[BUILD] 1176 Rev A - Back to the beginning...

[vrrs]

Likely a GR amp issue if you can't get proper GR. 

You'll need to run through the troubleshooting guide, specifically testing TP21 for DC, and TP22/CR2 for AC.  TP21 and TP22 are pads 21 and 22 on your PCB. If you have terminal blocks covering the designations, you can reference this doc to see what the PCB looks like under the blocks.

http://mnats.net/files/1176REVA_125_DOCUMENTATION.pdf

You can see 21/22 at the bottom of the PCB.

Trouble shooting doc is here:
https://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

Post your findings for #3,4, and 5.  They probably a little lower than what is posted but let's look at those first.

Mike

Thanks for the info, I went ahead and got these pretty wacky numbers:

#3 1 kHz tone at input at  0.775 VAC
all settings set to prescribed locations TESTING TP22:
20:1    2.440 VAC
12:1    1.617 VAC
8:1      1.052 VAC
4:1      0.506 VAC

#4  TESTING CR2 Anode
20:1  1.158 VAC
12:1  0.007 VAC
8:1      0.004 VAC
4:1      0.002 VAC

#5 TESTING TP21
20:1  -5.86 VDC
12:1  -3.214 VDC
8:1      -2.387 VDC
4:1      -1.558 VDC

 

[Echo North]

Thanks for the info, I went ahead and got these pretty wacky numbers:

#3 1 kHz tone at input at  0.775 VAC
all settings set to prescribed locations TESTING TP22:
20:1    2.440 VAC
12:1    1.617 VAC
8:1      1.052 VAC
4:1      0.506 VAC

#4  TESTING CR2 Anode
20:1  1.158 VAC
12:1  0.007 VAC
8:1      0.004 VAC
4:1      0.002 VAC

#5 TESTING TP21
20:1  -5.86 VDC
12:1  -3.214 VDC
8:1      -2.387 VDC
4:1      -1.558 VDC

#4 is your issue. Your side chain amp is not working.  #3 is high because of #4.  #5, you threshold levels, looks good.

There is a box on your PCB labeled "GR Control Amp". There is an error in there somewhere.

1. Confirm all of your component placement. There are a lot multiples in that section (4.7K, 47K, 470K).
2. Check/re-flow all solder joints that look suspect in the slightest.
3. Check for damaged pads, confirm trace continuity with a DMM.
4. Check the transistor DC voltages in that section. (http://mnats.net/files/1176REVA_125_VOLTAGES.pdf)

Mike

 

[vrrs]

#4 is your issue. Your side chain amp is not working.  #3 is high because of #4.  #5, you threshold levels, looks good.

There is a box on your PCB labeled "GR Control Amp". There is an error in there somewhere.

1. Confirm all of your component placement. There are a lot multiples in that section (4.7K, 47K, 470K).
2. Check/re-flow all solder joints that look suspect in the slightest.
3. Check for damaged pads, confirm trace continuity with a DMM.
4. Check the transistor DC voltages in that section. (http://mnats.net/files/1176REVA_125_VOLTAGES.pdf)

Mike

that's what I figured. I shall look into that. I'll post the values at the transistors in that section too.

These transistor measurements are from the leg facing the back plate, middle and then leg facing front face.
Q10 
5.7 VDC
30.31 VDC
5.13 VDC

Q9
4.81 VDC
5.72 VDC
4.22 VDC

Q8
26.24 VDC
30.29 VDC
25.65 VDC

Q7
1.048 VDC
26.23 VDC
3.053 VDC

 

[vrrs]

Thanks for the info, I went ahead and got these pretty wacky numbers:

#3 1 kHz tone at input at  0.775 VAC
all settings set to prescribed locations TESTING TP22:
20:1    2.440 VAC
12:1    1.617 VAC
8:1      1.052 VAC
4:1      0.506 VAC

#4  TESTING CR2 Anode
20:1  1.158 VAC
12:1  0.007 VAC
8:1      0.004 VAC
4:1      0.002 VAC

#5 TESTING TP21
20:1  -5.86 VDC
12:1  -3.214 VDC
8:1      -2.387 VDC
4:1      -1.558 VDC

that's what I figured. I shall look into that. I'll post the values at the transistors in that section too.

