  8.2k resistors ,  So i got some 8.2k metal film at this electronics store here in El paso , but i think they are not correct .  The color code  is correct but they test high at 8.8k ..  I order some high quality replacements from digikey to be safe

-c
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 22, 2016, 09:11:29 AM
I'll have to look at the schematic this weekend.  Something is happening right below.

You have the proper DC at 18 and you have no DC after the release.  It should be on the other side of the release.  Your PAD 21 is fine.

On the side of the release with no voltage...what is the resistance to ground?  Maybe there is a short there killing the DC.

Mike

Just measured the resistance to ground at CN12 and I get 0 resistance on pins 1, 2 and 5 (where 6 is the one carrying the q bias DC). I guess 5 shouldn't be shorted to ground. What about 1 and 2?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 22, 2016, 01:37:35 PM
Just measured the resistance to ground at CN12 and I get 0 resistance on pins 1, 2 and 5 (where 6 is the one carrying the q bias DC). I guess 5 shouldn't be shorted to ground. What about 1 and 2?

You can see them labeled in the schematic:
http://mnats.net/files/fetrack/fet_rack_a_doc_v1.12.pdf

Pin 1: Ground
Pin 2: When GR is ON and you have input signal, you'll have some AC here depending on your ratio setting. Low AC at 4:1 then higher as you move to 2:1. When GR is OFF it'll be grounded.
Pin 3: If you have input signal, you'll have some AC here depending on your ratio setting. Pin 1, 2 , and 3 are the attack switch. I think this is fine in your unit.
Pin 4: Tied to TP19 they should be the same. It's after the FH333 diode so you should have DC here as long as the DC is higher than the diode forward voltage.
Pin 5: This is where the bias DC V leaves the attack/release PCB. It should have very HIGH resistance to ground. This is your problem.
Pin 6: This is where the bias DC V enters the attack/release PCB.  Yours seems fine.

So what's happening at pin 5? It's getting grounded somewhere. Thoughts looking at the schematic:

- Bad solder at your RCA connector has pin 7 shorted to ground. If you can, you can try removing the RCA and see if that fixes it.
- Bad C22 or bad solder. If you can, you can try removing it and see if that fixes it.
- Bad Q1 or bad solder. If you can, you can try removing it and see if that fixes it.

That would be the easiest paths to ground that I can see with a quick look.

I'll be off line most of the weekend, but will pop on when I can. 

Good luck!

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mixmasta on October 23, 2016, 08:45:55 AM
- Bad solder at your RCA connector has pin 7 shorted to ground. If you can, you can try removing the RCA and see if that fixes it.
- Bad C22 or bad solder. If you can, you can try removing it and see if that fixes it.
- Bad Q1 or bad solder. If you can, you can try removing it and see if that fixes it.

Hi Mike,

I found it! I had the legs of the RCA bent to hold it better to the board but completely forgot that they were touching and shorting the middle pin to ground. Clipped the middle leg and voltages look good now. Have to check the other (working) unit now because I probably did a similar thing there.

Thank you so much for your help and good troubleshooting advice!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RR25 on November 11, 2016, 01:55:28 AM
Thanks for your help in the previous posts Mike and mnats. I'm back from a quick break and getting closer to finishing this rev A.

I fixed the issue i was having with a low amount of signal and not being able to compress 10dB to finish the calibration steps that I mentioned in previous posts.
(turns out I just wasn't paying enough attention and I had two resistors in each others places in the signal preamp section)

I have now finished the calibration and everything went great, although when I try and run audio through it I get a very weak and filtered signal, almost sounds like a bandpass at about 1KHz.

I have checked all of the resistors again and they are all correct (now). All of the voltages checked out too.

Any help in narrowing down what might be the culprit would be great.

Thanks again
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: oskura on November 13, 2016, 08:21:06 AM
I recently purchased a partial kit and the corresponding mousser cart of components. During calibration I have run into a problem with the attack and meter adjustments. I have gone back several times to make sure I have not missed a step and when it comes to the attack calibration with the trimmer R44 I just can not get any results.
With the attack cw to fully on I make the adjustments according to the hairball cal. guide, but I get no meter jump when the attack is switched off and no difference on my DMM reading.
Ive read that this version of the unit has very little possibility of wiring issues since the harnesses are premade and pretty dummy proof.
I did have a slight issue with a pad on the front of the board at Q3, the pad on the back was fine, could the copper pad on one side have caused the issue even if the pad on the back had a good joint?
Is there anyway to trouble shoot my transistors with a multimeter? My solder joints look good, I have touched up a few.


EDIT: I am working on a REV D v1.11 build
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 13, 2016, 11:15:17 PM
I recently purchased a partial kit and the corresponding mousser cart of components. During calibration I have run into a problem with the attack and meter adjustments. I have gone back several times to make sure I have not missed a step and when it comes to the attack calibration with the trimmer R44 I just can not get any results.
With the attack cw to fully on I make the adjustments according to the hairball cal. guide, but I get no meter jump when the attack is switched off and no difference on my DMM reading.
Ive read that this version of the unit has very little possibility of wiring issues since the harnesses are premade and pretty dummy proof.
I did have a slight issue with a pad on the front of the board at Q3, the pad on the back was fine, could the copper pad on one side have caused the issue even if the pad on the back had a good joint?
Is there anyway to trouble shoot my transistors with a multimeter? My solder joints look good, I have touched up a few.


EDIT: I am working on a REV D v1.11 build

Sounds like issues with you GR amp/ratio section.  Double check those two sections.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: oskura on November 14, 2016, 07:41:26 AM
Sounds like issues with you GR amp/ratio section.  Double check those two sections.

Should I be looking for anything specific as far as components go? Or just double checking solder joints?

I think I was on step 3 of the calibration section and when the attack knob is toggled there is no change on the meter.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on November 17, 2016, 05:50:24 PM
During calibration I have run into a problem with the attack and meter adjustments. I have gone back several times to make sure I have not missed a step and when it comes to the attack calibration with the trimmer R44 I just can not get any results.
With the attack cw to fully on I make the adjustments according to the hairball cal. guide, but I get no meter jump when the attack is switched off and no difference on my DMM reading.
I'm not sure why you have posted to the old Rev D thread as well but it doesn't help so please try to keep your comments to the relevant thread.

To be clear there is no 'attack' calibration. I believe you are getting stuck on the Gain Reduction Meter Tracking calibration. Your symptom appears to be "no gain reduction". Can you confirm that there is no limiting of the audio signal? When the attack knob is fully counter clockwise we call this "gain reduction off". This is a separate function from attack even though the controls are on the same knob.

There have been many instances of no gain reduction so if that is your symptom then try using those search terms to see earlier troubleshooting threads.

Is there anyway to trouble shoot my transistors with a multimeter?
This is exactly what you are doing when you check transistor voltages against the chart linked from the FAQ which is in turn linked from the first post of this thread.
Should I be looking for anything specific as far as components go? Or just double checking solder joints?
You should look for any of the conditions listed in the FAQ. Let us know what you find so others can learn.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Blahpstick on November 19, 2016, 05:32:13 PM
Hey guys!  Sorry, Mike.  I sent you an email with all of this info before so you're probably going to end up reading this again...   :-\:-X

I was building a Rev A + active stereo link kit to completion.  I was attempting to calibrate the unit's Q Bias.  I got a solid reading at the input for the necessary 0 dBu source.  I get the output signal at the proper 2.75 VAC and while not touching anything else except for my probes to the output test points, the signal would begin to drop slowly but steadily.  It bottomed out around 500mV below the initial signal reading and then the voltage starts to surge seemingly randomly in little bursts of 50 - 100 mV at a time every second or so.  I tried reading the test points 10 + 11 for the meter tracking adjustment and same problem with no signal generator attached.  The meter follows this voltage drop and I can watch the needle slowly come down with the readings.

This only seems to be the case when 20:1 is selected.  4, 8, and 12 all have a solid position on the meter and don't seem to move at all even when left for 30 minutes.  I tried pushing in 4 and 20 at the same time and the needle goes back to the same position as it would be in 4:1 instead of going up as the usual All Buttons In mode would do.

Forgive my less than graceful description of the issue.  I will be glad to provide more details.

Thank you so much for your time!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: rockprocess on November 20, 2016, 10:16:40 PM
I've completed the Rev D version and it works and functions fine except that I do have a pretty noticeable amount of hiss.  Is there anything I can check or consider to reduce the hiss?  The hiss is there with pretty reasonable levels, not cranking the input/output, etc.  I don't think its a gain staging issue.  Thoughts/suggestions?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: IndietownRecording on November 21, 2016, 04:03:14 PM
I haven't built this yet, but what is the small hole in the faceplate (between the input and output knobs) used for?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on November 24, 2016, 03:35:11 AM
I haven't built this yet, but what is the small hole in the faceplate (between the input and output knobs) used for?


That is for access to the meter zero trimmer.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hxcplayer on November 24, 2016, 09:12:12 AM
They are coupling caps. The connect two sections of the circuit together and block unwanted DC from one section from moving to the next. Since they are in series with the signal and the audio passes through them they have noticeable impact on the sound.

Deeper:
http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html

Mike

Hey Mike,

Quick question about those coupling caps for the orange drops. 
Do you know if they affect the attack and release time as well or is there no change whatsoever but just a colorization difference to the audio output. 
Also, are all four caps connected in series? I'm asking because I'm writing a paper for my university about the influence that capacitors have on analog compressors.
If by any chance you have some cool sources about capacitors in compressors, it would be awesome if you could recommend me something.

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RR25 on December 11, 2016, 12:40:46 AM
If anyone has any ideas what might be causing this I'd be very appreciative :)
Thanks in advance.

Thanks for your help in the previous posts Mike and mnats. I'm back from a quick break and getting closer to finishing this rev A.

I fixed the issue i was having with a low amount of signal and not being able to compress 10dB to finish the calibration steps that I mentioned in previous posts.
(turns out I just wasn't paying enough attention and I had two resistors in each others places in the signal preamp section)

I have now finished the calibration and everything went great, although when I try and run audio through it I get a very weak and filtered signal, almost sounds like a bandpass at about 1KHz.

I have checked all of the resistors again and they are all correct (now). All of the voltages checked out too.

Any help in narrowing down what might be the culprit would be great.

Thanks again
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on December 11, 2016, 06:37:02 PM
If anyone has any ideas what might be causing this I'd be very appreciative :)
Thanks in advance.
In my experience there are no issues that are not caused by one of more of the conditions listed in my FAQ linked from the first post. As also mentioned there, when you have an audio fault a signal tracer might be the best tool.

Once you've built it, connect the ground clip to the chassis. Inject audio into pins 2 and 3 of the input XLR or IN+ and IN- on the Main PCB. Start measuring audio from Test Point 1, then 15, 17 and OUT+. Keep in mind that the input and output controls have an influence at the various points on the circuit. Come back with the results.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: vtr on December 12, 2016, 02:06:10 PM
Hey all,
Just finished assembling a complete kit REV A (v1.12) and active stereo link. I’m onto the first calibration step (Q Bias) and having an issue. I am applying the test input 1k signal at .775 VAC. I have the unit’s controls configured as described in the Q Bias section. When I measure the output signal, I’m only measuring .14 VAC. If I max out the INPUT and OUTPUT controls on the front of the unit, the output I measure is 2.8 VAC.

With the unit’s controls setup for the Q Bias (input and output set to mid), I measure the following at the test points below:

TP1:
.114 VAC

TP15:
.049 VAC

TP17:
.025 VAC

Hope this information helps. Please advise. Thank you in advance for your assistance.
Matt

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RR25 on December 13, 2016, 09:21:20 AM
Thanks mnats! I'll give that a try tomorrow.

In my experience there are no issues that are not caused by one of more of the conditions listed in my FAQ linked from the first post. As also mentioned there, when you have an audio fault a signal tracer might be the best tool.

Once you've built it, connect the ground clip to the chassis. Inject audio into pins 2 and 3 of the input XLR or IN+ and IN- on the Main PCB. Start measuring audio from Test Point 1, then 15, 17 and OUT+. Keep in mind that the input and output controls have an influence at the various points on the circuit. Come back with the results.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on December 15, 2016, 05:14:42 AM
When I measure the output signal, I’m only measuring .14 VAC. If I max out the INPUT and OUTPUT controls on the front of the unit, the output I measure is 2.8 VAC.

With the unit’s controls setup for the Q Bias (input and output set to mid), I measure the following at the test points below:

TP1:
.114 VAC

TP15:
.049 VAC

TP17:
.025 VAC
Looks like the Signal Preamp stage isn't working properly. Find out where the voltages are different from the ones in the chart within that stage, then look for one or more of the conditions listed in the FAQ. Please report back what you found that was wrong.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RR25 on December 18, 2016, 03:37:19 AM
In my experience there are no issues that are not caused by one of more of the conditions listed in my FAQ linked from the first post. As also mentioned there, when you have an audio fault a signal tracer might be the best tool.

Once you've built it, connect the ground clip to the chassis. Inject audio into pins 2 and 3 of the input XLR or IN+ and IN- on the Main PCB. Start measuring audio from Test Point 1, then 15, 17 and OUT+. Keep in mind that the input and output controls have an influence at the various points on the circuit. Come back with the results.

Hi mnats, thanks for the help.

I've built a signal tracer and been through the board. The signal at the XLR input is strong (exactly 0.775 VAC) and I can follow it clearly to the attenuator with the signal tracer but the position of the input knob did not change the level of the signal through the signal tracer which seemed a bit weird.

The signal died down to 0.02 VAC at the output of the input transformer so would I be correct to assume that the issue lies in the signal preamp section of the PCB? I have also checked my voltages for Q2 and Q3 and they are well within spec.

These readings were done with the controls set for calibration using the chassis as ground:

IN + = 0.775 VAC
TP 1 = 0.02 VAC
TP 15 = 0.02 VAC
TP 17 = 0.01 VAC

Thanks again!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on December 18, 2016, 10:21:28 PM
Hi mnats, thanks for the help.

I've built a signal tracer and been through the board. The signal at the XLR input is strong (exactly 0.775 VAC) and I can follow it clearly to the attenuator with the signal tracer but the position of the input knob did not change the level of the signal through the signal tracer which seemed a bit weird.

The signal died down to 0.02 VAC at the output of the input transformer so would I be correct to assume that the issue lies in the signal preamp section of the PCB? I have also checked my voltages for Q2 and Q3 and they are well within spec.

These readings were done with the controls set for calibration using the chassis as ground:

IN + = 0.775 VAC
TP 1 = 0.02 VAC
TP 15 = 0.02 VAC
TP 17 = 0.01 VAC

Thanks again!
Didn't ask for a measurement at IN+ but it brings up something I neglected to mention. But first, what was your reference when measuring IN+? Since both the input and output are galvanically isolated by the audio transformers you'll need to measure your input signal between IN+ and IN-; similarly the output has to be measured between OUT+ and OUT-, not between OUT+ and ground as my previous post implied.

If the signal isn't making it to TP1 then there is something wrong with the circuit to the left of the test point, not necessarily to the right. Although a dead short at the test point to ground would also cause problems and might be seen as an issue with the Signal Preamp if you're feeling pedantic.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on December 27, 2016, 06:05:39 PM
Having a meter calibration issue with one of my new Rev D builds. (v.1.12) Q bias went fine. Then I was having troubles with the null adjust, there didn't seem to be enough resistance to get the meter zeroed with 0VDC at the test points. Subbed out the 2k for a 5k and was able to get that step ok. But now in the tracking adjust calibration step, with GR on (-10db) the meter is pinned to the left. Tracking adjust doesn't do anything. Replaced the tracking adjust 2k trimmer with a 5k I'd tested just to be safe there. Pulled and double checked that the HFE was matching on Q12/Q13, also tried replacing with another matched pair of 2n3708s I had lying around. Meter is still pinning left, even at lower gain reduction values.
Should I get another pair of 2n3707s in there, or is there some other likely avenue to look into first?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on December 28, 2016, 05:28:12 AM
Having a meter calibration issue with one of my new Rev D builds. (v.1.12) Q bias went fine. Then I was having troubles with the null adjust, there didn't seem to be enough resistance to get the meter zeroed with 0VDC at the test points. Subbed out the 2k for a 5k and was able to get that step ok. But now in the tracking adjust calibration step, with GR on (-10db) the meter is pinned to the left. Tracking adjust doesn't do anything. Replaced the tracking adjust 2k trimmer with a 5k I'd tested just to be safe there. Pulled and double checked that the HFE was matching on Q12/Q13, also tried replacing with another matched pair of 2n3708s I had lying around. Meter is still pinning left, even at lower gain reduction values.
Should I get another pair of 2n3707s in there, or is there some other likely avenue to look into first?
Is the shunt back in the "Normal" position? When you write "pinned to the left" do you mean the needle is moving past the -20dB point? What effect does the front panel zero adjust have? Understanding that the unit is still not calibrated, what do the voltages of the transistors look like in relation to the ones on the schematic with voltages? Most crucial is a ˜0.7 drop between base and emitter.

To answer your question, if you are able to measure the Hfe of your transistors they are unlikely to be faulty.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: frederickalonso on December 28, 2016, 08:29:39 AM
Great thread, thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on January 04, 2017, 05:18:50 PM
Is the shunt back in the "Normal" position? When you write "pinned to the left" do you mean the needle is moving past the -20dB point? What effect does the front panel zero adjust have? Understanding that the unit is still not calibrated, what do the voltages of the transistors look like in relation to the ones on the schematic with voltages? Most crucial is a ˜0.7 drop between base and emitter.

To answer your question, if you are able to measure the Hfe of your transistors they are unlikely to be faulty.
So ya I put the shunt back into normal position after the meter zero step, the front panel zero adjust does it's thing fine in that step with the shunt NOT in normal. The meter then jumps way way left to -20 when I put the shunt back to normal to the point where the front panel zero adjust barely moves it to the right even when it's turned full CW. I can get it centered if I set the tracking adjust full CCW, but testing the gain reduction (with a 10db drop) will pin it to -20 and I'm unable to both center the meter with 0db GR and get a remotely accurate reading of -10db.
Here's some readings:
Q13 E -2.6dcV    C 13dcV   B -2dcV
Q12 E -2.5dcV    C 13dcV   B -1.94dcV
Q11  D 13.75dcV   S  -1.95dcV     G  -1.66dcV
Q1 ,Q2,Q3 all pretty spot on with schematic
Q4   B 1 dcV       C 4.88 dcV     E 0.41 dcV
Q5 B 3.25 dcV     C 24.6 dcV    E 2.7 dcV
Q6 C 27.1dcV   E 2.1dcV
Q7 B 4.4 dcV   C 14.7dcV    E 3.9dcV
Q8 C 29.6dcV  E  14.1dcV
Q9  B 3.4dcV    C 16.9 dcV   E 2.8 dcV
Q10  C 29.6 dcV    E 16.2 dcV
Q14 B 11.4 dcV     E 10.8 dcV

So ya all of these are reasonably in line with the schematic, give or take, and the base to emitter drop is around .6 in every case.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on January 05, 2017, 05:02:49 PM
So ya I put the shunt back into normal position after the meter zero step, the front panel zero adjust does it's thing fine in that step with the shunt NOT in normal. The meter then jumps way way left to -20 when I put the shunt back to normal to the point where the front panel zero adjust barely moves it to the right even when it's turned full CW.
Remove the shunt then measure R44, the trim pot, while at either extreme.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Basti on January 06, 2017, 03:57:16 PM
Hi DIYers!

I've read so many forumpost the last week but i just cant find something similar to my problem...

So i have finished building the Rev D Hairball Kit(V1.11) and wanted to start the calibration,
in fact i made all 3 steps.
As i bypassed the test oscillator afterwards the 1KHz Signal jumped out of my speaker,
meaning there is definitely something wrong with my build... (Signal passing through, but too quiet)

So i checked every resistor and generally everything if its in place and in the right direction ->
everything is fine

i tried to recalibrate, didn't help

but i noticed some strange things:

-The Input and Output knob doesn't make the oscillator signal louder or quieter in my DAW and Speakers
-I hear the Signal out of my Outputtransformer when the output knob is turned heavily up
-I'm not quiet sure but i think the unit distorts the signal more than it should
-Signal is obviously passing through, but much too quiet

What are your suggestions?
Cold Solderjoint? Have i bridged somehting?

greetings from Austria
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 06, 2017, 04:02:27 PM
Hi DIYers!

I've read so many forumpost the last week but i just cant find something similar to my problem...

So i have finished building the Rev D Hairball Kit(V1.11) and wanted to start the calibration,
in fact i made all 3 steps.
As i bypassed the test oscillator afterwards the 1KHz Signal jumped out of my speaker,
meaning there is definitely something wrong with my build... (Signal passing through, but too quiet)

So i checked every resistor and generally everything if its in place and in the right direction ->
everything is fine

i tried to recalibrate, didn't help

but i noticed some strange things:

-The Input and Output knob doesn't make the oscillator signal louder or quieter in my DAW and Speakers
-I hear the Signal out of my Outputtransformer when the output knob is turned heavily up
-I'm not quiet sure but i think the unit distorts the signal more than it should
-Signal is obviously passing through, but much too quiet

What are your suggestions?
Cold Solderjoint? Have i bridged somehting?

greetings from Austria

Ya definitely something wrong. Audible signal out of the output tx is normal.

With the input and output midway and GR off (20:1) what your output level at each end of the qbias adjustment.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on January 06, 2017, 04:24:06 PM
Hey everyone!
Hope you're all having a great new year! I posted this on a different topic and never heard back. Let's see how this goes... I got my 1176 Rev D back from Mike a few months ago and I LOVE it.  One thing that I'm curious about though is whether or not I may need to recalibrate it. I was printing a vocal with it on (Input at 40, output at 6, 4:1 Ratio, Attack fully CW and Release at 5) and the amount of gain reduction seems rather extreme for the low input setting. The source signal was fairly low between -12dB to -10dB and the needle was floating around -10 to -20dB of gain reduction.  Doesn't seem like it really leaves me anywhere to go. haha. Could the adjustment pots have gotten shaken around during delivery or is this reading typical? I'm sure DDM readings would help but I figured I'd ask before taking it out of the rack and removing the top.

Thanks in advance!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Basti on January 06, 2017, 04:54:05 PM
Ya definitely something wrong. Audible signal out of the output tx is normal.

With the input and output midway and GR off (20:1) what your output level at each end of the qbias adjustment.

Mike

I'm not sure how to measure that...
from point 18 to the ends of the poti?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 06, 2017, 06:18:20 PM
I'm not sure how to measure that...
from point 18 to the ends of the poti?

At the XLR +/- test point.  AC.  What range do you get as you rotate the qbias under those conditions.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 06, 2017, 06:23:41 PM
Hey everyone!
Hope you're all having a great new year! I posted this on a different topic and never heard back. Let's see how this goes... I got my 1176 Rev D back from Mike a few months ago and I LOVE it.  One thing that I'm curious about though is whether or not I may need to recalibrate it. I was printing a vocal with it on (Input at 40, output at 6, 4:1 Ratio, Attack fully CW and Release at 5) and the amount of gain reduction seems rather extreme for the low input setting. The source signal was fairly low between -12dB to -10dB and the needle was floating around -10 to -20dB of gain reduction.  Doesn't seem like it really leaves me anywhere to go. haha. Could the adjustment pots have gotten shaken around during delivery or is this reading typical? I'm sure DDM readings would help but I figured I'd ask before taking it out of the rack and removing the top.

Thanks in advance!

Maybe not.  There are a few things going on.

One is that the input t-pad on the original units has a very unique taper.  Not very common today.  Our taper is a little different which just means the input runs hotter quicker. So instead of getting that classic compression setting at 30 (Dr. Pepper)...it's more like 36-40 .

Also the meter, while good, is not like they used to make them or like an equivalent meter costing around $110.  It does overshoot a little. When you combine that with medium to slower release settings, you'll see heaver compression. Especially at 4:1 which has a lower threshold.

Hope that makes sense.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Basti on January 07, 2017, 06:15:27 AM
At the XLR +/- test point.  AC.  What range do you get as you rotate the qbias under those conditions.

Ah okay! sorry for the dumb question mike! had to sleep a night over this  :o

okay i have: 0,25 VAC to 9,36 VAC

thank you for taking time!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 07, 2017, 11:15:58 AM
Ah okay! sorry for the dumb question mike! had to sleep a night over this  :o

okay i have: 0,25 VAC to 9,36 VAC

thank you for taking time!

That seems normal.

What is the issue again?  Just that the signal is too quiet?  Are you able to get through all of the calibration steps?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Basti on January 07, 2017, 02:57:52 PM
That seems normal.

What is the issue again?  Just that the signal is too quiet?  Are you able to get through all of the calibration steps?

Yes, the signal is way too quiet... may it be the preamp section, not pushing the signal enough?

Calibration steps are no problem..
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Basti on January 08, 2017, 12:35:54 PM
Yes, the signal is way too quiet... may it be the preamp section, not pushing the signal enough?

Calibration steps are no problem..

okay, spent some time now with the unit
checked the voltages with mnats schematics

preamp sections looks good except of Q3 instead of 12,58 V i have 11,77 v
Q14 has 11,14 V instead of 12 V

i dont know how much its allowed to differ..

biggest problem is the gain reduction driver..
nothing is near the Voltages
Q11 gets only 6 V instead of 10,56 V
and i Cant understand why, resistors are good

Trying to build a audio probe next week and seek on

Any Tipps or suggestions so far?



Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 09, 2017, 01:36:32 PM
okay, spent some time now with the unit
checked the voltages with mnats schematics

preamp sections looks good except of Q3 instead of 12,58 V i have 11,77 v
Q14 has 11,14 V instead of 12 V

i dont know how much its allowed to differ..

biggest problem is the gain reduction driver..
nothing is near the Voltages
Q11 gets only 6 V instead of 10,56 V
and i Cant understand why, resistors are good

Trying to build a audio probe next week and seek on

Any Tipps or suggestions so far?

You're signal looks good an strong with no GR.  There has to be something misplaced in the GR amp, bad semi, bad solder joint...something weird in there.

It sounds good and loud with no GR correct?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Basti on January 09, 2017, 01:59:14 PM
You're signal looks good an strong with no GR.  There has to be something misplaced in the GR amp, bad semi, bad solder joint...something weird in there.

It sounds good and loud with no GR correct?

I think i should have mentioned this earlier^^
The signal has the same low level -> bypassed or in gain reduction
Is that good to isolate the issue?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 09, 2017, 02:05:54 PM
I think i should have mentioned this earlier^^
The signal has the same low level -> bypassed or in gain reduction
Is that good to isolate the issue?

Hmmmm.  I would check your signal/patching coming into the unit.  You mentioned that under the conditions I mentioned, your unit was as loud as 9.36VAC before setting the bias?  That is an output of over 20dBu which is LOUD.  Even with the 1dBu qbias roll back you should be fine unless this output is all HF oscillation.

You're having no issue setting the qbias?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on January 09, 2017, 06:57:46 PM
Remove the shunt then measure R44, the trim pot, while at either extreme.
it goes from 0 to 0.1dcV
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on January 09, 2017, 08:12:10 PM
it goes from 0 to 0.1dcV
A trimmer is a variable resistor, so try measuring its resistance...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on January 09, 2017, 08:19:07 PM
A trimmer is a variable resistor, so try measuring its resistance...
it's working correctly, 0k up to 4.8k at full trim. had a 2k per the BOM, (measuring up 0 up to 1.8k) but put a 5k in there when I changed R75 out for 5k too.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on January 10, 2017, 04:11:26 AM
it's working correctly, 0k up to 4.8k at full trim. had a 2k per the BOM, (measuring up 0 up to 1.8k) but put a 5k in there when I changed R75 out for 5k too.
What this part of the circuit does is compare the voltage at the base of Q12 with the voltage at the base of Q13. The voltage at the base of Q12 will vary with gain reduction since Q11, the FET, sees the same input at its gate as Q1, the FET that is doing the audio gain reduction.

So let's take a step back. Did you measure and confirm all resistor values before they were soldered in place? If not, have you done a visual confirmation of resistor values in the GR Meter circuit after it was built? Right now I cannot see how changing R75's value would change the voltage produced at its wiper unless other values were incorrect. *edit: Yeah, of course it would.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on January 10, 2017, 05:33:33 PM
So let's take a step back. Did you measure and confirm all resistor values before they were soldered in place? If not, have you done a visual confirmation of resistor values in the GR Meter circuit after it was built? Right now I cannot see how changing R75's value would change the voltage produced at its wiper unless other values were incorrect. *edit: Yeah, of course it would.
Always measure before soldering, but JIC I just measured and confirmed all resistors in the GR Meter Driver amp. then rechecked earlier calibration steps, still having the same issue. It's compressing fine, sounding great, the meter just shows way too much GR, even when there is no actual reduction being applied to the signal (although the compressor is engaged on the attack switch).
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on January 10, 2017, 05:42:03 PM
Always measure before soldering, but JIC I just measured and confirmed all resistors in the GR Meter Driver amp. then rechecked earlier calibration steps, still having the same issue. It's compressing fine, sounding great, the meter just shows way too much GR, even when there is no actual reduction being applied to the signal (although the compressor is engaged on the attack switch).
With the unit on, set the meter switch in GR, ratio to 20:1 and the attack knob fully counter clockwise, no input, tracking adjust shunt removed, starting with the front panel meter zeroed. We'll assume the voltage across R74 is around 0.00VDC as you had measured when you did the meter null calibration but you may want to verify.

With your multimeter set to DC volts and the negative probe on the chassis, measure the voltage at the base of Q13. Measure the voltage at the base of Q12. Now measure the voltage at the base of Q13 while R75 is at each extreme. Please report your voltages.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on January 10, 2017, 06:16:34 PM
With the unit on, set the meter switch in GR, ratio to 20:1 and the attack knob fully counter clockwise, no input, tracking adjust shunt removed, starting with the front panel meter zeroed. We'll assume the voltage across R74 is around 0.00VDC as you had measured when you did the meter null calibration but you may want to verify.

With your multimeter set to DC volts and the negative probe on the chassis, measure the voltage at the base of Q13. Measure the voltage at the base of Q12. Now measure the voltage at the base of Q13 while R75 is at each extreme. Please report your voltages.
Across R74 with shunt in "normal" position is -0.1dcV or so
Q12 base: -1.95 dcV
Q13 base: -2.06 dcV

R75 FULL CCW
Q12 Base:-1.95 dcV
Q13 Base: 0 dcV

R75 FULL CW
Q12 base: -1.96 dcV
Q13 base: -3.52 dcV

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on January 11, 2017, 05:16:54 AM
Across R74 with shunt in "normal" position is -0.1dcV or so
Q12 base: -1.95 dcV
Q13 base: -2.06 dcV

R75 FULL CCW
Q12 Base:-1.95 dcV
Q13 Base: 0 dcV

R75 FULL CW
Q12 base: -1.96 dcV
Q13 base: -3.52 dcV
But with the VU meter zeroed and the shunt removed the voltage across R74 is 0.00, right?

With the shunt still removed and the meter at zero with 0.00v across R74 measure both sides of R70 relative to chassis ground. Measure both sides of R68 and R69. Please report your voltages.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on January 12, 2017, 03:40:21 PM
But with the VU meter zeroed and the shunt removed the voltage across R74 is 0.00, right?

With the shunt still removed and the meter at zero with 0.00v across R74 measure both sides of R70 relative to chassis ground. Measure both sides of R68 and R69. Please report your voltages.
ya the R74 reading is 0.00dcv with the meter zeroed and jumper in "not normal" or removed
keeping shunt in that position, i get the following readings
R70 -4.43dcV / -2.84dcV
R68 -2.53dcV / -2.84dcV
R69 -2.64dcV / -2.84dv
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: junkface on January 12, 2017, 09:59:46 PM
Gah, in an unrelated Rev A build, I'm also having a power supply issue. Was getting a hissing sound from that section, and what originally spec'd out (-10V and 30V) went down to basically nothing. Tried replacing the caps ( i figured the hissing might be coming from a bad one, not sure what axials do when they blow/fail) but the same sound came from the new ones as well. They supplied the proper voltages for a second but now again I'm getting next to nothing voltage wise at the test points. Nothing looks or tests burnt but something is obviously awry.
Should I just replace every component in the power supply?  I think I have all the parts, the only one I don't have the specs for is the diode at the 30v test point.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on January 12, 2017, 11:15:14 PM
Gah, in an unrelated Rev A build, I'm also having a power supply issue. Was getting a hissing sound from that section, and what originally spec'd out (-10V and 30V) went down to basically nothing. Tried replacing the caps ( i figured the hissing might be coming from a bad one, not sure what axials do when they blow/fail) but the same sound came from the new ones as well. They supplied the proper voltages for a second but now again I'm getting next to nothing voltage wise at the test points. Nothing looks or tests burnt but something is obviously awry.
Should I just replace every component in the power supply?  I think I have all the parts, the only one I don't have the specs for is the diode at the 30v test point.
Not enough information to diagnose but replacing every component is like throwing good money after bad. Have you built the power supply first as recommended in the build guide or have you populated the entire board? If fully populated, did you test the supply first? Have you checked the fuse (you don't check it for 'burnt' but for continuity). Show a picture of the power supply.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mnats on January 13, 2017, 05:21:46 AM
ya the R74 reading is 0.00dcv with the meter zeroed and jumper in "not normal" or removed
keeping shunt in that position, i get the following readings
R70 -4.43dcV / -2.84dcV
R68 -2.53dcV / -2.84dcV
R69 -2.64dcV / -2.84dv
Replace the shunt to the normal position and repeat all voltage measurements.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: JingleDjango on January 14, 2017, 02:16:16 PM
Is the 10MΩ resistor on the ratio pcb optional in both revisions? Neither of my Rev. D kits included one.

(I had a couple lying around from a another project which I used, I'm just curious.)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on January 16, 2017, 07:19:39 PM
Is the 10MΩ resistor on the ratio pcb optional in both revisions? Neither of my Rev. D kits included one.

(I had a couple lying around from a another project which I used, I'm just curious.)

From the Rev A build manual:

"Note: The revision A includes an optional 10M resistor on the ratio PCB (R-OPT). This resistor was not in the original revision A, but was added to later revisions to prevent audible pops when switching ratios. "

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ratty_7 on January 27, 2017, 10:37:12 PM
Hi Guys,
 
I have 2 new Rev A's V1.12
Build was great, however, 
I have a pretty interesting problem here with 3rd Calibration of my 2nd unit ....!!!

With the input at 0.775VAC  @ 1k
All other settings as per 3rd calibration steps

I can only get R44 to about -15db instead of -10db where it is suppose to be. No matter what I do with the R44 and the front panel pot, I cannot get the meter to -10db 

Any ideas
Mike :)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: StudioJakubka on January 28, 2017, 12:47:22 AM
HI there, Rev A v1.12 problem with Q bias adjustment. No reaction of output AV to R59 adjustment. On T18 I measure -1.75V to -1.01V when moved from CCW to CW, howeberoutput remains still the same. Any idea?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: YoDudeRock on January 31, 2017, 04:56:25 PM
I have built my 7th FET/RACK Rev A "Blue Stripe" (with Stereo Link), but encountered a problem this time.    In GR mode the needle doesn't go to 0 on the VU meter (just sits motionless on the left), but +4 and +8 DO seem to work properly.    Also, there's a low frequency rumble noise when I rotate the Output knob and more so at the top of the range of the knob.
Sound does come out of the output and it DOES seem to be compressing somewhat based on the sound.

Any ideas where I should start to get this thing going?

Thanks,
Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: dencul on February 01, 2017, 08:09:02 PM
Regarding recent build of Hairball Rack Revision D. 

Scratching my head here. Calibration steps 1 & 2 seem to go fine. Then, 3rd step I get no movement in the VU meter and no change in VAC (multimeter @ output xlr) when Attack is switched ON/OFF.

I measured all resistors with multimeter upon initial installation and have since double checked every resistor with the color code calculator. All check out fine.

I have inspected and reflowed solder joints, tested continuity of attack switch, and tested transistor voltages against “typical voltages” schematic, and followed many threads here to no avail.

Any help would be much appreciated.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 07, 2017, 03:23:40 PM
Hi Guys,
 
I have 2 new Rev A's V1.12
Build was great, however, 
I have a pretty interesting problem here with 3rd Calibration of my 2nd unit ....!!!

With the input at 0.775VAC  @ 1k
All other settings as per 3rd calibration steps

I can only get R44 to about -15db instead of -10db where it is suppose to be. No matter what I do with the R44 and the front panel pot, I cannot get the meter to -10db 

Any ideas
Mike :)

So you can get a 10dB drop at the output but can not get the meter to calibrate to show the 10dB drop?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 07, 2017, 03:24:47 PM
HI there, Rev A v1.12 problem with Q bias adjustment. No reaction of output AV to R59 adjustment. On T18 I measure -1.75V to -1.01V when moved from CCW to CW, howeberoutput remains still the same. Any idea?

What is the DC at the GATE of Q1 when you rotate the Qbias to both sides?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 07, 2017, 03:26:21 PM
I have built my 7th FET/RACK Rev A "Blue Stripe" (with Stereo Link), but encountered a problem this time.    In GR mode the needle doesn't go to 0 on the VU meter (just sits motionless on the left), but +4 and +8 DO seem to work properly.    Also, there's a low frequency rumble noise when I rotate the Output knob and more so at the top of the range of the knob.
Sound does come out of the output and it DOES seem to be compressing somewhat based on the sound.

Any ideas where I should start to get this thing going?

Thanks,
Chris

Sounds like you have 2 issues.

Issue 1: Meter sits left in GR mode, is most likely an issue with your GR AMP section.
Issue 2: Rumble. No idea...are you passing signal?  How did calibration go?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 07, 2017, 03:30:00 PM
Regarding recent build of Hairball Rack Revision D. 

Scratching my head here. Calibration steps 1 & 2 seem to go fine. Then, 3rd step I get no movement in the VU meter and no change in VAC (multimeter @ output xlr) when Attack is switched ON/OFF.

I measured all resistors with multimeter upon initial installation and have since double checked every resistor with the color code calculator. All check out fine.

I have inspected and reflowed solder joints, tested continuity of attack switch, and tested transistor voltages against “typical voltages” schematic, and followed many threads here to no avail.

Any help would be much appreciated.

Sounds like you have an issue with your GR Amp (which also includes the ratio PCB).

1. Set up your unit with a 0dB 1K signal on the input, in/out at 12 o'clock, attack release full CW.
2. Measure the AC at TP22 at each ratio setting
3. Measure the DC at TP21 at each ratio setting

Report here.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: dencul on February 07, 2017, 06:05:41 PM
Sounds like you have an issue with your GR Amp (which also includes the ratio PCB).

1. Set up your unit with a 0dB 1K signal on the input, in/out at 12 o'clock, attack release full CW.
2. Measure the AC at TP22 at each ratio setting
3. Measure the DC at TP21 at each ratio setting

Report here.

Mike

0dB 1K signal on the input, in/out at 12 o'clock, attack release full CW.

AC at TP22
20 = 0.856 VAC
12 = 0.509 VAC
  8 = 0.339 VAC
  4 = 0.191 VAC

DC at TP21
20 = -6.57 VDC
12 = -3.517 VDC
  8 = -2.379 VDC
  4 = -1.423 VDC

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 07, 2017, 06:48:25 PM
0dB 1K signal on the input, in/out at 12 o'clock, attack release full CW.

AC at TP22
20 = 0.856 VAC
12 = 0.509 VAC
  8 = 0.339 VAC
  4 = 0.191 VAC

DC at TP21
20 = -6.57 VDC
12 = -3.517 VDC
  8 = -2.379 VDC
  4 = -1.423 VDC

Nothing seems too wacky there.

Under the same conditions, what is your ACV with all 4 ratios at the anode (side without the line) of CR2?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: dencul on February 07, 2017, 07:36:20 PM
Nothing seems too wacky there.

Under the same conditions, what is your ACV with all 4 ratios at the anode (side without the line) of CR2?

Mike

VAC anode of CR2:

20 = 0.002 VAC
12 = 0.001 VAC
  8 = 0 VAC
  4 = 0 VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 07, 2017, 07:44:30 PM
VAC anode of CR2:

20 = 0.002 VAC
12 = 0.001 VAC
  8 = 0 VAC
  4 = 0 VAC

Ya your signal is dying in your GR AMP.

This is the old rev D voltage sheet but it should still apply:
http://mnats.net/files/1176REVD_VOLTS.pdf

Check your DC voltages in your GR AMP section.  Looks for misplaced resistors, bad joints, all that good stuff.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ratty_7 on February 07, 2017, 09:53:07 PM
So you can get a 10dB drop at the output but can not get the meter to calibrate to show the 10dB drop?

Mike
Ok....  With the Ratio at 20:1 and the meter at +4 and the input at around 11 o'clock and the out put at 9 o'clock attack off/on I get a drop of -10dB from 0db on the meter. After re-calibrating steps 1 & 2 on both units, when I turn the attack on and the meter from +4 to GR, I am now getting a drop of almost -10db. In the pic below the inputs and outputs ended up on both units and they were exactly the same, except the meter is a little out ....? 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 07, 2017, 10:36:12 PM
Ok....  With the Ratio at 20:1 and the meter at +4 and the input at around 11 o'clock and the out put at 9 o'clock attack off/on I get a drop of -10dB from 0db on the meter. After re-calibrating steps 1 & 2 on both units, when I turn the attack on and the meter from +4 to GR, I am now getting a drop of almost -10db. In the pic below the inputs and outputs ended up on both units and they were exactly the same, except the meter is a little out ....?

In +4?  Keep it in GR mode always.

http://www.hairballaudio.com/blog/resources/build-guides/fetrack-v2-buildbrstep-4-calibration

not sure what your calibration procedure is...nothing I've used.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: dencul on February 08, 2017, 02:08:52 AM
Ya your signal is dying in your GR AMP.

This is the old rev D voltage sheet but it should still apply:
http://mnats.net/files/1176REVD_VOLTS.pdf

Check your DC voltages in your GR AMP section.  Looks for misplaced resistors, bad joints, all that good stuff.

Mike

I measured and took notes for all on the Rev D voltages sheet.
Measurements of transistors were pretty close until Q8 , when emitter read 225 mV instead of 14.7v.
I've double checked resistors and touched up many solder joints
I wanted to remove the transistors and put in sockets, but I destroyed a 2N3787 trying to remove it from Q8 so now I'll have to source a replacement and wait for it's arrival. Not sure if there's much I can do until then.  doh! :P


Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ratty_7 on February 08, 2017, 07:55:36 PM
In +4?  Keep it in GR mode always.

http://www.hairballaudio.com/blog/resources/build-guides/fetrack-v2-buildbrstep-4-calibration

not sure what your calibration procedure is...nothing I've used.

yes your right Mike. Sorry  :o

I have followed Hairball 3rd calibration to point 4

Set controls as follows:
Input = "24" mid rotation
Output = "24" mid rotation
Attack = full CW
Release = full CW
Compression ratio = 20:1
Meter mode = "GR"

1. Apply a 1 KHz, 0dBu signal, confirmed with your DMM at IN + and IN - at the input XLR (0.775 VAC).
2. Moved myDMM to OUT + and OUT - at the output XLR.
3. Set output control for 0dBu (0.775 VAC) at the output.
4. Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

Now this is where things go wrong. The next step says....

5. Turn the attack control ON (Fully CW) and readjust the output level control for "0dBu" if necessary. 

Problem is my output control does not move the needle to 0db. In fact from CCW to CW the needle stays put and slightly quivers :(
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: petereugenefoley on February 08, 2017, 09:16:39 PM
So a friend sent me his Hairball 1176 Rev A for me to put in new Lundahl transformers, the LL5402 and LL1540. Is it possible to replace the EA trafos that were in there with these Lundahls?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jdier on February 09, 2017, 07:45:40 PM
Apologies... created a new thread before finding this.   If a mod could kill my other post (HERE:  https://groupdiy.com/index.php?topic=65149 ) it would be appreciated.

-------------------------------
Hairball 1176 - Discrete Meter Circuit/Null Adjust **GR Meter problem**
-------------------------------

Very much a newbie to electronics, but completed my Hairball 1176.  Power Supply test perfect, completed build and Q Bias went great.

When I get to Discrete Meter Circuit/Null Adjust, I am unable to make the meter move at all.   It sits < 0/-20 

It does not appear that I have blown the meter as I can put test tone to the input, choose +4 or +8, and my input and output controls appear effect the meter the way I would expect.

Once I switch back to GR, the meter remains all the way left, just under 0/-20.

I pulled the FET Meter board and there does not appear to be any shorts.   (however, I did notice that there are three points unused marked "22" "GRN" and "BLK"

Any help would be greatly appreciated.

