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

[Spanzor]

Spanzor,

Alright I'm back and ready to sort this for you. Poked around our Rev A just now trying to sort you.

You're voltage is high at pad 22 because you're not getting any compression.

Were you able to complete the Qbias adjustment?

Mike

Mike-

Yes Q bias goes okay, I can get all the way up to where I calibrate the meter with the trim pot on the front. 

Thanks,
Spencer

 

[Echo North]

Well it appears then that your side chain is not compressing.

http://mnats.net/files/fetrack/fet_rack_a_doc_v1.12.pdf

Carefully inspect all parts/values/solder joints/traces in the "GR Control Amp" section.

 

[Echo North]

Cleaned it with 99% alcohol and a toothbrush after I was finished and after doing my most recent touch ups. Looks pretty clean to me. Used Kester solder so hopefully nothing weird with that.

Thank you Mike!

Does the release sound right? Just effect the meter?

 

[thecmarus]

Does the release sound right? Just effect the meter?

The overall volume drops as well as the needle dropping even with attack off, so in that regard I'd say it's not just the meter doing something funny. If i want slower release I've just been increasing  the output gain by a few db and ignoring the meters and it seems to sound Okay so I assume the release is working fine.

 

[Spanzor]

Well it appears then that your side chain is not compressing.

http://mnats.net/files/fetrack/fet_rack_a_doc_v1.12.pdf

Carefully inspect all parts/values/solder joints/traces in the "GR Control Amp" section.

Okay, everything looks clean.  There's no breaks in any of the traces, all the resistors measure appropriately and/or match the corresponding color code.  All the caps look great and are in the right spot, diodes oriented the right way, etc.  Transistors all match up with the proper markings.

Is there anything else I could check?  Should I send it in?

Spencer

 

[Echo North]

The overall volume drops as well as the needle dropping even with attack off, so in that regard I'd say it's not just the meter doing something funny. If i want slower release I've just been increasing  the output gain by a few db and ignoring the meters and it seems to sound Okay so I assume the release is working fine.

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?

 

[Echo North]

Okay, everything looks clean.  There's no breaks in any of the traces, all the resistors measure appropriately and/or match the corresponding color code.  All the caps look great and are in the right spot, diodes oriented the right way, etc.  Transistors all match up with the proper markings.

Is there anything else I could check?  Should I send it in?

Spencer

You could always send it in.

You could test the DC voltages in the GR AMP section:

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Mike

 

[Diamondj421]

Greetings all!
My 1176s have been getting a lot of work recently but I've noticed that my 2nd units meter is fidgeting a lot while nothing is running through it. This unit was sent in for repair so I'm sure everything is in it's right place. Any idea what it could be?

 

[Echo North]

Greetings all!
My 1176s have been getting a lot of work recently but I've noticed that my 2nd units meter is fidgeting a lot while nothing is running through it. This unit was sent in for repair so I'm sure everything is in it's right place. Any idea what it could be?

Weird. There is no signal present?

You could try swapping the meters in your units and see it it is a bad meter.  If not email us and we can look at it again for free if it's already been looked at by us.

Mike

 

[Echo North]

You are losing signal after your input.  A bad input would be VERY rare so I would not expect that straight out.  Do you have the older version with input on its own PCB?

If so double check your wiring.

Using the test above, what is your AC at:

TPAD PCB in+
TPAD PCB out+
Input transformer  PCB in+
Input transformer  PCB out+

Mike
(I'll be offline the rest of the day)

Try removing the Q1 FET if you can...does that change the level?

Mike

 

[eriksunding]

I'm helping a friend out with a build he's doing. He's done 2 of the Rev A's and got one of them to work perfectly but not the second one.
Signal is passing thru but there is no compression. Also when switching to GR mode the needle isn't moving to 0.

From what I could find, so far, when comparing them both to each other the volt value of Q5 and Q6 are different. The one that isn't working are showing these values:
Q5
Base: 1,3v
Collector: 27v
Emitter: 0.7v

Q6
Base: 0.7v
Collector: 30v
Emitter: 0.1v

Any idea what might be the cause? Transistor broken or maybe something else affecting these? Anything I could look for?

Thanks

 

[eriksunding]

SOLVED! Faulty cable going from main pcb to ratio pcb. Two of the small wires had changed places with each other. Factory fault I assume.

 

[jgremlin]

Ok need help. First build of Rev D. Can do the Q bias calibration and seems to react as expected.
Discrete meter/null adjust also reacts as expected. But as soon as the jumper is put back in the normal ops position, meter drops to about -18 and with R71 max CW meter reads -10.

 

[Echo North]

Ok need help. First build of Rev D. Can do the Q bias calibration and seems to react as expected.
Discrete meter/null adjust also reacts as expected. But as soon as the jumper is put back in the normal ops position, meter drops to about -18 and with R71 max CW meter reads -10.

It should drop but not that much.

You're able to get the 0V DC null?

Mike

 

[jgremlin]

Yeah, it seemed to work. I couldn't really get it to zero, but I think I got it to something like 3.5mv. I figured that must be close enough.

 

[Echo North]

Yeah, it seemed to work. I couldn't really get it to zero, but I think I got it to something like 3.5mv. I figured that must be close enough.

Ya that's pretty good.

Did you get a full kit with the matched 2N3707's for Q12/13?

Mike

 

[jgremlin]

Yes, full kit, plus the orange drop caps.

 

[Echo North]

Yes, full kit, plus the orange drop caps.

Hmmm. not really sure. 

Check your DC voltages in the meter and GR amp compared to this:
http://mnats.net/files/1176REVD_VOLTS.pdf

Mike

 

[jgremlin]

Been away for a week. So I checked the DC volts against the schematic and it seems like all are pretty close to where they're supposed to be. I didn't find any that were wildly different from the spec.

However I think I may have found a clue.  I was going around the board with a finger applying pressure and bit of wiggle to the caps and FETs seeing if I could find any loose/suspect connections that might have an impact on the meter. That's when I touched Q6 and said holy toledo that's hot. And that's when I remembered that Q6 is supposed to have a heat sync. I completely forgot to install it before power up.

Any chance I might have cooked the Q6 and that could be my problem?

 

[Maxman]

Hi guys-I just finished building my first Fet Rack, and I'm having trouble doing the calibration:

The first two calibration steps were successful and yielded the proper voltages, but now I'm stuck on the third step (adjusting the meter to reflect GR). It seems at this stage that the unit isn't compressing at all (no compression showing on the meter/the DMM/ or happening audibly,) but the unit IS passing audio through very cleanly.  The Q bias was set per instructions and R74 is showing 0 voltage across it.

Is there any obvious places to start with troubleshooting that you can think of (a problem with the attack/release board, a burned out FET unit...)? To reiterate-I have audio passing cleanly but no compression despite the Q bias being set per instructions. Thanks so much for the help.