[BUILD] New FET/RACK Official Help Thread - Please read first post!

Help Support GroupDIY:

Echo North

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JMan check your attack/release PCB super closely.  Make sure the values are good and everything is soldered well and the release legs are ok.

Make sure those 6.8 tantalums are in correctly.

Make sure all your wire headers are in correctly.

Make sure you release and output pots are not swapped.  Release is blue, output is grey.

Mike
 

JMan

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Oh brother, I totally have the output and release pots swapped!

I’ll switch them tomorrow and try again.  Will report back!
 

JMan

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Okay, so I got the pots in the correct places.  I also found that R57 on the attack/release board was the wrong value by several orders of magnitude, so I put in the correct value.  I went through the entire circuit and triple checked my resistor color codes and other component values, and everything else checks out, including ratio and meter boards and now the attack/release board.

This mostly fixed the issue.  However...

In step 3 of calibration (where I was having trouble), turning on the attack pot does drop the voltage from 2.44v now that I've corrected those components, but not all the way back down to 0.775 -- only to 1.025.  If I adjust that down with the output control, then the "attack off" voltage drops accordingly.  In other words, I'm not getting the full 10dBu attenuation. 

Additionally, my voltages at TP22, Q7-10, and CR2 went further out of whack.  Most everything there shot high, particularly at the higher ratios (which it was already doing, but more so now -- for example, I've got 0.450v at Q7 as opposed to the expected 0.377v).  I've also still got a higher-than-expected voltage at Q5.

Having said all that, the unit does pass audio and compresses, and on a fun little test running bass guitar through it and then some drums, it sounds fabulous!  I'm just wondering what I'm still missing to get it all the way to where it's supposed to be.
 

Echo North

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JMan said:
Okay, so I got the pots in the correct places.  I also found that R57 on the attack/release board was the wrong value by several orders of magnitude, so I put in the correct value.  I went through the entire circuit and triple checked my resistor color codes and other component values, and everything else checks out, including ratio and meter boards and now the attack/release board.

This mostly fixed the issue.  However...

In step 3 of calibration (where I was having trouble), turning on the attack pot does drop the voltage from 2.44v now that I've corrected those components, but not all the way back down to 0.775 -- only to 1.025.  If I adjust that down with the output control, then the "attack off" voltage drops accordingly.  In other words, I'm not getting the full 10dBu attenuation. 

Additionally, my voltages at TP22, Q7-10, and CR2 went further out of whack.  Most everything there shot high, particularly at the higher ratios (which it was already doing, but more so now -- for example, I've got 0.450v at Q7 as opposed to the expected 0.377v).  I've also still got a higher-than-expected voltage at Q5.

Having said all that, the unit does pass audio and compresses, and on a fun little test running bass guitar through it and then some drums, it sounds fabulous!  I'm just wondering what I'm still missing to get it all the way to where it's supposed to be.

Those voltages are not crazy out.  They seem fine.

Not sure what's happening with your calibration step.  Have you looked at some of the calibration videos on you tube?  You might be doing it wrong?

Mike
 

JMan

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Well, whatever I was doing wrong before, I got it right this time.  Unit is fully calibrated and racked up, and it looks and sounds fabulous!  Thanks Mike for such a fun build.  I look forward to doing a few more of these units in the near future.
 

cameron spinks

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Aug 3, 2020
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Hi there,

I have just built a Rev A.
The unit will be working well passing audio normally but  will randomly shut down and turn back on or it will shut down and not turn on again for another 24 hrs or so.

It's like it has over heated and shut down. I'm not really quite sure what the problem is.

Any help would be appreciated
 

Andrei Timotin

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Jan 7, 2018
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Hello guys,need a lil bit of help here
So, I've built an 1176 rev F, calibration went well (checked it twice), when I set the ratio 8 ,12 or 20 everything works fine, but there is something wrong with ratio 4, meter hardly moves even when i crank the input to max, it shows me only 3 db of gr max. 