Jim
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: NickB Zar on February 10, 2017, 02:00:03 AM
New Hairball 1176 rev. A
I can't complete calibration # 3 the Gain Reduction Meter Tracking Adjustment.
 on step # 4  Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR. i only get 1.4 vac and i set input control all the way , and miter  dose not move in GR mode.
 i ran some drums thru the comp and it sounds great,  miter works in +8 and +4 mode BUT NOT MOVING IN GR mode.
 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 10, 2017, 10:50:14 AM
yes your right Mike. Sorry  :o

I have followed Hairball 3rd calibration to point 4

Set controls as follows:
Input = "24" mid rotation
Output = "24" mid rotation
Attack = full CW
Release = full CW
Compression ratio = 20:1
Meter mode = "GR"

1. Apply a 1 KHz, 0dBu signal, confirmed with your DMM at IN + and IN - at the input XLR (0.775 VAC).
2. Moved myDMM to OUT + and OUT - at the output XLR.
3. Set output control for 0dBu (0.775 VAC) at the output.
4. Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

Now this is where things go wrong. The next step says....

5. Turn the attack control ON (Fully CW) and readjust the output level control for "0dBu" if necessary. 

Problem is my output control does not move the needle to 0db. In fact from CCW to CW the needle stays put and slightly quivers :(

So you're getting the 10dB drop at the output but can't get the meter to move at all or calibrate in GR mode?

Does the needle just sit at 0 or site far left in GR mode?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 10, 2017, 10:51:52 AM
Apologies... created a new thread before finding this.   If a mod could kill my other post (HERE:  https://groupdiy.com/index.php?topic=65149 ) it would be appreciated.

-------------------------------
Hairball 1176 - Discrete Meter Circuit/Null Adjust **GR Meter problem**
-------------------------------

Very much a newbie to electronics, but completed my Hairball 1176.  Power Supply test perfect, completed build and Q Bias went great.

When I get to Discrete Meter Circuit/Null Adjust, I am unable to make the meter move at all.   It sits < 0/-20 

It does not appear that I have blown the meter as I can put test tone to the input, choose +4 or +8, and my input and output controls appear effect the meter the way I would expect.

Once I switch back to GR, the meter remains all the way left, just under 0/-20.

I pulled the FET Meter board and there does not appear to be any shorts.   (however, I did notice that there are three points unused marked "22" "GRN" and "BLK"

Any help would be greatly appreciated.

Jim

Sounds like you have the older boards, but it's ok to keep the post here.  Leave those pads unused.

Are you able to get the 10dB drop on the output?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 10, 2017, 10:54:14 AM
New Hairball 1176 rev. A
I can't complete calibration # 3 the Gain Reduction Meter Tracking Adjustment.
 on step # 4  Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR. i only get 1.4 vac and i set input control all the way , and miter  dose not move in GR mode.
 i ran some drums thru the comp and it sounds great,  miter works in +8 and +4 mode BUT NOT MOVING IN GR mode.

If you can't get the 10dB drop at the output, or the GR meter working, you may have a few different issues.  Start by going through your whole build and checking values and resistors.  If that looks ok you may want to try new FETs.  You can email us for those.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jdier on February 10, 2017, 11:20:55 AM
Sounds like you have the older boards, but it's ok to keep the post here.  Leave those pads unused.

Are you able to get the 10dB drop on the output?

Mike

I have not gotten to that step.   I did Q (which was successful) then when I went to this step, I cannot get the GR meter to move to the right when GR is engaged. 

(So I stopped there)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 10, 2017, 11:27:12 AM
I have not gotten to that step.   I did Q (which was successful) then when I went to this step, I cannot get the GR meter to move to the right when GR is engaged. 

(So I stopped there)

Ah so you can't even get to the null.

Here are a few things:

1. Start with your meter trimmers dead center. If you have the 20 turn trimmers turn one direction till you hear a little "clicking" that's the end....rotate back 10 turns the other way".

2. Check your meter section components and joints.

3. Check the dc voltages in the meter section...your unit is un-calibrated so it won't really match this, but it can provide info.
http://mnats.net/files/1176REVD_VOLTS.pdf

4. Check your wiring. If you used terminals make sure wires are fully seated.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jdier on February 10, 2017, 01:47:23 PM
Ah so you can't even get to the null.

Here are a few things:

1. Start with your meter trimmers dead center. If you have the 20 turn trimmers turn one direction till you hear a little "clicking" that's the end....rotate back 10 turns the other way".

2. Check your meter section components and joints.

3. Check the dc voltages in the meter section...your unit is un-calibrated so it won't really match this, but it can provide info.
http://mnats.net/files/1176REVD_VOLTS.pdf

4. Check your wiring. If you used terminals make sure wires are fully seated.

Mike

Centered all trimmers (except Q Bias which set correctly)

Checked and reflowed meter joints

CD Voltages:

Q11  14

Q12  -1.2    13.1     -1.8

Q13     -2      -1.9      -1.3

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ratty_7 on February 10, 2017, 05:03:09 PM
So you're getting the 10dB drop at the output but can't get the meter to move at all or calibrate in GR mode?

Does the needle just sit at 0 or site far left in GR mode?

Hi Mike
No I am not getting a 10db drop and yes the meter just sits there -1 to -2 in GR mode....
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: riddor74 on February 13, 2017, 04:18:56 AM
Just finished out build and completed calibration on our 2 x Rev D blackface hairballs.

They sound great and the quality of the kit is super,

We have once issue following calibration, the VU meters we perfectly sitting at 0 however after about 5/6 hours they have dropped to -1 on both units,

Is it just a case of using the zero adjust pot accessible via the front panel, if I do this does it effect any internal calibration?

Also are they specific settings you need to enagage before using the zero adjuster (if this is the way to over come this)?

Tristan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 13, 2017, 02:18:55 PM
Centered all trimmers (except Q Bias which set correctly)

Checked and reflowed meter joints

CD Voltages:

Q11  14

Q12  -1.2    13.1     -1.8

Q13     -2      -1.9      -1.3

Q13 is crazy off.  You may want to replace it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 13, 2017, 02:21:25 PM
Hi Mike
No I am not getting a 10db drop and yes the meter just sits there -1 to -2 in GR mode....

If you were able to set your Qbias but can't get a drop, you have issues in your GR amp. Look back a few posts and post the TP22 and 21 voltages as described:

https://groupdiy.com/index.php?topic=63600.msg825178#msg825178

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 13, 2017, 02:23:03 PM
Is it just a case of using the zero adjust pot accessible via the front panel, if I do this does it effect any internal calibration?

Hi,

Hes the discrete meter fluctuates. That's why UREI put an adjustment on the front.  You can turn that pot all you like, it won't harm the other adjustments. Just where the needle sits.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ratty_7 on February 14, 2017, 12:05:38 AM
If you were able to set your Qbias but can't get a drop, you have issues in your GR amp. Look back a few posts and post the TP22 and 21 voltages as described:

https://groupdiy.com/index.php?topic=63600.msg825178#msg825178

Mike

Set up both my units with a 0dB 1K signal on the input, in/out at 12 o'clock, attack release full CW.
       
       Unit A                      Unit B
VAC @ TP22         VAC @ TP22
20 =  381.8             20 = 0.55.6
12 = 188.2              12 = 032.6
   8 = 126.3                 8 = 023.1
   4 = 65.9                    4 = 12.7

VDC @ TP21        VDC @ TP21
20 = -05.91             20 = -05.91
12 = -3.395             12 = -3.388
   8 = -2.601                8 = -2.592
   4 = -1.809                4 = -1.793

Both VDC are about the same, but the VAC on both my units and are very different...!!!


Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 14, 2017, 12:11:17 AM
Set up both my units with a 0dB 1K signal on the input, in/out at 12 o'clock, attack release full CW.
       
       Unit A                      Unit B
VAC @ TP22         VAC @ TP22
20 =  381.8             20 = 0.55.6
12 = 188.2              12 = 032.6
   8 = 126.3                 8 = 023.1
   4 = 65.9                    4 = 12.7

VDC @ TP21        VDC @ TP21
20 = -05.91             20 = -05.91
12 = -3.395             12 = -3.388
   8 = -2.601                8 = -2.592
   4 = -1.809                4 = -1.793

Both VDC are about the same, but the VAC on both my units and are very different...!!!

Does it work fine in GR off mode? More specifically does it pass signal and sound good?

If so, those TP22 readings on unit B would indicate bad solder joints at either your output pot, attack switch, or a bad joint, incorrect resistor on your ratio board or ratio connectors.  Have a close look.  If you can't find it we'll trace through it.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ratty_7 on February 14, 2017, 01:13:46 AM
Does it work fine in GR off mode? More specifically does it pass signal and sound good?

If so, those TP22 readings on unit B would indicate bad solder joints at either your output pot, attack switch, or a bad joint, incorrect resistor on your ratio board or ratio connectors.  Have a close look.  If you can't find it we'll trace through it.

Mike
Seems like bad solder joints on input pot on Unit B the readings are now....

20 = 381.9
12 = 189.1
   8 = 128.3
   4 =    66.8

   
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 14, 2017, 11:26:07 AM
Seems like bad solder joints on input pot on Unit B the readings are now....

20 = 381.9
12 = 189.1
   8 = 128.3
   4 =    66.8

   

So can you calibrate now?  Is either unit working?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jdier on February 16, 2017, 04:48:37 PM
Q13 is crazy off.  You may want to replace it.

Just ordered new 2N3708's.   Will report back once i have one in.

Again, thanks for the support.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 16, 2017, 05:03:14 PM
Just ordered new 2N3708's.   Will report back once i have one in.

Again, thanks for the support.

Good luck!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RspenceT on February 16, 2017, 11:04:17 PM
Hi guys.
Just finished my second 1176 rev d rack build and I am glad to say the unit is working well with one small concern.
Compared to my other slightly older first gen build and to my vintage Urei unit, the input gain seems to be quite high. I have completed the calibration and the output seems to be  all good. But i seem to need very little gain to reach the compression threshold compared to the other units.  The input pot is right at the bottom of its travel and the output is high.
Could I have wired the input pot/pad wrong?
Seems to me that there is very little between the input and the q1 so perhaps I am not attenuating the input enough.

I have a very decent set of external meters for calibration and testing so I am certain that I am delivering +4dbm to the input.

As I say the unit otherwise is working perfectly. It is just that running the input down that low does not give me much flexibility of movement.
Normally I would run the input pot at around the 11 o'clock position. However on this unit it seems to want to run around  the 7 o'clock position  to produce the same gain reduction results.

Any insights would be much appreciated

Richard
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 16, 2017, 11:19:19 PM
Hi guys.
Just finished my second 1176 rev d rack build and I am glad to say the unit is working well with one small concern.
Compared to my other slightly older first gen build and to my vintage Urei unit, the input gain seems to be quite high. I have completed the calibration and the output seems to be  all good. But i seem to need very little gain to reach the compression threshold compared to the other units.  The input pot is right at the bottom of its travel and the output is high.
Could I have wired the input pot/pad wrong?
Seems to me that there is very little between the input and the q1 so perhaps I am not attenuating the input enough.

I have a very decent set of external meters for calibration and testing so I am certain that I am delivering +4dbm to the input.

As I say the unit otherwise is working perfectly. It is just that running the input down that low does not give me much flexibility of movement.
Normally I would run the input pot at around the 11 o'clock position. However on this unit it seems to want to run around  the 7 o'clock position  to produce the same gain reduction results.

Any insights would be much appreciated

Richard

Hi Richard,

One difference between your FET/RACK and a vintage unit...the input pot (t-pad attenuator) on the original units had a very odd taper. It’s not a taper you commonly see in potentiometers today. Your input attenuator has a more common taper, which leads it to be a little “hotter” earlier in the clockwise pot turn. Even compared to out old blue T-pad.

That said 7 o'clock seems low.  I suspect it's a combination of the hot input pot and our meter having a little more over shoot than the originals.  They have $150 meter in them, we decided not to go that route.  We feel like out meter is 90% as good at a fraction of the cost.

The meter should be a little more accurate in the full CW position and should show you less compression. Hard to say what is right because I don't know what your input level is compared to ours.

Mike

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ashtonv19 on February 19, 2017, 05:28:11 PM
Got ahead of myself and started a new thread before reading this thread!!  Sorry, I'll post my issue once again.


Just finished the build, cleaned up the wiring, calibrated, all is fine.  As soon as I attempt to test with a real track, I find that engaging the attack DRAMATICALLY reduces the output.  Also turning the output up past 24 results in a pop and nasty interference, pretty much with no output.  Completely reset the trim pots and tried calibration again, voltages on the money.  Same issue persists.  With the attack off, signal is fine until the same output threshold is reached, then the pop and noise is there once again.  Everything on the PCB looks fine, nothing is melting, no smoke.

Help?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: tkobrick on February 21, 2017, 12:18:59 AM
I got through 99% of the build this weekend on a pair of Rev. Ds.  Amazing instructions, BTW.  A couple of quick questions:

Question 1 - Build Guide says there will be a pair of 2n3707 transistors that are taped together because they have been matched, to use for Q12 and Q13.  Neither of my kits had a pair taped together, so I avoided putting any 2n3707s in for now - do I need to try and match the transistors myself, or are they all close enough to use any 2?

Question 2 - I put in header pins for the match pair of FETs for Q1 and Q11.  Instructions say to put the FETs in the header pins and solder.  Is this correct?  I should solder the FETs in the headers?  Want to make sure this is not a typo.

Thanks!  Can't wait to finish these puppies!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 21, 2017, 11:38:06 AM
Got ahead of myself and started a new thread before reading this thread!!  Sorry, I'll post my issue once again.


Just finished the build, cleaned up the wiring, calibrated, all is fine.  As soon as I attempt to test with a real track, I find that engaging the attack DRAMATICALLY reduces the output.  Also turning the output up past 24 results in a pop and nasty interference, pretty much with no output.  Completely reset the trim pots and tried calibration again, voltages on the money.  Same issue persists.  With the attack off, signal is fine until the same output threshold is reached, then the pop and noise is there once again.  Everything on the PCB looks fine, nothing is melting, no smoke.

Help?

Pretty stumped on this one.

If it calibrated normally, and the voltages are normal, it should work fine. However, what you are describing is not at all normal.

Check all the connector headers, especially the 6 pin, for shorts or bad joints. Make sure the pcb has been cleaned of flux.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 21, 2017, 11:40:08 AM
I got through 99% of the build this weekend on a pair of Rev. Ds.  Amazing instructions, BTW.  A couple of quick questions:

Question 1 - Build Guide says there will be a pair of 2n3707 transistors that are taped together because they have been matched, to use for Q12 and Q13.  Neither of my kits had a pair taped together, so I avoided putting any 2n3707s in for now - do I need to try and match the transistors myself, or are they all close enough to use any 2?

Question 2 - I put in header pins for the match pair of FETs for Q1 and Q11.  Instructions say to put the FETs in the header pins and solder.  Is this correct?  I should solder the FETs in the headers?  Want to make sure this is not a typo.

Thanks!  Can't wait to finish these puppies!

Q1: Weird, not sure what happened there. If you have a meter with a HFE function, use that to match them. If not just try a random pair. If you can calibrate the meter, all is good. If not send us an email.

Q2: That is a type-0...do not solder the FETs in the pins.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ashtonv19 on February 21, 2017, 12:59:11 PM
Pretty stumped on this one.

If it calibrated normally, and the voltages are normal, it should work fine. However, what you are describing is not at all normal.

Check all the connector headers, especially the 6 pin, for shorts or bad joints. Make sure the pcb has been cleaned of flux.

Mike

The only real struggle I had with a JST was CN10, I could barely get the leads halfway through the PCB.  There was no kink in the outside leads as the build guide suggested.  So perhaps that's the culprit.  All the other headers dropped in nicely.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 21, 2017, 01:15:47 PM
The only real struggle I had with a JST was CN10, I could barely get the leads halfway through the PCB.  There was no kink in the outside leads as the build guide suggested.  So perhaps that's the culprit.  All the other headers dropped in nicely.

So does the attack and release daughter board fit ok?

Do you get the weird noise with the unit in GR off mode?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ashtonv19 on February 21, 2017, 01:30:00 PM
So does the attack and release daughter board fit ok?

Do you get the weird noise with the unit in GR off mode?

Mike

The attack/return board fits fine, nothing is being strained.  CN10 is sitting 1 or 2mm off the PCB. 

Yes, I get the noise in any configuration regardless of meter, ratio, or attack/release, even with no signal present.  I can try to record a sample and send it later.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 21, 2017, 01:44:12 PM
The attack/return board fits fine, nothing is being strained.  CN10 is sitting 1 or 2mm off the PCB. 

Yes, I get the noise in any configuration regardless of meter, ratio, or attack/release, even with no signal present.  I can try to record a sample and send it later.

I doubt it would help to hear it.

With a 1K/0dB tone at the input, set your unit to:

in and out at 12 o'clock
attack in GR OFF
release FCW
20:1
Meter: GR

What is your AC V at TP1, TP15, TP17 and out + with respect to ground (chassis).

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: YoDudeRock on February 22, 2017, 10:23:07 PM
Mike,
    Thank you,  you were right, it was two separate issues.  And I got the meter working, I was a little sloppy with my solder and created a short.  That's fixed.
I thought everything was fine and got it calibrated with no problem, but realized when I twisted the Output knob, while in +4 or +8 meter mode,  the needle bounces.    All with The rumble is still there.

BTW, I have another working unit, to compare readings.
So, I checked the resistance on the R23 output resistor and it shows odd readings
It reads maximum around 38K ohms, but my working unit reads 128K ohms.
Another anomaly is,  the C7 Orange Drop capacitor reads 15VDC on one side and 2VDC on the other
My working unit reads 15VDC and 0VDC .
I was wondering if the Orange Drop is bad or the R23 potentiomenter is bad.

What do you think?   I hope all that makes sense.

Thanks,
Chris

Sounds like you have 2 issues.

Issue 1: Meter sits left in GR mode, is most likely an issue with your GR AMP section.
Issue 2: Rumble. No idea...are you passing signal?  How did calibration go?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 22, 2017, 10:32:57 PM
Mike,
    Thank you,  you were right, it was two separate issues.  And I got the meter working, I was a little sloppy with my solder and created a short.  That's fixed.
I thought everything was fine and got it calibrated with no problem, but realized when I twisted the Output knob, while in +4 or +8 meter mode,  the needle bounces.    All with The rumble is still there.

BTW, I have another working unit, to compare readings.
So, I checked the resistance on the R23 output resistor and it shows odd readings
It reads maximum around 38K ohms, but my working unit reads 128K ohms.
Another anomaly is,  the C7 Orange Drop capacitor reads 15VDC on one side and 2VDC on the other
My working unit reads 15VDC and 0VDC .
I was wondering if the Orange Drop is bad or the R23 potentiomenter is bad.

What do you think?   I hope all that makes sense.

Thanks,
Chris

That rumble is probably DC getting into the pot then. You shouldn't have DC in your pot, C7's job is to block that DC on the side. Though just because you have DC at the pot side of C7 it doesn't necessarily mean the DC is coming through the cap.  It could be come "backwards" from another location.

Do you get the rumble in GR OFF mode? (attack FCW)

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ilfungo on February 23, 2017, 10:04:31 AM
Hi Mike
Just to understand the schematics
Where the last R59 pin go?
Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 11:21:35 AM
Hi Mike
Just to understand the schematics
Where the last R59 pin go?
Thanks!

On the Rev A, nowhere. Unconnected.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ilfungo on February 23, 2017, 12:01:53 PM
Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 12:38:27 PM
Hello all,

So I finished the build and went to power up and it doesn't turn on. After building the power supply I tested it with my DMM following the build guide and the readings were accurate to what they should be. Now as I'm trying to trouble shoot they don't read the same, and I'm not sure why, nor do I really know where to begin, so what do I do? Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 12:41:43 PM
Hello all,

So I finished the build and went to power up and it doesn't turn on. After building the power supply I tested it with my DMM following the build guide and the readings were accurate to what they should be. Now as I'm trying to trouble shoot they don't read the same, and I'm not sure why, nor do I really know where to begin, so what do I do? Thanks!

You said it doesn't turn on but you were able to test the voltages accurately?  That would not be possible.

Confirm your fuse is in and not blown, confirm your voltage select switch is set correctly, confirm your DMM is set to AC V.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 12:47:29 PM
You said it doesn't turn on but you were able to test the voltages accurately?  That would not be possible.

Confirm your fuse is in and not blown, confirm your voltage select switch is set correctly, confirm your DMM is set to AC V.

Mike

I tested the power supply. It was all good, so I continued pressing on. I had finished assembly and I was getting ready to calibrate, when I pressed from off to GR, no lights no needle movement, nothing so I plugged in some signal still nothing. So I figured I'd test the power supply again, and the ground reads good, 0.2. 30v reads 0 and -10v also reads 0.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 12:52:50 PM
I tested the power supply. It was all good, so I continued pressing on. I had finished assembly and I was getting ready to calibrate, when I pressed from off to GR, no lights no needle movement, nothing so I plugged in some signal still nothing. So I figured I'd test the power supply again, and the ground reads good, 0.2. 30v reads 0 and -10v also reads 0.

Is your fuse blown?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 01:01:29 PM
Is your fuse blown?

No.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 01:08:24 PM
No.

If your fuse is not blown then something has changed since you last tested it.

Make sure all of your L brackets are installed and look for suspicious solder joints, bridges, bad connector connections.

You're just going to have to go over with a fine toothed comb.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 01:18:27 PM
Disconnect the 5 pin power header from the main PCB and see if you can measure the AC V between the middle yellow wire and each of the orange wires. Common probe on yellow.

Again disconnected from he PCB. You'll need to have thin meter probes to get in the connector.

Be very careful.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 01:31:56 PM
Disconnect the 5 pin power header from the main PCB and see if you can measure the AC V between the middle yellow wire and each of the orange wires. Common probe on yellow.

Again disconnected from he PCB. You'll need to have thin meter probes to get in the connector.

Be very careful.

Mike

Where exactly am i putting the probes? In the in the connector? If so, they don't fit.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 01:44:20 PM
Where exactly am i putting the probes? In the in the connector? If so, they don't fit.

Yes.

Not much I can say if your unit won't power up, the fuse it fine, and it was working early.  I'd have to look at, but obviously there is a cost to that. 

If you're super careful, you can disconnect the power transformer from the IEC and test the AC  V where the black connect would be (bottom tab) against the chassis ground.  You should have 120V AC there.

That's mains voltage so be very careful.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 01:49:23 PM
Yes.

Not much I can say if your unit won't power up, the fuse it fine, and it was working early.  I'd have to look at, but obviously there is a cost to that. 

If you're super careful, you can disconnect the power transformer from the IEC and test the AC  V where the black connect would be (bottom tab) against the chassis ground.  You should have 120V AC there.

That's mains voltage so be very careful.

Mike



I do have power coming in! I got a reading of 126.5 AC Volts. That sounds high.. but that's testing the IEC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 01:58:19 PM
I do have power coming in! I got a reading of 126.5 AC Volts. That sounds high.. but that's testing the IEC

Connect everything back like it should be, including the secondary of the power tx.

Now measure the AC at the secondary with the unit on (GR Mode). Test each of the orange wires compared agains chassis ground. You can test on the PCB since it's connected now.

What do they read?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 02:33:51 PM
Connect everything back like it should be, including the secondary of the power tx.

Now measure the AC at the secondary with the unit on (GR Mode). Test each of the orange wires compared agains chassis ground. You can test on the PCB since it's connected now.

What do they read?

Mike

They both read 0....
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 02:59:26 PM
So your mains supply voltage is dying between your IEC inlet and the PCB.

WITH THE UNIT UNPLUGGED. NO POWER.

1 . Measure the DC resistance (Ω) between the yellow wire and each of the oranges.
2. Measure the DC resistance (Ω) between the two outer pins of the 3 pin connector at the top of the voltage select PCB.  You can remove the header to get at the pins.

For both measurements you need to have the 5 pin secondary and 7 pin primary power TX headers plugged into those PCBS.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 03:18:43 PM
They both read 0....

The orange wires read 11.3 and 11.4
The putter wires on the 5 pin read  11.4

The 3 pin connector will not give a read.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 03:27:06 PM
The orange wires read 11.3 and 11.4
The putter wires on the 5 pin read  11.4

The 3 pin connector will not give a read.

What about the DC R between the two voltage select switch pins on the left side of the V select PCB (looking from the front of the compressor)...again two left pins top and bottom.

No power, make sure the 7 pin connector is plugged into the same PCB.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 03:37:44 PM
What about the DC R between the two voltage select switch pins on the left side of the V select PCB (looking from the front of the compressor)...again two left pins top and bottom.

No power, make sure the 7 pin connector is plugged into the same PCB.

are you talking about the 2 pins connected to the IEC? The 2 left pins on the IEC give no read, the 2 right pins on the IEC give a read of 1.1.

None of the pins on CN14 on the V Select PCB give a read no matter which configuration I try.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 03:44:27 PM
are you talking about the 2 pins connected to the IEC? The 2 left pins on the IEC give no read, the 2 right pins on the IEC give a read of 1.1.

None of the pins on CN14 on the V Select PCB give a read no matter which configuration I try.

You've either got an issue with you V select PCB soldering, the switch itself, or you power transformer (which would be weird).  You could try flipping the switch to 230 then back to 115 to see if the switch is just un seated.  Then try re flowing those joints on that PCB.

If that fails you'll have to email us.  You'll probably need to send in the power transformer so we can check it.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 03:46:11 PM
You've either got an issue with you V select PCB soldering, the switch itself, or you power transformer (which would be weird).  You could try flipping the switch to 230 then back to 115 to see if the switch is just un seated.  Then try re flowing those joints on that PCB.

If that fails you'll have to email us.  You'll probably need to send in the power transformer so we can check it.

Mike

Ok let me try all of that and see what happens! Thanks for everything Mike!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on February 23, 2017, 04:05:46 PM
Ok let me try all of that and see what happens! Thanks for everything Mike!

Ok so just to be thorough, I resoldered Everything on  the V Select PCB, plugged everything back in, pushed the switch to 230 and back and powered to (GR) still nothing. Not even a smell or a smoke or nothin.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 04:13:12 PM
Ok so just to be thorough, I resoldered Everything on  the V Select PCB, plugged everything back in, pushed the switch to 230 and back and powered to (GR) still nothing. Not even a smell or a smoke or nothin.

Send us an email with your address.  I'm going to send you a label to send in the V select PCB assembly and power transformer to test for you.

I *think* there may be an issue with your transformer.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: YoDudeRock on February 23, 2017, 07:32:34 PM
Mike,
It still happens with GR off (full CCW, click) and GR on.     It does get quieter with compression on.   The needle bounces with when turning the Output knob (in +4 and +8 meter mode).    In GR meter mode, the meter doesn't move at all, so it seems like the noise or isn't going through the compression circuit.
Thanks!
Chris

That rumble is probably DC getting into the pot then. You shouldn't have DC in your pot, C7's job is to block that DC on the side. Though just because you have DC at the pot side of C7 it doesn't necessarily mean the DC is coming through the cap.  It could be come "backwards" from another location.

Do you get the rumble in GR OFF mode? (attack FCW)

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 07:36:31 PM
Mike,
It still happens with GR off (full CCW, click) and GR on.     It does get quieter with compression on.   The needle bounces with when turning the Output knob (in +4 and +8 meter mode).    In GR meter mode, the meter doesn't move at all, so it seems like the noise or isn't going through the compression circuit.
Thanks!
Chris

C7, C8, and C17 should prevent DC from getting into you pot.

Check to make sure there are no solder bridges in their leads, and if polarized, they are inserted right.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jdier on February 23, 2017, 08:51:01 PM
Q13 is crazy off.  You may want to replace it.

OK, ordered and installed new 2N3708 for Q13.   Readings about the same.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 23, 2017, 08:54:44 PM
OK, ordered and installed new 2N3708 for Q13.   Readings about the same.

Check everything in the meter section including solder joints and values.  Check for continuity between traces.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cyberlogic on February 24, 2017, 05:16:18 PM
I doubt it would help to hear it.

With a 1K/0dB tone at the input, set your unit to:

in and out at 12 o'clock
attack in GR OFF
release FCW
20:1
Meter: GR

What is your AC V at TP1, TP15, TP17 and out + with respect to ground (chassis).

Mike
What should these be reading for a Rev A unit?

On both recent builds (A and B), I get (All VAC, ref to chassis GND):-
TP1: A-.140V, B-.145V
TP15: A- 3.72V, B- 3.72V
TP17: A- .67V, B- .71V

Output + to -: A- 10.23V, B- 10.90V

But the output is clipped, I have to reduce the input to around 34 to get rid of clipping and drop out to around 7.30V (+20dBu). Seems like the input gain is too high?

Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 24, 2017, 06:16:05 PM
What should these be reading for a Rev A unit?

On both recent builds (A and B), I get (All VAC, ref to chassis GND):-
TP1: A-.140V, B-.145V
TP15: A- 3.72V, B- 3.72V
TP17: A- .67V, B- .71V

Output + to -: A- 10.23V, B- 10.90V

But the output is clipped, I have to reduce the input to around 34 to get rid of clipping and drop out to around 7.30V (+20dBu). Seems like the input gain is too high?

Thanks

That's about right what you're getting.

The input pot (t-pad attenuator) on the original units had a very odd taper. It’s not a taper you commonly see in potentiometers today. Our input attenuator has a more common taper, which leads it to be a little “hotter” earlier in the clockwise pot turn.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cyberlogic on February 24, 2017, 06:32:00 PM
OK, good to know the numbers are close.

With a 250mV input signal at 1KHz and the output at +4dBu, THD is around .23%. Pretty much the same at 10kHz. Increasing output doesn't add more distortion. The input seems to be the stage that is sensitive to over-driving.

With the taper on the new pot and the fact that this is typically used on line level signals, would reducing input gain a bit not be an option worth considering? I also see a lot of signal bounce when making level adjustments at the lower levels...

Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 24, 2017, 06:36:31 PM
OK, good to know the numbers are close.

With a 250mV input signal at 1KHz and the output at +4dBu, THD is around .23%. Pretty much the same at 10kHz. Increasing output doesn't add more distortion. The input seems to be the stage that is sensitive to over-driving.

With the taper on the new pot and the fact that this is typically used on line level signals, would reducing input gain a bit not be an option worth considering? I also see a lot of signal bounce when making level adjustments at the lower levels...

Thanks

Certainly, it's on my "to do" list.

The D doesn't see as much of an issue because of the decreased gain. Generally, we just lower the signal coming in a little to compensate but I do plan on documenting a mode as you're suggesting.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cyberlogic on February 24, 2017, 07:56:25 PM
What should these be reading for a Rev A unit?

On both recent builds (A and B), I get (All VAC, ref to chassis GND):-
TP1: A-.140V, B-.145V
TP15: A- 3.72V, B- 3.72V
TP17: A- .67V, B- .71V

Output + to -: A- 10.23V, B- 10.90V

But the output is clipped, I have to reduce the input to around 34 to get rid of clipping and drop out to around 7.30V (+20dBu). Seems like the input gain is too high?

Thanks

Also, it seems to me this would affect your recommended Q Bis procedure. With .775VA in, Input at 24, etc, there is significant clipping in the input stage, typically on the positive side of the waveform here.  Shouldn't this be done using a linear signal?

Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 24, 2017, 08:06:04 PM
Also, it seems to me this would affect your recommended Q Bis procedure. With .775VA in, Input at 24, etc, there is significant clipping in the input stage, typically on the positive side of the waveform here.  Shouldn't this be done using a linear signal?

Thanks

Not with the way the GR FET is configured and not at that level.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 24, 2017, 08:33:15 PM
I should also mention that this asymmetrical distortion is part of what makes the Rev A so desirable for some. This aggressiveness is why so many changes were made to the Rev B after the Rev A and Rev AB of which only about a couple hundred were ever made.

The addition of the source resistor to Q1, switching the gain stages from FET to all BJT's and lowering the gain were all done to tame the aggressive sound (clipping) of the A and AB.

The nature of this Rev A, A/B beast is to clip and sound aggressive.  That's why it's sought after for things like snare and electric distorted guitars. If you changed the circuit to remove the early clipping you'd just be making something closer to a Rev D. That difference is why we differentiate between the A and D. Then of course the F and G go further to clean the signal.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 24, 2017, 10:34:08 PM
One last thing before I quit for the weekend.

Ultimately it's just gain staging. I was just running a signal in at 0dBu and could turn the input past noon before clipping. I'm not sure if +4 was established as standard in 1967, when this circuit was designed, but the original manual uses 0dBu for calibration and you may be much happier operating around that level.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cyberlogic on February 27, 2017, 12:02:35 AM
Thanks Mike, I appreciate all the information and you taking the time to consider all this and write back to me.

I really just want to make sure it is working as it would be back in the day, warts and all.

ds
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 27, 2017, 12:12:17 AM
Thanks Mike, I appreciate all the information and you taking the time to consider all this and write back to me.

I really just want to make sure it is working as it would be back in the day, warts and all.

ds

Definitely, anytime.

With these guys you definitely feel like you're trying to hit a moving target because they often changed suppliers of caps, transistors, and transformers.  Back in those days they just popped in whatever they got a good deal on I imagine. We've tried to stay true to the circuit and components using all the info we could get and comparing to originals.

Sounds like your unit is working!

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cyberlogic on February 27, 2017, 01:01:35 PM
Another question:

How much should the release and ratio controls affect the signal when the gain reduction is OFF (attack pot switch)?

Thx
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 27, 2017, 01:11:38 PM
Another question:

How much should the release and ratio controls affect the signal when the gain reduction is OFF (attack pot switch)?

Thx

As you switch ratios you'll hear a small change as the circuit re-stabalizes.  About 0.5s. But it should settle back to the same level.

Rotating the release will probably change the level by about 0.1dB and maybe a slight change in THD+N. Minimal.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ganymedestudios on February 28, 2017, 08:51:05 PM
I finished the assembly of the kit and first tested the ground as instructed and it came back at 0.2 Ω so I moved onto switching the Meter to GR to test the Cathode and -10V diode, neither of them came out to the proper voltage. The cathode that was supposed to be +30V is only +16V and the -10V diode is -6V. Any ideas what the problem could be?

Side note, earlier in the build, I broke a trace and fixed it by soldering some copper wire to the terminals that the trace connected. (Not sure if this could be causing the problem).
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 28, 2017, 08:55:13 PM
I finished the assembly of the kit and first tested the ground as instructed and it came back at 0.2 Ω so I moved onto switching the Meter to GR to test the Cathode and -10V diode, neither of them came out to the proper voltage. The cathode that was supposed to be +30V is only +16V and the -10V diode is -6V. Any ideas what the problem could be?

Side note, earlier in the build, I broke a trace and fixed it by soldering some copper wire to the terminals that the trace connected. (Not sure if this could be causing the problem).

Make sure the broken trace didn't have more connections coming off it. They are not always point A to point B. Sometimes they are Point A to point B, C, and D. Check both side of the board and check the schematic to confirm.

With the unit ON, what is your AC V between ground and each orange secondary wire?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ganymedestudios on February 28, 2017, 09:10:37 PM
Make sure the broken trace didn't have more connections coming off it. They are not always point A to point B. Sometimes they are Point A to point B, C, and D. Check both side of the board and check the schematic to confirm.

With the unit ON, what is your AC V between ground and each orange secondary wire?

Mike


The voltage between the ground and orange secondary wire seems to be -0.001V. The trace that I replaced was from R26 to C12. It doesn't appear to have any other connections but I'll keep looking.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 28, 2017, 09:16:50 PM

The voltage between the ground and orange secondary wire seems to be -0.001V. The trace that I replaced was from R26 to C12. It doesn't appear to have any other connections but I'll keep looking.

There are two orange wires on the secondary.  They should each have their own voltage. Are you measuring AC?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ganymedestudios on February 28, 2017, 09:38:01 PM
Sorry I must've been measuring the wrong wires, if you're talking about the orange wires running from the transformer, the measurements are 6.3V and 11V And no, I've been measuring in AC.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 28, 2017, 09:45:27 PM
Sorry I must've been measuring the wrong wires, if you're talking about the orange wires running from the transformer, the measurements are 6.3V and 11V And no, I've been measuring in AC.

Are you able to safely measure those two orange wires with the secondary disconnected from the main PCB. Like can you get your probe into the contacts where it goes into the white plastic header?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 28, 2017, 09:50:00 PM
Make sure your voltage selector switch is set right.

115 - Americas
230 - EU
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ganymedestudios on February 28, 2017, 10:30:57 PM
I did have it set incorrectly. Weird, I could've swore I followed those instructions early on in the process thoroughly. The cathode is now reaching 29.75 V, however the Diode is sitting around 0V though. Thank you for all the help, I appreciate it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 28, 2017, 10:35:50 PM
I did have it set incorrectly. Weird, I could've swore I followed those instructions early on in the process thoroughly. The cathode is now reaching 29.75 V, however the Diode is sitting around 0V though. Thank you for all the help, I appreciate it.

So your negative voltage still isn't sitting right?

Confirm all the diodes and 2 1K resistors are soldered correctly and the diodes are pointing in the correct directions.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ganymedestudios on February 28, 2017, 11:21:27 PM
I made sure the 1K resistors are correctly soldered and the diodes and now the voltage for the -10V diode is spiking from +6V to +0.5V.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 28, 2017, 11:37:51 PM
I made sure the 1K resistors are correctly soldered and the diodes and now the voltage for the -10V diode is spiking from +6V to +0.5V.

Ohhhhhh your whole board is stuffed.  i though you just had the power supply in.

That changes things.  You may have an error in your build dragging down the neg supply or a damaged component. So you were getting -6V DC now you're getting +6V DC to +0.5 V DC?

Mike


Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ganymedestudios on February 28, 2017, 11:45:18 PM
Yeah, sorry I thought I mentioned that in the first post. That's why I brought up the broken trace that I had fixed, thinking that might be the cause of it. Sorry for the confusion but now the -10V diode seems to be sitting right on 0 or -0.1 or so.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on February 28, 2017, 11:57:39 PM
Yeah, sorry I thought I mentioned that in the first post. That's why I brought up the broken trace that I had fixed, thinking that might be the cause of it. Sorry for the confusion but now the -10V diode seems to be sitting right on 0 or -0.1 or so.

That trace is a concern, there are a few traces between those two components. However, I don't think any of them sit on the neg rail so I don't think it would be the cause.

It's really hard to say. I'd have to look at.

You could check around R35, R60, and the Qbias for shorts or bad values. Check anything that sits near the negative rail. These neg rail issues ones are tough.  I assume you built and tested the supply first and it tested fine, at this point you need to double check all of your component values, placement, soldering etc.

You could always try replacing CR9 as a hail mary. That would probably be where I'd start if you sent it in.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ganymedestudios on March 01, 2017, 12:01:50 AM
Actually I did not check the power supply before populating the rest of the board so I suppose thats something I messed up.  I'll keep messing with it a little bit and if I can't figure it out, I'll probably just end up sending it in and learning my lesson for the next time I do this build.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 01, 2017, 12:06:11 AM
Actually I did not check the power supply before populating the rest of the board so I suppose thats something I messed up.  I'll keep messing with it a little bit and if I can't figure it out, I'll probably just end up sending it in and learning my lesson for the next time I do this build.

Ya it's critical to test the supply first.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: bazmcc on March 01, 2017, 02:29:28 PM
Hi all,

Just completed the build but having a couple of issues when beginning to cal the unit. I have an experienced tech friend who has looked at it but I have a couple of questions;

- When measuring VAC/dBU across the input XLR, my friend's Audio Precision sig gen / meter measures a drop of approx 7dBU as soon as I plug into the 1176, even when not powered up. Seems to be something like a dead short but beep testing across points suggests everything is good and there are no shorts. Any advice?

- Should the input transformer measure 50 ohms between XLR input points 2 & 3?

Thanks all!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 01, 2017, 02:50:09 PM
Hi all,

Just completed the build but having a couple of issues when beginning to cal the unit. I have an experienced tech friend who has looked at it but I have a couple of questions;

- When measuring VAC/dBU across the input XLR, my friend's Audio Precision sig gen / meter measures a drop of approx 7dBU as soon as I plug into the 1176, even when not powered up. Seems to be something like a dead short but beep testing across points suggests everything is good and there are no shorts. Any advice?

- Should the input transformer measure 50 ohms between XLR input points 2 & 3?

Thanks all!

When you don't have the AP plugged into anything it's unloaded. As soon as you plug it into the FET/RACK (powered or not) it now has a load.  Loading the signal generator will lower its output.  It's really a factor of the output impedance of the AP vs the input impedance of the FET/RACK that determines the signal drop.

If you want to lower this effect, lower the output impedance of the AP as much as you can (50Ω). You will not completely get rid of it though. You can still see a drop of 1 to 2dBu.

When you measure the resistance between 2 and 3 you're measuring the DC resistance which is different than AC impedance (which is higher). 50Ω of DC R on the primary sounds about right.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on March 05, 2017, 11:54:48 AM
I'm on the build of my 2nd RevA FET Rack and just finished building the power supply.  The first unit went well, though I've not calibrated it yet.  On this build I'm getting:

- IEC Inlet = 0.2 ohms as expected
- cathode of CR8 = +30V DC as expected
-  CR9 = -41.65V DC where I should have -10V

I double checked the C9 solder and it seemed fine.  I then tested the two 1K resistors (R81, R82).  I'm not getting a reading from R82.  Do I need to de-solder or anything to get a proper read?  R81 came back fine.  I think R82 is faulty.  Would that cause the faulty diode reading at C9?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 05, 2017, 12:27:45 PM
I'm on the build of my 2nd RevA FET Rack and just finished building the power supply.  The first unit went well, though I've not calibrated it yet.  On this build I'm getting:

- IEC Inlet = 0.2 ohms as expected
- cathode of CR8 = +30V DC as expected
-  CR9 = -41.65V DC where I should have -10V

I double checked the C9 solder and it seemed fine.  I then tested the two 1K resistors (R81, R82).  I'm not getting a reading from R82.  Do I need to de-solder or anything to get a proper read?  R81 came back fine.  I think R82 is faulty.  Would that cause the faulty diode reading at C9?

Best option would be to lift one leg on R82 off the PCB then test the Ω across the 2 legs.  You should get the 1K reading.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on March 05, 2017, 02:25:50 PM

I'm on the build of my 2nd RevA FET Rack and just finished building the power supply.  The first unit went well, though I've not calibrated it yet.  On this build I'm getting:

- IEC Inlet = 0.2 ohms as expected
- cathode of CR8 = +30V DC as expected
-  CR9 = -41.65V DC where I should have -10V

I double checked the C9 solder and it seemed fine.  I then tested the two 1K resistors (R81, R82).  I'm not getting a reading from R82.  Do I need to de-solder or anything to get a proper read?  R81 came back fine.  I think R82 is faulty.  Would that cause the faulty diode reading at C9?
Best option would be to lift one leg on R82 off the PCB then test the Ω across the 2 legs.  You should get the 1K reading.

Thank you.  I did that and got 1K as expected.  I did get a bit of a pop when removing my DMM probe.  That leads me to a new question.  How do I discharge the board when taking it out to continue work on it?  I hope that hasn't damaged anything.

And back to the original question: What else should I test regarding the -41.65V DC reading on CR9?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 05, 2017, 02:39:39 PM
Thank you.  I did that and got 1K as expected.  I did get a bit of a pop when removing my DMM probe.  That leads me to a new question.  How do I discharge the board when taking it out to continue work on it?  I hope that hasn't damaged anything.

And back to the original question: What else should I test regarding the -41.65V DC reading on CR9?

You can connect the across the terminals of the power supply caps with some insulated wire in series with a higher W resistor. Like 10K/5W. You can think about the charge across the power caps and relation to ohms law to make sure you have a reasonable W resistor that will work.

There are some other methods (insulated screwdriver) but I'll let you google that and decide for yourself if you think that's safe.

Seems like you're measuring closer to what the unregulated/dropped voltage would be directly off the secondary on the neg rail. You're using the chassis as your ground reference? You have all 3 L-Brackets securing the PCB to the enclosure (some of these have an grounding function)?

What is your DC voltage on all 4 of the 1K resistor pads?

Mike



Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on March 05, 2017, 03:07:50 PM
You can connect the across the terminals of the power supply caps with some insulated wire in series with a higher W resistor. Like 10K/5W. You can think about the charge across the power caps and relation to ohms law to make sure you have a reasonable W resistor that will work.

There are some other methods (insulated screwdriver) but I'll let you google that and decide for yourself if you think that's safe.

Seems like you're measuring closer to what the unregulated/dropped voltage would be directly off the secondary on the neg rail. You're using the chassis as your ground reference? You have all 3 L-Brackets securing the PCB to the enclosure (some of these have an grounding function)?

What is your DC voltage on all 4 of the 1K resistor pads?

Mike


Thanks for the quick reply, Mike!  Brilliant!  I don't know why, but I only secured 2 of the l-brackets.  I'll be that is it.  Thank you.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 05, 2017, 03:16:37 PM
Thanks for the quick reply, Mike!  Brilliant!  I don't know why, but I only secured 2 of the l-brackets.  I'll be that is it.  Thank you.

Nice!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on March 05, 2017, 03:50:19 PM

Seems like you're measuring closer to what the unregulated/dropped voltage would be directly off the secondary on the neg rail. You're using the chassis as your ground reference? You have all 3 L-Brackets securing the PCB to the enclosure (some of these have an grounding function)?

What is your DC voltage on all 4 of the 1K resistor pads?

