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

[Echo North]

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.

 

[TDJ]

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.

 

[Echo North]

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 +

 

[TDJ]

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

 

[YoDudeRock]

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

 

[Echo North]

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".

 

[Echo North]

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.

 

[TDJ]

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.

 

[Echo North]

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.

 

[TDJ]

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.

 

[thecmarus]

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?

 

[Echo North]

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?

 

[thecmarus]

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.

 

[Echo North]

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

 

[dbonin]

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!

 

[Echo North]

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.

 

[dbonin]

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!

 

[Echo North]

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

 

[thecmarus]

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!

 

[Echo North]

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