To give you more information I don't know if i've done something wrong or the issue was already, but after the calibration I did onlye these things :
1) Run some audio through it with ratio 8 -> worked well
2)Run audio with ratio 12 --> worked well
3) Then I've tried the all button setting --> meter went crazy all to the right in red, i've got scared by this weird response so I've turnt it off
4)Turn it back on, checked if all works fine, all good but 4 ratio issue, so at this point i'm not sure if the problem was already there or i've done something wrong (on point 3 maybe), it would be nice if someone can help me

Kind regards
 

GussyLoveridge

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Mar 15, 2012
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Hi Team.

Just starting into a Rev. A build.

I have completed the first build guide for Step 1: Building the Power Supply.

Starting to check the power supply:

I have 0.2-0.4Ω between chassis and IEC ground. Good.

Turned on - no smoke. Good.

Checking the voltage on the cathode of CR8.

This should read 30VDC +/- 5%.

I am getting 47.5 VDC here fluctuating up to 49 VDC. I am going to turn this off and drain the caps because I’m reading that same voltage across my 40V caps.

At -10V DC test point on CR9 I have -9.65 VDC. Good.

My mains voltage is 122.9 VAC is that high enough to throw this off? Naw.

Wouldn’t the Zener clamp the voltage at 30 VDC regardless? Isn’t that the point of one of those little dudelingers?
 

GussyLoveridge

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I am going to check the grounds on the L-brackets. Maybe I put one of those in the wrong way and am not getting a good connection. The build guide mentions that they're longer on one side than the other but boy oh boy it's pretty close eh?

I will as well read the resistance from the bottom of anode of the diode to ground and take a look there.
 

theposterkid

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Jun 20, 2015
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Andrei Timotin said:
3) Then I've tried the all button setting --> meter went crazy all to the right in red, i've got scared by this weird response so I've turnt it off

That's what happens when you push all the buttons in on any 1176. It's a good practice to set the meter to read output level instead of gain reduction when all buttons are in so that the meter isn't pegged for hours on end.
 

GussyLoveridge

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Okay.

Checked the anode of the stud diode to ground. Reading 0.2 ohm

Double checked all of the L brackets with a set of Vernier calipers and they were all installed correctly and are making good contact with the case.

My soldering iron is set somewhere between 600-650 Fahrenheit.

I have a reasonable skill with soldering. Not a pro, but I have been soldering for nearly 20 years and worked on my technique throughout the years.

I feel like such a dummy. I will pull the diode and test it out of circuit and if anyone can give me a solid lead on ordering another one from a reliable place that would be great. Not having much luck sourcing one through Mouser or Digikey.
 

JMan

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Andrei Timotin said:
3) Then I've tried the all button setting --> meter went crazy all to the right in red, i've got scared by this weird response so I've turnt it off

When I built my Rev D a few months ago, I had this same experience.  I had never used a real 1176 before, so I didn’t know to expect it (the plugins sure don’t model this aspect of the unit  ;D ), and I freaked out!  The suggestion above to switch the meter to output mode is a good one.  I’m in such a habit of always leaving all my meters in GR that this had never even occurred to me!
 

Derrick

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Sep 25, 2016
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Hi, I got the FET/RACK Revision D kit to build for a review we are doing, then we will implement into our studio.  I went through the calibration procedure, but I think the directions can use a lot of clarification.  Any tips on how to know if I got the Q bias correct, and clarification of the Null Adjust and Meter Tracking adjustments?

Thanks!
 

Tdo

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Feb 17, 2021
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Hey everyone,
Long time lurker and first post so first of all, thanks for all the help over the years.

I thought I would share the troubleshooting process I had after I completed my rev D.  I am extremely good with a soldering iron and very thorough with assembly but still had problems in step 3 of calibration...

It turned out that I hadn't realized that the attack knob actually CLICKS OFF when in fully CCW position.  In earlier calibration steps that required full CCW position, my knob hadn't been actually clicked off.  This mean't the compressor was in over compression because the q bias wasn't set correctly making step 3 impossible.  After repeating steps 1 and 2 with proper attack knob settings, step 3 went perfectly. So this is just a friendly PSA after a couple of days of frustration: The attack knob physically clicks OFF in full CCW position!  I felt very dumb.