Mike


Unfortunately that was not it.  Still measuring -45V range

4 Pads
R81 = -45.17 & -45.13
R82 = -45.36 & -45.19
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 05, 2017, 03:55:43 PM
Unfortunately that was not it.  Still measuring -45V range

4 Pads
R81 = -45.17 & -45.13
R82 = -45.36 & -45.19

You're not dropping any voltage across your resistors which would mean you're not drawing current on your negative rail.  I would suspect the zener diode (CR9).  Confirm it's soldered well, the pads look good, and it's oriented correctly. If all that looks good you may want to replace it. Email me for a new one.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Manswikenmo on March 06, 2017, 07:32:18 AM
Hi!
I just finished my two FET/RACK rev A kits. One is working perfectly and sounds amazing, but the other one is behaving really strange.. I have checked so that all the resistors, transistors, caps etc is at the right place in the right way and compared with the compressor that is working, there is no visual difference between the two.

The problems are as follows:
- The unit passes adio and the sound quality is good, no distortion or strange frequency response, but the signal is quite low.

- There is no compression happening what so ever.

- Also the meter is acting strange. In +8 and +4 mode it works fine, but in GR mode the meter stays at -20 even with "R71" full CW. When switching from "normal operation" to "calibration operation" the meter reaches -3 with R71 full CW.

- I haven't been able to do any of the three calibration steps.
Step 1: When I am adjusting the Q-bias (R59) nothing happens.
Step 2: With R75 full CCW and R71 full CCW I measure 0,922V across TP10/TP11. With R71 full CW and R75 full CCW I measure 1,379V.
Step 3: Since the meter stays at -20 in "normal operation" its not possible to do this step. And as written before, there is no compression going on.

I measured the voltages at the transistors and compared to your document, around Q12 and Q13 it looks REALLY strange but at the other places it seems quite ok. The PDF is attached, my measurements is in green.

Anyone have an idea of what could be the problem? Since everything is soldered the same way in the one not working as in the one that works my guess is that some component is broken, but witch one??

Any help is really appreciated!

Kindly
/Måns

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 06, 2017, 07:33:36 PM
Hi,

We need to get you calibrated, so let's start by looking at why your qbias in't working right.

With the unit powered on, what is your DC V at Pad 18 as you turn the Qbias?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Manswikenmo on March 07, 2017, 08:57:25 AM
Hi,

We need to get you calibrated, so let's start by looking at why your qbias in't working right.

With the unit powered on, what is your DC V at Pad 18 as you turn the Qbias?

Mike

I get 0V with qbias ccw and cw.

Måns
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 07, 2017, 10:06:06 AM
I get 0V with qbias ccw and cw.

Måns

Is your -10VDC power supply point testing ok?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Manswikenmo on March 07, 2017, 11:32:22 AM
Is your -10VDC power supply point testing ok?

Yes. The powersuply is working properly ad measures correctly.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 07, 2017, 12:18:12 PM
Yes. The powersuply is working properly ad measures correctly.

What's your DC V on either side of R83 and R60?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nsemanchik on March 11, 2017, 05:05:26 PM
Hello, this is my first post on this forum! I recently completed a Rev A kit, it powers on and passes audio. When I began to calibrate it I noticed that there was a very low output and high noise floor. I double checked all of my resistors, caps and transistors and they all are all in the correct positions. The goal of this build was to learn more about electronics so I would really like to be able to resolve this issue on my own before I send it out. Any thoughts or input?

Thank you!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 12, 2017, 09:09:32 PM
Finished my first DIY build on the 1176 Rev A. Powered it on, no smoke. Began the calibration procedure and got 1khz 0 dBu signal to input (verified by voltage and hz on DMM). However, when I went to measure the output, I couldn't even get 1 VAC, even with the output maxed. I am getting audible signal through the compressor and out of my system.

Power supply is good with 30.4 VDC at CR8 and -9.7VDC at CR9.

Checked voltage at base and emitters of transistors and received:

Q3:    -.590
Q5:   -.574
Q6:   -.509
Q7:   -.576
Q8:   -.604
Q9:   -.602
Q10:   -.610
Q12:   -.611
Q13:   -.578

As the expect result is -.7, are these values within tolerance? I am going to check the rest of the voltages provided by MNATS and check all my components for connectivity,  and solder joints. I double checked the polarity and value of all components during assembly, but will check that as well.

Thanks so much for your help!!
k

Title: Re: [BUILD] New FET/RACK Official Help Thread - Calibration
Post by: Dacey on March 13, 2017, 05:44:24 AM
FET/RACK calibration stage.
a) I can only get 0.677VAC on DMM at input, should be 0.755VAC. With the Input signal disconnected I get 1.5VAC.??
b)Metering the  Gain Reduction on any Ratio setting results in a max vu meter reading. Input and Output dials set to infinity is this normal? 
Please can to provide clues on were the fault(s) might be.
Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 01:29:04 PM
Hello, this is my first post on this forum! I recently completed a Rev A kit, it powers on and passes audio. When I began to calibrate it I noticed that there was a very low output and high noise floor. I double checked all of my resistors, caps and transistors and they all are all in the correct positions. The goal of this build was to learn more about electronics so I would really like to be able to resolve this issue on my own before I send it out. Any thoughts or input?

Thank you!


Start with the unit in GR OFF mode. Input a 0dBu 1kHz signal as described in the calibration guide. Using chassis GRN as your reference, what is the AC V:

TP1, TP15, TP17, Output Brown

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 01:30:10 PM
Finished my first DIY build on the 1176 Rev A. Powered it on, no smoke. Began the calibration procedure and got 1khz 0 dBu signal to input (verified by voltage and hz on DMM). However, when I went to measure the output, I couldn't even get 1 VAC, even with the output maxed. I am getting audible signal through the compressor and out of my system.

Power supply is good with 30.4 VDC at CR8 and -9.7VDC at CR9.

Checked voltage at base and emitters of transistors and received:

Q3:    -.590
Q5:   -.574
Q6:   -.509
Q7:   -.576
Q8:   -.604
Q9:   -.602
Q10:   -.610
Q12:   -.611
Q13:   -.578

As the expect result is -.7, are these values within tolerance? I am going to check the rest of the voltages provided by MNATS and check all my components for connectivity,  and solder joints. I double checked the polarity and value of all components during assembly, but will check that as well.

Thanks so much for your help!!
k

Same answer as above. Check those test points.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 01:32:24 PM
Set-up stage.  I can only get 0.677VAC on DMM at input, should be 0.755VAC, Input signal disconnected 1.5VAC.
Metering the  Gain Reduction on any Ratio setting results in a max uv meter reading. Input and Output dials set to infinity. 
Please can to provide clues on were the fault might be.
Thanks

What is your signal source?  The input of the FET/RACK is loading it, that's why you get the drop.

If it's not calibrated, ignore the meter. With this unit, the calibration is no fine tune adjustment, it's the difference between it working, and not working at all.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 13, 2017, 03:47:09 PM
Hi there, I hope I'm posting in the right place :-)

I'm pumped to be in the DIY world, its been awesome...until now :-/ haha

I'm just finishing the power supply on the 1176 rev A and after the first test, I'm getting these  results: CR8= 2.13v  CR9= -0.54v
I turned the power off and got the same results at CR8 & CR9
I'm getting .1 ohms on the IEC ground tab.

I also probed the hot wires following the 120v signal all the way to the transformer, then after the transformer i'm getting nothing...not even sure if thats a proper way to troubleshoot a PCB :-) just an oldschool way of thinking...any help getting me back in the studio doing what I love?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 03:53:01 PM
Hi there, I hope I'm posting in the right place :-)

I'm pumped to be in the DIY world, its been awesome...until now :-/ haha

I'm just finishing the power supply on the 1176 rev A and after the first test, I'm getting these  results: CR8= 2.13v  CR9= -0.54v
I turned the power off and got the same results at CR8 & CR9
I'm getting .1 ohms on the IEC ground tab.

I also probed the hot wires following the 120v signal all the way to the transformer, then after the transformer i'm getting nothing...not even sure if thats a proper way to troubleshoot a PCB :-) just an oldschool way of thinking...any help getting me back in the studio doing what I love?

Unplug the power transformer at both ends.  No need for power.  If you can get your probes into the contacts, measure the DC resistance (Ω) between WHT-BLK and RED-BRN on the primary, then ORG-ORG on the secondary.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 03:53:56 PM
Same answer as above. Check those test points.

Mike, not sure what you mean by GR OFF mode. I have the unit on with the GR button released (also  +8 and +4). Voltages are:

TP1 -       .1 VDC
TP15       .2 VDC
TP17       0.0 VDC (and starts to pick up radio signals)
Out Brown     27.7 VDC

Voltages are the same with GR button in.
Thanks Mike!!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 04:05:13 PM
Mike, not sure what you mean by GR OFF mode. I have the unit on with the GR button released (also  +8 and +4). Voltages are:

TP1 -       .1 VDC
TP15       .2 VDC
TP17       0.0 VDC (and starts to pick up radio signals)
Out Brown     27.7 VDC

Voltages are the same with GR button in.
Thanks Mike!!

Attack switched off = GR off.

Measure AC not DC volts.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 13, 2017, 04:10:18 PM
Hey Mike!
It's funny. As I purchased my second Rev D I pictured you being like "Not this guy again!" Haha. So I'm into the ever so treacherous calibration mode and I can't get R71 to zero. I checked all resistors last night and everything seems to be in its proper place. Am about to begin checking all capacitors but wanted to seek your wizardry for guidance. Also, where can I find the expected values for each test point. Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 04:12:56 PM
Hey Mike!
It's funny. As I purchased my second Rev D I pictured you being like "Not this guy again!" Haha. So I'm into the ever so treacherous calibration mode and I can't get R71 to zero. I checked all resistors last night and everything seems to be in its proper place. Am about to begin checking all capacitors but wanted to seek your wizardry for guidance. Also, where can I find the expected values for each test point. Thanks!

That's the 0 VDC adjustment?  Did you have matched 2N3707/2N37078 transistors in Q11/13?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 13, 2017, 04:40:00 PM
Unplug the power transformer at both ends.  No need for power.  If you can get your probes into the contacts, measure the DC resistance (Ω) between WHT-BLK and RED-BRN on the primary, then ORG-ORG on the secondary.

Mike

Ok, so I'm getting OLΩ between WHT-BLK and OLΩ between RED-(BLUE) I didn't see a brown :-)
then I got 22.5Ω between ORG-ORG
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 04:48:37 PM
Ok, so I'm getting OLΩ between WHT-BLK and OLΩ between RED-(BLUE) I didn't see a brown :-)

That ain't right.  Should be roughly 100Ω for each.

Sure you're getting to the contacts?  You may have to send that power transformer in.  Email us.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 13, 2017, 05:05:10 PM
That's the 0 VDC adjustment?  Did you have matched 2N3707/2N37078 transistors in Q11/13?

Mike

I'm using the Mouser BOM so I believe Q2-Q4 and Q14 were 2N3391A, Q5, Q7-Q10 and Q12-Q13 are 2N3708, Q6 is 2N3053 and Q11 is 2N5457.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 05:10:15 PM
I'm using the Mouser BOM so I believe Q2-Q4 and Q14 were 2N3391A, Q5, Q7-Q10 and Q12-Q13 are 2N3708, Q6 is 2N3053 and Q11 is 2N5457.

Q12/13 (2N3708) need to be matched for hFE. If you got a partial kit you need to that yourself.  Most meters have an hFE function.  If you don't match them there is still like a 60% you'll be fine.  Sounds like you might be in the 40%.

You could try swapping one out with another.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 05:26:23 PM
Attack switched off = GR off.

Measure AC not DC volts.

TP1   .1VAC
TP15   .2VAC
TP17   0.0VAC with lots of noise and radio signals
Out Brown   .08VAC

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 05:28:57 PM
TP1   .1VAC
TP15   .2VAC
TP17   0.0VAC with lots of noise and radio signals
Out Brown   .08VAC

Thanks!

Does rotating the Qbias help the AC V @ pad 15?

oh and have your in/out at 12 noon and ratio at 20:1
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 05:40:09 PM
Does rotating the Qbias help the AC V @ pad 15?

oh and have your in/out at 12 noon and ratio at 20:1

IN/OUT were at 12 noon and ration was 20:1 already . Rotating Qbias does not affect AC V at TP15.  Thanks!!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 05:45:43 PM
IN/OUT were at 12 noon and ration was 20:1 already . Rotating Qbias does not affect AC V at TP15.  Thanks!!

What is your DC V at TP18?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 05:54:53 PM
What is your DC V at TP18?

-1.019 VDC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 05:56:41 PM
-1.019 VDC

Can you safely remove Q1?  Does that increase your output?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 13, 2017, 06:15:51 PM
Q12/13 (2N3708) need to be matched for hFE. If you got a partial kit you need to that yourself.  Most meters have an hFE function.  If you don't match them there is still like a 60% you'll be fine.  Sounds like you might be in the 40%.

You could try swapping one out with another.

Mike

Which 2 would you recommend swapping? Are there any that will not affect the other components as much?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 13, 2017, 06:18:33 PM
Actually after further investigation, Q12-13 are both 2N3707.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 06:39:13 PM
Actually after further investigation, Q12-13 are both 2N3707.

Doesn't matter.  They still need hFE matching.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 13, 2017, 06:54:04 PM
Ohhhhhh. Ok. Now I understand. How does one do the HFe matching?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 06:58:08 PM
Ohhhhhh. Ok. Now I understand. How does one do the HFe matching?

It's covered in the older guide, you need a meter that can do it:
http://www.hairballaudio.com/blog/resources/build-guides/populating-the-pcb-

In the transistor section.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 07:42:19 PM
Can you safely remove Q1?  Does that increase your output?

Not sure that I will be able to remove Q1. That sucker is in there! Will keep working at it though. Anything else I can check in the mean time?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 07:49:28 PM
Not sure that I will be able to remove Q1. That sucker is in there! Will keep working at it though. Anything else I can check in the mean time?

Set your trimmer so you have the highest DC you can get at TP18, then test the DC resistance (Ω) across the S and D of Q1.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 08:20:06 PM
Set your trimmer so you have the highest DC you can get at TP18, then test the DC resistance (Ω) across the S and D of Q1.

Mike

Trimmer? Sorry, probably a dumb question, but want to make sure I do what you are asking...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 08:26:45 PM
Trimmer? Sorry, probably a dumb question, but want to make sure I do what you are asking...

Sorry qbias trimmer.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 08:38:07 PM
Set your trimmer so you have the highest DC you can get at TP18, then test the DC resistance (Ω) across the S and D of Q1.

Mike

27.10kΩ
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 08:57:21 PM
27.10kΩ

Hmmmm. You have something wrong in the "signal preamp" section of you build...it's on the far left of your PCBs.  Check all of those parts and soldering.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Foots on March 13, 2017, 09:23:24 PM
Hmmmm. You have something wrong in the "signal preamp" section of you build...it's on the far left of your PCBs.  Check all of those parts and soldering.

Mike

Thanks for your patience and help Mike! I will check that section and get back. BTW, what should the resistance be at Q1 between S and D?

k
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 13, 2017, 09:42:16 PM
Thanks for your patience and help Mike! I will check that section and get back. BTW, what should the resistance be at Q1 between S and D?

k

What you got seems right in circuit.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Dacey on March 14, 2017, 05:15:12 AM
What is your signal source?  The input of the FET/RACK is loading it, that's why you get the drop.

If it's not calibrated, ignore the meter. With this unit, the calibration is no fine tune adjustment, it's the difference between it working, and not working at all.

Mike

Signal source is RC Oscillator model 555.  I'm off to find a real one will get back to you if I encounter further issues. Thanks for your assistance Mike.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 14, 2017, 10:15:36 AM
Signal source is RC Oscillator model 555.  I'm off to find a real one will get back to you if I encounter further issues. Thanks for your assistance Mike.

If you have a sine wave generator in you DAW (protools has one). Check out the FET/500 calibration section for info on how to use it.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on March 15, 2017, 04:00:45 PM
You're not dropping any voltage across your resistors which would mean you're not drawing current on your negative rail.  I would suspect the zener diode (CR9).  Confirm it's soldered well, the pads look good, and it's oriented correctly. If all that looks good you may want to replace it. Email me for a new one.

Mike

Mike,

I meant to reply right away this week.  I got the replacement in very quick order, installed the zener diode, and all measured up as expected!  Thank you, guy!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 15, 2017, 04:21:07 PM
Mike,

I meant to reply right away this week.  I got the replacement in very quick order, installed the zener diode, and all measured up as expected!  Thank you, guy!

Awesome!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ilfungo on March 16, 2017, 06:23:25 AM
hi
how many mA the 1176 need on the 2 secondaries ( power transformer)?
Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 16, 2017, 01:17:09 PM
hi
how many mA the 1176 need on the 2 secondaries ( power transformer)?
Thanks!

In general, you need about a 25VA transformer.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 16, 2017, 11:45:57 PM
Disaster struck while removing transistors Q9, Q10, Q12 and Q13. This has become a P2P project at this point. I wanted help as to where each leg of the 4 transistors should go. Q10 appears to be reconnected properly. E and B of Q9 are right but I'm not sure where C goes. As for Q12 and Q13, the pads are too burnt up to decipher. I need a tutorial on properly removing parts from a PCB. I'm shooting at about a 25% right now and that doesn't fly for me.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 16, 2017, 11:46:38 PM
Here's the picture of Q12 and Q13.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 10:28:45 AM
Yikes. You may want to stop removing parts.

Use the schematic to confirm you're making the correct connections.

http://mnats.net/fetrack.html
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 17, 2017, 12:55:35 PM
In the schematic, which of the lines going from the transistors are B. C and E?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 01:20:12 PM
In the schematic, which of the lines going from the transistors are B. C and E?

http://www.physlink.com/education/askexperts/Images/ae430c.gif
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 17, 2017, 02:08:48 PM
Pardon the mess but is this right? I checked with the schematics and I'm fairly certain I got it but wanted to check with the master. If there is no lead coming from the point, the connection is still in tact.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 17, 2017, 02:14:23 PM
Pardon the mess but is this right? I checked with the schematics and I'm fairly certain I got it but wanted to check with the master. If there is no lead coming from the point, the connection is still in tact.
Actually I think the emitter from Q12 should go to R68... is that right? Sorry for all the questions. At this point I'd normally just send this to you but recently found out that I have my first baby on the way so I need to save money. :/
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 02:24:32 PM
Actually I think the emitter from Q12 should go to R68... is that right? Sorry for all the questions. At this point I'd normally just send this to you but recently found out that I have my first baby on the way so I need to save money. :/

Yes and R44
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 03:44:27 PM
OK, sad to say it wasn't the transformer :-( HELP :o
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 05:31:13 PM
OK, sad to say it wasn't the transformer :-( HELP :o

Go through all the tests I did with this user:

https://groupdiy.com/index.php?topic=63600.msg827887#msg827887
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 06:11:23 PM
Go through all the tests I did with this user:

https://groupdiy.com/index.php?topic=63600.msg827887#msg827887

OK, so I followed the thread, but I'm getting .312 ACv and .375 ACv on the 2 orange secondary leads...the reading is the same with the unit off/unplugged :-/ I double checked the 115 switch on the rear also...

This sounds strange, but i probed WHT/BLK and BLU/RED on the new transformer and still read OLΩ  :o
I tried it plugged in and unplugged...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 06:15:25 PM
OK, so I followed the thread, but I'm getting .312 ACv and .375 ACv on the 2 orange secondary leads...the reading is the same with the unit off/unplugged :-/ I double checked the 115 switch on the rear also...

This sounds strange, but i probed WHT/BLK and BLU/RED on the new transformer and still read OLΩ  :o
I tried it plugged in and unplugged...

Ya something is up there with your testing I think.  I tested both those windings before I shipped it out and the read the usual 100Ωish.

What if you measure Ω at the selector switch (unit unplugged from the wall....no power).

Let me find the terminals...one sec...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 06:24:54 PM
Power off (unplugged from wall).

With the transformer plugged in to the voltage select PCB...unplug the 3 pin connector at the top of the voltage PCB and measure the DC Ω between the two outer pins.  You should get 51Ω ish.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 06:29:04 PM
Power off (unplugged from wall).

With the transformer plugged in to the voltage select PCB...unplug the 3 pin connector at the top of the voltage PCB and measure the DC Ω between the two outer pins.  You should get 51Ω ish.

Mike

OLΩ nothing...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 06:41:26 PM
OLΩ nothing...

Unplug the transformer and the 3 pin from the V select PCB.  What is your DC Ω between pin 1 and pin 5 (where white and blue would be) and Pin 3 and Pin 7 where (where black and red would be).

Make sure your switch is on 115V.

Unplugged.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 06:53:11 PM
Unplug the transformer and the 3 pin from the V select PCB.  What is your DC Ω between pin 1 and pin 5 (where white and blue would be) and Pin 3 and Pin 7 where (where black and red would be).

Make sure your switch is on 115V.

Unplugged.

1 & 5 .2Ω
3 & 7 .2Ω
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 06:57:51 PM
1 & 5 .2Ω
3 & 7 .2Ω

Cool.

Now check between Pin 1 on the seven pin and pin 1 on the three pin connector above it. What do you get for DC Ω?

Then check between Pin 3 on the seven pin and pin 3 on the three pin connector above it. What do you get for DC Ω?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 07:01:11 PM
Cool.

Now check between Pin 1 on the seven pin and pin 1 on the three pin connector above it. What do you get for DC Ω?

Then check between Pin 3 on the seven pin and pin 3 on the three pin connector above it. What do you get for DC Ω?

Pin 1 on the seven pin and pin 1 on the three pin connector .1Ω
Pin 3 on the seven pin and pin 3 on the three pin connector .1Ω
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 07:13:56 PM
Pin 1 on the seven pin and pin 1 on the three pin connector .1Ω
Pin 3 on the seven pin and pin 3 on the three pin connector .1Ω

I'm stumped.

Having OLΩ on the outer pins of the three pin connector, would indicate that both your primary windings are broken. We've have yet to have a defective transformer. I also tested the second one I sent you and both were tested by the manufacturer.

I can't imagine anything you could be doing to damage them, that's what the fuse is there for.

You'll have to send them back for testing, email me.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 07:29:57 PM
I'm stumped.

Having OLΩ on the outer pins of the three pin connector, would indicate that both your primary windings are broken. We've have yet to have a defective transformer. I also tested the second one I sent you and both were tested by the manufacturer.

I can't imagine anything you could be doing to damage them, that's what the fuse is there for.

You'll have to send them back for testing, email me.

Mike

Hold up!!!!!! 

I switched back to the old transformer and now I'm getting all the correct readings...

around 100Ω on the BLK/WHT and BLU/RED...

now 52.8Ω on the outer 2 pins of the 3 connector...

I'm not sure if I am testing wrong, I have a Fluke 117...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 07:40:07 PM
Hold up!!!!!! 

I switched back to the old transformer and now I'm getting all the correct readings...

around 100Ω on the BLK/WHT and BLU/RED...

now 52.8Ω on the outer 2 pins of the 3 connector...

I'm not sure if I am testing wrong, I have a Fluke 117...

You must have a shady solder joint somewhere.  You might want to reflow everything. Your readings are good though.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 07:41:53 PM
You must have a shady solder joint somewhere.  You might want to reflow everything. Your readings are good though.

ok, on which PCB?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 07:47:28 PM
ok, on which PCB?

No idea. You're just getting weird inconsistent readings.

There is a bad connection somewhere. This old transformer had OL secondaries before, but now in parallel on the switch you're getting 52Ω which would indicate that they are both ok now.

How are you voltages? Working now?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 07:59:08 PM
No idea. You're just getting weird inconsistent readings.

There is a bad connection somewhere. This old transformer had OL secondaries before, but now in parallel on the switch you're getting 52Ω which would indicate that they are both ok now.

How are you voltages? Working now?

yeah, sorry about that...been using a mutimeter a long time... :-/ not sure whats going on......

so, I'm getting 3.4 VAC on the orange secondary (next to black) and 4.0 VAC on the orange secondary (next to white)
this is with the unit powered on and my black DDM lead in the chassis screw hole...
the secondary connector is unplugged from the main PBC and probing the red DMM lead in each orange connector...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 08:09:42 PM
yeah, sorry about that...been using a mutimeter a long time... :-/ not sure whats going on......

so, I'm getting 3.4 VAC on the orange secondary (next to black) and 4.0 VAC on the orange secondary (next to white)
this is with the unit powered on and my black DDM lead in the chassis screw hole...
the secondary connector is unplugged from the main PBC and probing the red DMM lead in each orange connector...

You sure you're measuring AC V and not AC mA or something?

Measure you primary. With the unit on and everything in place....BE CAREFUL....measure the two tabs on the V select PCB left side.   I'm talking about the 6 tabs between the 7 and 3 pin connector.  The two on the left. What does the top one read in AC referencing the chassis, and what does the bottom on read?

Also confirm your ground lug is solidly in place, and all three of your main PCB L brackets are solidly in place.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 08:18:27 PM
You sure you're measuring AC V and not AC mA or something?

Measure you primary. With the unit on and everything in place....BE CAREFUL....measure the two tabs on the V select PCB left side.   I'm talking about the 6 tabs between the 7 and 3 pin connector.  The two on the left. What does the top one read in AC referencing the chassis, and what does the bottom on read?

Also confirm your ground lug is solidly in place, and all three of your main PCB L brackets are solidly in place.

Mike

ok, Top left 43.8 VAC
bottom 55.8 VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 08:24:50 PM
ok, Top left 43.8 VAC
bottom 55.8 VAC

Wow. Ya that's crazy.

You have all the L brackets in place? They provide grounding to the chassis, not just structural support.

And both transformers behave differently?

You may just have to send the whole thing in. None of this adds up.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 08:25:26 PM
ok, Top left 43.8 VAC
bottom 55.8 VAC

OK, I'm having a twighlight zone moment...I SWEAR I checked the DC voltage 1,000 times on CR8!!!!
Now I'm getting the correct readings....30v and -10v
I am completely stumped and happy at the same time!

Sorry to waste your precious time!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 17, 2017, 08:28:01 PM
OK, I'm having a twighlight zone moment...I SWEAR I checked the DC voltage 1,000 times on CR8!!!!
Now I'm getting the correct readings....30v and -10v
I am completely stumped and happy at the same time!

Sorry to waste your precious time!

Glad it's sorted.

Please send back one of the transformers with the return label I send.  Whoop! Weekend!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 17, 2017, 08:29:46 PM
Glad it's sorted.

Please send back one of the transformers with the return label I send.  Whoop! Weekend!

Yes, of coarse...have a great weekend!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 18, 2017, 05:58:03 AM
Somehow, I reconnected everything and have made it through the first two steps of calibration. Now, on step 3, I can't seem to get the input pot to reach 2.44VAC at the output. I'm maxing out at 2.09VAC. Would this be caused by the ghetto rigging that just took place on Q9,10,12 and 13? I'm getting real close to just sending this in but would feel so much better if I could at least get through one of these beasts!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 19, 2017, 02:17:17 AM
Hey there...ALL the way to the last step and DANG! everything was going smooth until I got to:

"Set your DMM to measure DC volts and set it to measure the DC volts across TP10 and TP11 for the Rev A and accross R74 for the Rev D.

Zero the compressors "GR" meter with the R71 zero adjust pot on the front panel.
Adjust pot R75 (null adjust)  for 0.0 Volts across TP10/TP11 (Rev A) or R74 (Rev D).
Repeat 1 & 2 until both conditions are met."

I got 0.00 DCV between TP10/TP11, but my R71 adjust pot wont budge the GR meter...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 10:01:13 AM
Hey there...ALL the way to the last step and DANG! everything was going smooth until I got to:

"Set your DMM to measure DC volts and set it to measure the DC volts across TP10 and TP11 for the Rev A and accross R74 for the Rev D.

Zero the compressors "GR" meter with the R71 zero adjust pot on the front panel.
Adjust pot R75 (null adjust)  for 0.0 Volts across TP10/TP11 (Rev A) or R74 (Rev D).
Repeat 1 & 2 until both conditions are met."

I got 0.00 DCV between TP10/TP11, but my R71 adjust pot wont budge the GR meter...

Does the null adjust change the DC voltage?

You'll need to go through the values in the GR meter amp section, only a few parts, confirm them and reflow ant suspect joints.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 10:01:54 AM
Somehow, I reconnected everything and have made it through the first two steps of calibration. Now, on step 3, I can't seem to get the input pot to reach 2.44VAC at the output. I'm maxing out at 2.09VAC. Would this be caused by the ghetto rigging that just took place on Q9,10,12 and 13? I'm getting real close to just sending this in but would feel so much better if I could at least get through one of these beasts!

Are you sure your in GR OFF mode?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 20, 2017, 12:19:12 PM
Are you sure your in GR OFF mode?

Unless theres a difference between GR mode aka the top button and GR OFF, I should be good to go.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 01:59:20 PM
Does the null adjust change the DC voltage?

You'll need to go through the values in the GR meter amp section, only a few parts, confirm them and reflow ant suspect joints.

Mike

Hey thanks for the help, been fooling with it all weekend, The null adjust doesn't change anything...I'm getting 0.0 from full CCW to CW.

hopefully I didn't break R71, the meter wasn't moving from -20 in GR mode, so I kept turning it and it just kept turning, turning....then I realized it had a gentle stopping point each way...  :P
If I push +8, +4 on the meter while theres a signal, the needle jumps way up and seems to works fine....

also, CR10 diode had 2 different length through holes, I tried both, but couldn't tell which one was right :-/ I'm in the shorter one now...

Is there a list for the GR meter amp section?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 03:33:55 PM
Make sure in GR OFF mode pad 22 is shorted to the chassis (ground).

if so....

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

What is your AC V at pad 15 and at + output.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 03:34:58 PM
Hey thanks for the help, been fooling with it all weekend, The null adjust doesn't change anything...I'm getting 0.0 from full CCW to CW.

hopefully I didn't break R71, the meter wasn't moving from -20 in GR mode, so I kept turning it and it just kept turning, turning....then I realized it had a gentle stopping point each way...  :P
If I push +8, +4 on the meter while theres a signal, the needle jumps way up and seems to works fine....

also, CR10 diode had 2 different length through holes, I tried both, but couldn't tell which one was right :-/ I'm in the shorter one now...

Is there a list for the GR meter amp section?

Which build do you have?  What is the PCB version you have?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 03:48:10 PM
Which build do you have?  What is the PCB version you have?

v1.12
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 04:00:06 PM
CR 10 only has one set of pads.  The inner hole you're seeing is a VIA. It's there to allow a trace to move from one side of the board to the other. Do not put your diode in the VIA.

The GR parts are in the section lined out and labeled GR Meter Driver Amp...or something close to that.

Thanks!

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 05:12:23 PM
CR 10 only has one set of pads.  The inner hole you're seeing is a VIA. It's there to allow a trace to move from one side of the board to the other. Do not put your diode in the VIA.

The GR parts are in the section lined out and labeled GR Meter Driver Amp...or something close to that.

Thanks!

Mike

OK, so I put CR10 back in place...reflowed anything that looked even remotely weird in the meter driver amp section. same results.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 05:14:44 PM
OK, so I put CR10 back in place...reflowed anything that looked even remotely weird in the meter driver amp section. same results.

FYI, I'm not sure if I mentioned it, but I did test the ACV at the output XLR to see if the signal was getting compressed when I truned the attack up and it was working...so it looks like its just the GR meter...I think  :-\
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 05:20:11 PM
FYI, I'm not sure if I mentioned it, but I did test the ACV at the output XLR to see if the signal was getting compressed when I truned the attack up and it was working...so it looks like its just the GR meter...I think  :-\

1. Make sure you have all the wire harnesses in.
2. Double check your meter switch and 2-pin connector soldering.
4. Make sure the 3 pin jumper is in the right spot.
3. Check your Dc voltages in the GR meter amp section.

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 05:58:35 PM
1. Make sure you have all the wire harnesses in.
2. Double check your meter switch and 2-pin connector soldering.
4. Make sure the 3 pin jumper is in the right spot.
3. Check your Dc voltages in the GR meter amp section.

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Mike

Hey, it looks like I soldered the long side of the 3 pin jumper to the PCB ::) so the short side is up, it does look like its still making a connection though...

I'm embarrassed to say I'm not sure how to read the schematic  :-\ I can somewhat follow it, do you check voltages from the bottom of the PCB? I noticed some references to Q11, 12, 13 under there... keeping the black lead in the chassis?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 06:04:29 PM
Hey, it looks like I soldered the long side of the 3 pin jumper to the PCB ::) so the short side is up, it does look like its still making a connection though...

I'm embarrassed to say I'm not sure how to read the schematic  :-\ I can somewhat follow it, do you check voltages from the bottom of the PCB? I noticed some references to Q11, 12, 13 under there... keeping the black lead in the chassis?

DC voltages using the chassis as your reference.  Doesn't matter what side just identify the leads of the transistors.  You can google the datasheet or I think they are even labeled under the PCB.

http://www.hairballaudio.com/blog/resources/diy-resources/yes-you-can-read-a-schematic

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 06:46:10 PM
DC voltages using the chassis as your reference.  Doesn't matter what side just identify the leads of the transistors.  You can google the datasheet or I think they are even labeled under the PCB.

http://www.hairballaudio.com/blog/resources/diy-resources/yes-you-can-read-a-schematic

Mike

Great, starting to make more sense  :) but, I'm not getting the correct readings  :o
I started with  Q11 as it looks like one of the first components in the flow. results:
Q11  G= -.689  S= -.773  D= 16.58
Q12   E=  0.0  C= 16.61  B= -.775
Q13   E= 0.0  C= 0.0  B= -.924
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 07:03:21 PM
Great, starting to make more sense  :) but, I'm not getting the correct readings  :o
I started with  Q11 as it looks like one of the first components in the flow. results:
Q11  G= -.689  S= -.773  D= 16.58
Q12   E=  0.0  C= 16.61  B= -.775
Q13   E= 0.0  C= 0.0  B= -.924

Q13 or Q12 is either dead or you have bad R value or a bad joint in the GR section.   If you're confident in all the soldering and R values and confident in all the pads on the switch, you may want to try new transistors.

You have no voltage at the collector of Q13 though....which makes me think your GR push switch or 2 pin wire header isn't soldered right.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 07:11:44 PM
Q13 or Q12 is either dead or you have bad R value or a bad joint in the GR section.   If you're confident in all the soldering and R values and confident in all the pads on the switch, you may want to try new transistors.

You have no voltage at the collector of Q13 though....which makes me think your GR push switch or 2 pin wire header isn't soldered right.

Mike

the soldering at both ends of the 2 pin connector is hershey kiss heaven...and their both soldered with the gap facing the same as the silkscreen...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 07:13:46 PM
also, the voltages at TP10 & 11 are 16.5
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 07:18:39 PM
also, the voltages at TP10 & 11 are 16.5

TP11 is 16.5 VDC and the C of Q13 is 0 VDC?

That's impossible...they are connected.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 20, 2017, 07:21:17 PM
Make sure in GR OFF mode pad 22 is shorted to the chassis (ground).

if so....

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

What is your AC V at pad 15 and at + output.

Mike

Output + = 10.09 VAC
Pad 15 = 2.47 VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 07:25:52 PM
Output + = 10.09 VAC
Pad 15 = 2.47 VAC

What is your VAC across output + and output -?

Same conditions.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 07:29:13 PM
TP11 is 16.5 VDC and the C of Q13 is 0 VDC?

That's impossible...they are connected.

haha, of coarse this project is impossible! JK  :'(

I triple checked and thats the reading...I'm probing all the possible spots I can reach, bottom and top...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 20, 2017, 07:32:57 PM
What is your VAC across output + and output -?

Same conditions.

Mike
10.38VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 07:45:42 PM
haha, of coarse this project is impossible! JK  :'(

I triple checked and thats the reading...I'm probing all the possible spots I can reach, bottom and top...

Well everything seems to be working other than your GR meter.

If you don't have continuity between Q13's C and TP11...one of those pads is lifted off the trace.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 07:47:21 PM
10.38VAC

That's like 14dBu at your output.

Sure you're doing the calibration step right?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 07:58:06 PM
Well everything seems to be working other than your GR meter.

If you don't have continuity between Q13's C and TP11...one of those pads is lifted off the trace.

both the traces look solid....the soldering looks good too...I also checked the Ω between Q13's C and TP11 and got OL on the DMM
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 08:07:28 PM
Then one of those pads ain't good.

Should be like 0.2Ω.

Solder a short wire or leg clipping across those points.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 08:30:14 PM
Then one of those pads ain't good.

Should be like 0.2Ω.

Solder a short wire or leg clipping across those points.

Ok, (with wire) now I'm getting the right voltage at both points...

The meter didn't move, and I checked the DCV between TP10/11 still 0.0 VDC even when I move the null adjust
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 08:35:08 PM
Ok, (with wire) now I'm getting the right voltage at both points...

The meter didn't move, and I checked the DCV between TP10/11 still 0.0 VDC even when I move the null adjust

Do all those Q12/Q13 DC Voltages again.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 20, 2017, 09:15:33 PM
Do all those Q12/Q13 DC Voltages again.

OK, so now I'm getting...
Q12  E= 0.0  C= 16.61  B= -.775
Q13  E= 0.0  C= 16.59  B= -1.106
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 09:33:25 PM
OK, so now I'm getting...
Q12  E= 0.0  C= 16.61  B= -.775
Q13  E= 0.0  C= 16.59  B= -1.106

You most likely have something wrong in this attached section. You need to Ω test all of the trace connections, look for more dead pads. The schematic shows you what connects to what and looking at the traces will confirm that.  Your ohm meter is your friend.

That's about all I can do with out you sending it in for repair.

Good luck,

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 20, 2017, 11:43:05 PM
That's like 14dBu at your output.

Sure you're doing the calibration step right?

Dammit dammit dammit dammit. My DMM is definitely reading around .775VAC at the input. Do I need a cable running from the output or anything? Would that make a difference?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 20, 2017, 11:50:56 PM
Dammit dammit dammit dammit. My DMM is definitely reading around .775VAC at the input. Do I need a cable running from the output or anything? Would that make a difference?

You should load your output yes.  Double check your qbias.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 21, 2017, 05:32:35 AM
What is your VAC across output + and output -?

Same conditions.

Mike

Ok. Reset the Q Bias. Readings are now:
+ Output: 9.48 VAC
Pad 15: 2.45 VAC
Across Output+/-: 9.46 VAC

Note: After completing step 2 and resetting the shorting pin, the needle drops so low that R71 (the front zero pot) can only bring it back up to about -12dB, before attempting to begin step 3.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 21, 2017, 01:59:44 PM
Ok. Reset the Q Bias. Readings are now:
+ Output: 9.48 VAC
Pad 15: 2.45 VAC
Across Output+/-: 9.46 VAC

Note: After completing step 2 and resetting the shorting pin, the needle drops so low that R71 (the front zero pot) can only bring it back up to about -12dB, before attempting to begin step 3.

hmmmm, it should drop when you reset the pin, but only to like -3 or -5.

Are you able to get the 10dB drop at the output? Ignore the meter for now.

Those voltages look ok to me.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 21, 2017, 03:27:12 PM
hmmmm, it should drop when you reset the pin, but only to like -3 or -5.

Are you able to get the 10dB drop at the output? Ignore the meter for now.

Those voltages look ok to me.

When I'm getting the input to read .775vac across input -/+ do I want the input and output knobs turned all of the way down? Those would affect the reading pretty substantially, right?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 21, 2017, 03:31:11 PM
When I'm getting the input to read .775vac across input -/+ do I want the input and output knobs turned all of the way down? Those would affect the reading pretty substantially, right?

Don't touch the knobs. Start with them at 12 O'Clock.  Adjust the level of your signal source to get 0dBu at the input.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 22, 2017, 08:57:19 AM
Don't touch the knobs. Start with them at 12 O'Clock.  Adjust the level of your signal source to get 0dBu at the input.

Alright, so today is my birthday and I'm feeling good that we're gonna get this SOB figured out!!! So, Input is set to 0dBu with both knobs at 24. Turned output pot to about "48" and the output is reading 0dBu. I begin turning up the input pot and again it maxes out at about 2.09-2.10VAC. When I turn the Attack knob all the way CW, the output drops down to about 1.54VAC before climbing back up to 2.09-2.10VAC. It does this climb in about 5.5 seconds (I'm trying to be thorough so I broke out the stopwatch). 

I'm fairly certain at this point that the Q Bias has been calibrated properly. The Null Adjust I can get to about .003 but again, upon reinserting the shunt "normally", the needle drops to the far left and with R71 fully CW, can only reach about -12dB on the meter.

Let me know what the next step is oh great one!!!

Cheers.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 22, 2017, 11:15:32 AM
Alright, so today is my birthday and I'm feeling good that we're gonna get this SOB figured out!!! So, Input is set to 0dBu with both knobs at 24. Turned output pot to about "48" and the output is reading 0dBu.

Did you turn the attack from off to FCW before adjusting the output?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 22, 2017, 12:16:48 PM
Did you turn the attack from off to FCW before adjusting the output?

I set everything as stated before the step then went forward. So Attack FCW set Output to 0 dBu, turned Attack off and then attempted to set Input to 2.44 VAC. 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 22, 2017, 12:46:52 PM
I set everything as stated before the step then went forward. So Attack FCW set Output to 0 dBu, turned Attack off and then attempted to set Input to 2.44 VAC.

and that when you run out of gain?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 22, 2017, 12:54:34 PM
and that when you run out of gain?

Yea. Input FCW maxes out at 2.10 VAC.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 22, 2017, 12:58:49 PM
Yea. Input FCW maxes out at 2.10 VAC.

Guessing you have a side chain issue...too much compression maybe.  Go back several pages in this thread...look for the posts about measuring pad 22 and pad 21 at  all ratios.  I've gone through it a few times with people in this thread.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 22, 2017, 02:41:00 PM
Guessing you have a side chain issue...too much compression maybe.  Go back several pages in this thread...look for the posts about measuring pad 22 and pad 21 at  all ratios.  I've gone through it a few times with people in this thread.

Pad 21
4     -1.83 VDC
8     -2.74 VDC
12  -3.83 VDC
20  -6.75 VDC

Pad 22
4     .8 VAC
8     1.7 VAC
12  2.2 VAC
20  2.5 VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 22, 2017, 06:26:42 PM
Pad 21
4     -1.83 VDC
8     -2.74 VDC
12  -3.83 VDC
20  -6.75 VDC

Pad 22
4     .8 VAC
8     1.7 VAC
12  2.2 VAC
20  2.5 VAC

Pad 22 is hot as sh*t (level too high). That's the cause of the over compression you're seeing.

Double check all of your ratio PCB resistor values. Look for something like a 47K and 470Ω or similar mixed up on that PCB.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 22, 2017, 07:46:21 PM
Pad 22 is hot as sh*t (level too high). That's the cause of the over compression you're seeing.

Double check all of your ratio PCB resistor values. Look for something like a 47K and 470Ω or similar mixed up on that PCB.

Mike

Everything is kosher as far as resistors. Maybe reflow the solder to the resistors and switches?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 22, 2017, 08:17:33 PM
Everything is kosher as far as resistors. Maybe reflow the solder to the resistors and switches?

What revision do you have?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 22, 2017, 08:37:50 PM
What revision do you have?

D
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 22, 2017, 09:04:19 PM
D

Check R78, R22, R36, R37.

Real close.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 23, 2017, 09:53:31 AM
Check R78, R22, R36, R37.

Real close.

Ok. So everything seems fine with those. I cleaned up my P2P work and reflowed a bunch of my solder joints. I have lower values at Pad 22 but now can't get my output above 2.15VAC. Closer but still not 2.44VAC.

Pad 22
4 = .010VAC
8 = .014VAC
12 = .022VAC
20 = .036VAC

Thoughts?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 23, 2017, 10:55:25 AM
Ok. So everything seems fine with those. I cleaned up my P2P work and reflowed a bunch of my solder joints. I have lower values at Pad 22 but now can't get my output above 2.15VAC. Closer but still not 2.44VAC.

Pad 22
4 = .010VAC
8 = .014VAC
12 = .022VAC
20 = .036VAC

Thoughts?

That's too low. You should be at around 0.065V AC @ 4:1 and 0.375 V AC @ 20:1 (roughly).

Have a look at the schematic:
http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

Pad 15 is the output of the first amp stage and is right before the output pot. You'd mentioned that was around 2 to 2.5V AC with a 0dB input and you controls midway with GR off. That seems good.

When you turn on GR,  pad 15 is connected to the side chain amp in the lower right half of the schematic.  That 2.5V AC at pad 15 flows through a series of resistors (depending on the ratio selected) on it's way to the start of the side chain amp which is pad 22. Even out of cal and the q bias set for max output, that pad 2.5 V AC at pad 15 will most likely drop to under a volt when switched to GR mode. That's some compression kicking in.

In 20:1 that lower voltage from pad 22 hits only R78 before it heads down to pad 22. That's where is should dip down to 0.375VAC (ish) across that resistor if I recall. The rest of the resistors in that string play a role as part of the voltage divider.

