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

[Echo North]

I guess I should have post-poned my victory dance. Distortion is back. Swapped out my ratio assembly, no luck. Swapped out the Orange Drop caps in the GR section because they were making noise when I tapped them...no luck. Swapped out the FETs...no luck. I already replaced the transistors in that section, but I will replace them one more time. If that doesn't work, then I think I will concede and pull the components out and build another REV D...this thing has been ridiculous. It was working perfectly fine for 2 days. Sometimes you just shake your head.

Must be a weird solder joint or grounding issue.  Could always send it in.  Hate to see something fixable end up in the trash.

Only so much troubleshooting I can do on here.

Mike

 

[Xno]

Hello,

On FET RACK A MNATS v1.14 2017 ( ordered from europe from Hairball in 2017 , built it back then but there were problem that I'm looking only now)

GR on
20:1
Attack off knob
release CCW
input/output mid pos
null/track adj mid pos
QBias full CW

input 0.774 VAC
output 0.007 VAC and meter needle fully CW

Remark : if i turn on attack needle is fully CCW

All voltages in green are DC on attached piece

my first thought, is T1 or Q1 dead ?

*later* i just changed Q1 , value are in blue

any clue what should i do ?

Thanks, regards,
Anton

 

[Echo North]

Hello,

On FET RACK A MNATS v1.14 2017 ( ordered from europe from Hairball in 2017 , built it back then but there were problem that I'm looking only now)

GR on
20:1
Attack off knob
release CCW
input/output mid pos
null/track adj mid pos
QBias full CW

input 0.774 VAC
output 0.007 VAC and meter needle fully CW

Remark : if i turn on attack needle is fully CCW

All voltages in green are DC on attached piece

my first thought, is T1 or Q1 dead ?

*later* i just changed Q1 , value are in blue

any clue what should i do ?

Thanks, regards,
Anton

Start by posting these voltages from the 6 steps...

https://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

Specify AC or DC when doing these.

Mike

 

[Xno]

Ok Mike thank you :

step 1 Qbias : -1 VDC -1.74VDC

step 2 (unbiased):

TP1 :    0.110 VAC
TP15 : 3.04 VAC
TP17 : 0.522 VAC
BRN  : 0.155 VAC

TP15 and 17 are a litte off but BRN seems way more off so i'm first looking in this direction :

"Low voltage at Output Transformer BRN: have issues in your Signal Line Amp section marked on the PCB. Check the DC voltage chart for this section"


Edit : I add my DC voltage, gonna check resistor/ cond / Q5/ Q6 ( Q5/6 are soldered i will desolder and put female pin if you ask me to do so)
Thx for your support,
Anton

 

[Xno]

i checked all components value, everything is in place it seems ... so a broken component or bad solder ( though i resolder everything ...)

I will try to  exploit those DC voltages and transistor behavior , my electronic course is far  behind ^^

 

[Echo North]

i checked all components value, everything is in place it seems ... so a broken component or bad solder ( though i resolder everything ...)

I will try to  exploit those DC voltages and transistor behavior , my electronic course is far  behind ^^

Ya something is up in that last stage.

I would consider maybe swapping out those transistors in the last stage.

Mike

 

[Xno]

Just changed Q4 with a spare J309 i had ( by the way i just ordered NOS J309 branded "fairchild" are they good ?)

Q5 and Q6 coming ...

edit : there s a typo on schematic its "after Q4 change"

 

[Xno]

received Q5 and Q6, so with previous Q4 swap , all Q4/5/6 have been swapped, i now hear a hiss ( i guess the 1khz wave since when i increase input/ouput pot the sound is stronger) and there is some voltage to XLR output 3.8 VAC

here my TP voltage :

TP1 :    0.110 VAC
TP15 : 4.350 VAC
TP17 : 0.683 VAC
BRN  : 0 VAC

TP15 and 17 are good now but BRN not ...

 

[Echo North]

received Q5 and Q6, so with previous Q4 swap , all Q4/5/6 have been swapped, i now hear a hiss ( i guess the 1khz wave since when i increase input/ouput pot the sound is stronger) and there is some voltage to XLR output 3.8 VAC

here my TP voltage :

TP1 :    0.110 VAC
TP15 : 4.350 VAC
TP17 : 0.683 VAC
BRN  : 0 VAC

TP15 and 17 are good now but BRN not ...

What are the the DC voltages for those transistors?

Mike

 

[Xno]

oh yes forgot to post those , my apologies

on the drain of Q4 , sometimes i have 0.45 VDC and sometimes 1.72 VDC with a stronger audible hiss.

edit : I have 6.1 VAC at BRN now ... i resoldered 2-3 things around this place , DC voltage are still same, strange

Thx

 

[Echo North]

oh yes forgot to post those , my apologies

on the drain of Q4 , sometimes i have 0.45 VDC and sometimes 1.72 VDC with a stronger audible hiss.

edit : I have 6.1 VAC at BRN now ... i resoldered 2-3 things around this place , DC voltage are still same, strange

Thx

Are you passing clean signal now?