These transistor measurements are from the leg facing the back plate, middle and then leg facing front face.
Q10 
5.7 VDC
30.31 VDC
5.13 VDC

Q9
4.81 VDC
5.72 VDC
4.22 VDC

Q8
26.24 VDC
30.29 VDC
25.65 VDC

Q7
1.048 VDC
26.23 VDC
3.053 VDC

I've checked, double checked and checked again all the resistors in the area. They all check out. I even pulled some from the board to make sure they are the correct value in the DMM. I have checked all the traces, went over all the solder pads again with my iron and cleaned everything up as best I could. Nothing changed. The caps are the correct values. Could a transistor be the issue?

 

[Echo North]

Your transistor values are a mess.  They all feed one another, so if ones wrong, it can all cascade.

You're using 2N3707 or 2N3708's in that section?

If you have some on hand, I would start by replacing those.  See if that fixes it.

Mike

 

[vrrs]

Your transistor values are a mess.  They all feed one another, so if ones wrong, it can all cascade.

You're using 2N3707 or 2N3708's in that section?

If you have some on hand, I would start by replacing those.  See if that fixes it.

Mike

They're all 3708s
I just swapped Q10 and Q9 to see if the problem moves. The problem stays.  I don't have any on hand but I'll order a bunch from digikey.

 

[Echo North]

They're all 3708s
I just swapped Q10 and Q9 to see if the problem moves. The problem stays.  I don't have any on hand but I'll order a bunch from digikey.

If one has a broken junction, it'll mess up the voltage drop across it....in turn messing up all the voltages dividers in the section. Q7 is super suspect.

 

[vrrs]

If one has a broken junction, it'll mess up the voltage drop across it....in turn messing up all the voltages dividers in the section. Q7 is super suspect.

I just swapped Q7 with Q8. Same voltage readings. I'm scratching my head. If I move the transistors around and the readings are the same, that means the transistors aren't the problem, right? Unless that's how they function together in the circuit with one of them being bad. I don't have a transistor check in my DMM. So I can't measure them. Logically thinking, replacing the transistors with new ones won't fix the problem. Unless I'm missing something.

 

[Echo North]

I just swapped Q7 with Q8. Same voltage readings. I'm scratching my head. If I move the transistors around and the readings are the same, that means the transistors aren't the problem, right? Unless that's how they function together in the circuit with one of them being bad. I don't have a transistor check in my DMM. So I can't measure them. Logically thinking, replacing the transistors with new ones won't fix the problem. Unless I'm missing something.

Try all new transistors. 

Also, with you ohm meter, confirm every connection on your board referencing the schematic. Base of Q7 is connected to one side of R36 and R37 and so on. 

Your voltage drops of the 30VDC rail are all wrong. Q9 collector is way too low, that indicates a the drop across R51 and R47 is way too large. The only way that happens is if there is too much current across those resistors (ohms law). Could be a bad transistor or a lifted/burned pad messing up your dividers.

Mike

 

[vrrs]

Try all new transistors. 

Also, with you ohm meter, confirm every connection on your board referencing the schematic. Base of Q7 is connected to one side of R36 and R37 and so on. 

Your voltage drops of the 30VDC rail are all wrong. Q9 collector is way too low, that indicates a the drop across R51 and R47 is way to large. The only way that happens is if there is too much current across those resistors (ohms law). Could be a bad transistor or a lifted/burned pad messing up your dividers.

Mike

Ok. I've checked continuity and all traces pad to pad are ok. I'll order and replace the transistors. It's the only thing left to do. I checked the voltage drop across the preliminary resistors (ie 30 VDC coming in to R51 and 28 VDC coming out) but then the transistor following it can change the value of the voltage there so reading the voltage drops are going to be skewed by the transistors.  I'm calling it a night. Thanks for the help Mike. I'll get back on it as soon as the transistors arrive.
Elliott

 

[vrrs]

Ok. I've checked continuity and all traces pad to pad are ok. I'll order and replace the transistors. It's the only thing left to do. I checked the voltage drop across the preliminary resistors (ie 30 VDC coming in to R51 and 28 VDC coming out) but then the transistor following it can change the value of the voltage there so reading the voltage drops are going to be skewed by the transistors.  I'm calling it a night. Thanks for the help Mike. I'll get back on it as soon as the transistors arrive.
Elliott

I just replaced the 4 transistors on the GR part of the board. Sadly, they didn't rectify the situation. I'll keep hunting for the problem

 

[Echo North]

I just replaced the 4 transistors on the GR part of the board. Sadly, they didn't rectify the situation. I'll keep hunting for the problem

There is something in that part of the board. I've run into this exact situation a few times, it's always something weird.

