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

[Echo North]

-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?

 

[jgremlin]

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.

 

[Echo North]

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

 

[jgremlin]

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.

 

[TDJ]

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!

 

[TDJ]

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!

 

[Echo North]

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

 

[jgremlin]

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

 

[Echo North]

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?

 

[jgremlin]

That's with GR on?

Yes. Full CW

 

[Echo North]

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.

 

[jgremlin]

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.

 

[Echo North]

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

 

[jgremlin]

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.

 

[Echo North]

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?

 

[jgremlin]

In 20:1?

But nothing at pad 22?

Affirmative.

 

[Echo North]

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

 

[jgremlin]

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.

 

[Echo North]

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

 

[jgremlin]

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!