C17 blocks any DC and then R36 and R37 set conditions for Q7 (impedance/bias) that all effect your voltage. After the sidechain amp the voltage is converted to DC and sent back to the FET to apply GR.

My main point is that your having an issue between your 15 and 22 pads and mostly what's in that space is the ratio PCB.

Where on the PCB is your point to point work?

Remember we do flat rate repair on these.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 23, 2017, 06:01:16 PM
That's too low. You should be at around 0.065V AC @ 4:1 and 0.375 V AC @ 20:1 (roughly).

Have a look at the schematic:
http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

Pad 15 is the output of the first amp stage and is right before the output pot. You'd mentioned that was around 2 to 2.5V AC with a 0dB input and you controls midway with GR off. That seems good.

When you turn on GR,  pad 15 is connected to the side chain amp in the lower right half of the schematic.  That 2.5V AC at pad 15 flows through a series of resistors (depending on the ratio selected) on it's way to the start of the side chain amp which is pad 22. Even out of cal and the q bias set for max output, that pad 2.5 V AC at pad 15 will most likely drop to under a volt when switched to GR mode. That's some compression kicking in.

In 20:1 that lower voltage from pad 22 hits only R78 before it heads down to pad 22. That's where is should dip down to 0.375VAC (ish) across that resistor if I recall. The rest of the resistors in that string play a role as part of the voltage divider.

C17 blocks any DC and then R36 and R37 set conditions for Q7 (impedance/bias) that all effect your voltage. After the sidechain amp the voltage is converted to DC and sent back to the FET to apply GR.

My main point is that your having an issue between your 15 and 22 pads and mostly what's in that space is the ratio PCB.

Where on the PCB is your point to point work?

Remember we do flat rate repair on these.

Mike

All this stuff is so cool! This post is like poetry to me. Haha. So here's the skinny. While trying to replace Q12 and Q13 so they matched, I also removed Q9 and Q10 to shuffle them around. All of these PCB points were mangled in removal. I don't know if I have a sh*t desoldering pump (it heats and pumps with the same unit) or if my patience is lacking but it was a mess.

I'll describe where each leg of the transistor has been reconnected. This will help me for comparing it to the schematic and maybe you could just confirm for me.

Q9
B - R43
C - Q10(B)/R47
E - R48

Q10
B - Q9(C)/R47
C - R51
E - C19 +

Q12
B - R66/Q11(S)
C - R67/R74
E - R44

Q13
B - R75
C - R74
E - P2/R69

I just checked these as I went along and don't see any issues. I'm  new to reading schematics though so I guess let me know if I missed something. If I had the dough I would've sent this in already. Times are a little tough right now so thanks so much for all of your help, Mike!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 23, 2017, 07:13:05 PM
I opened up my other unit to compare since that unit works. It's v1.11 so I'm sure there are a few differences in the boards but right off the bat, I noticed that R13 and R36 on my older unit are 1M carbon film resistors and this new unit has 1M metal film resistors. I assume since they're the same value with different tolerances this shouldn't be a huge difference but I'm totally loss as to what else could be wrong at this point.

Also, R43 on my older unit has a 270k resistor vs v1.12 which has the 38.3k. This confuses me though because the schematic you gave me is for v1.11 and even that says 38.3k for R43 but again, that unit works. I have a few 270k and 38.3k resistors sitting around. Should I try switching those out?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 23, 2017, 07:33:56 PM
I opened up my other unit to compare since that unit works. It's v1.11 so I'm sure there are a few differences in the boards but right off the bat, I noticed that R13 and R36 on my older unit are 1M carbon film resistors and this new unit has 1M metal film resistors. I assume since they're the same value with different tolerances this shouldn't be a huge difference but I'm totally loss as to what else could be wrong at this point.

Also, R43 on my older unit has a 270k resistor vs v1.12 which has the 38.3k. This confuses me though because the schematic you gave me is for v1.11 and even that says 38.3k for R43 but again, that unit works. I have a few 270k and 38.3k resistors sitting around. Should I try switching those out?

There are no major differences. In fact I think the only difference is that we removed the top pads from the input transformer footprint.

1M carbon/metal makes no difference.

R43 should be 38.3 on both.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 23, 2017, 07:56:44 PM
All this stuff is so cool! This post is like poetry to me. Haha. So here's the skinny. While trying to replace Q12 and Q13 so they matched, I also removed Q9 and Q10 to shuffle them around. All of these PCB points were mangled in removal. I don't know if I have a sh*t desoldering pump (it heats and pumps with the same unit) or if my patience is lacking but it was a mess.

I'll describe where each leg of the transistor has been reconnected. This will help me for comparing it to the schematic and maybe you could just confirm for me.

Q9
B - R43
C - Q10(B)/R47
E - R48

Q10
B - Q9(C)/R47
C - R51
E - C19 +

Q12
B - R66/Q11(S)
C - R67/R74
E - R44

Q13
B - R75
C - R74
E - P2/R69

I just checked these as I went along and don't see any issues. I'm  new to reading schematics though so I guess let me know if I missed something. If I had the dough I would've sent this in already. Times are a little tough right now so thanks so much for all of your help, Mike!

Q9 B should have continuity to R43 and R44.
Q10  C should have continuity to R51 and Q8 C
Q10  E should have continuity to C19, R49, and E of Q7.

Look at the schem again.  Use your Ω tester to check connections.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 23, 2017, 11:53:57 PM
SUCCESSSSSSSS!!!!!  I seriously cannot express the satisfaction that I'm feeling right now. The ratio buttons had WAYYYYYY too much solder on them. Or a bad solder job because when I removed the excess, everything began working. Thanks so much for all of your help, Mike! You're the man and these compressors are barnone.  Hopefully, I'll be grabbing a pair of Rev A's in the next few months!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 23, 2017, 11:59:28 PM
SUCCESSSSSSSS!!!!!  I seriously cannot express the satisfaction that I'm feeling right now. The ratio buttons had WAYYYYYY too much solder on them. Or a bad solder job because when I removed the excess, everything began working. Thanks so much for all of your help, Mike! You're the man and these compressors are barnone.  Hopefully, I'll be grabbing a pair of Rev A's in the next few months!

Whoop! Enjoy.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 24, 2017, 10:49:16 PM
Well everything seems to be working other than your GR meter.

If you don't have continuity between Q13's C and TP11...one of those pads is lifted off the trace.

Hey Mike! Thanks for the parts!

I have an interesting question, with new parts installed...I can get voltage on the "leg" of Q13 C, but not on the bottom side of the PCB.

Its like its putting out the correct voltage, but not making contact with the PCB, I think the pad is shot...can I hard wire to something?

Also, R71 DOES change the Voltage on Q13 C....man, I'm close and I can feel it!!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 25, 2017, 12:21:49 AM
Hey Mike! Thanks for the parts!

I have an interesting question, with new parts installed...I can get voltage on the "leg" of Q13 C, but not on the bottom side of the PCB.

Its like its putting out the correct voltage, but not making contact with the PCB, I think the pad is shot...can I hard wire to something?

Also, R71 DOES change the Voltage on Q13 C....man, I'm close and I can feel it!!

Look at Q13 C on the schematic and look at the traces coming from it on the PCB. The collector of Q13 only attaches to Pin 2 of CN2 and TP11.  You should be able to use your Ω meter to look at the trace and confirm continuity.  If you have no continuity, the pad may be dead and you need to replace the trace with a bit of wire.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lackstudios on March 25, 2017, 05:01:15 AM
Look at Q13 C on the schematic and look at the traces coming from it on the PCB. The collector of Q13 only attaches to Pin 2 of CN2 and TP11.  You should be able to use your Ω meter to look at the trace and confirm continuity.  If you have no continuity, the pad may be dead and you need to replace the trace with a bit of wire.

Mike

PRAISE THE LORD IN HEAVEN!!!!!!

It's finally working! Man, that was a tough one....I had to connect a wire on the TOP side of the PCB,( Q13 C to TP11) no idea why...but who cares ;D
Thanks again Mike! I'm sure you'll be seeing more of me, hopefully just for more gear, not support  :D
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 25, 2017, 10:05:51 AM
Next set of questions. So I have both units calibrated properly but when running the same signal through both units, one is dramatically louder than the other. This is without the active link. With the active link turned on I barely get any signal out of the second unit regardless of which is set to send and receive. Any ideas?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 25, 2017, 11:19:38 AM
PRAISE THE LORD IN HEAVEN!!!!!!

It's finally working! Man, that was a tough one....I had to connect a wire on the TOP side of the PCB,( Q13 C to TP11) no idea why...but who cares ;D
Thanks again Mike! I'm sure you'll be seeing more of me, hopefully just for more gear, not support  :D

Nice!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 25, 2017, 11:21:59 AM
Next set of questions. So I have both units calibrated properly but when running the same signal through both units, one is dramatically louder than the other. This is without the active link. With the active link turned on I barely get any signal out of the second unit regardless of which is set to send and receive. Any ideas?

Surely a bad component value or bad solder joint somewhere. Start be determining if the difference is in the amp stages or the sidechain.  Is there a level difference between the two units if both are in GR OFF and the in/outs are set the same?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 25, 2017, 01:43:48 PM
Surely a bad component value or bad solder joint somewhere. Start be determining if the difference is in the amp stages or the sidechain.  Is there a level difference between the two units if both are in GR OFF and the in/outs are set the same?

Mike

Wow. Yea. The newest one is way louder in GR OFF.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 26, 2017, 12:05:11 PM
Wow. Yea. The newest one is way louder in GR OFF.

1. Make sure they are both QBiased properly.

2. Go through the top half of the schematic and check the DC voltages on both units. Signal and line amp.

http://mnats.net/files/1176REVD_VOLTS.pdf

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cl on March 26, 2017, 03:43:52 PM
For the coupling capacitors (Rev A, Orange Drops): Is it possible to use a value other than 0.15uF, such as 0.1uF or 0.22uF? And without needing to change anything else in the circuit? Some brands of film capacitors are unavailable in 0.15uF values.

For the power supply: Can the 2,200uF capacitors be substituted with 1,000uF or 3,300uF? I remember seeing a 1176 schematic that was using 1,000uF in the power supply section.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 27, 2017, 12:44:28 PM
For the coupling capacitors (Rev A, Orange Drops): Is it possible to use a value other than 0.15uF, such as 0.1uF or 0.22uF? And without needing to change anything else in the circuit? Some brands of film capacitors are unavailable in 0.15uF values.

For the power supply: Can the 2,200uF capacitors be substituted with 1,000uF or 3,300uF? I remember seeing a 1176 schematic that was using 1,000uF in the power supply section.

I wouldn't change the value.  They filter DC, get too off the value and you're a) not filtering DC which leads to noise issues or b) start rolling off your low end.

The power supply caps are always selected based on voltage and current relationships for that particular circuit for max smoothing.

You should have no issues finding those values at a proper shop.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cl on March 27, 2017, 03:10:40 PM
I wouldn't change the value.  They filter DC, get too off the value and you're a) not filtering DC which leads to noise issues or b) start rolling off your low end.

The power supply caps are always selected based on voltage and current relationships for that particular circuit for max smoothing.

You should have no issues finding those values at a proper shop.

Mike

Thank you for helping a DIY newbie! I will stick with using the orange drops for now. I am learning a lot! :D

I've read that polypropylene film caps sound better than their polyethylene counterparts. Is this not always the case?

Does the capacitor begin failing to filter the DC when going down in value? And same for the low end roll off?

Can too much smoothing on the power supply be a bad thing? Adding extra capacitance here slows it down?

It looks like I have my electronics homework cut out.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 27, 2017, 03:17:38 PM
Thank you for helping a DIY newbie! I will stick with using the orange drops for now. I am learning a lot! :D

I've read that polypropylene film caps sound better than their polyethylene counterparts. Is this not always the case?

Does the capacitor begin failing to filter the DC when going down in value? And same for the low end roll off?

Can too much smoothing on the power supply be a bad thing? Adding extra capacitance here slows it down?

It looks like I have my electronics homework cut out.

You can google the rest of the stuff, but saying one capacitor sounds better than another is just plain wrong. They all sound different, and we select capacitors based on how they compliment the sound we're looking for. One sounding "better" than the other is just one persons taste. It's like saying one EQ setting sounds getter than another. The rev a is a gritty unit, it's full of color, especially when pushed in to saturation. The orange drops compliment that wonderfully.

IMO the orange drops are part of the finishing touch on the A. I for one would hate to see them switched out, but that's your call.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: cl on March 27, 2017, 03:36:11 PM
You can google the rest of the stuff, but saying one capacitor sounds better than another is just plain wrong. They all sound different, and we select capacitors based on how they compliment the sound we're looking for. One sounding "better" than the other is just one persons taste. It's like saying one EQ setting sounds getter than another. The rev a is a gritty unit, it's full of color, especially when pushed in to saturation. The orange drops compliment that wonderfully.

IMO the orange drops are part of the finishing touch on the A. I for one would hate to see them switched out, but that's your call.

Mike

Glad to hear. Thank you for all the info! :)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 28, 2017, 03:18:16 AM
1. Make sure they are both QBiased properly.

2. Go through the top half of the schematic and check the DC voltages on both units. Signal and line amp.

http://mnats.net/files/1176REVD_VOLTS.pdf

Mike

First off, I need to increase the volume of my test signal between the two units to get them to .775VAC. I assume that, since it's being measured right at the input, .775VAC should be .775VAC as it's not affected by the circuit. Is this correct? The new unit was the first to be calibrated and the test signal which read .775VAC on that unit was .740VAC on the first build.  This lead me to think that it could be a faulty cable so I checked all connections and everything seems fine. Moving on...

Here are my readings for the DC voltages of the newest unit [measured (expected)]:

Unit 1 (First Unit)
Signal Preamp
Q2   B=1.07v (1.05v)
          C=1.78v (1.75v)
          E= 0.57v (0.54v)
Q3   C= 12v (12.58v)
          E= 1.19v (1.15v)
Q14 E = 11.44v (12v)

Signal Line Amp
Q4  B= 1.01v (1.02v)
         C= 4.3v (4.2v)
         E= 0.433v (0.46v)
Q5  B= 3.30v (3.25v)
         C= 24.9v (26.18v)
         E= 2.74v (2.72v)
Q6  C= 27.6v (25.13v)
         E= 2.21v (2.2v)

Unit 2 (Newest Unit)
Signal Preamp
Q2   B=1.07v (1.05v)
          C=1.79v (1.75v)
          E= 0.58v (0.54v)
Q3   C= 12.3v (12.58v)
          E= 1.19v (1.15v)
Q14 E = 11.69v (12v)

Signal Line Amp
Q4  B= 1.02v (1.02v)
         C= 5.17v (4.2v)
         E= 0.453v (0.46v)
Q5  B= 3.36v (3.25v)
         C= 25.7v (26.18v)
         E= 2.82v (2.72v)
Q6  C= 25.7v (25.13v)
         E= 2.82v (2.2v)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 28, 2017, 08:36:06 PM
No the input impedance of the unit will slightly change the level at the input. The input impedance is effected by the position of the input and it's tolerance. 

Try this:
nput: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

What is the ACV for each unit at these points:

TP1, TP15, TP17, Output Transformer Brown.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 29, 2017, 01:48:34 AM
No the input impedance of the unit will slightly change the level at the input. The input impedance is effected by the position of the input and it's tolerance. 

Try this:
nput: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

What is the ACV for each unit at these points:

TP1, TP15, TP17, Output Transformer Brown.

Mike

Older Unit
TP1 =.111VAC
TP15 = 2.00VAC
TP17 = .304VAC
Brown = 7.42VAC

Newer Unit
TP1 = .132VAC
TP15 = 2.36VAC
TP17 = .360VAC
Brown =10.32VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Einestad on March 29, 2017, 04:58:28 AM
Hi, im new to building DIY equipment and got a question for the pros.
Im populating the PCB on my 1176 rev D and got a problem with the slot where my trim pots are supposed to go. There are 7 pads on each slot for the 4 trim pots but only 2 of the slots for the pots have holes in all 7 pads. This means that i cant insert two of the trimmers the correct way.. But i looks like the pads are connected on the bottom of the PCB so could i just bend the trimmers and use the other pads with holes in them? Aren't all pads supposed to have holes in them or im a missing something here?

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 11:59:08 AM
Older Unit
TP1 =.111VAC
TP15 = 2.00VAC
TP17 = .304VAC
Brown = 7.42VAC

Newer Unit
TP1 = .132VAC
TP15 = 2.36VAC
TP17 = .360VAC
Brown =10.32VAC

I'm pretty sick right now so I can't do comparative tests on this end today.

That's about a 3dBu difference and might have more to do with input/output pot tolerance. I can't remember if the pots are 10% or 20% but that can account for that.

Try adjusting one input so you have the same voltage at TP1. See if you're output is within a dB now. How much did you have to adjust it? Like a half dot or less? if so then that's just pot tolerance. Try just adjusting the output how far do you need to adjust that one keeping the inputs matched?

Because of all the tolerances in the unit every unit is going to be a little different.

Also before doing that make sure the input and the output skirt line on each unit lines up perfectly with "0" on the scale.

3dB seems a bit high, but confirm those pots are lined up and adjust the input (and output) a little to get them to match. See how far you have to adjust the knobs.

Whenever you use a pair on something there is always a little trimming to be done. It's 60's analog gear.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 12:00:40 PM
Hi, im new to building DIY equipment and got a question for the pros.
Im populating the PCB on my 1176 rev D and got a problem with the slot where my trim pots are supposed to go. There are 7 pads on each slot for the 4 trim pots but only 2 of the slots for the pots have holes in all 7 pads. This means that i cant insert two of the trimmers the correct way.. But i looks like the pads are connected on the bottom of the PCB so could i just bend the trimmers and use the other pads with holes in them? Aren't all pads supposed to have holes in them or im a missing something here?

Thanks!

What PCB version do you have?  1.11? Is your trim pot short and square?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on March 29, 2017, 03:57:11 PM
File this under [im an idiot], but in the photo I have my the PCB boards to both of my Rev As.  As you can see, in the bottom PCB, I have oriented my output transformer incorrectly.  I'm sure this is a good reason not to work on these projects at 2AM.  My leads are all correctly placed.

Does it go without saying that I should de-solder and correct this or is it acceptable if there is clearance for the bottom plate of the unit to be attached?

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 04:25:03 PM
File this under [im an idiot], but in the photo I have my the PCB boards to both of my Rev As.  As you can see, in the bottom PCB, I have oriented my output transformer incorrectly.  I'm sure this is a good reason not to work on these projects at 2AM.  My leads are all correctly placed.

Does it go without saying that I should de-solder and correct this or is it acceptable if there is clearance for the bottom plate of the unit to be attached?

Whoops.

You'll have to see if there is clearance.  If there is you could leave it like that.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: musicaudioworks on March 29, 2017, 05:00:46 PM
Hello,

I'm building two rev d racks. One calibrated properly. But the other one is giving me some trouble.

While calibrating the tracking adjustment, the VU stays at -10 when the attack is turned on or off. This is after adjusting for the 10db drop with the front panel R and tracking adjustment R.

Meter functions normally when in +4 or +8.

Any ideas?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 05:14:03 PM
Hello,

I'm building two rev d racks. One calibrated properly. But the other one is giving me some trouble.

While calibrating the tracking adjustment, the VU stays at -10 when the attack is turned on or off. This is after adjusting for the 10db drop with the front panel R and tracking adjustment R.

Meter functions normally when in +4 or +8.

Any ideas?

Does the trimmer on the front (R71) do anything when turned?
You were able to set the NULL?
You're getting a 10dB drop at the output?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: musicaudioworks on March 29, 2017, 05:57:18 PM
Does the trimmer on the front (R71) do anything when turned?
You were able to set the NULL?
You're getting a 10dB drop at the output?


Hey mike,

Thanks for getting back to me!

Yes yes and yes. All VR pots work. Null adjust moves the needle as expected.

Just went threw and calibrated it from scratch.

The VU shows no gain reduction when the input is increased with the attack and release full CW with 20:1 ratio and GR button depressed.

Could it be a short in a switch?


Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: musicaudioworks on March 29, 2017, 06:27:25 PM
I just checked every component in the GR meter driver amp section. Everything looks correct. All the pots are functioning properly.

Could it be my matched transistors?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on March 29, 2017, 06:48:28 PM
A question about cleaning the solder side of the PCB on the FET rack. I've used 91% isopropyl alcohol, as well as tried some commercial flux cleaner spray.
I'm trying not to slather the stuff on. Just applying it with a Qtip or soft toothbrush and scrubbing.

They both seem to leave a filmy (slightly tacky?) residue behind. (as opposed to the more glossy, smooth top surface).

A. Is this normal?
B. Will this affect anything?

Is there a better way to clean it?

thanks
Carlos

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 07:29:21 PM
When I adjust the Q bias, the voltage does not move until I'm over half way. Then it's extremely touchie. Very hard to get 2.44 exactly. Is this a bad VR?

No, It's a touchy adjustment. Get it as close as you can. That sounds right.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: musicaudioworks on March 29, 2017, 07:33:03 PM
Well when I turn the attack on, I still don't see the 10db drop. The output voltage stays the same as does the VU meter. The input control does not drop the voltage when increased.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 07:33:27 PM
Does the trimmer on the front (R71) do anything when turned?
You were able to set the NULL?
You're getting a 10dB drop at the output?


Hey mike,

Thanks for getting back to me!

Yes yes and yes. All VR pots work. Null adjust moves the needle as expected.

Just went threw and calibrated it from scratch.

The VU shows no gain reduction when the input is increased with the attack and release full CW with 20:1 ratio and GR button depressed.

Could it be a short in a switch?

- If you're getting 10 db of GR, then the sidechain should be ok.

- If you we're able to NULL the meter, your transistors should be matched.

Start with the tracking adjust centered and set your unit to have 10dB of gain reduction on the output. With the unit in GR OFF (10dB on the output) trim the R71 zero adjust to 0 on the meter. Then switch to GR ON (0dB on the output) and adjust the tracking for -10.

Where does this go wrong for you?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 07:34:13 PM
Well when I turn the attack on, I still don't see the 10db drop. The output voltage stays the same as does the VU meter. The input control does not drop the voltage when increased.

Then you have a sidechain (GR AMP) error.

Hold on one sec...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 07:38:24 PM
A question about cleaning the solder side of the PCB on the FET rack. I've used 91% isopropyl alcohol, as well as tried some commercial flux cleaner spray.
I'm trying not to slather the stuff on. Just applying it with a Qtip or soft toothbrush and scrubbing.

They both seem to leave a filmy (slightly tacky?) residue behind. (as opposed to the more glossy, smooth top surface).

A. Is this normal?
B. Will this affect anything?

Is there a better way to clean it?

thanks
Carlos

Soak the bottom.

Hold it at a 90 degree angle to the sink and drench the bottom of the PCB so the cleaner runs off (keep the output transformer dry).

Scrub as it runs off. Let it sit and evaporate.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 07:41:48 PM
musicaudioworks:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: musicaudioworks on March 29, 2017, 07:45:34 PM
Then you have a sidechain (GR AMP) error.

Hold on one sec...

It must be. When the input is turned up, the VU meter does not move. It should obviously show db drop when the input is increased in GR mode.

I triple checked the components. Everything is correct. Solder joints look good.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 08:12:30 PM
With GR Active you should see AC voltage.  Very small at 4:1 and larger at 20:1.

Check all of your ratio PCB solder points and the relay on the main PCB.  Also check the solder points for the Ratio to Main PCB connector.

Do that first.

If you still have nothing @ 22 ....then see what you AC is on either side of R78 with all of the same signal and control conditions as before....make sure GR is ON.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on March 29, 2017, 08:19:25 PM
Soak the bottom.

Hold it at a 90 degree angle to the sink and drench the bottom of the PCB so the cleaner runs off (keep the output transformer dry).

Scrub as it runs off. Let it sit and evaporate.

Mike

Thanks Mike. Just to clarify, you mean drench the bottom with CLEANER, (alcohol or the flux cleaner spray),   NOT WATER to rinse off the cleaner. Right?

Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 08:22:42 PM
Thanks Mike. Just to clarify, you mean drench the bottom with CLEANER, (alcohol or the flux cleaner spray),   NOT WATER to rinse off the cleaner. Right?

Carlos

I've always drenched with isopropyl alcohol.  If you have something more intense you might want to read its label.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: musicaudioworks on March 29, 2017, 09:35:29 PM
With GR Active you should see AC voltage.  Very small at 4:1 and larger at 20:1.

Check all of your ratio PCB solder points and the relay on the main PCB.  Also check the solder points for the Ratio to Main PCB connector.

Do that first.

If you still have nothing @ 22 ....then see what you AC is on either side of R78 with all of the same signal and control conditions as before....make sure GR is ON.

Mike

Figured it out! Working. Sounds amazing!  Thanks for your help. Feel better!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 09:48:51 PM
Figured it out! Working. Sounds amazing!  Thanks for your help. Feel better!

Whoop!

Thanks, I'm going to go to bed for like 30 hours.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on March 29, 2017, 10:03:13 PM
I've always drenched with isopropyl alcohol.  If you have something more intense you might want to read its label.

Thanks Mike.
Sorry to be thick on this...last thing.  I shouldn't use water to rinse off the alcohol right? Just straight alcohol and let it dry?

thanks
Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 29, 2017, 10:26:59 PM
Thanks Mike.
Sorry to be thick on this...last thing.  I shouldn't use water to rinse off the alcohol right? Just straight alcohol and let it dry?

thanks
Carlos

No water,  alcohol is a volatile liquid.  It'll evaporate in seconds.  Water will just sit on there.




Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on March 30, 2017, 10:55:31 AM
Greetings.

I'm confirming that the resistors at R210 and R211 on the Active Link are 10R and not 10k.  Unfortunately I received (2)10k.

Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 30, 2017, 02:49:54 PM
Greetings.

I'm confirming that the resistors at R210 and R211 on the Active Link are 10R and not 10k.  Unfortunately I received (2)10k.

Thanks

There are 2 10Ω and 2 10K resistors on the PCB.  Official BOM:

http://mnats.net/files/fetrack/fet_rack_link_doc_v1.2.pdf

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Einestad on March 30, 2017, 04:50:16 PM
What PCB version do you have?  1.11? Is your trim pot short and square?

The PCB you provided, the trim pots are like the ones in your build guide for the latest version of the rev d (short and square) But the question remains, is there something wrong with the trimmer pads on the pcb? Considering that the build guide says the trimmers should fit easily and two of them does. Its the bottom left holes in two of the slots that are plugged, so could i perhaps use a needle two enlarge them or should i use the other pads on those trimmer slots?

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 30, 2017, 08:00:29 PM
The PCB you provided, the trim pots are like the ones in your build guide for the latest version of the rev d (short and square) But the question remains, is there something wrong with the trimmer pads on the pcb? Considering that the build guide says the trimmers should fit easily and two of them does. Its the bottom left holes in two of the slots that are plugged, so could i perhaps use a needle two enlarge them or should i use the other pads on those trimmer slots?

Thanks!

I'm not sure what you mean.  You have pads that are filled with solder?  Can you post an image here?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 30, 2017, 10:31:04 PM
I'm pretty sick right now so I can't do comparative tests on this end today.

That's about a 3dBu difference and might have more to do with input/output pot tolerance. I can't remember if the pots are 10% or 20% but that can account for that.

Try adjusting one input so you have the same voltage at TP1. See if you're output is within a dB now. How much did you have to adjust it? Like a half dot or less? if so then that's just pot tolerance. Try just adjusting the output how far do you need to adjust that one keeping the inputs matched?

Because of all the tolerances in the unit every unit is going to be a little different. 

Also before doing that make sure the input and the output skirt line on each unit lines up perfectly with "0" on the scale.

3dB seems a bit high, but confirm those pots are lined up and adjust the input (and output) a little to get them to match. See how far you have to adjust the knobs.

Whenever you use a pair on something there is always a little trimming to be done. It's 60's analog gear.

Mike

Hope you're feeling better!
I had to turn the older units input up about 2/3 of the way from 24 and the next dot (22 since each dot is 3 units). 
Older unit: 6.63VAC
Newer unit: 9.98VAC

With the inputs matched, I had to turn the output of the older unit up to what would be 17 (1/3 between 18 and the next dot)

Let me know what you think!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on March 30, 2017, 11:47:15 PM
Hey Mike,

Just a small discrepancy I noticed in the FET Rack build guide. In the assembly section, the third photo shows the ratio card installed with one orientation (switches solder tabs facing out), then a little later on, it shows it differently (switches solder tabs facing in towards the meter card).

I was having a little issue with getting the ratio buttons to center themselves properly in the panel, then I noticed the latter picture, flipped the card and voila!

Just figured you might want to know, in case anyone else has a little difficulty.

Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 31, 2017, 01:05:13 AM
Hey Mike,

Just a small discrepancy I noticed in the FET Rack build guide. In the assembly section, the third photo shows the ratio card installed with one orientation (switches solder tabs facing out), then a little later on, it shows it differently (switches solder tabs facing in towards the meter card).

I was having a little issue with getting the ratio buttons to center themselves properly in the panel, then I noticed the latter picture, flipped the card and voila!

Just figured you might want to know, in case anyone else has a little difficulty.

Carlos

One of the images was from an early prototype.  I was to go in a certain way, with the 20:1 ratio on the top. That should be labeled on the PCB.

I believe the 6-pin connector should be facing out towards the main PCB.

I'm too sick to double check one right now.  Look for the 20:1 on the PCB.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on March 31, 2017, 01:07:58 AM
Hope you're feeling better!
I had to turn the older units input up about 2/3 of the way from 24 and the next dot (22 since each dot is 3 units). 
Older unit: 6.63VAC
Newer unit: 9.98VAC

With the inputs matched, I had to turn the output of the older unit up to what would be 17 (1/3 between 18 and the next dot)

Let me know what you think!

Sounds like you're having to tweek the in out by about 1/2 a dot.

That's just tolerance.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on March 31, 2017, 01:50:00 AM
Sounds like you're having to tweek the in out by about 1/2 a dot.

That's just tolerance.

Mike

Alright. So I'll just have to tweak a little when running both simultaneously? I can live with that.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on March 31, 2017, 11:01:02 AM
One of the images was from an early prototype.  I was to go in a certain way, with the 20:1 ratio on the top. That should be labeled on the PCB.

I believe the 6-pin connector should be facing out towards the main PCB.

I'm too sick to double check one right now.  Look for the 20:1 on the PCB.

Mike

I hadn't noticed the labeling on the PCB. My bad.
Feel better.

Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on March 31, 2017, 01:35:36 PM
No water,  alcohol is a volatile liquid.  It'll evaporate in seconds.  Water will just sit on there.

So doing as you described and cleaning the bottom of PCB with 91% isopropyl alcohol and soft toothbrush, leaves a little whitish residue behind after drying. Tried it a few times.
Is this just a cosmetic thing and should I just leave it alone and not worry about this?


thanks
Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: clockworkonions on April 01, 2017, 06:02:32 PM
Hi Mike. So I have and issue with the GR. I accidentally put in C21 backwards. the cap bloated so i disregarded and replaced with a new one.  With a 1k load, i get 0vac at TP22 on all ratios. I get -5.5, - 3.2, -2.3, -1.5DCV at PT21. I've read other posts with similar problems and i've checked, double checked my solder joints and component values. Any help is much appreciated! Thanks

-Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 03, 2017, 05:08:06 PM
So doing as you described and cleaning the bottom of PCB with 91% isopropyl alcohol and soft toothbrush, leaves a little whitish residue behind after drying. Tried it a few times.
Is this just a cosmetic thing and should I just leave it alone and not worry about this?


thanks
Carlos

I wouldn't worry about that. We get that too.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 03, 2017, 05:08:49 PM
Hi Mike. So I have and issue with the GR. I accidentally put in C21 backwards. the cap bloated so i disregarded and replaced with a new one.  With a 1k load, i get 0vac at TP22 on all ratios. I get -5.5, - 3.2, -2.3, -1.5DCV at PT21. I've read other posts with similar problems and i've checked, double checked my solder joints and component values. Any help is much appreciated! Thanks

-Chris

You're checking with a signal and with GR turned on?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on April 03, 2017, 06:37:47 PM
Alright. So I'll just have to tweak a little when running both simultaneously? I can live with that.

The difference between the output knobs when both units are compressing  the same source material is REALLY vast. I have to turn the original unit up to 24 to match the newer unit which is only at 36. Also when I have the active links engaged, the newer unit stops reading. Should I go through and check the active link PCBs? I can't seem to find much info about those.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 03, 2017, 06:40:15 PM
The difference between the output knobs when both units are compressing  the same source material is REALLY vast. I have to turn the original unit up to 24 to match the newer unit which is only at 36. Also when I have the active links engaged, the newer unit stops reading. Should I go through and check the active link PCBs? I can't seem to find much info about those.

Ya that's not right.  I would start there, with the links.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on April 03, 2017, 11:16:12 PM
Ya that's not right.  I would start there, with the links.

I went through and checked all of the components. Everything is in its place so I went through and reflowed the solder. Is there any test I can do on this before putting it back in and reassembling the whole compressor?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 03, 2017, 11:18:23 PM
I went through and checked all of the components. Everything is in its place so I went through and reflowed the solder. Is there any test I can do on this before putting it back in and reassembling the whole compressor?

Swap the active links...see if the issue fallows the links.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on April 04, 2017, 01:53:18 AM
Swap the active links...see if the issue fallows the links.

Switched the links. No difference. The newer unit sounds muffled though in comparison to the original. Does this give us any direction?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 04, 2017, 12:21:13 PM
Switched the links. No difference. The newer unit sounds muffled though in comparison to the original. Does this give us any direction?

Not really.  Are you loosing high end on one unit? Is that what you mean by "muffled".
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: clockworkonions on April 04, 2017, 03:34:30 PM
You're checking with a signal and with GR turned on?

Mike
Yes sir. So i figured i must have messed something up in my GR circuit. could putting C21 backwards have fried one of the semiconductors? the voltages(DC) for the transistors with attack all the way up and no input are:
            B          C           E
Q7     4.4      14.7    4.7
Q8     14.9   29.6    14.08
Q9     3.4      17.1    2.8
Q10  17.1    29.6   16.9
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on April 04, 2017, 05:32:46 PM
Not really.  Are you loosing high end on one unit? Is that what you mean by "muffled".

Correct.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 04, 2017, 08:23:37 PM
Yes sir. So i figured i must have messed something up in my GR circuit. could putting C21 backwards have fried one of the semiconductors? the voltages(DC) for the transistors with attack all the way up and no input are:
            B          C           E
Q7     4.4      14.7    4.7
Q8     14.9   29.6    14.08
Q9     3.4      17.1    2.8
Q10  17.1    29.6   16.9

I doubt it. Did you ruin a solder pad when you flipped C21?.

If you have no AC voltage at pad 22 in GR mode you have an issue with your ratio PCB probably.  Look at the schematic...there is a linear path from pad 15, where the AC V is, to pad 22.  Where does it die?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 04, 2017, 08:26:28 PM
Correct.

Feed the unit a 200 Hz, 1kHz, and 10 kHz signal with GR off.  Measure them at TP1, TP15, TP17, Output tX Brown and then output between +/-.

They should be roughly the same regardless of frequency.  See if there is a point in the circuit where the HF starts to dip.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on April 04, 2017, 11:34:58 PM
Feed the unit a 200 Hz, 1kHz, and 10 kHz signal with GR off.  Measure them at TP1, TP15, TP17, Output tX Brown and then output between +/-.

They should be roughly the same regardless of frequency.  See if there is a point in the circuit where the HF starts to dip.

Mike

Jebus! I've never had such a hard time getting readings before. Even now, I'm getting different measurements but these readings were obtained 2 or more times. The numbers that were still reading differently have 2 values and hopefully one will make more sense to you. I know this isn't super pro on my behalf but I've spend about an hour testing and still can't get a consistent reading. Maybe it's my cheap DMM or maybe it's the unit. Hopefully, you will know!

                          200 Hz                                   1kHz                                              10kHz
TP1                 .186VAC                                 .186VAC                                          .166VAC
TP15              3.28VAC                                  3.32VAC                                         5.57VAC
TP17              436VAC                                   496VAC                                          .471VAC
Brown           1.905/25.03VAC                .532/14.08VAC                          17.07VAC
Output          24.5VAC                                 11.88VAC                                      17.19VAC

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 04, 2017, 11:57:12 PM
Jebus! I've never had such a hard time getting readings before. Even now, I'm getting different measurements but these readings were obtained 2 or more times. The numbers that were still reading differently have 2 values and hopefully one will make more sense to you. I know this isn't super pro on my behalf but I've spend about an hour testing and still can't get a consistent reading. Maybe it's my cheap DMM or maybe it's the unit. Hopefully, you will know!

                          200 Hz                                   1kHz                                              10kHz
TP1                 .186VAC                                 .186VAC                                          .166VAC
TP15              3.28VAC                                  3.32VAC                                         5.57VAC
TP17              436VAC                                   496VAC                                          .471VAC
Brown           1.905/25.03VAC                .532/14.08VAC                          17.07VAC
Output          24.5VAC                                 11.88VAC                                      17.19VAC

Thanks!

Ya that doesn't really help if readings are inconsistent and bobbing around.

If you have a missed up unit it could be anything. Swapped resistor values or cap values can create low pass filters. Bad solder joints can alter feedback networks or how gain stages work.

These are tough ones.  If you don't want to send it in for repair, you'll just have to poke through the gain stages comparing it to your other unit. Again try lower and higher frequencies and see if you can pin point where it differs and look there.

Ya cheep DMM's are pretty worthless above 1kHz.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on April 05, 2017, 01:16:50 AM
Ya that doesn't really help if readings are inconsistent and bobbing around.

If you have a missed up unit it could be anything. Swapped resistor values or cap values can create low pass filters. Bad solder joints can alter feedback networks or how gain stages work.

These are tough ones.  If you don't want to send it in for repair, you'll just have to poke through the gain stages comparing it to your other unit. Again try lower and higher frequencies and see if you can pin point where it differs and look there.

Ya cheep DMM's are pretty worthless above 1kHz.

Mike

I really wanted to have the satisfaction of completing one of these but I think at this point I've tried everything I can on my end. Plus, I had the feeling of satisfaction when I thought I finished it before. haha. I have a big gig this Friday night so Monday, I'll send it in. I'll keep trying to figure it out until then but come Monday, she's all yours!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: clockworkonions on April 05, 2017, 11:19:50 AM
I doubt it. Did you ruin a solder pad when you flipped C21?.

If you have no AC voltage at pad 22 in GR mode you have an issue with your ratio PCB probably.  Look at the schematic...there is a linear path from pad 15, where the AC V is, to pad 22.  Where does it die?

Mike
I found it! The GR switch on the attack knob is faulty. Both sides stay open whether the switch is on or off. It's grounding my GR input even when it's turned on.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 05, 2017, 12:30:01 PM
I found it! The GR switch on the attack knob is faulty. Both sides stay open whether the switch is on or off. It's grounding my GR input even when it's turned on.

Send us an email...we'll send you a new one.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Einestad on April 05, 2017, 12:52:32 PM
I'm not sure what you mean.  You have pads that are filled with solder?  Can you post an image here?

Solved the problem however i noticed that in the build guide the pcb for ratio is in some pictures mounted with the CN2 pin connecter towards the vu meter and in some towards the main PCB. Im in the final assemby stage so need to know in which direction the ratio PCB should be so i can connect the 6 pin between CN2 to CN3.

Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 05, 2017, 01:24:58 PM
Solved the problem however i noticed that in the build guide the pcb for ratio is in some pictures mounted with the CN2 pin connecter towards the vu meter and in some towards the main PCB. Im in the final assemby stage so need to know in which direction the ratio PCB should be so i can connect the 6 pin between CN2 to CN3.

Thanks

This is correct.

http://library.hairballaudio.com/images/fetrack/assembly_pushbutton_switches_vu_meter_rear.jpg
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Einestad on April 05, 2017, 04:46:36 PM
This is correct.

http://library.hairballaudio.com/images/fetrack/assembly_pushbutton_switches_vu_meter_rear.jpg

So should the pin connector face towards the vu meter or the main PCB?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 05, 2017, 05:18:21 PM
So should the pin connector face towards the vu meter or the main PCB?

Like the image I linked to.  Connector on the side with the silkscreen for the connector. Facing the main PCB. If it's on the other side the cable won't reach.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on April 05, 2017, 06:46:21 PM
There are 2 10Ω and 2 10K resistors on the PCB.  Official BOM:

http://mnats.net/files/fetrack/fet_rack_link_doc_v1.2.pdf

Mike

Thanks Mike.  I had not soldered yet and found my "swap" mistake. 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on April 05, 2017, 06:57:16 PM
Greetings.

Is it just me or is there some switch-a-roo going on in some of the photos regarding the install of the Ratio PCB? 

In "Part 3. Final Assembly" guide, the photo following install of the Plastite screws into the XLR connectors, there is a photo of the Ratio PCB in which the CN2 is facing the VU meter.   Later in the guide is shows that it is installed with CN2 facing the Main PCB as it should (i'm guessing) in order to all the wiring bridge between CN2 and CN3.

I made the same mistake on both builds.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 05, 2017, 06:58:39 PM
Greetings.

Is it just me or is there some switch-a-roo going on in some of the photos regarding the install of the Ratio PCB? 

In "Part 3. Final Assembly" guide, the photo following install of the Plastite screws into the XLR connectors, there is a photo of the Ratio PCB in which the CN2 is facing the VU meter.   Later in the guide is shows that it is installed with CN2 facing the Main PCB as it should (i'm guessing) in order to all the wiring bridge between CN2 and CN3.

I made the same mistake on both builds.

Ya look at the conversation right above ours.

I'll clarify it in the guide.
Title: Meter adjust?
Post by: fiddlefro on April 06, 2017, 05:46:52 PM
Hi There,
Just walking through the calibration settings of the Fet Rack Rev A that I just built.
When adjusting meter settings, the little meter adjustment trim on the front panel is acting really odd.  The needle jumps around almost randomly when it's being adjusted, and comes to rest at what seems like a random location.  It's very heard to get it to end up anywhere in particular...
Any chance the trim is busted? 
thanks
Drew
Title: Re: Meter adjust?
Post by: Hairball Audio on April 07, 2017, 01:04:25 PM
Hi There,
Just walking through the calibration settings of the Fet Rack Rev A that I just built.
When adjusting meter settings, the little meter adjustment trim on the front panel is acting really odd.  The needle jumps around almost randomly when it's being adjusted, and comes to rest at what seems like a random location.  It's very heard to get it to end up anywhere in particular...
Any chance the trim is busted? 
thanks
Drew

Could be. Could also be a poor solder joint or short.

You can pull it out and test it with the ohm setting on your DMM.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on April 08, 2017, 02:31:25 PM
Question about the calibration process. I completed the calibration on the FET rack and everything went well.
Then I started thinking. When taking DMM measurements at the output XLR, does it matter if there's a physical xlr cable plugged into the output, or if I just use the test points I soldered in on either side of the connector, without the cable plugged in?
Would it affect the readings or calibration at all?

thanks
Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 09, 2017, 01:00:22 PM
Question about the calibration process. I completed the calibration on the FET rack and everything went well.
Then I started thinking. When taking DMM measurements at the output XLR, does it matter if there's a physical xlr cable plugged into the output, or if I just use the test points I soldered in on either side of the connector, without the cable plugged in?
Would it affect the readings or calibration at all?

thanks
Carlos

You should load the output with a load that is realistic to what it would usually be plugged in to.  The DMM loads it, but not the same as say your A/D converter input.

Mike
Title: No audible compression
Post by: csavetman on April 11, 2017, 05:48:05 PM
I finished building 2 FET racks. Both calibrated -no problems.
One of them works fantastic. The other one, passes audio, but I'm getting no audible compression at all.
Unit powers on fine and VU meter shows compression happening, but switching the attack knob from off to on, I'm hearing no change. (No momentary change in audio level as compression is turned on, like on the working unit.)

VU meter responding to ratio button switching as well, again,  just no audible change.
The attack knob seemed to be working during calibration, as going between CCW off and full CW, was giving me alternate AC voltage values on the DMM. (.775v / 2.44v)

Visually, everything looks good (no missing solder points that I can see)

I'm at a loss. Could it be a bad FET. (Q1 or Q11)?
Would swapping either or both out require a re calibration? I have the GR and meter FET's that originally came with the units as extra since I ordered a stereo matched set afterwards.

thanks
Carlos
Title: Re: No audible compression
Post by: Hairball Audio on April 11, 2017, 05:53:00 PM
I finished building 2 FET racks. Both calibrated -no problems.
One of them works fantastic. The other one, passes audio, but I'm getting no audible compression at all.
Unit powers on fine and VU meter shows compression happening, but switching the attack knob from off to on, I'm hearing no change. (No momentary change in audio level as compression is turned on, like on the working unit.)