 

[Xno]

Hi Mike,

Actually its the first time i listen to the output ever, there is a big noise unrelated to input that get lower if i remove the CN8-CN9 link

i need to check R23 cause i have some big crackling when playing with this knob

Also, needle is totally CW, i see it compressing sometimes though if i activate attack

edit: Also when i turn off the unit i have an alien noise spike

Thx,

Anton

 

[Echo North]

Hi Mike,

Actually its the first time i listen to the output ever, there is a big noise unrelated to input that get lower if i remove the CN8-CN9 link

i need to check R23 cause i have some big crackling when playing with this knob

Also, needle is totally CW, i see it compressing sometimes though if i activate attack

edit: Also when i turn off the unit i have an alien noise spike

Thx,

Anton

Did you see the note in the active link about installing a couple caps backwards if you have a certain active link PCB revision? 1.2 or earlier I think?

Mike

 

[Xno]

Hmm I'm not using Active Stereo Link, i just have 1 unit, i was just speaking of wire linking CN8 and CN9

edit : I fried CR9 diode ... ordering it

Also , would it be possible to have complete release pot reference ? i'm thinking of something like 91A1A-G28-C22 ?

 

[d3n5ity]

Hi Mike, Finished a REV F build and having an issue with R54 Tracking adjustment during Calibration step 3. The R54 does not change the meter, just sits at -20. The meter functions, the unit is passing signal . Any insight to where i should look? I have reflowed solder in the GR Meter Driver Amp secton.

Thanks!

 

[Echo North]

Hi Mike, Finished a REV F build and having an issue with R54 Tracking adjustment during Calibration step 3. The R54 does not change the meter, just sits at -20. The meter functions, the unit is passing signal . Any insight to where i should look? I have reflowed solder in the GR Meter Driver Amp secton.

Thanks!

Confirm IC1 is a TL071 and that it is installed in the correct location.  Also confirm your trimmer is the correct value and confirm your connection headers are in the correct orientation.  Reflow the GR meter switch.

Mike

 

[d3n5ity]

Confirm IC1 is a TL071 and that it is installed in the correct location.  Also confirm your trimmer is the correct value and confirm your connection headers are in the correct orientation.  Reflow the GR meter switch.

Mike

I had two trimmers swapped. Calibrated and working! Thank you

 

[Deejsirois]

REV D Build

All calibrations went normal. Then I listened to the audio and discovered that something is not quite right. The low end is very pronounced, and on an analyzer, 62 hz is jacked and everything above it exponentially decreases, like I had a low-pass applied. I tested another compressor (REV F) through the exact same signal path and the signal on the analyzer is almost flat across the full frequency span  (62-16kHz).

My first instinct is to go after transformers, but thought I would check in before doing surgery. Thoughts?

Thanks!

 

[Echo North]

REV D Build

All calibrations went normal. Then I listened to the audio and discovered that something is not quite right. The low end is very pronounced, and on an analyzer, 62 hz is jacked and everything above it exponentially decreases, like I had a low-pass applied. I tested another compressor (REV F) through the exact same signal path and the signal on the analyzer is almost flat across the full frequency span  (62-16kHz).

My first instinct is to go after transformers, but thought I would check in before doing surgery. Thoughts?

Thanks!

Test it through all of the signal amp test points per the trouble shooting guide.  See where a 60Hz and 1KHz signal start to differ in level.

Mike

 

[Deejsirois]

Test it through all of the signal amp test points per the trouble shooting guide.  See where a 60Hz and 1KHz signal start to differ in level.

Mike

The collector of Q4 is where 62Hz is getting crazy amplified (and everywhere after). I have double checked values around that area and everything checks out. I replaced one by one, Q4, C8, R24, R25, R26, and C10. In the process, I discovered that my output pot's middle pin had continuity with the right pin, so I grabbed a spare I had, which also had the same problem. I had one left and thankfully that one is good. I thought that would be the answer, but nope. DC voltages are good.

Edit: Ok DC voltages are NOT good. Specifically, at R34 I am getting 31.07 VDC on one side and 7.88 VDC on the other. On a working unit, I get 30.59 VAC on one side and 26.26VDC on the other. What is pulling my voltage down so much? I even replaced R34 for good measure. Both R34 resistors (old and new) tested at 8.2k.

Q14: B=12.47 VDC, C= 30.92 VDC, E= 11.87 VDC (normal)
Q4: B= 0.579 VDC, C= 2.482 VDC, E= 0.112 VDC (off)