Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1760 on: October 21, 2019, 03:14:38 PM »
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
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
http://facebook.com/hairballaudio


Xno

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1761 on: November 20, 2019, 05:21:39 PM »
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

Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1762 on: November 20, 2019, 05:24:31 PM »
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
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
http://facebook.com/hairballaudio

Xno

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1763 on: November 21, 2019, 03:42:51 AM »
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
« Last Edit: November 21, 2019, 08:43:50 AM by Xno »

Xno

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1764 on: November 21, 2019, 01:29:29 PM »
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 ^^

Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1765 on: November 21, 2019, 10:32:08 PM »
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
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
http://facebook.com/hairballaudio

Xno

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1766 on: November 24, 2019, 04:15:01 PM »
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"
« Last Edit: November 26, 2019, 04:29:54 AM by Xno »

Xno

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1767 on: December 02, 2019, 07:23:23 AM »
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 ...

Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1768 on: December 04, 2019, 06:46:32 PM »
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
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
http://facebook.com/hairballaudio

Xno

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post! New
« Reply #1769 on: December 06, 2019, 08:34:53 AM »
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
« Last Edit: December 06, 2019, 09:06:57 AM by Xno »