VU meter responding to ratio button switching as well, again,  just no audible change.
The attack knob seemed to be working during calibration, as going between CCW off and full CW, was giving me alternate AC voltage values on the DMM. (.775v / 2.44v)

Visually, everything looks good (no missing solder points that I can see)

I'm at a loss. Could it be a bad FET. (Q1 or Q11)?
Would swapping either or both out require a re calibration? I have the GR and meter FET's that originally came with the units as extra since I ordered a stereo matched set afterwards.

thanks
Carlos

No idea.  If you're getting compression during the calibration where you set the 10dB drop, you're getting compression.  If Q1 was dead you'd never get the 10dB drop, that's the unit compressing and working correctly.

Something else is going on. Feed it a steady tone with GR OFF, then turn it on...if you see a drop on the output...that's compression.

Does the release work?

Mike

Title: Re: No audible compression
Post by: csavetman on April 11, 2017, 06:19:34 PM
No idea.  If you're getting compression during the calibration where you set the 10dB drop, you're getting compression.  If Q1 was dead you'd never get the 10dB drop, that's the unit compressing and working correctly.

Something else is going on. Feed it a steady tone with GR OFF, then turn it on...if you see a drop on the output...that's compression.

Does the release work?

Mike

Just fed it a steady 1k sine wave. Went from attack full CCW off to on, NO change at all in output volume. (Vu meters did respond)

Carlos
Title: Re: No audible compression
Post by: csavetman on April 11, 2017, 08:11:40 PM
Just fed it a steady 1k sine wave. Went from attack full CCW off to on, NO change at all in output volume. (Vu meters did respond)

Carlos

So I decided to recalibrate the unit to try to see what's up. I reset all the trimmer pots to their initial state, and now i can't get the Q bias  adjust to drop the AC voltage. It stays at 2.75VAC, after moving the adjust all the way from CW to CCW.

Carlos


Any thoughts?

Carlos
Title: Re: No audible compression
Post by: csavetman on April 11, 2017, 11:48:22 PM
So I decided to recalibrate the unit to try to see what's up. I reset all the trimmer pots to their initial state, and now i can't get the Q bias  adjust to drop the AC voltage. It stays at 2.75VAC, after moving the adjust all the way from CW to CCW.

Any thoughts?

Carlos

Figured it out. Bad Q1 FET. Changed out Q1 and Q11 with the ones that came with the kit. Re-calibrated.
Working now.

Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ffarrell on April 12, 2017, 08:34:13 AM
Wrong Thread sorry.
Title: Re: No audible compression
Post by: csavetman on April 12, 2017, 09:20:45 AM
Figured it out. Bad Q1 FET. Changed out Q1 and Q11 with the ones that came with the kit. Re-calibrated.
Working now.

Carlos

Actually, looks like the 'bad" Q1 FET is ok after all. Decided to try and re seat it in socket and calibrate. Worked this time.

Carlos
Title: Re: No audible compression
Post by: Hairball Audio on April 12, 2017, 12:45:53 PM
Actually, looks like the 'bad" Q1 FET is ok after all. Decided to try and re seat it in socket and calibrate. Worked this time.

Carlos

Ya that's the give and take with sockets.  They make switching the FETs out super easy, but they also create another point where you can have a bad connection.

That all makes sense based on what you were seeing.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 12, 2017, 12:48:07 PM
HI

Clarification on power Transformers for a  Mnat stereo D build and a Mnat stereo F build.

Will the Y236207 work for both builds?

thanks
fvf

Wrong thread. I assume you're talking about the old PCBs.  Yes it should work.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: landispearce on April 12, 2017, 02:54:46 PM
Hello,

New to this so bare with me here. Built a few of these in the past and now with one  i've built (blue stripe) I am running into an issue on the last step of calibration whilst setting the meter. I attempted to contact and they sent me here to ask. The FAQ says to go to Ed's post, which I did but I was told I would not need to change out any components by someone at hairball via their support line. My input won't go to the desired +10 dbu while metering from the output XLR, and I have taken it apart multiple times and checked everything and cannot seem to figure out what to do. Did not run into this in the past and just purchased 3 more, if anyone has any help please let me know!

thanks,
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 12, 2017, 03:04:25 PM
Hello,

New to this so bare with me here. Built a few of these in the past and now with one  i've built (blue stripe) I am running into an issue on the last step of calibration whilst setting the meter. I attempted to contact and they sent me here to ask. The FAQ says to go to Ed's post, which I did but I was told I would not need to change out any components by someone at hairball via their support line. My input won't go to the desired +10 dbu while metering from the output XLR, and I have taken it apart multiple times and checked everything and cannot seem to figure out what to do. Did not run into this in the past and just purchased 3 more, if anyone has any help please let me know!

thanks,

1. Make sure all 3 L brackets are secured to the PCB and enclosure. They are not just there for stability, they are part of the grounding system.

2. You were able to set the Q-Bias?

3.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ffarrell on April 12, 2017, 03:40:55 PM
Wrong thread. I assume you're talking about the old PCBs.  Yes it should work.

Mike

thanks Mike,

 I started these in 2012,    how is that for procrastination.   
 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: landispearce on April 13, 2017, 01:19:26 PM
1. Make sure all 3 L brackets are secured to the PCB and enclosure. They are not just there for stability, they are part of the grounding system.

2. You were able to set the Q-Bias?

3.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike

Call me stupid but I can't seem to find TP 21 and 22. I can only find 10 and 11.

but yes I can set Q Bias
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 14, 2017, 12:05:41 PM
Call me stupid but I can't seem to find TP 21 and 22. I can only find 10 and 11.

but yes I can set Q Bias

Are you not working on one of the large new PCBs? Is this an older build?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: landispearce on April 18, 2017, 01:59:32 PM
I just bought these 3 less than 2 weeks ago. I don't think these are old builds. I ordered them from you directly.  can attach photos if need be.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 18, 2017, 02:03:30 PM
I just bought these 3 less than 2 weeks ago. I don't think these are old builds. I ordered them from you directly.  can attach photos if need be.

They should have those TP points then. 22 should be near 10 (might be hidden by an orange drop, and 21 is by C21.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: landispearce on April 18, 2017, 02:35:32 PM
AH got it okay.

For AC at 22. all of them are 0.000
For DC at 21.
20:1 =5.91
12:1 = 3.304
8:1 = keeps declining and doesn't stop. changes .001 every second or so.
4:1 = -1.659
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 18, 2017, 02:42:58 PM
AH got it okay.

For AC at 22. all of them are 0.000
For DC at 21.
20:1 =5.91
12:1 = 3.304
8:1 = keeps declining and doesn't stop. changes .001 every second or so.
4:1 = -1.659

All the DC readings at TP21 should be negative DC values.

You get no AC voltage at TP22 with GR on?  Again:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: landispearce on April 18, 2017, 02:46:40 PM
Apologies, all the values are negative for the DC but the number are correct.  new meter. not used to where the negative is. and no. I have no reading at Test Point 22, GR on, 20:1 and input and input both at 12 o'clock (24)

landis
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 18, 2017, 02:50:24 PM
Apologies, all the values are negative for the DC but the number are correct.  new meter. not used to where the negative is. and no. I have no reading at Test Point 22, GR on, 20:1 and input and input both at 12 o'clock (24)

landis

What is your AC at TP15 with the same settings (ratio 20:1 only).
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: landispearce on April 18, 2017, 02:54:13 PM
4.56
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 18, 2017, 03:00:50 PM
4.56

You've got some disconnect between your TP15 and TP22.  Have a look at the schematic:

http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

This is the D but this part is the same for the A other than a few resistor values. Or you can go to MNATS.NET and download the A if that's what you're working on.

http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

Find TP15...it's right before the output pot along the top in the middle. Look how the AC travels down through the relay then to the ratio PCB, exists the ratio PCB at the bottom depending on what switch is enabled then through the attack switch to PAD 22.

See if you can trace that AC to pad 22...it's dying somewhere along that short linear path.

Probably a bad joint or lifted pad somewhere.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Pfgdad on April 18, 2017, 03:31:54 PM
Hi everyone I'm currently building my second rev D and have an issue with the power supply.

When testing for 30 volts I'm getting a reading of 32.07 volts. In the build guide it is stated that +- 5% is ok but this is a little higher. On the second test point I'm getting a reading of -9.87 volts which seems to be right on.

Is this cause for alarm?  If so any advice or info that could assist the resolution would be greatly appreciated.

Thank you
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 18, 2017, 03:43:50 PM
Hi everyone I'm currently building my second rev D and have an issue with the power supply.

When testing for 30 volts I'm getting a reading of 32.07 volts. In the build guide it is stated that +- 5% is ok but this is a little higher. On the second test point I'm getting a reading of -9.87 volts which seems to be right on.

Is this cause for alarm?  If so any advice or info that could assist the resolution would be greatly appreciated.

Thank you

Hard to say, that should be fine though. The stud diode should be regulating to 30V +/- 5%. That is assuming you have the 1N2989B we ship with the kits. The 1N2989A regulates +/- 10%.

Keep in mind your meter also has a tolerance, could be pretty high if it's cheaper.

I think you're fine. Particularly if it ready high in the other unit which you mentioned in your email.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Pfgdad on April 18, 2017, 03:55:54 PM
Hard to say, that should be fine though. The stud diode should be regulating to 30V +/- 5%. That is assuming you have the 1N2989B we ship with the kits. The 1N2989A regulates +/- 10%.

Keep in mind your meter also has a tolerance, could be pretty high if it's cheaper.

I think you're fine. Particularly if it ready high in the other unit which you mentioned in your email.

Mike


Thanks Mike for the quick response.  The first build to further explain did measure 30.3 volts so it was a little lower than this one.  Also I'm using only components included in the kit. Good to know the slightly higher voltage isn't cause for concern. 

Thank you
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 18, 2017, 03:59:51 PM

Thanks Mike for the quick response.  The first build to further explain did measure 30.3 volts so it was a little lower than this one.  Also I'm using only components included in the kit. Good to know the slightly higher voltage isn't cause for concern. 

Thank you

It would be nice if you were within the tolerance of the diode. However, you're barely out of the tolerance and I suspect there may be some weird measurement anomaly going on I can't sort out without checking out the unit myself. With it only being a 1% or so out of normal tolerance, I would not worry.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: landispearce on April 18, 2017, 04:16:14 PM
You've got some disconnect between your TP15 and TP22.  Have a look at the schematic:

http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

This is the D but this part is the same for the A other than a few resistor values. Or you can go to MNATS.NET and download the A if that's what you're working on.

http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

Find TP15...it's right before the output pot along the top in the middle. Look how the AC travels down through the relay then to the ratio PCB, exists the ratio PCB at the bottom depending on what switch is enabled then through the attack switch to PAD 22.

See if you can trace that AC to pad 22...it's dying somewhere along that short linear path.

Probably a bad joint or lifted pad somewhere.

Mike

Mike, So i was able to find the issue, it was in the ratio board. I was able to complete the calibration without  problem. Thank you for your help!

Also, seems to be quite distorted when i test with actual audio. I understand that blue stripes are indeed distorted more so but it seems like there is something wrong. First blue stripe I've built so I could just be wrong.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 18, 2017, 04:53:12 PM
Mike, So i was able to find the issue, it was in the ratio board. I was able to complete the calibration without  problem. Thank you for your help!

Also, seems to be quite distorted when i test with actual audio. I understand that blue stripes are indeed distorted more so but it seems like there is something wrong. First blue stripe I've built so I could just be wrong.

The Rev A is pretty hot on the front end and has 5dB more gain overall.  If you're running a line level signal in and your input is past 9 o'clock it's going to clip. Try turning down the signal source and or the input. That should clean it up.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on April 19, 2017, 06:52:33 PM
Hi,

I'm building the revA new kit and just finished the power supply. When I go to check voltage measurements I am getting the same readings as when the unit is not connected to power

1) I'm measuring -0.275V where I should be measuring -10V at the capacitor.

2) I'm measuring 0.181V where I should be measuring 30V at CR8

I tried using different power cords and different multimeters but get the same readings. I am switched to 115V and double and triple checked I followed all instructions.

The only confusing thing is I was sent two IEC connectors in the build. I used the one that already as the nut/bolt grounding assembly on it, and followed instructions.

Please help!

Thank you
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 19, 2017, 07:06:15 PM
Hi,

I'm building the revA new kit and just finished the power supply. When I go to check voltage measurements I am getting the same readings as when the unit is not connected to power

1) I'm measuring -0.275V where I should be measuring -10V at the capacitor.

2) I'm measuring 0.181V where I should be measuring 30V at CR8

I tried using different power cords and different multimeters but get the same readings. I am switched to 115V and double and triple checked I followed all instructions.

The only confusing thing is I was sent two IEC connectors in the build. I used the one that already as the nut/bolt grounding assembly on it, and followed instructions.

Please help!

Thank you

Weird that you got an IEC without ground on it. That was definitely a mistake.

1. Check your fuse. Make sure it's in there, not blown, and seated correctly.
2. Confirm you are measuring DC V
3. Confirm the unit is on, which means you have GR, +4, or +8 pushed in and not the "OFF" button.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on April 19, 2017, 09:54:00 PM
Hey Mike, it wasn't that I received an IEC without ground, but I received TWO IECs (both with ground green wire), but one already had the nut/bolt/screw assembly on it, so I used that one.

I'm using a DMM that I believe automatically reads in DC or AC V. It's radio shacks DMM.

I had the unit set to GR so it was on.

Also, I'm measuring 0.3 ohms resistance at IEC ground.

Just tried switching out the fuse since the pack came with two (the one I had in didn't look blown), and still not getting good readings.

Any other ideas?

Thank you!

Weird that you got an IEC without ground on it. That was definitely a mistake.

1. Check your fuse. Make sure it's in there, not blown, and seated correctly.
2. Confirm you are measuring DC V
3. Confirm the unit is on, which means you have GR, +4, or +8 pushed in and not the "OFF" button.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on April 19, 2017, 10:51:43 PM
P.S. the DMM was correctly set to DC voltage measurement.

Hey Mike, it wasn't that I received an IEC without ground, but I received TWO IECs (both with ground green wire), but one already had the nut/bolt/screw assembly on it, so I used that one.

I'm using a DMM that I believe automatically reads in DC or AC V. It's radio shacks DMM.

I had the unit set to GR so it was on.

Also, I'm measuring 0.3 ohms resistance at IEC ground.

Just tried switching out the fuse since the pack came with two (the one I had in didn't look blown), and still not getting good readings.

Any other ideas?

Thank you!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 20, 2017, 12:11:33 PM
P.S. the DMM was correctly set to DC voltage measurement.

You need to consider how the voltage moves through the circuit and figure out where it's stopping.

AC enters at the IEC and travel to and back from the OFF switch where it enters the voltage select switch and exists to the power transformer primary. Then the AC leaves the transformer secondary to the PCB where it's rectified to DC. Let's work our way back.

With the unit ON. Check for AC V between chassis ground and each orange wire coming off the secondary into the PCB.

Please keep in mind for your unit to be properly grounded, you need to have all 3 L brackets screwed in place from the PCB to chassis.

When measuring these voltages use caution.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on April 20, 2017, 03:55:14 PM
I'm only getting 0.9 V at both of the orange wires measured at the secondary transformer where they leave to go to the PCB.

The PCB is screwed in. I also tried switching out the IEC with the second IEC you sent.

Could it be a bad transformer?

Thanks

You need to consider how the voltage moves through the circuit and figure out where it's stopping.

AC enters at the IEC and travel to and back from the OFF switch where it enters the voltage select switch and exists to the power transformer primary. Then the AC leaves the transformer secondary to the PCB where it's rectified to DC. Let's work our way back.

With the unit ON. Check for AC V between chassis ground and each orange wire coming off the secondary into the PCB.

Please keep in mind for your unit to be properly grounded, you need to have all 3 L brackets screwed in place from the PCB to chassis.

When measuring these voltages use caution.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 20, 2017, 04:31:57 PM
I'm only getting 0.9 V at both of the orange wires measured at the secondary transformer where they leave to go to the PCB.

The PCB is screwed in. I also tried switching out the IEC with the second IEC you sent.

Could it be a bad transformer?

Thanks

It's always possible it's the transformer. However, that is the last part I would suspect. They are tested before they ship and we haven't had a bad new version yet. Odds are you have a bad solder joint somewhere or bad measurement set up. It's funny how people always assume it a transformer issue (power and audio) and it pretty much never is. They are very simple parts that don't really break.

We can figure out the issue, we just need to walk through it and you need to be careful because at some point I make ask you to test areas that carry mains AC voltage.

FOR THIS PART UNPLUG THE UNIT FROM THE WALL

Again remove the power cord completely, no power. We're just checking continuity.

1. Make sure the unit is switched to GR mode on the meter switch. We just need the switch in the position but NO POWER.
2. Disconnect the 7 pin transformer connector from the voltage selector switch.
3. Pull back the N (white) IEC upper connector so you can probe N tab but keep the connector connected to the tab. What is the DC resistance (Ω) between that N IEC tab and the far left pin on the 7 pin connector (the one closest to the main PCB).
3. Pull back the L (Black) IEC lower connector so you can probe L tab but keep the connector connected to the tab. What is the DC resistance (Ω) between that L IEC tab and the far right pin on the 7 pin connector (closest to the enclosure side).

4. Plug the 7 pin connector back in (still no power to the unit). There are 6 soldered tabs on the voltage selector switch sticking out. Measure the DC resistance (Ω) between the two on the far left.  By the words "High" and "Do".
5. Measure the DC resistance (Ω) between the yellow secondary wire and each orange.

Report all that back. Again, at no point should you have your unit plugged into the wall.  You need to have it in GR metering however.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on April 21, 2017, 07:49:46 PM
See below for resistance measurements. Thanks Mike.

It's always possible it's the transformer. However, that is the last part I would suspect. They are tested before they ship and we haven't had a bad new version yet. Odds are you have a bad solder joint somewhere or bad measurement set up. It's funny how people always assume it a transformer issue (power and audio) and it pretty much never is. They are very simple parts that don't really break.

We can figure out the issue, we just need to walk through it and you need to be careful because at some point I make ask you to test areas that carry mains AC voltage.

FOR THIS PART UNPLUG THE UNIT FROM THE WALL

Again remove the power cord completely, no power. We're just checking continuity.

1. Make sure the unit is switched to GR mode on the meter switch. We just need the switch in the position but NO POWER.
2. Disconnect the 7 pin transformer connector from the voltage selector switch.
3. Pull back the N (white) IEC upper connector so you can probe N tab but keep the connector connected to the tab. What is the DC resistance (Ω) between that N IEC tab and the far left pin on the 7 pin connector (the one closest to the main PCB).
0 ohms

3. Pull back the L (Black) IEC lower connector so you can probe L tab but keep the connector connected to the tab. What is the DC resistance (Ω) between that L IEC tab and the far right pin on the 7 pin connector (closest to the enclosure side).
0 ohms

4. Plug the 7 pin connector back in (still no power to the unit). There are 6 soldered tabs on the voltage selector switch sticking out. Measure the DC resistance (Ω) between the two on the far left.  By the words "High" and "Do".

I don't get a measurement... I tried several times and the 7 pin connector and other two connectors on the IEC are connected


5. Measure the DC resistance (Ω) between the yellow secondary wire and each orange.

11.2 ohms (top orange on pcb and yellow middle)
11.6 ohms (bottom orange on pcb and yellow middle)

Report all that back. Again, at no point should you have your unit plugged into the wall.  You need to have it in GR metering however.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 22, 2017, 11:04:37 AM
Step 4 is your problem.

Try this, remove the power transformer from the build. See if you can get your DMM probes to the metal contacts in the 7 pin header. This is easier to do from the side where the wire goes into the header. See if you can get a DMM Ω reading between white and black and then red and blue.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on April 22, 2017, 08:42:32 PM
I can't get my DMM probe into the metal contacts, the opening is much too small for my probe.

Are there other measurements I can do to check where the failure point is?

If it's easier to walk thru other troubleshooting by phone I'm available at 6087129753

Thanks again Mike.



Step 4 is your problem.

Try this, remove the power transformer from the build. See if you can get your DMM probes to the metal contacts in the 7 pin header. This is easier to do from the side where the wire goes into the header. See if you can get a DMM Ω reading between white and black and then red and blue.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 23, 2017, 11:29:59 AM
Actually just remove your voltage selector PCB from the enclosure and your power transformer.

Then plug just the power transformer primary into the 7 pin connector. With the 7 pin connector attached to voltage select PCB, you can now measure the Ω between blk/wht and blu/red by using the 7 pin connector solder pads that correspond with those wires.

Mesure those Ω with the switch in 115 and 230.

Mike

I can't get my DMM probe into the metal contacts, the opening is much too small for my probe.

Are there other measurements I can do to check where the failure point is?

If it's easier to walk thru other troubleshooting by phone I'm available at 6087129753

Thanks again Mike.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on April 23, 2017, 06:04:34 PM
with the switch in 115V...

blk/wht resistance: not getting a reading
blu/red resistance: not getting a reading

with the switch in 230V...

blk/wht resistance: 97.6 ohms
blu/red resistance: 116.2 ohms

is the voltage selector switch bad in 115V (my region)?



Actually just remove your voltage selector PCB from the enclosure and your power transformer.

Then plug just the power transformer primary into the 7 pin connector. With the 7 pin connector attached to voltage select PCB, you can now measure the Ω between blk/wht and blu/red by using the 7 pin connector solder pads that correspond with those wires.

Mesure those Ω with the switch in 115 and 230.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on April 24, 2017, 12:44:53 PM
with the switch in 115V...

blk/wht resistance: not getting a reading
blu/red resistance: not getting a reading

with the switch in 230V...

blk/wht resistance: 97.6 ohms
blu/red resistance: 116.2 ohms

is the voltage selector switch bad in 115V (my region)?

Possible, but I'd first suspect a solder issue.

Your transformer seems fine. The 115V switching is problematic. I would start by reflowing the solder joints on the voltage switch PCB including those on the 7 pin connector. If you can see the traces on the PCB follow them to the next pad and check for continuity.

Make sure the switch is full in place in the 115V position and test again after examining all joints for continuity.

If it's still bad after that, we'll send you a new switch/PCB.

Mike
Title: Rev D v1.12 input transformer
Post by: csavetman on May 02, 2017, 02:18:23 PM
Hey Mike,

Just wanted to check something with you.
The build guide says on V 1.11 PCB of Rev D FET rack, that input transformer should be soldered slightly off the PCB because of the soldering pads on the top.

There's no need to do that on the newest version 1.12 PCB, right?

Carlos
Title: Re: Rev D v1.12 input transformer
Post by: Hairball Audio on May 02, 2017, 02:22:41 PM
Hey Mike,

Just wanted to check something with you.
The build guide says on V 1.11 PCB of Rev D FET rack, that input transformer should be soldered slightly off the PCB because of the soldering pads on the top.

There's no need to do that on the newest version 1.12 PCB, right?

Carlos

Correct. Top pads were removed.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on May 02, 2017, 02:43:38 PM
Hey Mike,

One more thing. On the Rev D PCB, there's a spot for a diode, CR10 next to the stereo link relay. I don't see CR10 on the BOM however. Does that get left empty?

Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: csavetman on May 02, 2017, 02:54:19 PM
Hey Mike,

One more thing. On the Rev D PCB, there's a spot for a diode, CR10 next to the stereo link relay. I don't see CR10 on the BOM however. Does that get left empty?

Carlos

Never mind. I see it listed on the components print out that came with the kit. It was just ommited from the online BOM.

Carlos
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on May 04, 2017, 06:24:26 PM

Hey Mike I just soldered the replacement pcb/IEC switch and am getting the same exact readings as below... I didn't try going fwd any further since these are bad readings.

Please advise

Thank you

Possible, but I'd first suspect a solder issue.

Your transformer seems fine. The 115V switching is problematic. I would start by reflowing the solder joints on the voltage switch PCB including those on the 7 pin connector. If you can see the traces on the PCB follow them to the next pad and check for continuity.

Make sure the switch is full in place in the 115V position and test again after examining all joints for continuity.

If it's still bad after that, we'll send you a new switch/PCB.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: galloni21 on May 04, 2017, 06:41:05 PM
Sorry I meant I'm still getting these readings below with the replacement pcb and switch...


with the switch in 115V...

blk/wht resistance: not getting a reading
blu/red resistance: not getting a reading

with the switch in 230V...

blk/wht resistance: 97.6 ohms
blu/red resistance: 116.2 ohms

is the voltage selector switch bad in 115V (my region)?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 04, 2017, 07:29:01 PM
If you're in the USA it might be best for you to send in the Voltage SW, Power Tx, and Meter Switch.

I could try sending you a new TX but it seems fine in 230V mode and I hate to just keep sending you stuff when nothing really adds up.

Email me.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 19, 2017, 05:05:13 PM
Hi,

I have strange issues regarding my REV A build (the new one).

First I have unfortunately missplaced CR 10. Repaired it and everything was pretty nice working. When compared to my other unit they were sonically as twin brothers.

After some time though the unit sounds quite unpleasantly distorted pretty soon and seems not compressing as it should.
Also the unit starts to distort pretty soon when adjusting input gain. under 36 marking already. And to get any compression I need to drive it quite hot (around 18). Funny though as soon as I turn off compression (with attack knob) sound is nice and clear as it should.

I have followed DC voltages and found out these problematic values:



Q3:  B:      7.04 VDC (should be 6.73 VDC)
          C:   16.02 VDC (13.74 VDC)
´         E:       6.44 VDC (6.13)

Q7  B:  4.6VDC (5.22)
         C: 
         E:  4.05VDC (4.71)

Q8  B: 15.28VDC (16.93)
         C:  30,5VDC
         E:  14.6 VDC (16.31)

Q9: B: 3.5 VDC (3.6)
         C: 17.3 VDC (14.96)
         E:  2.97 VDC (3.09)

Q10  B: 17.3 VDC (14.96)
            C: 30,5 VDC
            E:16.7 VDC (14.39)

Everything else seems more or less on the place (cca 0.1- 0.2 VDC variations)
My PSU gives 30.5VDC/-9,7VDC

I have checked visually all resistors in GR CONTROL AMP circuit, such as all of them around problematic transistors and did not find any false piece.

Unfortunately I do not have access to oscilloscope at the moment to see where and when is something wrong going on.

Calibration can be made correctly, but  audibly generates  unit when fed with  +10dBU  for step 3. quite lots of harmonics content.

Thanks for any suggestion where should i look at

Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 22, 2017, 01:51:36 PM
Hi,

I have strange issues regarding my REV A build (the new one).

First I have unfortunately missplaced CR 10. Repaired it and everything was pretty nice working. When compared to my other unit they were sonically as twin brothers.

After some time though the unit sounds quite unpleasantly distorted pretty soon and seems not compressing as it should.
Also the unit starts to distort pretty soon when adjusting input gain. under 36 marking already. And to get any compression I need to drive it quite hot (around 18). Funny though as soon as I turn off compression (with attack knob) sound is nice and clear as it should.

I have followed DC voltages and found out these problematic values:



Q3:  B:      7.04 VDC (should be 6.73 VDC)
          C:   16.02 VDC (13.74 VDC)
´         E:       6.44 VDC (6.13)

Q7  B:  4.6VDC (5.22)
         C: 
         E:  4.05VDC (4.71)

Q8  B: 15.28VDC (16.93)
         C:  30,5VDC
         E:  14.6 VDC (16.31)

Q9: B: 3.5 VDC (3.6)
         C: 17.3 VDC (14.96)
         E:  2.97 VDC (3.09)

Q10  B: 17.3 VDC (14.96)
            C: 30,5 VDC
            E:16.7 VDC (14.39)

Everything else seems more or less on the place (cca 0.1- 0.2 VDC variations)
My PSU gives 30.5VDC/-9,7VDC

I have checked visually all resistors in GR CONTROL AMP circuit, such as all of them around problematic transistors and did not find any false piece.

Unfortunately I do not have access to oscilloscope at the moment to see where and when is something wrong going on.

Calibration can be made correctly, but  audibly generates  unit when fed with  +10dBU  for step 3. quite lots of harmonics content.

Thanks for any suggestion where should i look at

Jan

Start by reading that. There are a few nuggets in there.

http://www.hairballaudio.com/blog/resources/post/fetrack-operational-faq

Also if you're input signal is +10dBu, that is way too high.

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 22, 2017, 07:07:06 PM

Start by reading that. There are a few nuggets in there.

http://www.hairballaudio.com/blog/resources/post/fetrack-operational-faq

Also if you're input signal is +10dBu, that is way too high.

Mike

Hi Mike,
Thanks for response.
I have read that already, such as whole forum. I have misled you by saying I fed the unit with 10 dB. What I meant was when I pushed input to gain 10dB for step 3 in calibration procedure I had these distorted harmonics audible at the output. I fed the unit with 0dBU from my Neutrik signal generator. Also my unit does not compress until I am with inout at way beyond "noon". First I thought I had the problem at preamp stage, but as I have said, when I bypass compression by using attack knob, signal is clear. So I think there is probably something in GR circuit. But I have found out these weird voltages around transistors as stated in my first post. Unfortunately I am not so expert in electronic to see where else should I look at. I think to swap Q1 and Q11 to see if it helps. I thought to ask you first about any other ideas or if these voltages is somewhat ok. Or I should look at transistors.

Thanks for suggestions
Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 22, 2017, 07:17:32 PM
Hi Mike,
Thanks for response.
I have read that already, such as whole forum. I have misled you by saying I fed the unit with 10 dB. What I meant was when I pushed input to gain 10dB for step 3 in calibration procedure I had these distorted harmonics audible at the output. I fed the unit with 0dBU from my Neutrik signal generator. Also my unit does not compress until I am with inout at way beyond "noon". First I thought I had the problem at preamp stage, but as I have said, when I bypass compression by using attack knob, signal is clear. So I think there is probably something in GR circuit. But I have found out these weird voltages around transistors as stated in my first post. Unfortunately I am not so expert in electronic to see where else should I look at. I think to swap Q1 and Q11 to see if it helps. I thought to ask you first about any other ideas or if these voltages is somewhat ok. Or I should look at transistors.

Thanks for suggestions
Jan

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on May 23, 2017, 06:42:01 AM
Question.. so how much would replacing R70 with a 5% tolerance resistor instead of 1% effect the meter and the accuracy. Will it even work? Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 23, 2017, 11:10:03 AM
Question.. so how much would replacing R70 with a 5% tolerance resistor instead of 1% effect the meter and the accuracy. Will it even work? Thanks!

Doesn't mater. It's calibrated anyway.

The original units used 10% resistors.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 23, 2017, 11:59:37 AM
Hi Mike

here are my voltages:

TP 21
20:1   -5.84   VDC
12:1   -3.177 VDC
  8:1    -2.341 VDC
  4:1    -1.505 VDC

TP 22
20:1   0.511 VAC
12:1   0.246 VAC
  8:1    0.160 VAC
  4:1    0.075 VAC

Thanks

Jan


Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on May 23, 2017, 12:10:42 PM
Question.. so how much would replacing R70 with a 5% tolerance resistor instead of 1% effect the meter and the accuracy. Will it even work? Thanks!

Ok so another question. With my signal generator set at 1khz and as loud is my system can physically output it, my DMM on the input gives me a reading of anywhere between 0.066-0.093 never does it give me a reading of the suggested 0.775. So what is wrong, also the needle on the meter stays and -20, and can be adjusted as high as -10 I can get it no where near 0.

This is after following all the calibration steps

Thanks.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 23, 2017, 12:22:34 PM
Ok so another question. With my signal generator set at 1khz and as loud is my system can physically output it, my DMM on the input gives me a reading of anywhere between 0.066-0.093 never does it give me a reading of the suggested 0.775. So what is wrong, also the needle on the meter stays and -20, and can be adjusted as high as -10 I can get it no where near 0.

This is after following all the calibration steps

Thanks.

If you can't get 0.775 VAC at your input, it's most likely an issue with your set up.  What is your signal generator termination? XLR? Try seeing what you have across pin 2 and pin 3 of the terminating connector when it's disconnected from the FET/RACK.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 23, 2017, 12:24:09 PM
Hi Mike

here are my voltages:

TP 21
20:1   -5.84   VDC
12:1   -3.177 VDC
  8:1    -2.341 VDC
  4:1    -1.505 VDC

TP 22
20:1   0.511 VAC
12:1   0.246 VAC
  8:1    0.160 VAC
  4:1    0.075 VAC

Thanks

Jan

Doesn't seem off.

What is your VAC in the same set up at + side of CR2?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 23, 2017, 12:48:47 PM
Doesn't seem off.

What is your VAC in the same set up at + side of CR2?

Mike

CR2 Anode:
20:1   4.58VAC
12:1   2.21VAC
   8:1   1.446VAC
   4:1   0.698VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 23, 2017, 01:02:31 PM
CR2 Anode:
20:1   4.58VAC
12:1   2.21VAC
   8:1   1.446VAC
   4:1   0.698VAC

Seems good.

You sure you're calibrating the QBias and Meter correctly?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 23, 2017, 01:16:08 PM
Seems good.

You sure you're calibrating the QBias and Meter correctly?

Mike
Pretty much. I did it several times already... This is second unit I have built. 
And the unit did sound ok. The nasty dostortions and funny behavior started a bit later. Like after couple days of using it. I mean distortion is really unpleasant.... and if i stay with input knob under the distortion level I cannot reach compression "threshold"
That is why I have started to look at possible issues.
So you mean these shifted DC voltages I have sent before around transistors are ok?

Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 23, 2017, 01:23:26 PM
Pretty much. I did it several times already... This is second unit I have built. 
And the unit did sound ok. The nasty dostortions and funny behavior started a bit later. Like after couple days of using it. I mean distortion is really unpleasant.... and if i stay with input knob under the distortion level I cannot reach compression "threshold"
That is why I have started to look at possible issues.
So you mean these shifted DC voltages I have sent before around transistors are ok?

Jan

Nothing these seems crazy.

And it sounds fine in GR off?

What if you increase the level going into the unit? Maybe you input is not high enough?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 23, 2017, 01:34:08 PM
Nothing these seems crazy.

And it sounds fine in GR off?

What if you increase the level going into the unit? Maybe you input is not high enough?

Yes it does. It sounds wonderfull with GR off. I have tried with hotter signal with same effect. I mean the harmonics sounds like too much transistor O/L. All buttons in mode is unusable whil it was pretty great on drums before...  I will give it one more shot though... and see what happens.... maybe I will post audio so you can hear for yourselves...

Besides of this one problem I have I have to say you guys did absolutely amazing job. These beasts sound great and build quality is awesome. I must have f**ked it up somewhere :(...
Thanks again
Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 23, 2017, 01:37:07 PM
Yes it does. It sounds wonderfull with GR off. I have tried with hotter signal with same effect. I mean the harmonics sounds like too much transistor O/L. All buttons in mode is unusable whil it was pretty great on drums before...  I will give it one more shot though... and see what happens.... maybe I will post audio so you can hear for yourselves...

Besides of this one problem I have I have to say you guys did absolutely amazing job. These beasts sound great and build quality is awesome. I must have f**ked it up somewhere :(...
Thanks again
Jan

We'll get it sorted. Even if you have to send one in.

Sounds like something is off in your GR amp.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 23, 2017, 02:31:06 PM
We'll get it sorted. Even if you have to send one in.

Sounds like something is off in your GR amp.

Mike

So I have tried to recalibrate again using DMM and if I send from my neutrik 0dBu it reads 0.552 VAC at input testpoints
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 23, 2017, 02:32:19 PM
So I have tried to recalibrate again using DMM and if I send from my neutrik 0dBu it reads 0.552 VAC at input testpoints

That's impedance loss.  Just boost your signal till you see 0dBu.
Title: Re: [BUILD] New FET/RACK Official Help Thread
Post by: Spaceyjb on May 23, 2017, 02:56:21 PM
That's impedance loss.  Just boost your signal till you see 0dBu.

Funny thing. I had to push my generator to about 3,4 dBu and now when i try to set output knob in step 3 calibration to read 0dB/0.775V it is really hard to do as output oscilates in between 0.775-.774V (-0.03 and -0.11dBu)

EDIT: Fully calibrated and does not oscilates...

EDIT: checked voltages at TP21/22/CR2+  about the same...
Title: Re: [BUILD] New FET/RACK Official Help Thread
Post by: Hairball Audio on May 23, 2017, 03:19:28 PM
Funny thing. I had to push my generator to about 3,4 dBu and now when i try to set output knob in step 3 calibration to read 0dB/0.775V it is really hard to do as output oscilates in between 0.775-.774V (-0.03 and -0.11dBu)

EDIT: Fully calibrated and does not oscilates...

EDIT: checked voltages at TP21/22/CR2+  about the same...

Same issues?
Title: Re: [BUILD] New FET/RACK Official Help Thread
Post by: Spaceyjb on May 23, 2017, 03:51:33 PM
Same issues?

EDIT: After studio test: unfortunately the problem is persisting. What has definitely change for better is character of the distortion. It is much more pleasant, but as soon as I set input knob so to compression start level it starts to distort. it seems attack / release knobs has not any influence with exception of bypass, so the time is super super fast at all circumstances and maybe that is the reason of distortion... I will check there.

Jan



audibly it is much better... lesson made.  I would not say I shouldn't use professional generator/analyzer gear to calibrate... I still feel there is something weird with transients, but i need to do preper tests in the studio.
Do you think it would make sanse to set qbias just slightly softer: not for 1dB loss but maybe 0.7 and the beast would be a bit softer on these transients. Or should I have a look on attack/release and ratio boards?

But what I do not get is, how the hell it just drifted to the distorted state after couple weeks of normal operation... there must be something wrong with my soldering job. I mean these ground points are pretty hard to solder. even with paste and a bit higher temperatures i had really hard time to solder them to board properly. Could it be the reason? I checked them all and measured resistance and they seem ok. I just love your builds as I really learn so much

anyways thanks a million for your help. I will let you know the final resume.

Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on May 23, 2017, 04:01:48 PM
ok so got the input to read .775, now getting nothing on the output. I'm getting a 0.000 reading. and to get sound I have to crank the input of my returning input al the way! what could be the issue? Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spaceyjb on May 24, 2017, 01:59:47 PM
Hi Mike,

could it be faulty R56 (Release pot?). I found out one of its legs is broken. I soldered it out and now I am looking for subtitute as mouser doesn't have them stocked. And I have quite hard time. Is there any chance you can sell me one?

Thanks

Jan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: mrbobbailey on May 24, 2017, 06:08:31 PM
Greetings

I've finished 2 FET/Rack Bluestripes and calibrated to what I thought was success.  Q Bias set, and the GR Meter measuring properly at 0 and a 20db drop when loaded with signal.  When I put the top plate on and packed it into the rack, however, both VU meters read roughly +1db. 

When I took one back out of the rack and removed the top plate, I discovered my VU meter on that read 0db again.  What is causing this?

Thanks in advance,

Bob B
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 25, 2017, 03:58:57 PM
Hi Mike,

could it be faulty R56 (Release pot?). I found out one of its legs is broken. I soldered it out and now I am looking for subtitute as mouser doesn't have them stocked. And I have quite hard time. Is there any chance you can sell me one?

Thanks

Jan

Absolutely could be your issue. Send us an email.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 25, 2017, 04:02:29 PM
ok so got the input to read .775, now getting nothing on the output. I'm getting a 0.000 reading. and to get sound I have to crank the input of my returning input al the way! what could be the issue? Thanks

Ya your signal isn't making it through the circuit.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 25, 2017, 04:07:05 PM
Greetings

I've finished 2 FET/Rack Bluestripes and calibrated to what I thought was success.  Q Bias set, and the GR Meter measuring properly at 0 and a 20db drop when loaded with signal.  When I put the top plate on and packed it into the rack, however, both VU meters read roughly +1db. 

When I took one back out of the rack and removed the top plate, I discovered my VU meter on that read 0db again.  What is causing this?

Thanks in advance,

Bob B

The VUs are prone to drift with heat, that why the have the 0 adjustment on the front panel. But what you're describing sounds weird. I could see popping the panel on would cause heat to build faster and change the meter.

Do the units work and sound good?

Maybe pop it in with the lid on, let it sit for a while and set the zero. See how it sounds. Keep in mind when you tuen it off and cool it down, when you restart the meter will probably start at -1dB, then over an hour or 2 of use will creep back to 0.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on May 25, 2017, 09:33:50 PM
Ya your signal isn't making it through the circuit.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +

-Input XLR + -- 0.775
- TP1 -- 0.137
- TP15 -- 0.010
- TP17 -- 0.000
- Output Transformer BRN -- 0.033
- Output XLR -- 0.000
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: exfakto on May 26, 2017, 09:40:17 AM
Hi There,

I just finished building a FET Rack Revision A and everything went pretty smooth. During calibration, the meter was working perfectly. When I was almost done with the calibration, all of a sudden the meter stopped reading in GR mode. It works fine on +8 and +4 but just drops completely to the left and does not move on GR more. I can hear the signal being compressed but to the gauge. I've spent a good 4 hours yesterday trying to figure it out with no success. Please help.

Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 27, 2017, 11:44:19 AM
-Input XLR + -- 0.775
- TP1 -- 0.137
- TP15 -- 0.010
- TP17 -- 0.000
- Output Transformer BRN -- 0.033
- Output XLR -- 0.000

Your signal is dying  between TP1 and TP15.

This stuff is in the box labeled "Signal Preamp" in the lower corner. Check all of your components and soldering there including the output pot soldering.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on May 27, 2017, 11:46:21 AM
Hi There,

I just finished building a FET Rack Revision A and everything went pretty smooth. During calibration, the meter was working perfectly. When I was almost done with the calibration, all of a sudden the meter stopped reading in GR mode. It works fine on +8 and +4 but just drops completely to the left and does not move on GR more. I can hear the signal being compressed but to the gauge. I've spent a good 4 hours yesterday trying to figure it out with no success. Please help.

Thanks

You might have a wonky solder joint in your GR control amp section or on your meter switch. Try reflowing those parts.

If that fails, check your DC voltages in the GR control amp:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

It's called GR Meter Driver in that PDF.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on June 12, 2017, 04:40:39 PM
Hey Mike
So both 1176s that I have have been up and running for a few weeks now. They sound so good. Only issue I'm having still is with the stereo links. I've been having to run them in dual mono mode because they don't seem to work when I switch them to stereo. I'm turning both stereo links on, setting one to send and one to receive but at that point one units  suffers from a fairly drastic signal reduction.  So if they're set up as L/R in Mono mode, they're reading at the same level on my DAW's meter but once I activate the link, the left channel drops by about 7dB. The left unit's meter while set to GR maxes out while the right continues to function as expected. That being said, I'm getting the left unit is applying more compression. Is this user error or is there something going on here? I've tried changing the settings as described on the link build page but nothing seems to change. Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 12, 2017, 11:35:08 PM
Hey Mike
So both 1176s that I have have been up and running for a few weeks now. They sound so good. Only issue I'm having still is with the stereo links. I've been having to run them in dual mono mode because they don't seem to work when I switch them to stereo. I'm turning both stereo links on, setting one to send and one to receive but at that point one units  suffers from a fairly drastic signal reduction.  So if they're set up as L/R in Mono mode, they're reading at the same level on my DAW's meter but once I activate the link, the left channel drops by about 7dB. The left unit's meter while set to GR maxes out while the right continues to function as expected. That being said, I'm getting the left unit is applying more compression. Is this user error or is there something going on here? I can't seem to find anything posted about the links on here. Thanks!

Did you read the link user guide at the end of the link build guide?  Also are you FETs reasonably matched? Did you buy the units at the same time?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on June 12, 2017, 11:41:14 PM
Did you read the link user guide at the end of the link build guide?  Also are you FETs reasonably matched? Did you buy the units at the same time?

Not sure about the FETs being matched. I actually damaged my PCB trying to correct the FETs on my second build and had to send it in to you to fix if you recall. They were not both purchased at the same time.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on June 12, 2017, 11:45:00 PM
Not sure about the FETs being matched. I actually damaged my PCB trying to correct the FETs on my second build and had to send it in to you to fix if you recall. They were not both purchased at the same time.

But yes, did read the end of the build guide. Changing the four settings don't seem to make a difference.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 12, 2017, 11:46:43 PM
Not sure about the FETs being matched. I actually damaged my PCB trying to correct the FETs on my second build and had to send it in to you to fix if you recall. They were not both purchased at the same time.

Your FET's don't need to be stereo matched, but they need to be reasonably matched.

Think you could get 2 new sets in if we sent them to you?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on June 13, 2017, 02:37:39 AM
Your FET's don't need to be stereo matched, but they need to be reasonably matched.

Think you could get 2 new sets in if we sent them to you?

While mildly terrified, I feel up to the task! Should I just shoot you guys an email?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 13, 2017, 11:16:11 AM
While mildly terrified, I feel up to the task! Should I just shoot you guys an email?

Yup.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on June 13, 2017, 11:58:57 AM
I've reached at the step where I calibrate my unit.  It powers on, passes signal, and overall tone sounds really good on the vocal I have it inserted on.  On to calibration.   


It's a Blue Stripe.

PSU tested and working perfectly.  When I calibrate it, the output knob hitting the 11dBu mark seems extraordinarily low for the knob, down near the bottom of the range.  My Q bias adjustment is probably 20% from all the way counterclockwise.  Upon adjusting the R75 null pot together the trim pot on the front, my meter sits nicely at 0 and everything is good up to this point. 