You could try removing C19/C20 and see if that helps your voltages. At the very least it'll isolate that circuit from the downstream attack/release network.

Once you do that try inserting transistors Q7->Q10 in order and see where the voltages start to get off.

Mike

 

[Matgre]

Hi all,

posted this already in the "[BUILD] New FET/RACK Official Help Thread - Please read first post!" , not really sure if this was correct, so i´ll post it here aswell.

And sorry if its a total noob question, but couldn´t find an answer jet.. or might have just overlooked it.

Is it a problem if the input transformers (T1) metalhousing touches the orange drop cap (C10) on its coating sitting just beside it?
I installed the orange drops before the transformers.. and they touched a tiny bit, did bent the cap backwards a bit, so it sits just slightly off now, about 0,5mm, but still wondering if it could be an issue if they would touch?

Thanks for help!
Mat

 

[Echo North]

Hi all,

posted this already in the "[BUILD] New FET/RACK Official Help Thread - Please read first post!" , not really sure if this was correct, so i´ll post it here aswell.

And sorry if its a total noob question, but couldn´t find an answer jet.. or might have just overlooked it.

Is it a problem if the input transformers (T1) metalhousing touches the orange drop cap (C10) on its coating sitting just beside it?
I installed the orange drops before the transformers.. and they touched a tiny bit, did bent the cap backwards a bit, so it sits just slightly off now, about 0,5mm, but still wondering if it could be an issue if they would touch?

Thanks for help!
Mat

You don't want them touching, though if the coating is there it'll be fine.  You can bend the lead and sit it a little off center.

 

[andia]

Im trying to repair a hairball 1176 rev a (old version with mnats board)

the unit behaves very strange after some minutes.
I was trying to recalibrate and all works well, but after some minutes, when I try to calibrate the GR metering it seems that the unit does not recover from the applied compression when set into bypass mode.

the meter stays at -10 on the VU and also the output level stays where it was as the unit is bypassed via the attack-switch. you can then see that the meter and outputlevel recover veeeeeeeeeery slowly. (takes like minutes).

I can reset that behaviour by powering of the unit for a second. it will then work as expected for some more minutes before it all starts again...

does anyone have ideas?

as always thank you!
andi

 

[Che_Guitarra]

Hi guys.  I'm looking to fix a quirk i've been living with for a few years.

Hairball Rev A.  The meter doesn't work in Gain Reduction mode.  Perfectly fine at +4 or +8.

It gets too much use, so yet to take it out of the rack to see if I can visually identify the issue. 

This thread is huuuge, so i've only just skimmed in search of a solution.

Any suggestions and i'm all ears 

 

[Potato Cakes]

Hi guys.  I'm looking to fix a quirk i've been living with for a few years.

Hairball Rev A.  The meter doesn't work in Gain Reduction mode.  Perfectly fine at +4 or +8.

It gets too much use, so yet to take it out of the rack to see if I can visually identify the issue. 

This thread is huuuge, so i've only just skimmed in search of a solution.

Any suggestions and i'm all ears 

Bad news. You will have to take it out of the rack if you want to fix it. More than likely, as it the case with most issues, you have a bad/missing solder joint/component placement. Fortunately, if the compressor is indeed working, then most likely the issue is the at the meter board or a connection to it. But again, it's got to come out of the rack to verify. Otherwise, like in so many other studios with analog gear, you just know how that piece of gear works with it's issues and never think about it.

Thanks!

Paul

 

[Che_Guitarra]

No gasps of horror from forum dwellers, so that's a positive sign.  Not that many components on the meter board if I remember correctly, so a cold solder in this ballpark would be ideal. 

I had a broken trace on the main board - that was a *nightmare* to diagnose and isolate!  I suspect the board was dropped in transit, somewhere on the way here to Australia  :-\

Hasn't really bugged me enough to fix, but it does bug the other guys who like that visual confirmation from the meter. 

Will get onto it on the weekend.  Thanks 

 

[Palmito]

Hi guys
i'm having trouble with a Rev 1 v1.2.5. the first one i built works perfectly, but the second one seems to lack input gain.

I checked the voltages at the power supply section, i get -9.7V at CR6 and 29v at the 30V test point.
Are these values ok ?
If not, does that mean the problem is at the power supply section or can it be somewhere else in the circuit ?

I double checked all solders and components, eveything looks fine...
thanks in advance
Alex

 

[thomasdf]

If you have one that's acting fine, it's easy to measure / test them side by side, compare voltages, wiring etc until you find differences