Also I had seen a couple of varying pinouts on this forum when using a utc o-12 so I verified all pinouts before assembly.  I made a little jumper for the shield ground.  I had to mount my o-17 shield so I used one of these screws to mount my jumper to and then soldered this to pad 6.  One screw tested at a lower resistance than the other to the trans can so I went with that one.  Below is how I wired up the trans:

500 ohm of o-12
pads 1 and 4

200 ohm of 0-12
pins 5 and 8

mu-shield
pin 6

Transformer is wired in reverse of how utc labels its primary and secondary. 

I hope this helps some people in the future and a huge thanks to Mike! 

This thing has the magic.  I missed having access to a well maintained rev D. This thing delivers, plus it's brand new so no need to cycle the pots 10 times just to get the crackle out. Thumbs up.
 

AeonMajesty

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Sep 11, 2020
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Hi everyone, first post here.
I've built my rev A and I got two issues.
Firstly when I turned CCW the Q-bias adj R59 trimmer VU meter started oscillating slightly back and forth for almost 0.1 volt range (looking at the DMM)dgt. All this happened during the step 1 calibration.
Second, if I ignore this issue and I go on with the calibration (which is kind of difficult and inaccurated as voltage keeps oscilating), then I push ratio 4:1, 8:1 or 12:1, VU meter slams all the way to the right.

I checked the voltages on the troubleshooting guide and I have 0.5 to 1V more than average values on almost any transistor pin.
I've already cleaned the pcb from the flux and I've checked all resistor values before mounting and soldering.

What could it be?

Thanks
 

Potato Cakes

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AeonMajesty said:
Hi everyone, first post here.
I've built my rev A and I got two issues.
Firstly when I turned CCW the Q-bias adj R59 trimmer VU meter started oscillating slightly back and forth for almost 0.1 volt range (looking at the DMM)dgt. All this happened during the step 1 calibration.
Second, if I ignore this issue and I go on with the calibration (which is kind of difficult and inaccurated as voltage keeps oscilating), then I push ratio 4:1, 8:1 or 12:1, VU meter slams all the way to the right.

I checked the voltages on the troubleshooting guide and I have 0.5 to 1V more than average values on almost any transistor pin.
I've already cleaned the pcb from the flux and I've checked all resistor values before mounting and soldering.

What could it be?

Thanks

You will have to pull it apart and check for bad (or even missed) solder joints again as well as misplaced components. Also check for continuity of your header connections. If you don't find anything then check again. Something is feeding voltage to the meter when you have those ratios selected. You can start there.

Thanks!

Paul
 

Aesacus

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Sep 29, 2019
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I've just about finished a weekend build of 2 Rev F's and have begun the calibration process for the first unit. With 775mv of 1k coming in and the panel controls set as recommended, I can't reach the 2.44VAC when I crank the output in order to complete the biasing.

The unit passes audio, and both the input and output knob are amplifying and registering on the VU. With the gain reduction meter engaged the needle is stuck far left.

Aside from double checking correct components, connections and soldering - as I've done - how can I begin diagnosing? Any thoughts on what this could be caused by?

Thanks for any input!
 

MiKa84

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Oct 13, 2017
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Hi fellow DIY'ers,

Just finished a Rev F build. This is my third Hairball FET/Rack build, the first two went all smooth but on this one I'm having trouble.
When I turn it on the 75R 3W (R84) resistor in the power supply turns smoking hot after a few seconds. Obviously something is drawing way to much current. What have I done so far?
Checked all the components if they are the correct values - should be good on that
Checked the polarity on all electrolytic caps - good
At this point I'm a bit lost and I would very much appreciate it if someone that maybe had a similar issue before or someone that has an idea on where to look could chime in and point me in the direction on where to look next.
If it wasn't all on a pcb board I would disconnect the gain reduction or the signal path but since that is not an option I'm hoping for someone with a good idea on how to proceed without desoldering all the components.
Help is very much appreciated.

Thanks
 
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