Upon adjusting for the meter tracking, I begin to notice an issue.  My output knob reaches .775VAC, which is near "48" on the output markings (very low).  When I use the input pot to try and trim the output up to 2.44VAC, I run out of room.  The pot is maxed out around 1.659VAC.

Another thing I notice, which may be related, is that the two lower ratios don't seem to be showing compression on the VU meter.  The top two ratios show significant reduction just with the test tone, but the lower two I can't get the move.  I have metered every single one of the risistors on the ratio board and they all reflect what the schematic shows they should be.

Thanks for the help!

Spencer
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 13, 2017, 01:14:27 PM
I've reached at the step where I calibrate my unit.  It powers on, passes signal, and overall tone sounds really good on the vocal I have it inserted on.  On to calibration.   


It's a Blue Stripe.

PSU tested and working perfectly.  When I calibrate it, the output knob hitting the 11dBu mark seems extraordinarily low for the knob, down near the bottom of the range.  My Q bias adjustment is probably 20% from all the way counterclockwise.  Upon adjusting the R75 null pot together the trim pot on the front, my meter sits nicely at 0 and everything is good up to this point. 

Upon adjusting for the meter tracking, I begin to notice an issue.  My output knob reaches .775VAC, which is near "48" on the output markings (very low).  When I use the input pot to try and trim the output up to 2.44VAC, I run out of room.  The pot is maxed out around 1.659VAC.

Another thing I notice, which may be related, is that the two lower ratios don't seem to be showing compression on the VU meter.  The top two ratios show significant reduction just with the test tone, but the lower two I can't get the move.  I have metered every single one of the risistors on the ratio board and they all reflect what the schematic shows they should be.

Thanks for the help!

Spencer

Start with the TP21/22 test as shown below.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jacob123588 on June 16, 2017, 06:29:12 PM
Your signal is dying  between TP1 and TP15.

This stuff is in the box labeled "Signal Preamp" in the lower corner. Check all of your components and soldering there including the output pot soldering.

Mike

Hey Mike, So after fixing a few solder points, I get tone through the compressor and musch high through the output. now my readings are as followed

-Input XLR + -- 0.775
- TP1 -- 0.150
- TP15 -- 4.29
- TP17 -- 0.813
- Output Transformer BRN -- 0.156
- Output XLR -- 0..285

now a new problem has come up, the output knob changes volume ok until 12 o'clock, from then on it jumps in volume up and down and wile turning the knob from -48 to 0 the tone changes quite a bit and at various random points. it also seems to take a second to "settle into" a volume position. sorry I'm a bit late following up this has made me want to bang my head against a wall hahaha thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 20, 2017, 12:36:11 AM
Hey Mike, So after fixing a few solder points, I get tone through the compressor and musch high through the output. now my readings are as followed

-Input XLR + -- 0.775
- TP1 -- 0.150
- TP15 -- 4.29
- TP17 -- 0.813
- Output Transformer BRN -- 0.156
- Output XLR -- 0..285

now a new problem has come up, the output knob changes volume ok until 12 o'clock, from then on it jumps in volume up and down and wile turning the knob from -48 to 0 the tone changes quite a bit and at various random points. it also seems to take a second to "settle into" a volume position. sorry I'm a bit late following up this has made me want to bang my head against a wall hahaha thanks!

You've got an error somewhere in your "Signal Line Amp" section. It's labeled on the PCB.

Check all joints, all components.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on June 23, 2017, 04:35:54 PM
Hey Mike,
Got the FETs already. You're the man! So these are replacing q1 and q11, correct? Thanks again!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 23, 2017, 04:38:42 PM
Hey Mike,
Got the FETs already. You're the man! So these are replacing q1 and q11, correct? Thanks again!

yes
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: rubberband on June 24, 2017, 02:53:44 PM
Hello<
 
I completed my REV A Version 1.14 last night and had the following issue:

When calibrating the Q Bias, the AC voltage between (out +) and (out -) was  0 .391 with the setup configuration as published:

Input = "24" mid rotation
Output = "24" mid rotation
Attack = full CCW (switched to off position)
Release = full CW
Compression ratio = 20:1
Meter mode = "GR"
Q-bias adjustment = full CW (Higest Output)
 
With the output full clockwise, AC voltage measures 2.43, at full counter clockwise it is 0.0

AC voltage at test pad (1) (with output full clockwise) 0.136, Test pad (15)  0.192, Test pad (17)  0.030.

everything in the preamp section is in order: re-folwed joints, all correct resistors etc.

could this be a problem with Q1 FET?
Ideas?

Thanks!!!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on June 25, 2017, 08:20:38 AM
Start with the TP21/22 test as shown below.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike

Thanks Mike,

My test points read as follows:

TP22 at ratios 20,12,8,4, respectively

2.21, 2.04, 1.525, 0.733, all measurements in AC

TP21 at ratios 20,12,8,4, respectively

-5.87, -3.23, -2.4, -1.57, all measurements DC


Best,

Spencer



Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: bcwiz on June 26, 2017, 12:20:56 AM
Hi Richard,

One difference between your FET/RACK and a vintage unit...the input pot (t-pad attenuator) on the original units had a very odd taper. It’s not a taper you commonly see in potentiometers today. Your input attenuator has a more common taper, which leads it to be a little “hotter” earlier in the clockwise pot turn. Even compared to out old blue T-pad.

That said 7 o'clock seems low.  I suspect it's a combination of the hot input pot and our meter having a little more over shoot than the originals.  They have $150 meter in them, we decided not to go that route.  We feel like out meter is 90% as good at a fraction of the cost.

The meter should be a little more accurate in the full CW position and should show you less compression. Hard to say what is right because I don't know what your input level is compared to ours.

Mike

Mike
Can I replace the Hairball Rev A input attenuator with an original 1176 600 ohm t-pad? I prefer that taper to the more common standard.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 26, 2017, 02:44:09 PM
Can I replace the Hairball Rev A input attenuator with an original 1176 600 ohm t-pad? I prefer that taper to the more common standard.

Absolutely.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 26, 2017, 02:45:14 PM
Hello<
 
I completed my REV A Version 1.14 last night and had the following issue:

When calibrating the Q Bias, the AC voltage between (out +) and (out -) was  0 .391 with the setup configuration as published:

Input = "24" mid rotation
Output = "24" mid rotation
Attack = full CCW (switched to off position)
Release = full CW
Compression ratio = 20:1
Meter mode = "GR"
Q-bias adjustment = full CW (Higest Output)
 
With the output full clockwise, AC voltage measures 2.43, at full counter clockwise it is 0.0

AC voltage at test pad (1) (with output full clockwise) 0.136, Test pad (15)  0.192, Test pad (17)  0.030.

everything in the preamp section is in order: re-folwed joints, all correct resistors etc.

could this be a problem with Q1 FET?
Ideas?

Thanks!!!

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 26, 2017, 02:48:29 PM
Thanks Mike,

My test points read as follows:

TP22 at ratios 20,12,8,4, respectively

2.21, 2.04, 1.525, 0.733, all measurements in AC

TP21 at ratios 20,12,8,4, respectively

-5.87, -3.23, -2.4, -1.57, all measurements DC


Best,

Spencer

Pad 22 seems really high.  Check all the resistors on the ratio PCB.  Make sure you don't have a 47K swapped with a 4.7K or something.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: rubberband on June 26, 2017, 04:05:08 PM
Hi Mike:

The AC is a s follows:


-Input XLR +  0.385
-TP1                   0 .184
-TP15                 2.016
-TP17                  0.313
-Output Transformer BRN  5.073
-Output XLR +                              4.861
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 26, 2017, 05:32:31 PM
Hi Mike:

The AC is a s follows:


-Input XLR +  0.385
-TP1                   0 .184
-TP15                 2.016
-TP17                  0.313
-Output Transformer BRN  5.073
-Output XLR +                              4.861

That seems normal.

What's your AC between out + and out - under those same conditions?

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: rubberband on June 27, 2017, 09:10:00 AM
That seems normal.

What's your AC between out + and out - under those same conditions?

Mike

Mike,

I put a load on the output and got 8.5 VAC. The unit then calibrated normally.

In running some material through it, It is too hot on the input, understanding the taper issue with the potentiometer. With a vocal track, I couldn't get it to the first dot before 20 db of compression, on other lower amplitude material of bass and acoustic guitar I am having the same issue. Essentially it is either on or off with the full range of input between full CCW to 48.

Thanks !
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on June 27, 2017, 12:05:55 PM
Pad 22 seems really high.  Check all the resistors on the ratio PCB.  Make sure you don't have a 47K swapped with a 4.7K or something.

Mike

Thanks Mike-

These seem okay, biggest discrepancies I could find on the ratio board were R63 metering at 1.23k ohms instead of 1.5k, and R64 metering 1.62k instead of 2.2k.  I checked these against similar values on the main PCB to make sure nothing was switched around and it seems like they're okay.  Let me know if you think I should get a few resistors closer to 2.2k for R64 and I can drop that in, or if it's something different.  Really appreciate your help man!!

Best,
Spencer
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 27, 2017, 05:17:51 PM
Mike,

I put a load on the output and got 8.5 VAC. The unit then calibrated normally.

In running some material through it, It is too hot on the input, understanding the taper issue with the potentiometer. With a vocal track, I couldn't get it to the first dot before 20 db of compression, on other lower amplitude material of bass and acoustic guitar I am having the same issue. Essentially it is either on or off with the full range of input between full CCW to 48.

Thanks !

Sounds like your source material might be too loud.  The input is a 40db attenuator.  It it's having problems attenuating in the normal range, my guess is that the the source needs to be turned down.

Also if your release is slower, the meter will kind of bottom out and never make it back.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 27, 2017, 05:19:31 PM
Thanks Mike-

These seem okay, biggest discrepancies I could find on the ratio board were R63 metering at 1.23k ohms instead of 1.5k, and R64 metering 1.62k instead of 2.2k.  I checked these against similar values on the main PCB to make sure nothing was switched around and it seems like they're okay.  Let me know if you think I should get a few resistors closer to 2.2k for R64 and I can drop that in, or if it's something different.  Really appreciate your help man!!

Best,
Spencer

If you're measuring them in circuit, often the value will be lower than you expect. This is because the resistors are in parallel with other components in the circuit.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 27, 2017, 05:22:14 PM
Thanks Mike-

These seem okay, biggest discrepancies I could find on the ratio board were R63 metering at 1.23k ohms instead of 1.5k, and R64 metering 1.62k instead of 2.2k.  I checked these against similar values on the main PCB to make sure nothing was switched around and it seems like they're okay.  Let me know if you think I should get a few resistors closer to 2.2k for R64 and I can drop that in, or if it's something different.  Really appreciate your help man!!

Best,
Spencer

Your Qbias went fine right?

Try the same test as Rubberband above.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: MeesterZee on June 27, 2017, 07:07:49 PM
Hi all, finally got my build completed and calibrated. Everything is sounding great.

However, I'm having some trouble with the knobs not sitting flush to the face. I have large gaps of different widths. It seems that some of the pots have a longer shaft that others, preventing the knobs from sitting closer. After spending so many hours on the internal build, I want the outside to look clean too! Any solutions?

Pics here:
http://i.imgur.com/mLtbrhN.jpg
http://i.imgur.com/RR55QDn.jpg

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on June 27, 2017, 07:11:12 PM
Hi all, finally got my build completed and calibrated. Everything is sounding great.

However, I'm having some trouble with the knobs not sitting flush to the face. I have large gaps of different widths. It seems that some of the pots have a longer shaft that others, preventing the knobs from sitting closer. After spending so many hours on the internal build, I want the outside to look clean too! Any solutions?

Pics here:
http://i.imgur.com/mLtbrhN.jpg
http://i.imgur.com/RR55QDn.jpg

Thanks!

That is how they should sit. You don't want them dragging on the nut or even worse the faceplate which will leave bad marks.  Just pull the closer one out a little to match the other and lock it down.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on June 27, 2017, 09:26:27 PM
Your Qbias went fine right?

Try the same test as Rubberband above.

Mike

Thanks Mike!  That's what I figured about the parallel resistors.  All these measurements are in AC voltage

-Input XLR +  = .373
-TP1=  .15
-TP15 =4.658
-TP17 =.872
-Output Transformer BRN  =13.38
-Output XLR + =13.14


Thanks dude!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 01, 2017, 03:07:52 PM
Okay,

At a complete loss as to what might be my issue. New FET Rev A I just finished building.

Q1 shows 1db drop no problem. Null adjust is fine.

Last step involves no compression. Attack knob makes the needle twitch when engaged but that's it. Moving the release from clockwise to CCW actually makes the volume drop.

Checked all the solder connections and everything seems okay.

I've built 4 hairball Lolas, 1 FET 500, and this is my second FET rack and I've never had an issue up until now. It's driving me crazy and I'm sure I made a careless mistake somewhere. I'm gonna just start checking the resistors to start with to make sure I didn't mix up a value.

Edit: Can't find an obvious resistor error. There is some compression if I crank the input all the way, but the release knob still acts wonky.

Edit #2.

Checked every resistor using a color calculator and they all check out. Checked every solder joint. Unit passes audio and sounds great. I can even hear the compression happening it's just not showing it properly on the meter.

The release knob somehow has the most control over the VU meter. The needle follows the knob as I turn it from left to right, and there's a few DB drop in volume as a result.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 03, 2017, 01:43:37 PM
Thanks Mike!  That's what I figured about the parallel resistors.  All these measurements are in AC voltage

-Input XLR +  = .373
-TP1=  .15
-TP15 =4.658
-TP17 =.872
-Output Transformer BRN  =13.38
-Output XLR + =13.14


Thanks dude!

Seems ok.

Can you set the QBias?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 03, 2017, 01:45:06 PM
Okay,

At a complete loss as to what might be my issue. New FET Rev A I just finished building.

Q1 shows 1db drop no problem. Null adjust is fine.

Last step involves no compression. Attack knob makes the needle twitch when engaged but that's it. Moving the release from clockwise to CCW actually makes the volume drop.

Checked all the solder connections and everything seems okay.

I've built 4 hairball Lolas, 1 FET 500, and this is my second FET rack and I've never had an issue up until now. It's driving me crazy and I'm sure I made a careless mistake somewhere. I'm gonna just start checking the resistors to start with to make sure I didn't mix up a value.

Edit: Can't find an obvious resistor error. There is some compression if I crank the input all the way, but the release knob still acts wonky.

Edit #2.

Checked every resistor using a color calculator and they all check out. Checked every solder joint. Unit passes audio and sounds great. I can even hear the compression happening it's just not showing it properly on the meter.

The release knob somehow has the most control over the VU meter. The needle follows the knob as I turn it from left to right, and there's a few DB drop in volume as a result.

Is this the older build? With all the wiring?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 03, 2017, 02:53:48 PM
Is this the older build? With all the wiring?

Mike

Nope. New model FET A build. I don't even think it's possible I wired it wrong!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 04, 2017, 02:07:12 PM
Seems ok.

Can you set the QBias?

The Q bias I can set, and I can get through the null adjustment also. 

When I get to the bit where I need to adjust the GR meter tracking, I get stuck after switching the attack off.  My XLR output reads at .775ACV and is almost all the way down.  When I bring up the input knob, I max it out before I get the output to read +10dBu.  It maxes out at about 1.54ACV.

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 05, 2017, 11:34:09 AM
Nope. New model FET A build. I don't even think it's possible I wired it wrong!

Maybe a side chain issue then.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 05, 2017, 11:42:31 AM
The Q bias I can set, and I can get through the null adjustment also. 

When I get to the bit where I need to adjust the GR meter tracking, I get stuck after switching the attack off.  My XLR output reads at .775ACV and is almost all the way down.  When I bring up the input knob, I max it out before I get the output to read +10dBu.  It maxes out at about 1.54ACV.

Thanks!

Right, because your TP22 AC is so damn high.

Has to be a short or bad R value on your ratio PCB.

What revision do you have again?  What is the rec number of the PCB? (1.11, 1.14...)

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 05, 2017, 01:48:15 PM
Right, because your TP22 AC is so damn high.

Has to be a short or bad R value on your ratio PCB.

What revision do you have again?  What is the rec number of the PCB? (1.11, 1.14...)

Mike

I'll double double check for anything weird on the board.  All the resistors measure pretty close to what they're spec'd at aside from being in parallel with others.  Looks like my PCB is v1.14.

Spencer
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 05, 2017, 01:49:33 PM
Right, because your TP22 AC is so damn high.

Has to be a short or bad R value on your ratio PCB.

What revision do you have again?  What is the rec number of the PCB? (1.11, 1.14...)

Mike

Meant to add this too, I'm building the newest revision of the Rev A, only ordered it around 1 month ago. 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 05, 2017, 10:12:46 PM
Maybe a side chain issue then.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike

Okay so TP22 AC volts;

20:1 = .200
12:1 = .110
8:1 = .072
4:1 = .042

TP21 DC volts;

20:1 = -6.027
12:1 = -3.49
8:1 = -2.69
4:1 = -1.90

Thanks for getting back to me Mike!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 06, 2017, 12:27:23 PM
I'll double double check for anything weird on the board.  All the resistors measure pretty close to what they're spec'd at aside from being in parallel with others.  Looks like my PCB is v1.14.

Spencer

With the same set-up as above, what is your AC at PAD 15, 16, 17.

Just do them all at 20:1...GR off.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 06, 2017, 12:30:41 PM
Okay so TP22 AC volts;

20:1 = .200
12:1 = .110
8:1 = .072
4:1 = .042

TP21 DC volts;

20:1 = -6.027
12:1 = -3.49
8:1 = -2.69
4:1 = -1.90

Thanks for getting back to me Mike!

Does the unit sound right? Compressing ok?

The voltages seem ok, wondering if it's just a GR Meter Driver issue. Meaning the unit works, just not the GR metering.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 06, 2017, 12:55:41 PM
Does the unit sound right? Compressing ok?

The voltages seem ok, wondering if it's just a GR Meter Driver issue. Meaning the unit works, just not the GR metering.

Unit sounds great. Seems like the threshold is a little high after poking around more and experimenting.  Setting the q bias works fine but when trying to set the metering I can't get the 10db drop when attack is engaged. I don't know how to convert VAC to DB offhand, but it's probably only a few db from in to out if I had to guess.

However if I pass sound through it it sounds great and I can hear some compression happening with vocal and guitar tracks. When I slow the release the Vu Meter drops and the volume drops as well. 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 06, 2017, 12:57:43 PM
Unit sounds great. Seems like the threshold is a little high after poking around more and experimenting.  Setting the q bias works fine but when trying to set the metering I can't get the 10db drop when attack is engaged. I don't know how to convert VAC to DB offhand, but it's probably only a few db from in to out if I had to guess.

However if I pass sound through it it sounds great and I can hear some compression happening with vocal and guitar tracks. When I slow the release the Vu Meter drops and the volume drops as well.

Hmmm that seems wrong. You should be able to get a 10dB drop.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 06, 2017, 03:42:11 PM
With the same set-up as above, what is your AC at PAD 15, 16, 17.

Just do them all at 20:1...GR off.

Okay so:

15:   4.639v
17:  .869v

For the life of me, I couldn't find a test pad 16 after looking for about 20 minutes.  I'm building the Blue Stripe Rev A 2017 v1.14- maybe I'm missing it?

Here's a few other pads:

1:  .149v
7:   0v (bad?)
18:  0v
21:  0v
22:  2.257v

Thanks man
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 06, 2017, 04:20:45 PM
Okay so:

15:   4.639v
17:  .869v

For the life of me, I couldn't find a test pad 16 after looking for about 20 minutes.  I'm building the Blue Stripe Rev A 2017 v1.14- maybe I'm missing it?

Here's a few other pads:

1:  .149v
7:   0v (bad?)
18:  0v
21:  0v
22:  2.257v

Thanks man

Sorry, Pad 16 is just ground. Ignore that.

I'll need to get back to you in a day or so.  I'm in the middle of 10 days semi-off (home project).  I need to take some measurements.

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 06, 2017, 06:59:42 PM
Hmmm that seems wrong. You should be able to get a 10dB drop.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15

Mike

XLR+ = .388 VAC
TP1 = .184
TP15 = .303
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 06, 2017, 09:39:12 PM
Sorry, Pad 16 is just ground. Ignore that.

I'll need to get back to you in a day or so.  I'm in the middle of 10 days semi-off (home project).  I need to take some measurements.

Right on man, no rush!  Really appreciate your help on this stuff- I'm sure I speak for many of us.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on July 08, 2017, 04:31:31 AM
Since installing the new FETs, both compressors operate identically now! Woohoo! However, the stereo links are still not working. When I turn the links on, one of the compressor's meter just stops working. Even if I switch the send/receive on both units, the same compressor has no meter movement. Thoughts?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on July 08, 2017, 12:47:07 PM
Swap the Active stereo link cards and see if the problem persists. If the compressor is working then that part should be fine. Also double check your soldering for the Active Link board connectors.


Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on July 09, 2017, 03:31:14 AM
Thanks Paul!
I actually went through and checked my solder points (easier than switching them) out and I feel like I'm closer to my final goal. Now however both compressors, while reacting to the same transients, seem to have a very different range of compression. Let's call them "A" and "B", While passing a drum track through the pair, "A" will compress anywhere from -1dB to -7dB. "B" on the other hand "B" stays pinned to -20dB until I increase the speed of the release to ~"6". At this point, the compression range is anywhere from -1dB to -20dB. Changing the attack and/or input on either unit has no effect. Does this sound like anything you've dealt with?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Potato Cakes on July 09, 2017, 07:28:37 AM
Mike has a guide on how to properly set up both units for stereo linking on the page for the Active Link cards. The controls are not going to match as linking 1176's isn't perfect. Once you do get them set they do track well with each other when using music. They don't match up nearly as well when just using tone. Both of mine work in stereo very well after I read the Active Link guide and set it up properly.

Thanks!

Paul
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 10, 2017, 08:59:14 PM
XLR+ = .388 VAC
TP1 = .184
TP15 = .303

TP15 is way too low. Should be about 2.5VAC for a D and 4.00VAC for an A.

Can you easily remove Q1? If so do you get more signal?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 11, 2017, 05:38:13 PM
TP15 is way too low. Should be about 2.5VAC for a D and 4.00VAC for an A.

Can you easily remove Q1? If so do you get more signal?

Mike

Removed Q1 and getting over 4.00 VAC plus some! I assume I should replace Q1 and Q11 with some matched 2n5457s and report back?

The release knob still has control over the GR meter but theres no volume drop going on now. Maybe I'm having more than one issue here?

Thanks for getting back to me Mike I greatly appreciate the help.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 16, 2017, 09:04:29 PM
Sorry, Pad 16 is just ground. Ignore that.

I'll need to get back to you in a day or so.  I'm in the middle of 10 days semi-off (home project).  I need to take some measurements.

Hey Mike-

Any thoughts on what could be the issue?  No rush

Best,
Spencer
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 17, 2017, 10:14:18 AM
Hey Mike-

Any thoughts on what could be the issue?  No rush

Best,
Spencer

Just getting back to the office.  Will have something for you tonight or tomorrow am.  Sorry for the delay.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: RobertCheek on July 18, 2017, 02:11:14 AM
Hello there

I just got started yesterday on building a pair of Rev As. I completed the power supplies for both and one tested great. The other however is reading +20 VDC on CR8 and the correct -10 VDC on CR9... also the power transformer is getting super hot.

Ideas ? Thanks for your time - Robert
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: MeesterZee on July 18, 2017, 12:23:30 PM
I saw some other users added a custom power light above the meter on their builds to mimic the original Rev A cosmetics. Can I safely draw power for a 110VAC LED off the terminals of the power switch?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 19, 2017, 10:28:15 PM
Hey Mike-

Any thoughts on what could be the issue?  No rush

Best,
Spencer

Hi Spencer,

I've been off most of July so I've been unable to assist you with this deeper issue. I'll be back full time this coming monday and we'll get this banged out.

In the mean time we know your bad 22 voltage seems way too high.

With the same test set up, and in 20:1 ratio, measure your AC:

Pad 15
Both sides of R78 (confirm it's 47K)

Thanks!

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 19, 2017, 10:29:58 PM
Hello there

I just got started yesterday on building a pair of Rev As. I completed the power supplies for both and one tested great. The other however is reading +20 VDC on CR8 and the correct -10 VDC on CR9... also the power transformer is getting super hot.

Ideas ? Thanks for your time - Robert

Hmmmm. The heat thing concerns me.

Try swapping the power transformers. If you have the same issue, we know it's a PCB level issue. If it works fine with the other transformer, you may have a bad transformer. In that case don't use it anymore and email me.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 21, 2017, 05:11:35 PM
Hi Spencer,

I've been off most of July so I've been unable to assist you with this deeper issue. I'll be back full time this coming monday and we'll get this banged out.

In the mean time we know your bad 22 voltage seems way too high.

With the same test set up, and in 20:1 ratio, measure your AC:

Pad 15
Both sides of R78 (confirm it's 47K)

Thanks!

Mike

Thanks Mike!

My  pad15 measures 4.592ACV

R78 measures 43.94K ohms.  Voltage for the upper leg (towards top of unit, towards 20:1) my ACV measures 3.796v.  The lower leg (closer to the bottom of the unit and towards 4:1 ratio) measures 4.589v.

Thank you!
Spencer
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 24, 2017, 09:15:25 PM
Removed Q1 and getting over 4.00 VAC plus some! I assume I should replace Q1 and Q11 with some matched 2n5457s and report back?

The release knob still has control over the GR meter but theres no volume drop going on now. Maybe I'm having more than one issue here?

Thanks for getting back to me Mike I greatly appreciate the help.

Okay, just to follow up. I'm getting a nice strong signal now at TP15 with some tweaking. I touched up all the pads that even looked slightly off. I'm not sure which joint it was, but it's now fixed.

I'm still getting the weirdness with the release knob. When I slow the release the meter follows it to the left and the volume drops even with the attack knob off.

Any hints as to where I should look to solve this problem?

Thank you Mike. I'll keep poking at it but I'm not sure where to start with this one.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 26, 2017, 02:02:51 PM
Okay, just to follow up. I'm getting a nice strong signal now at TP15 with some tweaking. I touched up all the pads that even looked slightly off. I'm not sure which joint it was, but it's now fixed.

I'm still getting the weirdness with the release knob. When I slow the release the meter follows it to the left and the volume drops even with the attack knob off.

Any hints as to where I should look to solve this problem?

Thank you Mike. I'll keep poking at it but I'm not sure where to start with this one.

Were you able to calibrate anything?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 26, 2017, 03:12:50 PM
Spanzor,

Alright I'm back and ready to sort this for you. Poked around our Rev A just now trying to sort you.

You're voltage is high at pad 22 because you're not getting any compression.

Were you able to complete the Qbias adjustment?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 26, 2017, 05:19:26 PM
Were you able to calibrate anything?

Yes calibration went perfectly well after clearing up my other issue, and the unit behaves in what I would perceive as a normal fashion as long as the release time is at the fastest speed.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on July 28, 2017, 02:06:28 PM
Yes calibration went perfectly well after clearing up my other issue, and the unit behaves in what I would perceive as a normal fashion as long as the release time is at the fastest speed.

Is the PCB clean? Does it have a lot of flux?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on July 28, 2017, 03:15:18 PM
Is the PCB clean? Does it have a lot of flux?

Mike

Cleaned it with 99% alcohol and a toothbrush after I was finished and after doing my most recent touch ups. Looks pretty clean to me. Used Kester solder so hopefully nothing weird with that.

Thank you Mike!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickmorzov on July 28, 2017, 06:37:09 PM
Just finished my Rev D FET rack and i'm getting an extremely quiet and distorted signal, my build didn't come with a socket for CN15 and it seems i've got a fat blue resistor for that PCB (not set up or mounted yet) i can't imagine this having an impact over the sound... any help would be greatly appreciated!!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on July 31, 2017, 09:36:53 AM
Spanzor,

Alright I'm back and ready to sort this for you. Poked around our Rev A just now trying to sort you.

You're voltage is high at pad 22 because you're not getting any compression.

Were you able to complete the Qbias adjustment?

Mike

Mike-

Yes Q bias goes okay, I can get all the way up to where I calibrate the meter with the trim pot on the front. 

Thanks,
Spencer
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 02, 2017, 02:50:44 PM
Well it appears then that your side chain is not compressing.

http://mnats.net/files/fetrack/fet_rack_a_doc_v1.12.pdf

Carefully inspect all parts/values/solder joints/traces in the "GR Control Amp" section.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 02, 2017, 02:52:46 PM
Cleaned it with 99% alcohol and a toothbrush after I was finished and after doing my most recent touch ups. Looks pretty clean to me. Used Kester solder so hopefully nothing weird with that.

Thank you Mike!

Does the release sound right? Just effect the meter?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on August 03, 2017, 10:49:08 PM
Does the release sound right? Just effect the meter?

The overall volume drops as well as the needle dropping even with attack off, so in that regard I'd say it's not just the meter doing something funny. If i want slower release I've just been increasing  the output gain by a few db and ignoring the meters and it seems to sound Okay so I assume the release is working fine.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Spanzor on August 04, 2017, 03:04:32 PM
Well it appears then that your side chain is not compressing.

http://mnats.net/files/fetrack/fet_rack_a_doc_v1.12.pdf

Carefully inspect all parts/values/solder joints/traces in the "GR Control Amp" section.

Okay, everything looks clean.  There's no breaks in any of the traces, all the resistors measure appropriately and/or match the corresponding color code.  All the caps look great and are in the right spot, diodes oriented the right way, etc.  Transistors all match up with the proper markings.

Is there anything else I could check?  Should I send it in?

Spencer
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 07, 2017, 10:46:02 PM
The overall volume drops as well as the needle dropping even with attack off, so in that regard I'd say it's not just the meter doing something funny. If i want slower release I've just been increasing  the output gain by a few db and ignoring the meters and it seems to sound Okay so I assume the release is working fine.


So weird.  You could send it in for repair but obviously there is a cost to that.  Is the release pot ok, is one of the legs broken off?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 07, 2017, 10:47:37 PM
Okay, everything looks clean.  There's no breaks in any of the traces, all the resistors measure appropriately and/or match the corresponding color code.  All the caps look great and are in the right spot, diodes oriented the right way, etc.  Transistors all match up with the proper markings.

Is there anything else I could check?  Should I send it in?

Spencer

You could always send it in.

You could test the DC voltages in the GR AMP section:

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Diamondj421 on August 08, 2017, 12:35:18 PM
Greetings all!
My 1176s have been getting a lot of work recently but I've noticed that my 2nd units meter is fidgeting a lot while nothing is running through it. This unit was sent in for repair so I'm sure everything is in it's right place. Any idea what it could be?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 10, 2017, 12:01:59 PM
Greetings all!
My 1176s have been getting a lot of work recently but I've noticed that my 2nd units meter is fidgeting a lot while nothing is running through it. This unit was sent in for repair so I'm sure everything is in it's right place. Any idea what it could be?

Weird. There is no signal present?

You could try swapping the meters in your units and see it it is a bad meter.  If not email us and we can look at it again for free if it's already been looked at by us.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 16, 2017, 06:43:42 PM
You are losing signal after your input.  A bad input would be VERY rare so I would not expect that straight out.  Do you have the older version with input on its own PCB?

If so double check your wiring.

Using the test above, what is your AC at:

TPAD PCB in+
TPAD PCB out+
Input transformer  PCB in+
Input transformer  PCB out+

Mike
(I'll be offline the rest of the day)

Try removing the Q1 FET if you can...does that change the level?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: eriksunding on August 23, 2017, 06:49:11 AM
I'm helping a friend out with a build he's doing. He's done 2 of the Rev A's and got one of them to work perfectly but not the second one.
Signal is passing thru but there is no compression. Also when switching to GR mode the needle isn't moving to 0.

From what I could find, so far, when comparing them both to each other the volt value of Q5 and Q6 are different. The one that isn't working are showing these values:
Q5
Base: 1,3v
Collector: 27v
Emitter: 0.7v

Q6
Base: 0.7v
Collector: 30v
Emitter: 0.1v

Any idea what might be the cause? Transistor broken or maybe something else affecting these? Anything I could look for?

Thanks
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: eriksunding on August 24, 2017, 08:26:14 AM
SOLVED! Faulty cable going from main pcb to ratio pcb. Two of the small wires had changed places with each other. Factory fault I assume.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on August 24, 2017, 10:19:05 PM
Ok need help. First build of Rev D. Can do the Q bias calibration and seems to react as expected.
Discrete meter/null adjust also reacts as expected. But as soon as the jumper is put back in the normal ops position, meter drops to about -18 and with R71 max CW meter reads -10.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 24, 2017, 10:39:07 PM
Ok need help. First build of Rev D. Can do the Q bias calibration and seems to react as expected.
Discrete meter/null adjust also reacts as expected. But as soon as the jumper is put back in the normal ops position, meter drops to about -18 and with R71 max CW meter reads -10.

It should drop but not that much.

You're able to get the 0V DC null?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on August 24, 2017, 10:45:10 PM
Yeah, it seemed to work. I couldn't really get it to zero, but I think I got it to something like 3.5mv. I figured that must be close enough.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 24, 2017, 10:53:16 PM
Yeah, it seemed to work. I couldn't really get it to zero, but I think I got it to something like 3.5mv. I figured that must be close enough.

Ya that's pretty good.

Did you get a full kit with the matched 2N3707's for Q12/13?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on August 24, 2017, 11:00:15 PM
Yes, full kit, plus the orange drop caps.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on August 28, 2017, 11:33:56 AM
Yes, full kit, plus the orange drop caps.

Hmmm. not really sure. 

Check your DC voltages in the meter and GR amp compared to this:
http://mnats.net/files/1176REVD_VOLTS.pdf

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 03, 2017, 11:36:51 PM
Been away for a week. So I checked the DC volts against the schematic and it seems like all are pretty close to where they're supposed to be. I didn't find any that were wildly different from the spec.

However I think I may have found a clue.  I was going around the board with a finger applying pressure and bit of wiggle to the caps and FETs seeing if I could find any loose/suspect connections that might have an impact on the meter. That's when I touched Q6 and said holy toledo that's hot. And that's when I remembered that Q6 is supposed to have a heat sync. I completely forgot to install it before power up.

Any chance I might have cooked the Q6 and that could be my problem?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Maxman on September 05, 2017, 03:23:43 AM
Hi guys-I just finished building my first Fet Rack, and I'm having trouble doing the calibration:

The first two calibration steps were successful and yielded the proper voltages, but now I'm stuck on the third step (adjusting the meter to reflect GR). It seems at this stage that the unit isn't compressing at all (no compression showing on the meter/the DMM/ or happening audibly,) but the unit IS passing audio through very cleanly.  The Q bias was set per instructions and R74 is showing 0 voltage across it.

Is there any obvious places to start with troubleshooting that you can think of (a problem with the attack/release board, a burned out FET unit...)? To reiterate-I have audio passing cleanly but no compression despite the Q bias being set per instructions. Thanks so much for the help.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 05, 2017, 01:51:13 PM
Been away for a week. So I checked the DC volts against the schematic and it seems like all are pretty close to where they're supposed to be. I didn't find any that were wildly different from the spec.

However I think I may have found a clue.  I was going around the board with a finger applying pressure and bit of wiggle to the caps and FETs seeing if I could find any loose/suspect connections that might have an impact on the meter. That's when I touched Q6 and said holy toledo that's hot. And that's when I remembered that Q6 is supposed to have a heat sync. I completely forgot to install it before power up.

Any chance I might have cooked the Q6 and that could be my problem?

Usually if Q6 has failed, R32 will be burned.

I would suspect something in your GR meter section which should be marked on the box.  Make sure you don't have your 100Ω and 2KΩ trimmer swapped.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 05, 2017, 01:52:21 PM
Hi guys-I just finished building my first Fet Rack, and I'm having trouble doing the calibration:

The first two calibration steps were successful and yielded the proper voltages, but now I'm stuck on the third step (adjusting the meter to reflect GR). It seems at this stage that the unit isn't compressing at all (no compression showing on the meter/the DMM/ or happening audibly,) but the unit IS passing audio through very cleanly.  The Q bias was set per instructions and R74 is showing 0 voltage across it.

Is there any obvious places to start with troubleshooting that you can think of (a problem with the attack/release board, a burned out FET unit...)? To reiterate-I have audio passing cleanly but no compression despite the Q bias being set per instructions. Thanks so much for the help.

If no GR, start with measuring the side chain voltages.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Maxman on September 06, 2017, 07:05:56 PM
If no GR, start with measuring the side chain voltages.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike

Hi Mike-Thanks so much for the quick response!  Here are the voltages I measured:

TP 22   @   20:1   --  .69VAC
                        12:1   --  .113
                         8:1     --  .07
                         4:1     --   .056

TP 21  @    20:1   --   -6.83VDC
                        12:1  --    -3.923
                         8:1    --    -2.839
                         4:1   --     -1.927
Thanks!
-Max
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on September 06, 2017, 08:09:29 PM
Try removing the Q1 FET if you can...does that change the level?

Mike

hi mike. I've been MIA for a couple weeks doing an art installation.

I had no signal at T1. I just pulled Q1.. and now i have a tiny waveform coming through at T1.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 06, 2017, 09:24:16 PM
Usually if Q6 has failed, R32 will be burned.

I would suspect something in your GR meter section which should be marked on the box.  Make sure you don't have your 100Ω and 2KΩ trimmer swapped.
R32 shows no sign of burns and still measures 38.7 ohm.

I haven't measured them yet but R44, R59 and R75 are all marked 202 so I assume they're all 2k. Excuse my ignorance but what do you mean when you say 'should be marked on the box'?

Although you weren't intending it for me, I went ahead and did the test you recommended for Maxman. With no input signal, here's my results.

TP21:
20:1 -6.79VDC
12:1  -3.89VDC
8:1     -2.81VDC
4:1    -1.90VDC

TP22:
20:1   0.000VAC
12:1   0.000VAC
8:1     0.000VAC
4:1     0.000VAC

Based on what Maxman is reporting, I'm guessing (well hoping really) all those zeros might be a clue?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 07, 2017, 12:31:50 PM
hi mike. I've been MIA for a couple weeks doing an art installation.

I had no signal at T1. I just pulled Q1.. and now i have a tiny waveform coming through at T1.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 07, 2017, 12:33:12 PM
R32 shows no sign of burns and still measures 38.7 ohm.

I haven't measured them yet but R44, R59 and R75 are all marked 202 so I assume they're all 2k. Excuse my ignorance but what do you mean when you say 'should be marked on the box'?

Although you weren't intending it for me, I went ahead and did the test you recommended for Maxman. With no input signal, here's my results.

TP21:
20:1 -6.79VDC
12:1  -3.89VDC
8:1     -2.81VDC
4:1    -1.90VDC

TP22:
20:1   0.000VAC
12:1   0.000VAC
8:1     0.000VAC
4:1     0.000VAC

Based on what Maxman is reporting, I'm guessing (well hoping really) all those zeros might be a clue?

Is that with GR turned on? All zeros is normal with GR OFF. But not switched on.

Sorry I meant "marked on the PCB".
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 07, 2017, 12:36:05 PM
Hi Mike-Thanks so much for the quick response!  Here are the voltages I measured:

TP 22   @   20:1   --  .69VAC
                        12:1   --  .113
                         8:1     --  .07
                         4:1     --   .056

TP 21  @    20:1   --   -6.83VDC
                        12:1  --    -3.923
                         8:1    --    -2.839
                         4:1   --     -1.927
Thanks!
-Max

Seems good.

With the same conditions, what is your AC at each ratio on the positive side (side without the stripe) of CR2 and CR3.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Maxman on September 07, 2017, 05:16:13 PM
Seems good.

With the same conditions, what is your AC at each ratio on the positive side (side without the stripe) of CR2 and CR3.

Mike

I'm getting zero volts AC across each positive side for all ratios.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 07, 2017, 05:28:06 PM
Is that with GR turned on? All zeros is normal with GR OFF. But not switched on.
Attack full clockwise.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Maxman on September 07, 2017, 07:13:46 PM
Attack full clockwise.
Yep the attack is on fully CW.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Maxman on September 07, 2017, 07:17:09 PM
I can see a small amount of voltage is quickly sent across CR2 and CR3 when I push in the buttons (.5 volts) but the meter quickly rests on Zero VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 08, 2017, 02:59:21 PM
I'm getting zero volts AC across each positive side for all ratios.

Something is wrong in the GR AMP section then.  Go through that box carefully.  Check every trace, component, joint.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 12, 2017, 10:57:22 PM
Ok here's what I've done.
1. Since I ran it for a while with no heat shield on Q6, I ordered replacements and replaced Q6. I know I probably didn't have to, just trying to be thorough.
2. I retouched every trace in the GR control amp section plus any others I could find that looked wonky.
3. Seeing that there are 3 holes where CR10 goes, I pulled out CR10 and ordered a replacement. I then read that the outer holes are what I should use (which is what I had in the first place), installed a replacement 1N914 in outer holes of CR10.

When I powered up and tried to retest volts at tp21/tp22 it seemed like I had some volts going on. But something wasn't right. So I went back to do all the calibrations from scratch. I verified 0.775VAC at the input pins. But the output pins were all over the map as I moved the output knob.

Unmuted the output and sure enough I've now got myself a nice little noise maker. With nothing on the input, I get radio frequency interference type tones through most of the sweep of the output knob. But near the top of the travel of the knob it switches over to an oscillation noise with the frequency going up as I raise the knob more.

Recording of the noise during up/down knob sweep here: https://soundcloud.com/juliet-hotel/1176-noise-1/s-mPZvG (https://soundcloud.com/juliet-hotel/1176-noise-1/s-mPZvG)

So feeling pretty stupid but puzzled where to look to find the source of the noise.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 12:31:26 PM
Ok here's what I've done.
1. Since I ran it for a while with no heat shield on Q6, I ordered replacements and replaced Q6. I know I probably didn't have to, just trying to be thorough.
2. I retouched every trace in the GR control amp section plus any others I could find that looked wonky.
3. Seeing that there are 3 holes where CR10 goes, I pulled out CR10 and ordered a replacement. I then read that the outer holes are what I should use (which is what I had in the first place), installed a replacement 1N914 in outer holes of CR10.

When I powered up and tried to retest volts at tp21/tp22 it seemed like I had some volts going on. But something wasn't right. So I went back to do all the calibrations from scratch. I verified 0.775VAC at the input pins. But the output pins were all over the map as I moved the output knob.

Unmuted the output and sure enough I've now got myself a nice little noise maker. With nothing on the input, I get radio frequency interference type tones through most of the sweep of the output knob. But near the top of the travel of the knob it switches over to an oscillation noise with the frequency going up as I raise the knob more.

Recording of the noise during up/down knob sweep here: https://soundcloud.com/juliet-hotel/1176-noise-1/s-mPZvG (https://soundcloud.com/juliet-hotel/1176-noise-1/s-mPZvG)

So feeling pretty stupid but puzzled where to look to find the source of the noise.

There are only 2 holes for CR10.  There may be a via close by. That is a small hole that allows a trace on opposite sites of the PCB to connect through the PCB.

Have you done this:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +

That will tell you where your signal is dying.

Also we offer flat rate repair on those.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 09:31:37 PM
Configured as indicated in previous post and with 0.775 VAC measured between input XLR+ and XLR- I get the following using chassis as ground.

Input XLR+                          .438VAC
TP1                                     63.9
TP15                                  60.5
TP17                                     5.72
Transformer Brn          59.0
Out XLR+                         55.6
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 09:41:05 PM
Configured as indicated in previous post and with 0.775 VAC measured between input XLR+ and XLR- I get the following using chassis as ground.

Input XLR+                          .438VAC
TP1                                     63.9
TP15                                  60.5
TP17                                     5.72
Transformer Brn          59.0
Out XLR+                         55.6

You sure you have 60.5VAC at 15 and 5.72VAC at 17?

That's super weird.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 09:46:55 PM
You sure you have 60.5VAC at 15 and 5.72VAC at 17?

That's super weird.
Yep. Just double checked.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 10:01:15 PM
1. Check you DC V bias at PAD 18.  Rotate the pot. You should have between 0 VDC and about -2.9VDC.  Set it at the most negative position (about -2.9 VDC).

2. Make sure your GR OFF. Confirm your pad 22 is shorted to ground (chassis).

Try the AC test as described above again. Do you get anything different?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 10:10:57 PM
1. Check you DC V bias at PAD 18.  Rotate the pot. You should have between 0 VDC and about -2.9VDC.  Set it at the most negative position (about -2.9 VDC).
Ok a few dumb questions.
Is this still with a 1k test tone?
Rotate which pot? R59?

Quote
2. Make sure your GR OFF. Confirm your pad 22 is shorted to ground (chassis).
GR is definitely off. How do I confirm tp22 is shorted to ground? Ohms setting?

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 10:16:32 PM
Ok a few dumb questions.
Is this still with a 1k test tone?
Rotate which pot? R59?
GR is definitely off. How do I confirm tp22 is shorted to ground? Ohms setting?

Yes, you should see less than 1Ω between pad 22 and the enclosure.

Yes R59. No test tone needed.

Then when you do the recheck, with test tone.

Also make sure the 100Ω trim pot it in R86. The others are 2K.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 10:29:17 PM
Ok with the unit off, ohms between TP22 and ground are nill. Appears to be no connection there.

No joy setting R59 though. With unit on, no test tone, I get anywhere between +20 mVDC and -100mVDC through the range of travel on the pot.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 10:32:09 PM
Ok with the unit off, ohms between TP22 and ground are nill. Appears to be no connection there.

No joy setting R59 though. With unit on, no test tone, I get anywhere between +20 mVDC and -100mVDC through the range of travel on the pot.

What is your DC V on each side of R35 and R60 (chassis as common)?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 10:41:58 PM
R35: about +4mVDC to the rear, +14mVDC to the front
R60: about +13mVDC to the left, +24mVDC to the right
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 10:47:53 PM
R35: about +4mVDC to the rear, +14mVDC to the front
R60: about +13mVDC to the left, +24mVDC to the right

I'm not sure what you're measuring. Nothing makes sense.

Do the +30VDC an -10VDC power supply voltage check out?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 10:55:32 PM
Oh boy, as a matter of fact they do not check out.
CR8 is jumps around just under +1VDC
CR9 jumps around just under -1VDC

Perhaps we've hit paydirt...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 11:03:08 PM
Oh boy, as a matter of fact they do not check out.
CR8 is jumps around just under +1VDC
CR9 jumps around just under -1VDC

Perhaps we've hit paydirt...

1. Did they originally checkout after you built/tested the power supply?
2. Do you have your voltage selector switch set to you local mains voltage?
3. What is your AC V on the orange wires where the terminate to the PCB (careful).
4. You have it ON right? Meaning the GR switch is pushed in unlatching the OFF button?

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 11:07:29 PM
Yeah, power supply definitely checked out right on the money when I built it. Voltage selector is set correctly. I'm getting 70 VAC on both orange wire pads on the main PCB.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 11:29:36 PM
Yeah, power supply definitely checked out right on the money when I built it. Voltage selector is set correctly. I'm getting 70 VAC on both orange wire pads on the main PCB.

70 VAC on each separately against ground/chassis?
or
70VAC measuring against each other? One probe on one orange and one on the other orange?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 11:36:49 PM
70VAC on each against ground/chassis.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 11:41:49 PM
70VAC on each against ground/chassis.

That's not right.

Turn the unit off. 

Set your meter to measure resistance.

1. What's the Ω between that power transformer yellow wire (where it meets the PCB) and chassis?
2. What's the Ω between that power transformer yellow wire and each of the oranges?
3. What's the Ω between the oranges?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 11:49:12 PM
No continuity between yellow wire pad and chassis.
10.9 ohm between yellow wire and rear orange.
11.4 ohm between yellow wire and front orange.
22 ohm between the oranges.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 13, 2017, 11:53:30 PM
No continuity between yellow wire pad and chassis.

That's your problem.

Do you have all 3 metal L brackets installed that attach the PCB to the enclosure?

All three need to be screwed into the PCB and chassis tightly.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 13, 2017, 11:58:14 PM
Checked all three. All are tight. Then I rechecked yellow to chassis and I get 0 ohms now.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 14, 2017, 12:01:09 AM
Checked all three. All are tight. Then I rechecked yellow to chassis and I get 0 ohms now.

How are your supply voltages now? (DC)

What are the voltages of the oranges to chassis? (AC)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 14, 2017, 12:06:12 AM
Back in business now, 30.4 and -9.7
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 14, 2017, 12:12:24 AM
Back in business now, 30.4 and -9.7

Now what do you get at pad 18 when you turn R59?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 14, 2017, 12:39:59 AM
Now what do you get at pad 18 when you turn R59?
Between 0 and -3.09
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 14, 2017, 12:45:40 AM
Between 0 and -3.09

Cool. Set it to -3.09 and do this again:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 14, 2017, 08:38:06 PM
-Input XLR +                                            .430 VAC
-TP1                                                              .123
-TP15                                                           2.46
-TP17                                                           .382
-Output Transformer BRN            7.13
-Output XLR +                                      5.44
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 14, 2017, 08:57:09 PM
-Input XLR +                                            .430 VAC
-TP1                                                              .123
-TP15                                                           2.46
-TP17                                                           .382
-Output Transformer BRN            7.13
-Output XLR +                                      5.44

Looks good.  Can you calibrate now?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 14, 2017, 09:18:26 PM
Looks good.  Can you calibrate now?
Negative. Same as before. I can set Q bias ok. I set meter circuit null adjust and that seems to fine up until I move the shunt back to the normal pins. At that point, the meter goes from 0dB to -20dB and R71 runs out of travel long before the meter hits 0dB.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 14, 2017, 09:22:10 PM
Negative. Same as before. I can set Q bias ok. I set meter circuit null adjust and that seems to fine up until I move the shunt back to the normal pins. At that point, the meter goes from 0dB to -20dB and R71 runs out of travel long before the meter hits 0dB.

Well if it makes you feel any better, it seems your compressor is compressing normally. You just have a meter issue at this point.

You need to go through the section labeled "Gain Meter Driver Amp".  There are about 20 components in there, make sure they are the correct value and solder joints look good.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 16, 2017, 11:05:00 PM
I went through the gain meter driver amp section and the gr control amp section. All the values are correct and all the joints look good to me. But I can't get the calibrations done and near I can tell, the reason is because its not compressing.

With meter in +4 mode I can feed a test tone and raise the input knob pretty hot then bring up the output knob enough to get the meter around zero. If I then turn the attack knob from off to full cw, the meter doesn't move. In addition, level of the signal going back to my DAW doesn't change. Tried all the ratios, same result. No drop in level when you go from off to full CW on the attack knob.

She ain't compressing and I'm kind of out of ideas. I've checked everything on the boards multiple times. It all looks right. Might be time to box it up and let you guys have a crack at it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on September 17, 2017, 03:12:36 PM
Hello, all!

I've e-mailed hairball about my issue, but I thought I would get everyone elses input in the meantime. I just finished my 3rd blue stripe. When I went to begin the calibration process, i set up my signal generator - then noticed that my output knob had little to no effect on the output volume. I measured my output and was getting very low readings (around .4VAC with the knob cranked, i believe). So, I took the bottom off and measured resistance between the middle lug and a side. My reading would jump around and never got above 40-50k'ish. I realize that you can't get an accurate measurement in the circuit, so I decided to take the pot out to test it. When I was removing it, one of the lugs on the pot came right out. I don't know whether this was my problem to begin with, or if I got it too hot when removing it. So, in the meantime, until I get another one, do you guys have any suggestions of other things to check? I've given everything a good look over, and can't seem to find anything installed wrong. I've even checked to make sure i didn't mix up any 470, 4.7k, or 470k's etc. Thanks in advance!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on September 17, 2017, 04:02:48 PM
I also failed to mention - just for the sake of knowing things are functioning - i messed with the other controls and q-bias and it IS passing audio AND compressing. Thanks.

Hello, all!

I've e-mailed hairball about my issue, but I thought I would get everyone elses input in the meantime. I just finished my 3rd blue stripe. When I went to begin the calibration process, i set up my signal generator - then noticed that my output knob had little to no effect on the output volume. I measured my output and was getting very low readings (around .4VAC with the knob cranked, i believe). So, I took the bottom off and measured resistance between the middle lug and a side. My reading would jump around and never got above 40-50k'ish. I realize that you can't get an accurate measurement in the circuit, so I decided to take the pot out to test it. When I was removing it, one of the lugs on the pot came right out. I don't know whether this was my problem to begin with, or if I got it too hot when removing it. So, in the meantime, until I get another one, do you guys have any suggestions of other things to check? I've given everything a good look over, and can't seem to find anything installed wrong. I've even checked to make sure i didn't mix up any 470, 4.7k, or 470k's etc. Thanks in advance!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 12:09:44 PM
I went through the gain meter driver amp section and the gr control amp section. All the values are correct and all the joints look good to me. But I can't get the calibrations done and near I can tell, the reason is because its not compressing.

With meter in +4 mode I can feed a test tone and raise the input knob pretty hot then bring up the output knob enough to get the meter around zero. If I then turn the attack knob from off to full cw, the meter doesn't move. In addition, level of the signal going back to my DAW doesn't change. Tried all the ratios, same result. No drop in level when you go from off to full CW on the attack knob.

She ain't compressing and I'm kind of out of ideas. I've checked everything on the boards multiple times. It all looks right. Might be time to box it up and let you guys have a crack at it.

I see. Side chain issue then.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.
3. Using chassis as your ground reference, what is your AC V at anode (side with no line) of CR2for all 4 ratio settings.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 18, 2017, 09:00:31 PM
TP22
20:1 - .003 VAC
12:1 - .002
8:1 - .002
4:1 - .002

TP21
20:1 - -6.8 VAC
12:1 - -3.89
8:1 - -2.8
4:1 - -1.896

CR2
20:1 - .001 VDC
12:1 - .000
8:1 - .000
4:1 - .000
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 09:02:19 PM
TP22
20:1 - .003 VAC
12:1 - .002
8:1 - .002
4:1 - .002

TP21
20:1 - -6.8 VAC
12:1 - -3.89
8:1 - -2.8
4:1 - -1.896

CR2
20:1 - .001 VDC
12:1 - .000
8:1 - .000
4:1 - .000

That's with GR on?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 18, 2017, 09:10:43 PM
That's with GR on?
Yes. Full CW
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 09:15:52 PM
Yes. Full CW

What is your AC at PAD 15 under the same conditions?  Ratio doesn't mater.

Give me your AC at pad 15 with GR ON and GR OFF.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 18, 2017, 09:27:28 PM
TP15 GR on: 1.783 VAC
TP15 GR off: 1.783 VAC

Not sure if normal but volts will move a bit if I gently tap the output control post.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 09:34:35 PM
TP15 GR on: 1.783 VAC
TP15 GR off: 1.783 VAC

Not sure if normal but volts will move a bit if I gently tap the output control post.

1. You have a rev D right?
2. With GR ON, what if you AC V at either side of R78 (Ratio PCB)?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 18, 2017, 09:40:41 PM
1. You have a rev D right?
2. With GR ON, what if you AC V at either side of R78 (Ratio PCB)?

Mike
1.785  side toward the connector
1.420 toward edge of board

That's GR on with the test tone going.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 09:45:41 PM
1.785  side toward the connector
1.420 toward edge of board

That's GR on with the test tone going.

In 20:1?

But nothing at pad 22?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 18, 2017, 09:47:56 PM
In 20:1?

But nothing at pad 22?
Affirmative.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 09:52:47 PM
Affirmative.

Hmmmmm.

You have a problem with your switch or connector or side chain input.

Reflow the solder joints on your ratio switch and both ends of the 6 pin connector that attach it to the PCB. 

Confirm your wire connector isn't weird, like two wires are crossed over. Pin 1 should go to pin 1 and so on.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 18, 2017, 09:55:56 PM
Ok I'll dig into it. I've already reflowed the connector on the main board but I'll pull the ratio PCB and go over everything. Thanks for the help Mike.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 10:03:59 PM
Ok I'll dig into it. I've already reflowed the connector on the main board but I'll pull the ratio PCB and go over everything. Thanks for the help Mike.

Check the resistors values on the ratio PCB too. Specifically R78, R19, R20, R21, R22.

Also reflow your Attack SW.

Audio isn't getting to your sidechain which is why you don't have compression.  Pad 22 is at the start of the side chain, when you have GR ON and a signal, you should have some AC down there.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: jgremlin on September 18, 2017, 10:38:59 PM
That's got it! I'll check the values and reflow the knobs before I button it up, but I got through the calibrations and it seems to passing audio and compressing. Thanks a billion for the help!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 18, 2017, 10:40:19 PM
That's got it! I'll check the values and reflow the knobs before I button it up, but I got through the calibrations and it seems to passing audio and compressing. Thanks a billion for the help!

Awesome.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on September 21, 2017, 01:49:25 PM
Hey guys, I'm the one that posted a few back about my output knob not changing anything upon calibration. So, I got my new output pot in the mail, and turns out that wasn't my problem. I got everything hooked back up for calibration and my output pot is still doing nothing. During step 1 of calibration - i set up for .775 at the input and when i measure the output, i'm getting .53 - and adjusting the output knob does nothing. Ideas? Thanks.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 21, 2017, 01:53:56 PM
Hey guys, I'm the one that posted a few back about my output knob not changing anything upon calibration. So, I got my new output pot in the mail, and turns out that wasn't my problem. I got everything hooked back up for calibration and my output pot is still doing nothing. During step 1 of calibration - i set up for .775 at the input and when i measure the output, i'm getting .53 - and adjusting the output knob does nothing. Ideas? Thanks.

Are you even passing signal?

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu
QBias set for most negative DC @ pad 18.

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on September 21, 2017, 02:22:12 PM
Yes, I am passing signal. It is also compressing when I adjust controls.

Input XLR - .423 on positive side & .305 negative side
TP1 - .115
TP15 - 4.03
TP17 - .550
BRN - .131 (every time I touch, it jumps from .6ish and settles down to .131)
OUTPUT XLR - .063 Both Sides
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: YoDudeRock on September 21, 2017, 06:17:42 PM
I'm building  my 13th Rev D with the Orange Drop upgrade.   I am missing one of the parts  (ordered them from Mouser) .   It's "C11" a 10pF capacitor in the Line Amp.    In my parts bin, I have a 6.8 pF.    Would this be an acceptable replacement??   If not, I can run to the local electronics store tomorrow.

Thanks!
Chris
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 22, 2017, 01:08:00 PM
Yes, I am passing signal. It is also compressing when I adjust controls.

Input XLR - .423 on positive side & .305 negative side
TP1 - .115
TP15 - 4.03
TP17 - .550
BRN - .131 (every time I touch, it jumps from .6ish and settles down to .131)
OUTPUT XLR - .063 Both Sides

Your BRN is super low.

Check everything in the box labeled "Signal Line Amp".
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 22, 2017, 01:09:42 PM
I'm building  my 13th Rev D with the Orange Drop upgrade.   I am missing one of the parts  (ordered them from Mouser) .   It's "C11" a 10pF capacitor in the Line Amp.    In my parts bin, I have a 6.8 pF.    Would this be an acceptable replacement??   If not, I can run to the local electronics store tomorrow.

Thanks!
Chris

Totally fine.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on September 22, 2017, 10:40:03 PM
Your BRN is super low.

Check everything in the box labeled "Signal Line Amp".

I think I've got it pretty narrowed down. I've got 2.07VDC on the gate of q4, and 4.62 on the + side of C9. This would mean that q4 is either biased improperly, or bad, correct? My knowledge isn't vast, but doesn't the gate have to have a larger voltage than the source to amplify? My values of R24-R28 are all correct, and i can beep test them all. Any advice is appreciated. Thanks.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 25, 2017, 01:48:33 PM
I think I've got it pretty narrowed down. I've got 2.07VDC on the gate of q4, and 4.62 on the + side of C9. This would mean that q4 is either biased improperly, or bad, correct? My knowledge isn't vast, but doesn't the gate have to have a larger voltage than the source to amplify? My values of R24-R28 are all correct, and i can beep test them all. Any advice is appreciated. Thanks.

Ya that all seems off.

You should triple check the components in that area and traces.

Consider replacing Q4.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on September 25, 2017, 01:51:55 PM
Ya that all seems off.

You should triple check the components in that area and traces.

Consider replacing Q4.

I've triple checked them. Traces all test fine for continuity. Every retailer is out of stock of J309's so I have one on order from France. I will report back with my findings. Thanks for you guys' help.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on September 27, 2017, 09:36:19 AM

So weird.  You could send it in for repair but obviously there is a cost to that.  Is the release pot ok, is one of the legs broken off?

Delayed response on my end. Thanks for getting back to me.

Yes the release pot seems okay. The issue is still going on but I normally just leave the release on 7 anyways, but I'd like to get it figured out eventually. Could the release pot be defective?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 27, 2017, 01:28:48 PM
Delayed response on my end. Thanks for getting back to me.

Yes the release pot seems okay. The issue is still going on but I normally just leave the release on 7 anyways, but I'd like to get it figured out eventually. Could the release pot be defective?

Probably not.  Sorry what is the issue again? Release time weird?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on September 28, 2017, 11:44:57 AM
Probably not.  Sorry what is the issue again? Release time weird?

The Gain reduction moves to the left as I slow the release. Seems like it's working fine as far as compression goes, but I can't trust the GR meter on anything less than the release on 7.

I've been just setting it by ear.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 28, 2017, 01:30:21 PM
The Gain reduction moves to the left as I slow the release. Seems like it's working fine as far as compression goes, but I can't trust the GR meter on anything less than the release on 7.

I've been just setting it by ear.

Hmmmm.

Have you cleaned the bottom of the PCB?  I think I recall seeing this issue with excessive flux in the high impedance areas. Make sure you have flux scrubbed clean, particularity around Q1/Q11.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: dbonin on September 29, 2017, 01:11:56 PM
This new 1176 Fet Rack kit is one of the best audio gear kits I have seen yet.  I've built a ton of gear from scratch and this kit was so easy and enjoyable to put together I would highly recommend giving it a try. 
But it wont build itself!
Yes, you need to take your time and pre read all the build guides - which are excellent, btw.
Yes, you need to be able to use a  DMM and be able to carefully check and solder a few small parts.
Yes,  you can build your own gear - the new 1176 Fet Rack kit is all you need.

You have totally nailed it.  You have removed all of the complexity of your older kits , greatly reducing the number of possible points of error.   

Great Design, great quality, excellent value.  Well done!

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on September 29, 2017, 01:17:13 PM
This new 1176 Fet Rack kit is one of the best audio gear kits I have seen yet.  I've built a ton of gear from scratch and this kit was so easy and enjoyable to put together I would highly recommend giving it a try. 
But it wont build itself!
Yes, you need to take your time and pre read all the build guides - which are excellent, btw.
Yes, you need to be able to use a  DMM and be able to carefully check and solder a few small parts.
Yes,  you can build your own gear - the new 1176 Fet Rack kit is all you need.

You have totally nailed it.  You have removed all of the complexity of your older kits , greatly reducing the number of possible points of error.   

Great Design, great quality, excellent value.  Well done!

Thanks!

Thanks!

We have a couple amazing documents coming out in the next couple weeks that will really help builders narrow down any issues they may have.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: dbonin on October 01, 2017, 11:27:26 AM
Calibration went smoothly.  GR is spot on.  Sounds perfect.

However,  the +8 and +4 meter modes that should be showing output barely move with live material.  In GR mode the meter deflects precisely both with test tone and with live material. 

Is there a simple test I could do to verify the +8+4 meter modes are behaving  normally compared to one of your hairball calibrated units?
Thanks!
 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 01, 2017, 11:44:26 AM
Calibration went smoothly.  GR is spot on.  Sounds perfect.

However,  the +8 and +4 meter modes that should be showing output barely move with live material.  In GR mode the meter deflects precisely both with test tone and with live material. 

Is there a simple test I could do to verify the +8+4 meter modes are behaving  normally compared to one of your hairball calibrated units?
Thanks!

Not much to go wrong there.  Just those two resistors on the meter PCB.

- Get +4dBu (1.23VAC) signal across input output +/- and the meter should be at around 0  in +4.
- Get+8dBu (1.95VAC) signal  across input output +/- and the meter should be at around 0  in +8.

You can just use a 0dBu signal on the input like setting Qbias, then increase the output to get +4 and +8.  You'll need to be in GR off.  With GR on the signal will probably be too low.  That might be what you're seeing.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on October 02, 2017, 10:31:48 AM
Hmmmm.

Have you cleaned the bottom of the PCB?  I think I recall seeing this issue with excessive flux in the high impedance areas. Make sure you have flux scrubbed clean, particularity around Q1/Q11.

Mike

I thoroughly cleaned it, but tomorrow I can do it again just for the sake of it. Not sure what to look for if that fails to fix the issue.

Thank you for your time Mike!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 02, 2017, 12:33:17 PM
I thoroughly cleaned it, but tomorrow I can do it again just for the sake of it. Not sure what to look for if that fails to fix the issue.

Thank you for your time Mike!

Post back after you try that...I'll give you some other stuff to check.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: dbonin on October 02, 2017, 04:24:30 PM
Not much to go wrong there.  Just those two resistors on the meter PCB.

- Get +4dBu (1.23VAC) signal across input output +/- and the meter should be at around 0  in +4.
- Get+8dBu (1.95VAC) signal  across input output +/- and the meter should be at around 0  in +8.

You can just use a 0dBu signal on the input like setting Qbias, then increase the output to get +4 and +8.  You'll need to be in GR off.  With GR on the signal will probably be too low.  That might be what you're seeing.

Mike

That was quick and easy.  Spot on again!
Thanks Mike.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on October 03, 2017, 01:15:28 PM
Post back after you try that...I'll give you some other stuff to check.

Mike

Scrubbed with 99% isopropyl and a toothbrush, dried it with a cloth, repeated again twice. Issue is still going on. PCB looked pretty clean to begin with as I did this a couple times already.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2017, 01:22:07 PM
Scrubbed with 99% isopropyl and a toothbrush, dried it with a cloth, repeated again twice. Issue is still going on. PCB looked pretty clean to begin with as I did this a couple times already.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

1. What are those readings?
2. Do they change as you rotate the release?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on October 03, 2017, 02:34:52 PM
Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

1. What are those readings?
2. Do they change as you rotate the release?

Mike

4        -1.606
8        -2.435
12     -3.265
20     -5.9

No change in DC as I rotate.

On another note after a thorough warmup after the last cleaning the problem seems to have lessened. It used to swing from 0 to -7 or -10 and now it's only going down to about 0 to -1.

Going to clean again a couple more times and see if it makes a difference. Thank you for your time Mike! This is making me want to rescrub all my Lola and Gold preamps I built!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2017, 03:34:28 PM
4        -1.606
8        -2.435
12     -3.265
20     -5.9

No change in DC as I rotate.

On another note after a thorough warmup after the last cleaning the problem seems to have lessened. It used to swing from 0 to -7 or -10 and now it's only going down to about 0 to -1.

Going to clean again a couple more times and see if it makes a difference. Thank you for your time Mike! This is making me want to rescrub all my Lola and Gold preamps I built!

Those readings look good and it's good they are not changing with rotation.

Report back after a deep scrub....don't be afraid to soak the back side and let it run off the edge of the PCB. Get the ratio board too.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: thecmarus on October 03, 2017, 06:57:16 PM
Those readings look good and it's good they are not changing with rotation.

Report back after a deep scrub....don't be afraid to soak the back side and let it run off the edge of the PCB. Get the ratio board too.

Mike

Mike,

Bought a gallon jug of isopropyl from my local hardware store and went buck wild on all the PCBs. Still getting the 1db drop on the VU meter when I put the release on 1, which is still better than my original problem which was from 0 to -7 or -10. A few things I've noted are that it is definitely worse until the unit has been on for over an hour or more. The VU meter takes a substantial amount of time to reach 0db, and I know this is normal for an 1176, but this is more dramatic than my Rev D kit.

Maybe if I'm feeling adventurous tonight I'll give it another scrub.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 03, 2017, 07:03:11 PM
Mike,

Bought a gallon jug of isopropyl from my local hardware store and went buck wild on all the PCBs. Still getting the 1db drop on the VU meter when I put the release on 1, which is still better than my original problem which was from 0 to -7 or -10. A few things I've noted are that it is definitely worse until the unit has been on for over an hour or more. The VU meter takes a substantial amount of time to reach 0db, and I know this is normal for an 1176, but this is more dramatic than my Rev D kit.

Maybe if I'm feeling adventurous tonight I'll give it another scrub.

You shouldn't have to scrub that much.

We need to figure out where the voltage is fluctuating to get to the root of it. I would have expected Pad 21, but no dice.

Scrub that attack/release PCB too!  Confirm all those values.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jec909 on October 06, 2017, 12:54:30 PM
Hi everyone,

I've sent a mail to hairball but I thought I'd write here as well as Mike answers in this thread as well.

I've built two Rev D . nothing to report regarding the built, well documented, really top notch.

Seems my device is not even passing audio

On both of my FETs when calibrating Qbias, I get no AC reading on the output between OUT + and OUT -.
Also I understand that when the device is on OFF,, it should be in pass trough. Is that right? Because I also get no AC reading on the output between OUT + and OUT -. in OFF

I do get a reading on the output between OUT + and OUT - but only when i turn up and down the output control then it briefly reads between 0 VAC to 1.5 VAC or so but drops right ways to 0 VAC

To this question:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu 0.775 VAC

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR + = FET1: 0.387 VAC / FET2 0.383 VAC
-TP1 = FET1: 0.110 VAC/ FET2 0.139 VAC
-TP15 = FET 1 0VAC / FET2 0VAC
-TP17 = FET 1 0VAC / FET2 0VAC
-Output Transformer BRN = Where is it?
-Output XLR + =  FET 1 0VAC / FET2 0VAC

The issue is consistent on both device, I need some heads up

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 06, 2017, 12:58:51 PM
Hi everyone,

I've sent a mail to hairball but I thought I'd write here as well as Mike answers in this thread as well.

I've built two Rev D . nothing to report regarding the built, well documented, really top notch.

Seems my device is not even passing audio

On both of my FETs when calibrating Qbias, I get no AC reading on the output between OUT + and OUT -.
Also I understand that when the device is on OFF,, it should be in pass trough. Is that right? Because I also get no AC reading on the output between OUT + and OUT -. in OFF

I do get a reading on the output between OUT + and OUT - but only when i turn up and down the output control then it briefly reads between 0 VAC to 1.5 VAC or so but drops right ways to 0 VAC

To this question:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu 0.775 VAC

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR + = FET1: 0.387 VAC / FET2 0.383 VAC
-TP1 = FET1: 0.110 VAC/ FET2 0.139 VAC
-TP15 = FET 1 0VAC / FET2 0VAC
-TP17 = FET 1 0VAC / FET2 0VAC
-Output Transformer BRN = Where is it?
-Output XLR + =  FET 1 0VAC / FET2 0VAC

The issue is consistent on both device, I need some heads up

Your signal is dying in your first amp stage. The signal pre amp.

Set your compressor controls:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: None

With your DMM measure DC at TP18 using the chassis as you reference (black probe). Rotate the Qbias pot (R59) and note the DCV at each extreme of the pot. What are those 2 reading?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jec909 on October 06, 2017, 01:13:26 PM
Your signal is dying in your first amp stage. The signal pre amp.

Set your compressor controls:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: None

With your DMM measure DC at TP18 using the chassis as you reference (black probe). Rotate the Qbias pot (R59) and note the DCV at each extreme of the pot. What are those 2 reading?

Mike


Thanks for the quick answer Mike
I get -00.3 mVDC with r59 full CCW and -2.97 VDC with r59 full CW
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 06, 2017, 01:16:01 PM
Thanks for the quick answer Mike
I get -00.3 mVDC with r59 full CCW and -2.97 VDC with r59 full CW

Set it to -2.97 VDC then try those readings in your first post again.

Lets just stick to unit 1 for now.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jec909 on October 06, 2017, 01:29:21 PM
Set it to -2.97 VDC then try those readings in your first post again.

Lets just stick to unit 1 for now.

Mike

Sure!

With r59 at  -2.97 VDC full cw and 1000 Hz 0 dBu (0.775VDC)  signal to the input

-Input XLR +  = 0.383 VAC
-TP1 = 0.139 VAC
-TP15 = 0 VAC
-TP17 = 0 VAC
-Output Transformer BRN = Where is it?
-Output XLR + =   0 VAC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 06, 2017, 01:36:37 PM
Sure!

With r59 at  -2.97 VDC full cw and 1000 Hz 0 dBu (0.775VDC)  signal to the input

-Input XLR +  = 0.383 VAC
-TP1 = 0.139 VAC
-TP15 = 0 VAC
-TP17 = 0 VAC
-Output Transformer BRN = Where is it?
-Output XLR + =   0 VAC

Don't worry about BRN right now.

Your signal is dying in the Signal Preamp stage marked on the PCB.

Try removing you Q1 FET carefully and see if you get signal at TP15.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jec909 on October 06, 2017, 02:14:25 PM
Don't worry about BRN right now.

Your signal is dying in the Signal Preamp stage marked on the PCB.

Try removing you Q1 FET carefully and see if you get signal at TP15.

Mike

I unsoldered Q1 FET

And signal do not reach tp15

No VAC reading between chassis and 15
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 06, 2017, 02:20:45 PM
I unsoldered Q1 FET

And signal do not reach tp15

No VAC reading between chassis and 15

You need to search through that Signal Preamp section marked on the PCB.  Triple check all component values, solder joints, and continuity. Something is a miss in there.

Check you transistor values against this chart in that section:
http://mnats.net/files/1176REVD_VOLTS.pdf

Make sure your power supply voltages are still good (+30VDC and -10VDC).

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jec909 on October 06, 2017, 02:28:30 PM
You need to search through that Signal Preamp section marked on the PCB.  Triple check all component values, solder joints, and continuity. Something is a miss in there.

Check you transistor values against this chart in that section:
http://mnats.net/files/1176REVD_VOLTS.pdf

Make sure your power supply voltages are still good (+30VDC and -10VDC).

Mike

thanks mike. will do and report
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 06, 2017, 02:29:53 PM
thanks mike. will do and report

Also make sure all of your L brackets are secure in place.

Good luck! 

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jec909 on October 07, 2017, 06:34:59 AM
Mike, feeling a bit confused.

On these test points, I should see DC or AC current?

I've been measuring  AC all the time :S
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 07, 2017, 11:38:11 AM
Mike, feeling a bit confused.

On these test points, I should see DC or AC current?

I've been measuring  AC all the time :S

Depends on what your looking for.

In the first step we did (TP1, TP15) we're looking for actual audio signal, which is AC.  You input your signal (0dBu @ 1Khz) and trace that AC through the gain stages.  Your signal is measuring fine at TP1 which is after the T-Pad and input transformer and at the beginning of the signal preamp.

For a Revision D you should then see about 2 VAC (8 dBu) at the output of the signal pre amp which is TP15.

You have nothing there so your signal is dying in that signal preamp section. You have a wrongly paced component, damaged component, or bad solder joint/pad.  Measuring the DC V at the transistor leads as shown in that schematic with voltages, can help us narrow down the issue further.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Jec909 on October 08, 2017, 01:29:18 PM
I found the problem. I deserve a big slap . The issue was a missing resistor  LOL   :-[ (r8, which was hidden below the orange drop cap. )

I mostly wasted your time but I did learn a lot!  Many many thanks for your extremely valuable help and time.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 09, 2017, 11:15:09 AM
I found the problem. I deserve a big slap . The issue was a missing resistor  LOL   :-[ (r8, which was hidden below the orange drop cap. )

I mostly wasted your time but I did learn a lot!  Many many thanks for your extremely valuable help and time.

Glad you found it!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Mkvy83 on October 16, 2017, 01:24:45 AM
Hey so I just finished building the 1176 Rev D and calibrated it yesterday after letting it warm up for awhile. Today I noticed some screws were loose on the Main pcb brackets that connect to the chassis. When I tightened them back in, and turned on the 1176 today the VU meter is hitting +2 db with no signal going through it, attack off, releases CCW, ratio at 20:1, and meter on GR.  Would i need to recalibrate the compressor due to lose chassis screws on the brackets or can I just adjust the meter back to zero and it'll be fine?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 16, 2017, 12:58:00 PM
Hey so I just finished building the 1176 Rev D and calibrated it yesterday after letting it warm up for awhile. Today I noticed some screws were loose on the Main pcb brackets that connect to the chassis. When I tightened them back in, and turned on the 1176 today the VU meter is hitting +2 db with no signal going through it, attack off, releases CCW, ratio at 20:1, and meter on GR.  Would i need to recalibrate the compressor due to lose chassis screws on the brackets or can I just adjust the meter back to zero and it'll be fine?

I would probably re-calibrate.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on October 23, 2017, 10:47:32 AM
Hey all, sad story ahead. This weekend during a session, we were moving a few pieces of gear into our studio B, and one of the clients knocked my Rev A off of a chair from about 15" off of the ground. Now I'm having an issue where I have a very faint signal, and my output knob has very little affect on the volume. The compression, attack, release etc all seem to be working properly. It's just a very faint signal. Any ideas on where to start? Thanks.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 23, 2017, 12:20:55 PM
Hey all, sad story ahead. This weekend during a session, we were moving a few pieces of gear into our studio B, and one of the clients knocked my Rev A off of a chair from about 15" off of the ground. Now I'm having an issue where I have a very faint signal, and my output knob has very little affect on the volume. The compression, attack, release etc all seem to be working properly. It's just a very faint signal. Any ideas on where to start? Thanks.

Maybe the output pot got torn off a bit?  Start here:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Kevin Prochnow on October 23, 2017, 01:41:17 PM
Hello people!

My Rev A is killing voltage and obscuring my input signal between TP1 and TP15, in the signal preamp section. I have replaced the Q1FET multiple times. Power supply seems fine. PLEASE HELP!!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 23, 2017, 02:05:38 PM
Hello people!

My Rev A is killing voltage and obscuring my input signal between TP1 and TP15, in the signal preamp section. I have replaced the Q1FET multiple times. Power supply seems fine. PLEASE HELP!!

What about with no Q1 FET in there? Still not signal at TP15?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on October 23, 2017, 02:09:54 PM
Maybe the output pot got torn off a bit?  Start here:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
[/quote

INPUT, TP1, AND TP15 are where they're supposed to be. TP 17 is reading virtually nothing at .009. Then BRN and Output + we have .420 (I'm assuming low since they aren't getting the proper signal earlier in the circuit). Thanks in advance!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 23, 2017, 02:15:37 PM
Maybe the output pot got torn off a bit?  Start here:

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
[/quote

INPUT, TP1, AND TP15 are where they're supposed to be. TP 17 is reading virtually nothing at .009. Then BRN and Output + we have .420 (I'm assuming low since they aren't getting the proper signal earlier in the circuit). Thanks in advance!

Check your output pot. Maybe remove and test it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on October 23, 2017, 02:37:52 PM
Check your output pot. Maybe remove and test it.

Good call, two broken legs. Not completely sure how that happened. After some internet research, looks like it's not an easy pot to find. Is there a way I can purchase one from you guys directly?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Kevin Prochnow on October 23, 2017, 04:58:01 PM
What about with no Q1 FET in there? Still not signal at TP15?
Just took it out and checked and still shows low voltage at tp15 (100mV when i think its supposed to be about 4V?)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 23, 2017, 08:10:13 PM
Good call, two broken legs. Not completely sure how that happened. After some internet research, looks like it's not an easy pot to find. Is there a way I can purchase one from you guys directly?

Yup, shoot us an email.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 23, 2017, 08:11:41 PM
Just took it out and checked and still shows low voltage at tp15 (100mV when i think its supposed to be about 4V?)

Ya.

You got something bad in that first amp section.  The voltages in the signal preamp should line up with this:

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Anything off with Q2 or Q3?

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TDJ on October 26, 2017, 12:47:31 PM
Yup, shoot us an email.

Got my new output pot in today, and all is well again! Hopefully it won't be dropped off of a chair again anytime soon. Thanks for the help! Now off to build my LOLA!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Kevin Prochnow on October 26, 2017, 03:48:20 PM
Ya.

You got something bad in that first amp section.  The voltages in the signal preamp should line up with this:

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Anything off with Q2 or Q3?

Mike

The voltages at Q2 and Q3 are off. The 30V supply on the other side of R17 is present and correct.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 27, 2017, 12:10:56 PM
The voltages at Q2 and Q3 are off. The 30V supply on the other side of R17 is present and correct.

Something is off in there. Bad resistor/cap value, solder joint, lifted pad (check continuity), or bad transistor.

If you're convinced everything is ok we can fire you out a couple transistors.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on October 27, 2017, 02:51:03 PM
Hey, this is from a ways back.. just back in town and at the bench.. My Q1 was pulled per our previous discussion, which then gave us signal at T1.

Did you want me to replace Q1 and then do the test below? or do the test without replacing? just wanna be sure before I put in this transistor.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Kevin Prochnow on October 30, 2017, 12:25:31 PM
Something is off in there. Bad resistor/cap value, solder joint, lifted pad (check continuity), or bad transistor.

If you're convinced everything is ok we can fire you out a couple transistors.

There is a tiny lead stuck in the middle hole of the Q1 footprint from one of the times I've replaced it, but I don't believe that is the issue since I am still able to connect all 3 leads when I put a different one in, and this signal issue was happening before I took the original Q1 transistor out in the first place. The continuity around Q1 all checks out, and I will check other areas. If you could send replacement transistors for Q2 and Q3, that would be cool, too. 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 30, 2017, 09:14:31 PM
There is a tiny lead stuck in the middle hole of the Q1 footprint from one of the times I've replaced it, but I don't believe that is the issue since I am still able to connect all 3 leads when I put a different one in, and this signal issue was happening before I took the original Q1 transistor out in the first place. The continuity around Q1 all checks out, and I will check other areas. If you could send replacement transistors for Q2 and Q3, that would be cool, too.

Shoot us an email.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on October 30, 2017, 09:15:07 PM
Hey, this is from a ways back.. just back in town and at the bench.. My Q1 was pulled per our previous discussion, which then gave us signal at T1.

Did you want me to replace Q1 and then do the test below? or do the test without replacing? just wanna be sure before I put in this transistor.

Start by testing without.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 02, 2017, 04:50:51 PM
Hi. I just finished both a rev. A and D. My D works perfectly, but I have issues with my A.
Only the 20:1 ratio is working - when I change to other ratios, the meter still zeroes, but shows and makes no compression. I haven’t measured excactly, but I can’t hear any difference between bypass mode and the compressor engaged. I checked all the connectors between the ratio board and the main board, and all seems good. Any suggestions for troubleshooting?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 02, 2017, 04:59:13 PM
Hi. I just finished both a rev. A and D. My D works perfectly, but I have issues with my A.
Only the 20:1 ratio is working - when I change to other ratios, the meter still zeroes, but shows and makes no compression. I haven’t measured excactly, but I can’t hear any difference between bypass mode and the compressor engaged. I checked all the connectors between the ratio board and the main board, and all seems good. Any suggestions for troubleshooting?


Side-chain has kind of a cascading ladder thing happening. If only one ratio works, it's going to be 20:1.  Most likely you have a ratio PCB issue.

Set your compressor controls:

Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (fully CW)
Release: Full CW
Ratio: Check All
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

1. With your DMM measure AC at TP22 for each ratio setting using the chassis as you reference (black probe).
2. With your DMM measure AC at the anode of CR2 for each ratio setting using the chassis as you reference (black probe). The anode is the positive lead and is the lead without the line.
3. With your DMM measure DC at TP21 for each ratio setting using the chassis as you reference (black probe).

Make sure to note #1 and #2 are AC and #3 is DC. Report those 3 voltages for each ratio.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 02, 2017, 06:21:29 PM
Thanks, Mike.
I’m in Europe, so it’s getting late, and I’ve left the studio. I’ll report back tomorrow.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 03, 2017, 06:18:22 AM
Okay, here we go:
AC @tp22:
4:1    .044v
8:1    .09v
12:1 .022v
20:1 .41v

AC @CR2
4:1    .6v
8:1   1.2v
12:1   .2v
20:1    3.6v

DC @tp21
4:1    -1.46
8:1    -2.3
12:1 -3.15
20:1 -5.85
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 03, 2017, 11:37:03 AM
Okay, here we go:
AC @tp22:
4:1    .044v
8:1    .09v
12:1 .022v
20:1 .41v

AC @CR2
4:1    .6v
8:1   1.2v
12:1   .2v
20:1    3.6v

DC @tp21
4:1    -1.46
8:1    -2.3
12:1 -3.15
20:1 -5.85

It's really just your 12:1 ratio that looks bad.  Are 8 and 4:1 not compressing?

Check your ratio PCB, particularly around R19-R22.  Check all values, reflow solder, check pads, check soldering for the 12:1 switch.


Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 03, 2017, 01:07:52 PM
No, only 20:1 compresses. I’ll be back, when I’m back in the studio.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 06, 2017, 09:18:46 AM
Resistor values are correct, as far as I can see. Doesn’t everything look correct here?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 06, 2017, 09:21:02 AM
Soldering side:
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 06, 2017, 05:49:31 PM
Pictures don't really help, it's usually something that needs to be tested with continuity. 

Pop the ratio PCB in from your working D. Does that fix it or same issue?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 07, 2017, 03:29:58 AM
Well, I had to hard-wire the ratio board to my D, because the CN10 was missing. The replacement  you sent has not been delivered yet, and tracking says it’s still in transit, with the latest registration Oct. 19th. So I had to do something  to have a working compressor :-)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 07, 2017, 06:34:49 AM
Oh, I mixed up the ratio and attack/release boards. I tried to go through all the solder points before switching boards - and now it seems to work, although 8:1 didn’t work at one point, but then it came back again. Have you had idle switches?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 07, 2017, 06:39:46 AM
Now, everything seems to be fine with my rev. A. But now, all of a sudden, my D starts to crap out. It has worked before, calibrated and fine. But now it just farts, when I feed a bass signal to it. There meter shows what I hear. Any troubleshooting tips?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: beaustep on November 07, 2017, 07:30:17 PM
Hey Mike!

I am so stuck on my Rev A power supply. I've read through all the power supply posts for the new build.

It's all assembled and the ohms are all reading fine, but when I power up, the DC voltage is extremely low.

Any ideas on what I am missing?

THANK YOU!!

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 08, 2017, 01:54:43 PM
Hey Mike!

I am so stuck on my Rev A power supply. I've read through all the power supply posts for the new build.

It's all assembled and the ohms are all reading fine, but when I power up, the DC voltage is extremely low.

Any ideas on what I am missing?

THANK YOU!!

Few things:

1. Fuse is in?
2. All three L brackets have the PCB secured to the enclosure?
3. DMM set to DC?
4. Do you have <0 ohm of resistance between the transformer yellow lead pad and enclosure? (power off)
5. What are your +30VDC and -10VDC readings?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 08, 2017, 01:56:49 PM
Now, everything seems to be fine with my rev. A. But now, all of a sudden, my D starts to crap out. It has worked before, calibrated and fine. But now it just farts, when I feed a bass signal to it. There meter shows what I hear. Any troubleshooting tips?

Bad switches are rare.

If you're getting cutting in and cutting out I would suspect either some joints are unsoldered/cold soldered. You should reflow suspect joints.

Also all L brackets must be secure to the PCB chassis. They are part of the grounding system.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 09, 2017, 04:42:00 PM
Hi Mike
Checked the L brackets and any suspicious solderings. Still no luck.
It’s not that it pops in and out, more like a fuzz pedal with a very dying battery...
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 13, 2017, 12:32:04 PM
Hi Mike
Checked the L brackets and any suspicious solderings. Still no luck.
It’s not that it pops in and out, more like a fuzz pedal with a very dying battery...

Is this the Rev D?

Set your compressor controls:

Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

With your DMM measure AC at the following test points using the chassis as you reference (black probe).

TP1
TP15
BRN Wire on Output

Then measure between + and - on the output XLR.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: frenkonio on November 13, 2017, 12:41:26 PM
Hi guys, maybe it has been already written... I read on the BOM of the REV. D that C2 caps is 27pF and C13 is 270pF but in the bag there are only 2 blu caps (ceramic) with "271" written on. I also saw other two REV. D (that I still didn't assembled yet) and both ceramic caps bags have the same 2 "271" blu caps. What's wrong?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 13, 2017, 12:48:27 PM
Hi guys, maybe it has been already written... I read on the BOM of the REV. D that C2 caps is 27pF and C13 is 270pF but in the bag there are only 2 blu caps (ceramic) with "271" written on. I also saw other two REV. D (that I still didn't assembled yet) and both ceramic caps bags have the same 2 "271" blu caps. What's wrong?

Hmmm I'll have to look into it.  May be a kitting error on our side.

You can fill out a missing parts form on the site. 

Hairballaudio.com/missing
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 13, 2017, 02:58:11 PM
Hmmm I'll have to look into it.  May be a kitting error on our side.

You can fill out a missing parts form on the site. 

Hairballaudio.com/missing

You should have a 10pF, 27pF, 2 x 220pF, and a 270pF correct?

What do you have?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: beaustep on November 14, 2017, 06:58:57 PM
Few things:

1. Fuse is in?
2. All three L brackets have the PCB secured to the enclosure?
3. DMM set to DC?
4. Do you have <0 ohm of resistance between the transformer yellow lead pad and enclosure? (power off)
5. What are your +30VDC and -10VDC readings?

Mike

1: Fuse is definitely in. Double/triple checked.
2: All 3 brackets are secured.
3: DMM is set to DC
4. 0.2 ohms
5. 0.003VDC
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 14, 2017, 07:05:48 PM
1: Fuse is definitely in. Double/triple checked.
2: All 3 brackets are secured.
3: DMM is set to DC
4. 0.2 ohms
5. 0.003VDC

1. You have 0.003 VDC at your +30 VDC test point AND you -10 VDC test point?
2. You have the unit turned on and plugged in correct? Meaning you have the GR pushbutton selected?
3. What is your AC V between the yellow secondary pad and each orange (give me 2 readings).

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 20, 2017, 08:21:27 AM
Hi Mike.
Here’s what I measured:
TP1: 0.122V
TP15: 2.10V
Brown wire: 6.25V
Output xlr: 6.22V

Is this the Rev D?

Set your compressor controls:

Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu (0.775 VAC across input + and -)

With your DMM measure AC at the following test points using the chassis as you reference (black probe).

TP1
TP15
BRN Wire on Output

Then measure between + and - on the output XLR.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: stringmike on November 21, 2017, 03:55:46 PM
And yes, it’s the D
Hi Mike.
Here’s what I measured:
TP1: 0.122V
TP15: 2.10V
Brown wire: 6.25V
Output xlr: 6.22V
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on November 24, 2017, 01:06:49 PM
Start by testing without.

test results with Q1 pulled.
input XLR    0.777V
TP1     2.5mV
TP15     139mV
tp17    20mV
brown    nothing?
out     310mV


Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 27, 2017, 11:47:50 AM
Hey Guys,

Sorry was out of the country for a week.

We have a new help doc.  Start with this and post back:

http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: beaustep on November 27, 2017, 04:09:40 PM
Thank you Mike for the troubleshooting guide! Fantastic. I just read through it to see if my answer was there.

Quick question for you.

I am at the stage where I am adding all of the resistors and at R012, it calls for a 2.2k ohm that is brown brown black red red. I cannot find that color combo anywhere in my kit.

Since I've purchased 2 kits, I looked in the other and do not see it there either.

Is there another color combo that will work? I can't remember which one it was, but I used my meter to test them all and found a few that measure at about 2.35k ohms. The color combo is something like brown brown black yellow red.

Thanks Mike!!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 27, 2017, 11:48:57 PM
Thank you Mike for the troubleshooting guide! Fantastic. I just read through it to see if my answer was there.

Quick question for you.

I am at the stage where I am adding all of the resistors and at R012, it calls for a 2.2k ohm that is brown brown black red red. I cannot find that color combo anywhere in my kit.

Since I've purchased 2 kits, I looked in the other and do not see it there either.

Is there another color combo that will work? I can't remember which one it was, but I used my meter to test them all and found a few that measure at about 2.35k ohms. The color combo is something like brown brown black yellow red.

Thanks Mike!!

RED-YELLOW-BLACK-BROWN-BROWN is 2.4K.

Is there a 2.4K on that board?

Mike

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on November 29, 2017, 03:37:43 PM
hey mike!

I had pulled q1 based on bad early tests. and now i have tests with Q1 pulled. but don't know what to make of that in terms of  the new guide.

thanks

input XLR    0.777V
TP1     2.5mV
TP15     139mV
tp17    20mV
brown    nothing?
out     310mV
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 30, 2017, 12:16:16 PM
hey mike!

I had pulled q1 based on bad early tests. and now i have tests with Q1 pulled. but don't know what to make of that in terms of  the new guide.

thanks

input XLR    0.777V
TP1     2.5mV
TP15     139mV
tp17    20mV
brown    nothing?
out     310mV

Hmmmm something is wrong early on.  Is your input transformer and t-pad soldered properly?
All your L brackets in plate?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on November 30, 2017, 04:47:49 PM
Hmmmm something is wrong early on.  Is your input transformer and t-pad soldered properly?
All your L brackets in plate?

Mike

L brackets are all good.. continuity to chassis. transformer is not installed backwards. T-pad looks superb on all 9 pads
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on November 30, 2017, 04:49:43 PM
L brackets are all good.. continuity to chassis. transformer is not installed backwards. T-pad looks superb on all 9 pads

Under the original test conditions above. What is your AC V between the two outer pins on the primary side and two outer pins on the secondary side of the transformer?

Mike
Title: bad input?
Post by: nickcion on November 30, 2017, 05:36:54 PM
i feel like my meter doesn't do so hot on the 1 kHz signal if i move my common off chassis?

I have the input 1 khz signal across my primary when i scope the primary and nothing on the secondary.

but the crappy meter is struggling to do much in that same measurement.
Noticing i have some low resistance between TP1 and chassis.

(also noting i have my signal on the output xlr when i scope)

Should i be trying to pull T1 and ohm it out?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Silmica on December 02, 2017, 01:33:51 AM
Built a Rev D with 1.14 board. But something is not right.

I checked the power supply before continuing on and got the proper voltages on CR8(30vdc) & CR9(-10VDC).

Now that I have continued building the unit and went to calibrate it and I am not getting any voltage out of the output with the .775VAC 1K sine wave on the input. I then checked my CR8 & CR9 again and I get 30.95Vdc on CR8 but 0Vdc on CR9. I poked around with other measurements on various areas of the board and compared to the schematic and got similar results but I am a bit stumped on this one and could used some help. I re-flowed many of the pads on the board just to see if that would do it but nothing. :(

At TP18 I get 0Vdc no mater where I put R59 at. What would make the voltage go to 0Vdc?

When building it, I double checked every resistor with a multi-meter just to be sure I was putting in the proper resistor in place.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Silmica on December 02, 2017, 12:01:05 PM
Built a Rev D with 1.14 board. But something is not right.

I checked the power supply before continuing on and got the proper voltages on CR8(30vdc) & CR9(-10VDC).

Now that I have continued building the unit and went to calibrate it and I am not getting any voltage out of the output with the .775VAC 1K sine wave on the input. I then checked my CR8 & CR9 again and I get 30.95Vdc on CR8 but 0Vdc on CR9. I poked around with other measurements on various areas of the board and compared to the schematic and got similar results but I am a bit stumped on this one and could used some help. I re-flowed many of the pads on the board just to see if that would do it but nothing. :(

At TP18 I get 0Vdc no mater where I put R59 at. What would make the voltage go to 0Vdc?

When building it, I double checked every resistor with a multi-meter just to be sure I was putting in the proper resistor in place.

Well I pulled out the zener diode and measured the resistance both ways and get .2 ohms on either side of it. That does not seem right. I have no clue on what happened here. I will see if I can get another one to try.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Silmica on December 02, 2017, 01:35:50 PM
Well I pulled out the zener diode and measured the resistance both ways and get .2 ohms on either side of it. That does not seem right. I have no clue on what happened here. I will see if I can get another one to try.

Okay, got a new zener diode from a local electronic store and just tacked it into place (having trouble getting the leads through the holes right now as they are a little thicker than the one that came with the unit).

Now I get -9.88Vdc on the -10 side of the zener diode - Great! :)

Now trying calibration but now I still get 0vac at the output. I can measure between 0vdc and -2.982vdc at TP18 when I sweep the R59 pot. So that is good it seems.

Now what is next that could be the problem?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Silmica on December 02, 2017, 06:48:42 PM
Okay, got a new zener diode from a local electronic store and just tacked it into place (having trouble getting the leads through the holes right now as they are a little thicker than the one that came with the unit).

Now I get -9.88Vdc on the -10 side of the zener diode - Great! :)

Now trying calibration but now I still get 0vac at the output. I can measure between 0vdc and -2.982vdc at TP18 when I sweep the R59 pot. So that is good it seems.

Now what is next that could be the problem?

Well working through this some more (by myself apparently LOL) i found that the signal was only getting to TP1. I found out that if I play with C1 by wiggling it I could get the signal to TP15 and 17 and the output which is good. So I tried various times re-soldering C1 but still have that problem. I'm wondering if my 1uF cap has a intermittent problem within itself. i got the Orange drop upgraded caps. i may just put the 1uF electrolytic in to see if I have any problems with that. i may need to have a new 1uF cap sent to me but I will see.

Now either way when I can the cap to work i can actually calibrate it now which is good but still the C1 is an issue that needs to be resolved.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: lunchbox06452 on December 03, 2017, 05:22:50 PM
Hi Hairball team,

Currently am on my second FET/RACK Rev A. everything has gone great with the build and calibration went about the same as my first unit. I am noticing that my second rack is showing that it is much more aggressive with the same compression settings. often reading 5db more reduction then my first unit. So much so when I was using it on a session the input was nearly off in order to not have it drop the needle.

Do we have a recommendation on where I should start. I have got through calibration from top down and even opened up my first unit as reference to make sure I didn't get anything wrong. 

I also thought it could have been a mixed resistor value in the signal preamp or the signal line amp but everything is checking out to spec and each other.
Thank you.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 04, 2017, 01:20:31 PM
Hi Hairball team,

Currently am on my second FET/RACK Rev A. everything has gone great with the build and calibration went about the same as my first unit. I am noticing that my second rack is showing that it is much more aggressive with the same compression settings. often reading 5db more reduction then my first unit. So much so when I was using it on a session the input was nearly off in order to not have it drop the needle.

Do we have a recommendation on where I should start. I have got through calibration from top down and even opened up my first unit as reference to make sure I didn't get anything wrong. 

I also thought it could have been a mixed resistor value in the signal preamp or the signal line amp but everything is checking out to spec and each other.
Thank you.

Could be the t-pad itself, they have tolerances. Also make sure it's mounted so the line is in the same spot FCW. Are both T-pads grey?

Start by going through here:
http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

Particularly the Pad 22/21/CR stuff.

Mike
Title: Re: bad input?
Post by: Hairball Audio on December 04, 2017, 01:29:17 PM
i feel like my meter doesn't do so hot on the 1 kHz signal if i move my common off chassis?

I have the input 1 khz signal across my primary when i scope the primary and nothing on the secondary.

but the crappy meter is struggling to do much in that same measurement.
Noticing i have some low resistance between TP1 and chassis.

(also noting i have my signal on the output xlr when i scope)

Should i be trying to pull T1 and ohm it out?

TP1 low resistance is normal.  What is it?  Something like 16Ω (I can't remember exactly).

Which pins on T1 are shorted to the can of T1 (using your Ω meter)?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 04, 2017, 01:31:19 PM
Well working through this some more (by myself apparently LOL) i found that the signal was only getting to TP1. I found out that if I play with C1 by wiggling it I could get the signal to TP15 and 17 and the output which is good. So I tried various times re-soldering C1 but still have that problem. I'm wondering if my 1uF cap has a intermittent problem within itself. i got the Orange drop upgraded caps. i may just put the 1uF electrolytic in to see if I have any problems with that. i may need to have a new 1uF cap sent to me but I will see.

Now either way when I can the cap to work i can actually calibrate it now which is good but still the C1 is an issue that needs to be resolved.

Hi,

Sorry, big weekend, family was in town.

Did you ever get a new cap? We can send you new one.  Maybe a loose lead.

Mike
Title: Re: bad input?
Post by: nickcion on December 04, 2017, 05:32:03 PM
TP1 low resistance is normal.  What is it?  Something like 16Ω (I can't remember exactly).

Which pins on T1 are shorted to the can of T1 (using your Ω meter)?

Mike

13 ohms from t1 to chassis.

both sides of the secondary are shorted to can.. (and the pin for the can, on that same side) 5,6,8
Title: Re: bad input?
Post by: Hairball Audio on December 04, 2017, 05:41:37 PM
13 ohms from t1 to chassis.

both sides of the secondary are shorted to can.. (and the pin for the can, on that same side) 5,6,8

That's not good.  Might be happening down the line.  Can you pull the transformer and test it off the PCB?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 04, 2017, 05:42:42 PM
6 in the can.  8 get's shorted in the circuit.

5 should not be shorted.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on December 04, 2017, 06:10:55 PM
t1 pulled

55ohm primary
14.6 ohm secondary

secondary is isolated from the can
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 04, 2017, 06:13:22 PM
t1 pulled

55ohm primary
14.6 ohm secondary

secondary is isolated from the can

Seems right.  I'll double check tomorrow.  However, in the PCB BOTH secondary pins were shorted to the can?

What rev do you have? Is Q 1 installed?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on December 04, 2017, 07:07:10 PM
i believe the newest revision..  just got back to school.

I did install a new Q1 over the weekend.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 04, 2017, 07:11:08 PM
i believe the newest revision..  just got back to school.

I did install a new Q1 over the weekend.

I mean Rev A or Rev D?

Those ohm readings are good.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on December 04, 2017, 09:11:12 PM
Rev A
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 05, 2017, 11:46:51 AM
Rev A

Is the input transformer still removed from the PCB? If so, what is the DC R (Ω) between TP1 and chassis ground?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nickcion on December 05, 2017, 05:25:01 PM
Is the input transformer still removed from the PCB? If so, what is the DC R (Ω) between TP1 and chassis ground?

Mike

T1 is out. Q1 is in..

chassis to TP1 is 267 ohms.. (but I'm unsure of DCR as a term)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 05, 2017, 05:38:52 PM
T1 is out. Q1 is in..

chassis to TP1 is 267 ohms.. (but I'm unsure of DCR as a term)

That seems good.

Maybe try putting T1 back in.

Make sure your QBias is set as described in the troubleshooting guide and try again. If your Qbias is messed up you'll never get output.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Silmica on December 05, 2017, 10:01:20 PM
Hi,

Sorry, big weekend, family was in town.

Did you ever get a new cap? We can send you new one.  Maybe a loose lead.

Mike

I found out it was not the cap. I think because these leads on the orange drop caps are fairy thick that pushing it through the holes maybe damaging the trace around the holes possibly? I put the cap in holes that were more inward (was fun doing that with short leads) and managed to get it to work well. I am able to calibrate it and it works great now.

It's funny that I was putting up messages hoping someone could chime in with some help but after working through it all and looking at the schematic and thinking about it logically I was able to get it to work. Strange though that the CR9 zener diode went bad on me. I tested the power supply before continue stuffing the board. I got one from a local electronics store but the leads on it are very thick and I kind of just have it tacked in there and it is working. Not sure if you have ever had that problem before. When I took the zener out and tested it with a meter I got .2ohm either way that I put the leads on it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 07, 2017, 05:55:41 PM
I found out it was not the cap. I think because these leads on the orange drop caps are fairy thick that pushing it through the holes maybe damaging the trace around the holes possibly? I put the cap in holes that were more inward (was fun doing that with short leads) and managed to get it to work well. I am able to calibrate it and it works great now.

It's funny that I was putting up messages hoping someone could chime in with some help but after working through it all and looking at the schematic and thinking about it logically I was able to get it to work. Strange though that the CR9 zener diode went bad on me. I tested the power supply before continue stuffing the board. I got one from a local electronics store but the leads on it are very thick and I kind of just have it tacked in there and it is working. Not sure if you have ever had that problem before. When I took the zener out and tested it with a meter I got .2ohm either way that I put the leads on it.

Glad you got it sorted!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ElSmurf on December 10, 2017, 01:29:27 PM
Started building my REV D partial kit yesterday and was a bit puzzled by the Zener heat sink. I got the Aavid heatsink from the Mouser BOM which doesn't seem to fit the diode. Did I miss something?

Also, my input transformer got a bit roughed up during shipping and all the pins seem to be bent. Is there any way to test it before soldering it in?

Cheers!

*edit* I just figured out that the Aavid heat sink is supposed to go on the 2N3053, is this correct? And was the Zener heat sink supposed to be in my kit?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 10, 2017, 06:51:02 PM
Started building my REV D partial kit yesterday and was a bit puzzled by the Zener heat sink. I got the Aavid heatsink from the Mouser BOM which doesn't seem to fit the diode. Did I miss something?

Also, my input transformer got a bit roughed up during shipping and all the pins seem to be bent. Is there any way to test it before soldering it in?

Cheers!

*edit* I just figured out that the Aavid heat sink is supposed to go on the 2N3053, is this correct? And was the Zener heat sink supposed to be in my kit?

Did you get a complete kit? You should have 2 heatsinks. One for the 2N3053 and one for the diode.  We have a missing parts form if you're missing it.  You can test your supply without it, it's not crucial.

Sorry about the input.  Bend the leads straight and make sure the are not touching the holes in the can. If they are secure you're fine.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: ElSmurf on December 11, 2017, 01:54:48 PM
Did you get a complete kit? You should have 2 heatsinks. One for the 2N3053 and one for the diode.  We have a missing parts form if you're missing it.  You can test your supply without it, it's not crucial.

Sorry about the input.  Bend the leads straight and make sure the are not touching the holes in the can. If they are secure you're fine.

Mike

Mike, thanks for getting back to me. I just filled out the form. I bent the leads on the transformer back into place and everything looks fine now.

While going through my kit  to make sure nothing else was missing, I noticed my VU meter has an LED instead of a lamp, does that make any difference for the resistor on the VU lamp board?

Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on December 12, 2017, 08:02:52 PM
Mike, thanks for getting back to me. I just filled out the form. I bent the leads on the transformer back into place and everything looks fine now.

While going through my kit  to make sure nothing else was missing, I noticed my VU meter has an LED instead of a lamp, does that make any difference for the resistor on the VU lamp board?

Thanks!

Oh that is really weird.

The resistor would need to be different.

We can send you a lamp insert for the mere....just shoot me an email to the [email protected]  email.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Madgan on December 30, 2017, 02:23:45 PM
Hello all - I apologize in advance for being the newbie with the newbie question...

Recently finished a Rev. D build v1.12. Everything seemingly went smooth throughout the entire build without a hiccup.

My problem surfaced when I was unable to successfully set the Q-Bias. With the input signal level set properly I was only able to generate approx. 1V AC at the output with the output pot fully CW.  I checked the power supply  and I'm seeing +30V DC at CR8 but I am not getting -10 V DC at CR9. The voltage is hovering somewhere around -5mV DC. The power supply passed the initial test before populating the boards however... Here's what I have done since:

Reflowed all capacitor, resistor and diode connections in power section.
Rechecked the values and placements of all resistors on all boards with my DMM and a color coding chart.
Checked for continuity and then the DC voltage readings on all transistors.
I found no issues or readings out of whack...

The capacitor voltages:
40V DC on the + of C23 and -.5mV on the -
30V DC on the + of C24 and -.5mV on the -
-.5mV DC on the + of C25 and -16.4V DC on the -
-.5mV DC on the + of C26 and -5.2mV on the -


With my limited understanding and troubleshooting knowledge I am at a wall. It appears nothing else will work properly without the power supply operating correctly.

Thanks you for any help that can be thrown my way


Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Madgan on January 01, 2018, 11:19:41 AM
Hello all - I apologize in advance for being the newbie with the newbie question...

Recently finished a Rev. D build v1.12. Everything seemingly went smooth throughout the entire build without a hiccup.

My problem surfaced when I was unable to successfully set the Q-Bias. With the input signal level set properly I was only able to generate approx. 1V AC at the output with the output pot fully CW.  I checked the power supply  and I'm seeing +30V DC at CR8 but I am not getting -10 V DC at CR9. The voltage is hovering somewhere around -5mV DC. The power supply passed the initial test before populating the boards however... Here's what I have done since:

Reflowed all capacitor, resistor and diode connections in power section.
Rechecked the values and placements of all resistors on all boards with my DMM and a color coding chart.
Checked for continuity and then the DC voltage readings on all transistors.
I found no issues or readings out of whack...

The capacitor voltages:
40V DC on the + of C23 and -.5mV on the -
30V DC on the + of C24 and -.5mV on the -
-.5mV DC on the + of C25 and -16.4V DC on the -
-.5mV DC on the + of C26 and -5.2mV on the -


With my limited understanding and troubleshooting knowledge I am at a wall. It appears nothing else will work properly without the power supply operating correctly.

Thanks you for any help that can be thrown my way

Spent a few more hours inspecting, reflowing, etc... I have -15V DC going into the R82 resistor but only -5mV DC comes out. That seems to be the start (or a byproduct?) of where things go bad. The resistor tests fine (1k) out of the circuit.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: scott2000 on January 01, 2018, 07:05:44 PM
I checked the power supply  and I'm seeing +30V DC at CR8 but I am not getting -10 V DC at CR9. The voltage is hovering somewhere around -5mV DC.

Post #149 Mentions a similar issue

https://groupdiy.com/index.php?topic=63600.140
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 02, 2018, 12:38:31 PM
Spent a few more hours inspecting, reflowing, etc... I have -15V DC going into the R82 resistor but only -5mV DC comes out. That seems to be the start (or a byproduct?) of where things go bad. The resistor tests fine (1k) out of the circuit.

Could be anything on the negative rail dragging the voltage down.

1) Check that R82, C26, CR9 all have good continuity between pads that should be connected (do this with power off using your Ω meter).
2) Test CR9 with the diode function of your DMM, you can google how to do that. You may have to remove it.

Report back.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: shane on January 03, 2018, 05:05:55 AM
Ok, so this is a terribly n00by question, I know, but I'm a terrible n00b. I accidentally put the connector on the Rev A Attack/Release Board on upside down (duh) and didn't realise until I started assembling the unit. It unfortunately got trashed while I was removing it. Anybody know where I could get a replacement? The only place I can find that has them is Digikey, and they want to charge $24 shipping (I'm in Australia). Are there any other options or do I have to swallow the $24 for a $0.60 component..

Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 04, 2018, 10:12:12 PM
Ok, so this is a terribly n00by question, I know, but I'm a terrible n00b. I accidentally put the connector on the Rev A Attack/Release Board on upside down (duh) and didn't realise until I started assembling the unit. It unfortunately got trashed while I was removing it. Anybody know where I could get a replacement? The only place I can find that has them is Digikey, and they want to charge $24 shipping (I'm in Australia). Are there any other options or do I have to swallow the $24 for a $0.60 component..

You could email us and we could drop one out to you letter mail.  Would take a couple weeks but only be a couple dollars.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 05, 2018, 04:00:37 AM
First post here. Since I'm a newbie I'm building the Lola first, but I ordered the Rev A (with the Active Link) at the same time. The plan is to move onto the Rev. A after the Lola so I'm asking way ahead, and reading every manual about 16 times. So far no issues but a paranoid Rev A/Active Link question....(I searched the archives to make sure I couldn't find an answer without repeating a question if it has already been asked/answered elsewhere)

In the Active Link manual it says "For version 1.12 PCBs. C200 and C201 should be inserted backward...."

My Active Link PCB says version 1.2

I wanted to confirm this was not a typo in the manual and that I should insert C200 & 201 as normal.

Also, where can I purchase sockets for the Q1 and Q11 FETs? I looked on the Parts Store and then scoured the web but had trouble locating them.

Thanks,

Sean
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Madgan on January 06, 2018, 12:03:33 PM
Could be anything on the negative rail dragging the voltage down.

1) Check that R82, C26, CR9 all have good continuity between pads that should be connected (do this with power off using your Ω meter).
2) Test CR9 with the diode function of your DMM, you can google how to do that. You may have to remove it.

Report back.

Mike

Thank you for your input!

R82 checks out ok as does C26. However, I removed and tested the diode at CR9 and it appears that may be the issue. I've got no flow in either direction when testing (.001v or so both ways - no change when switching testing leads). Fingers crossed that's the sole problem.

I had planned on grabbing a FET/Rack Rev. A from you shortly. Is it possible to add an extra diode to the order?










 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 07, 2018, 07:43:53 PM
Thank you for your input!

R82 checks out ok as does C26. However, I removed and tested the diode at CR9 and it appears that may be the issue. I've got no flow in either direction when testing (.001v or so both ways - no change when switching testing leads). Fingers crossed that's the sole problem.

I had planned on grabbing a FET/Rack Rev. A from you shortly. Is it possible to add an extra diode to the order?

Definitely, just shoot us an email.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: shane on January 09, 2018, 07:13:25 AM
You could email us and we could drop one out to you letter mail.  Would take a couple weeks but only be a couple dollars.

Many thanks for that offer but impatience got the better of me so i just paid the extra (grabbed a few other things to make it worth my while)..  my next question is, where should the line on the input/output knobs be pointing at full CCW? I assume they should start at infinity and rotate to 3 at full CW?

Everything powers up A-OK so far, this has been a fun and super easy build, kudos to Hairball Audio! The Build Guide is great! Can’t wait to build some more of your kits a bit later in the year!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 09, 2018, 01:55:02 PM
Many thanks for that offer but impatience got the better of me so i just paid the extra (grabbed a few other things to make it worth my while)..  my next question is, where should the line on the input/output knobs be pointing at full CCW? I assume they should start at infinity and rotate to 3 at full CW?

Everything powers up A-OK so far, this has been a fun and super easy build, kudos to Hairball Audio! The Build Guide is great! Can’t wait to build some more of your kits a bit later in the year!

It's up to you.  We line them up to 0 FCW. 

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 11, 2018, 01:48:37 PM
First post here. Since I'm a newbie I'm building the Lola first, but I ordered the Rev A (with the Active Link) at the same time. The plan is to move onto the Rev. A after the Lola so I'm asking way ahead, and reading every manual about 16 times. So far no issues but a paranoid Rev A/Active Link question....(I searched the archives to make sure I couldn't find an answer without repeating a question if it has already been asked/answered elsewhere)

In the Active Link manual it says "For version 1.12 PCBs. C200 and C201 should be inserted backward...."

My Active Link PCB says version 1.2

I wanted to confirm this was not a typo in the manual and that I should insert C200 & 201 as normal.

Also, where can I purchase sockets for the Q1 and Q11 FETs? I looked on the Parts Store and then scoured the web but had trouble locating them.

Thanks,

Sean

Oh weird, i thought they were 1.12. Anyway, for all version they should be installed backwards.

Sockets are something like mouser Part# 855-D01-9973242.   You break away as many as you need.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 11, 2018, 02:45:20 PM
Oh weird, i thought they were 1.12. Anyway, for all version they should be installed backwards.

Sockets are something like mouser Part# 855-D01-9973242.   You break away as many as you need.

Mike

Thank you Mike. Just ordered the sockets now. Good to know about the Active Link board. Wanted to make sure because something tells me that you'll be seeing another 1176 order from me on down the line :-) 

(would seem useful for running drums through, stereo miked acoustic guitars, etc.) -- just starting with this first to get my feet wet with the build process.

Thanks again for the kits and your time.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: frenkonio on January 14, 2018, 11:27:05 AM
Hi, before going on with the building.. I am getting 32.6v at CR8 and - 9.72v DC at CR9. Is the first value good? Because it is more than a +/-5% of tolerance. Let me know 😉
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 15, 2018, 12:03:29 PM
Hi, before going on with the building.. I am getting 32.6v at CR8 and - 9.72v DC at CR9. Is the first value good? Because it is more than a +/-5% of tolerance. Let me know 😉

Seems a little off, but it probably has more to do with something locally in your set up.  It's within 10% which is good.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: frenkonio on January 15, 2018, 12:13:59 PM
Seems a little off, but it probably has more to do with something locally in your set up.  It's within 10% which is good.

Mike
Yeah. I proceeded with the building and was able to have perfect calibrations on every aspect. A nice Bluestripe done! Thanks!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Madgan on January 15, 2018, 01:13:59 PM
Thank you for your input!

R82 checks out ok as does C26. However, I removed and tested the diode at CR9 and it appears that may be the issue. I've got no flow in either direction when testing (.001v or so both ways - no change when switching testing leads). Fingers crossed that's the sole problem.

I had planned on grabbing a FET/Rack Rev. A from you shortly. Is it possible to add an extra diode to the order?

Just wanted to thank you Mike! I replaced the bad diode at CR9, voltage readings are now good and the unit calibrated like a champ. Up and running 100%!
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 17, 2018, 07:26:39 PM
Hi Mike,

Mid-build don't want to screw it up question. I built the power supply the other night and it tested fine. When returning to the build, I needed to touch up a joint on CR9 and the diode may have been damaged (I used a Fluke 179). I ordered a replacement but am on a sort timeline and continuing the build.

Can I re-test the power supply at any time after adding a new CR9 in a couple of days or do I need to complete the entire build first?

Thanks,

Sean 
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 17, 2018, 07:28:24 PM
Hi Mike,

Mid-build don't want to screw it up question. I built the power supply the other night and it tested fine. When returning to the build, I needed to touch up a joint on CR9 and the diode may have been damaged (I used a Fluke 179). I ordered a replacement but am on a sort timeline and continuing the build.

Can I re-test the power supply at any time after adding a new CR9 in a couple of days or do I need to complete the entire build first?

Thanks,

Sean

You should be fine to test it.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 17, 2018, 08:20:43 PM
Thanks Mike. Had to remove the diode. Thanks to Curtis for sending a new one. The top of one pad looks muddied up, but not necessarily lifted. Connections look good to the surrounding board? I think it should be fine when we re-solder a new diode. How does it look to you? (photo should be attached). The bottom looks fine. Is this a ground lug and are the top and bottom connected to ground so it would be ok even if this was damaged? Thanks very much.

Sean

(http://i167.photobucket.com/albums/u137/1992guitars/CR9%20Upper%20Pad.jpg)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 17, 2018, 09:49:45 PM
Thanks Mike. Had to remove the diode. Thanks to Curtis for sending a new one. The top of one pad looks muddied up, but not necessarily lifted. Connections look good to the surrounding board? I think it should be fine when we re-solder a new diode. How does it look to you? (photo should be attached). The bottom looks fine. Is this a ground lug and are the top and bottom connected to ground so it would be ok even if this was damaged? Thanks very much.

Sean

(http://i167.photobucket.com/albums/u137/1992guitars/CR9%20Upper%20Pad.jpg)

It only connects to the ground plane on the top side.  Looks like it should be ok.  After you install it, check the continuity of that lead to another ground pad. They all have the cross hairs look.  If it's damaged you'll have to wire the lead to the next closest ground pad with a wire jumper.

Mike

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 17, 2018, 10:13:30 PM
Many thanks Mike. It tests to other cross-hairs on the top side and I will check it when I put in the new diode. I'm a bit confused, because there are cross-hairs on the bottom of that hole also, so aren't the ground planes connected on both since there are cross-hairs on both sides of that hole? Much appreciation for a great product.
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 17, 2018, 10:49:15 PM
Many thanks Mike. It tests to other cross-hairs on the top side and I will check it when I put in the new diode. I'm a bit confused, because there are cross-hairs on the bottom of that hole also, so aren't the ground planes connected on both since there are cross-hairs on both sides of that hole? Much appreciation for a great product.

True, looks like the board has a dual plane (I didn't lay it out).
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 21, 2018, 02:52:00 AM
I owe you guys a handwritten thank-you note. The replacement CR9 diode showed up in the mail yesterday and the reinstall went well. Onto the Q1 & Q11 FET's with the sockets I ordered from your Mouser link, I got a little confused...In the Build Guide it says, "Note that the sockets are soldered to the PCB, the transistors are pushed into the sockets and soldered."

I wasn't sure how that would make removal/troubleshooting any easier with the transistors soldered into sockets instead of onto the PCB, but did solder them into the sockets before realizing that maybe I was misunderstanding the build guide to say they should be pushed into the sockets and then the sockets are soldered? I noticed in the pictures that there was no solder on the transistor/socket joints in the Build Guide pictures....after the whole thing was soldered!  If by some chance I did not misunderstand and did this exactly as intended by the manual, what would the advantage be of soldering to the sockets?

Thanks again Mike,

Sean

(p.s. in any event, I learned from the CR9 fiasco to not mess with anything unless it's broken but clarification would be helpful for the next order (as soon as I finish this one and get a few more funds together you'll get another Rev. A order from me; the idea is a pair for stereo linking. It'll happen....I want you to take my money again soon (as soon as I get one working first). Thanks again for being top class).

(http://i167.photobucket.com/albums/u137/1992guitars/IMG_3922.jpg)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 22, 2018, 10:56:39 AM
You shouldn't solder into the sockets.  However I would just leave it unless you have an issue.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nolanthies on January 22, 2018, 03:36:52 PM
(Hopefully posting this in the correct spot) I got to the final stage of calibrating my Rev A and everything is good besides it not compressing. I went thru the troubleshooting guide and narrowed it down to my GR Control Amp In and Out due to reading basically no voltage when testing against TP22 and CR2 (the GR Control Amp Threshold voltages looked good tho). I think all my solder joints look good and all the correct parts are in place, but I did put some transistors in the wrong place earlier in my build (prior to testing) and had to de-solder them to switch them. I feel like maybe I burned up one or more of the transistors. Does this seem logical based on what I've said (passes signal fine and all the other calibration was good)? I'd imagine it's best to re-install the Q7-Q10 transistors to start with? Since I can't remember which ones I switched them with, am I safer buying a complete set of all the transistors that look like those (Q12/13 are correct for sure)?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 23, 2018, 12:10:16 AM
(Hopefully posting this in the correct spot) I got to the final stage of calibrating my Rev A and everything is good besides it not compressing. I went thru the troubleshooting guide and narrowed it down to my GR Control Amp In and Out due to reading basically no voltage when testing against TP22 and CR2 (the GR Control Amp Threshold voltages looked good tho). I think all my solder joints look good and all the correct parts are in place, but I did put some transistors in the wrong place earlier in my build (prior to testing) and had to de-solder them to switch them. I feel like maybe I burned up one or more of the transistors. Does this seem logical based on what I've said (passes signal fine and all the other calibration was good)? I'd imagine it's best to re-install the Q7-Q10 transistors to start with? Since I can't remember which ones I switched them with, am I safer buying a complete set of all the transistors that look like those (Q12/13 are correct for sure)?

You should be getting AC voltage to pad 22 with signal as described in the troubleshoot guide.  if you can't get AC V to there with GR ON, you have something wrong on your ratio PCB.

If you are, but seeing nothing on the output of the control amp it's possible you burned out a transistor desoldering it.  You can look at the schematic linked in the guide to test the voltages of the transistor legs to see which one is funky.

Q12/13 have to do with your meter.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 23, 2018, 04:10:47 AM
You shouldn't solder into the sockets.  However I would just leave it unless you have an issue.

Mike

Thanks Mike. I gathered that after they were soldered!  I ordered a replacement matched pair from your site tonight just to be thorough, since I  figured it wouldn't hurt to have an extra set in any event
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nolanthies on January 25, 2018, 07:02:12 PM
You should be getting AC voltage to pad 22 with signal as described in the troubleshoot guide.  if you can't get AC V to there with GR ON, you have something wrong on your ratio PCB.

If you are, but seeing nothing on the output of the control amp it's possible you burned out a transistor desoldering it.  You can look at the schematic linked in the guide to test the voltages of the transistor legs to see which one is funky.

Q12/13 have to do with your meter.

Mike


Seems to be something wrong with my ratio PCB then I think.   What's my best course of action to test here?
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 25, 2018, 08:22:34 PM

Seems to be something wrong with my ratio PCB then I think.   What's my best course of action to test here?

With GR ON and a 0dB signal on the input, you should have AC signal at PAD 15. Do you?

If so with GR ON do you have ACV @ either side of R78?

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nolanthies on January 26, 2018, 06:24:03 PM
With GR ON and a 0dB signal on the input, you should have AC signal at PAD 15. Do you?

If so with GR ON do you have ACV @ either side of R78?


Yes, 4.009 ACV @ Pad 15.
No ACV on R78



Mike
You should be getting AC voltage to pad 22 with signal as described in the troubleshoot guide.  if you can't get AC V to there with GR ON, you have something wrong on your ratio PCB.

If you are, but seeing nothing on the output of the control amp it's possible you burned out a transistor desoldering it.  You can look at the schematic linked in the guide to test the voltages of the transistor legs to see which one is funky.

Q12/13 have to do with your meter.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 27, 2018, 03:57:53 AM
The Rev A. is up and running, no smoke or fire but all is not well. I went through the calibration twice and can hear the compressor working but there are issues.

1. After calibration, when the Release knob is rotated back CCW, the meter drops. A lot. Like the meter goes back to -3  to -4 dB as my Release becomes more and more CCW. This is without any signal. I wasn't sure if that was an issue (I've never had an original and am always on the other side of the glass in sessions) but it didn't seem right to my limited mind and sent me through the troubleshooting guide to check all test points which is where it's become obvious it's not just my OCD or lack of understanding....(I'm using a Fluke 179 so the readings should be good)

2. With the Input knob all the way down, when I turn the knob up, the signal just comes "on" and then increases in volume naturally throughout the full rotation. But it's not a slow, even fade up from 0. It's off, on, then an increase through the knob rotation. Is this normal?

3. The power supply tests fine. 30 VDC on CR8 and -9.75VDC on CR9. 

4.  All test points are low in the Amplification Stages, but TP1 is only .1072 VAC (maybe that's still too far off but then it got worse). TP15 is an entire volt low and coming in at 2.86 VAC. TP17 comes in between .381 & .383.  The output transformer BRN and output XLR are way off though. Output BRN is 5.944 - 6.007. The XLR is only reading 5.858 VAC (which would've been pretty close if I'd tried a Rev. D!)

5. I put together Mark Burnley's signal tracer linked to from the mnat's website. But since I have a clear input and output signal is there any use in using it?

6. I didn't want to barrage you with listing every voltage in this note so I recorded them all in spreadsheet form for easy quick comparison if that helps at all https://drive.google.com/file/d/1LgX5w_UCuGMmMJVLTsXB6lBaI7ciC6-L/view?usp=sharing

I was dreading the troubleshooting because I was aware these are complex, everything took longer than intended, and my timeline to finish it up here is running out. I'm going home to Nashville on Monday but it probably makes a lot more sense to send it to you (and pay you of course) from Olympia than shipping it from TN...for shipping rates alone but to some extent I wanted to learn even more than to have a working compressor so that's what creates the conundrum.  Given endless time I'm sure I could see this through. With two days left...maybe not. I'm at a loss and a bit discouraged now so I guess I'll try some more tomorrow and see how in over my head I really am (lots, I suspect)...I guess I'll start with checking all solder joints again after I sleep the depression off. I spent hours with the eevblog videos and then practiced tons before the Lola build which went perfectly. Every component the Fluke could measure was measured, labeled in a bag, and then measured like 2,000 times again moments before installation, so it's something in my build (I read every word on your site & mnat's and really thought I could do this!!!)
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: nolanthies on January 27, 2018, 11:52:26 AM
With GR ON and a 0dB signal on the input, you should have AC signal at PAD 15. Do you?

If so with GR ON do you have ACV @ either side of R78?

Mike




Yes, 4.009 ACV @ Pad 15.
No ACV on R78

-Nolan
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 27, 2018, 01:24:39 PM
With GR ON and a 0dB signal on the input, you should have AC signal at PAD 15. Do you?

If so with GR ON do you have ACV @ either side of R78?

Mike


Yes, 4.009 ACV @ Pad 15.
No ACV on R78

-Nolan

Check your relay and ratio PCB connectors.  Make sure all the solder joints look good and reflow/test again.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: Hairball Audio on January 27, 2018, 01:39:02 PM
The Rev A. is up and running, no smoke or fire but all is not well. I went through the calibration twice and can hear the compressor working but there are issues.


1. After calibration, when the Release knob is rotated back CCW, the meter drops. A lot. Like the meter goes back to -3  to -4 dB as my Release becomes more and more CCW. This is without any signal. I wasn't sure if that was an issue (I've never had an original and am always on the other side of the glass in sessions) but it didn't seem right to my limited mind and sent me through the troubleshooting guide to check all test points which is where it's become obvious it's not just my OCD or lack of understanding....(I'm using a Fluke 179 so the readings should be good)

The release/attack setting should not hugely change your meter with no signal just sitting there.  Maybe fractions of a dB but not that much.  Not sure what that could be,  Maybe a bad pot or leaky FH333 diode. I know I've seen that issue before and fixed it, I just don't remember what it was. I'll have to think about that one.

Quote
2. With the Input knob all the way down, when I turn the knob up, the signal just comes "on" and then increases in volume naturally throughout the full rotation. But it's not a slow, even fade up from 0. It's off, on, then an increase through the knob rotation. Is this normal?

That's normal for those pots.  There is no perfect TPad out there. The UA ones are smoother from zero, but are prone to crackle in the first year. It's all a compromise. It should be noted that the input is not a volume pot, it's a variable 30dBish. So as you turn it down, just before it cuts out, is actually the end of the tpad.

Quote
3. The power supply tests fine. 30 VDC on CR8 and -9.75VDC on CR9. 

4.  All test points are low in the Amplification Stages, but TP1 is only .1072 VAC (maybe that's still too far off but then it got worse). TP15 is an entire volt low and coming in at 2.86 VAC. TP17 comes in between .381 & .383.  The output transformer BRN and output XLR are way off though. Output BRN is 5.944 - 6.007. The XLR is only reading 5.858 VAC (which would've been pretty close if I'd tried a Rev. D!)

Do you have your knobs on right? Line on the skirt lined up with "0"? 

Quote
5. I put together Mark Burnley's signal tracer linked to from the mnat's website. But since I have a clear input and output signal is there any use in using it?

Probably not.

Quote
6. I didn't want to barrage you with listing every voltage in this note so I recorded them all in spreadsheet form for easy quick comparison if that helps at all https://drive.google.com/file/d/1LgX5w_UCuGMmMJVLTsXB6lBaI7ciC6-L/view?usp=sharing

I was dreading the troubleshooting because I was aware these are complex, everything took longer than intended, and my timeline to finish it up here is running out. I'm going home to Nashville on Monday but it probably makes a lot more sense to send it to you (and pay you of course) from Olympia than shipping it from TN...for shipping rates alone but to some extent I wanted to learn even more than to have a working compressor so that's what creates the conundrum.  Given endless time I'm sure I could see this through. With two days left...maybe not. I'm at a loss and a bit discouraged now so I guess I'll try some more tomorrow and see how in over my head I really am (lots, I suspect)...I guess I'll start with checking all solder joints again after I sleep the depression off. I spent hours with the eevblog videos and then practiced tons before the Lola build which went perfectly. Every component the Fluke could measure was measured, labeled in a bag, and then measured like 2,000 times again moments before installation, so it's something in my build (I read every word on your site & mnat's and really thought I could do this!!!)

There is no shame in sending it in.  I've been repairing these builds for 10 years and they can still take me hours to figure out.  Sometimes it's just a perfect looking solder joint that isn't perfect underneath.

Check your transistor voltages in the signal and line amp sections.  There are links to those in the troubleshooting guide.  If your knobs are on right, it seems like you may have an under performing transistor. Maybe a 470Ω and 4.7K are swapped or something.

Mike
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: TonyW on January 27, 2018, 02:07:24 PM
My kit did not come with 2n3707 transistors that were matched, to use for Q12 and Q13 also.
How did it work out for you?

Thanks Tony
Title: Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
Post by: seanweaverguitar on January 28, 2018, 05:13:29 AM
The release/attack setting should not hugely change your meter with no signal just sitting there.  Maybe fractions of a dB but not that much.  Not sure what that could be,  Maybe a bad pot or leaky FH333 diode. I know I've seen that issue before and fixed it, I just don't remember what it was. I'll have to think about that one.
Thanks.  I spent the day reading every single one of the 973 (now 974) posts on this thread while taking meticulous notes on everything you and mnats said...while continuing to study the schematic which I don't really know how to read but am trying to learn. It gave me some more ideas for troubleshooting strategies but as usual am thinking about everything in the world that could ever go wrong now or in 20 years and way too out of touch with the moment. If I keep chasing this and if there is a faulty pot, I have deduced that the Bourns B25 is exceedingly hard to source. I couldn't find any in the store but would you have another for sale if need be? Otherwise, would something like the 5 Mohm Alpha pot (with that round base behind the shaft) have enough room to clear the Ratio board behind the front panel, like, if I had to wire one up from the pads? I don't want to waste your time with hypothetical questions but since now I'm wondering about the pot it made me wonder. Any perspective would be valued.
Do you have your knobs on right? Line on the skirt lined up with "0"? 
Yes. Exactly like that.
There is no shame in sending it in.  I've been repairing these builds for 10 years and they can still take me hours to figure out
Thanks for the kindness. I beat up on myself often and that makes me feel much better
Check your transistor voltages in the signal and line amp sections.  There are links to those in the troubleshooting guide.  If your knobs are on right, it seems like you may have an under performing transistor. Maybe a 470Ω and 4.7K are swapped or something.
First thing I did notice visually is that R4 looks noticeably damaged. It's been chipped away somehow. Maybe from the Hekko getting too close to it while removing the hard-wired Q1 from the sockets and replacing the matched pair. In any event, it's reading way low. Like 12-ohms. I realize that's in circuit so I can see what it reads after taking one lead out but it seems to be a bit of a no-brainer & the first thing I'll try. I may just replace R5 along with it. I ran the transistor voltage tests & most of them looked  unsuspicious but....

At Q4, I got 1.91 VDC at the gate (you'd listed 2.21 VDC).  Then 4.72 VDC for Source (not 4.32). Then 12.22 VDC for Drain (13.38 was the number in your guide). On Q2 the Gate matched up but I was a little off on Source. I get 4.995 VDC (not 4.79). For the Drain I get 6.68 VDC (instead of 6.94). As I recall Q2 & Q4 are matched, correct? I looked in the store but could not find J309s. If it comes to replacing those let me know if you have a set available. I realize R4 is the obvious place to start and maybe it wouldn't hurt to replace R5 too. I should've left the soldered socket debacle alone like you said and probably screwed it up in the pursuit of perfection.

Right now I've put life on hold so much over the holidays that my visit up here's been extended to Wednesday to tie loose ends together like pack