[BUILD] New FET/RACK Official Help Thread - Please read first post!
- Thread starter mnats
- Start date
Help Support GroupDIY Audio Forum:
Echo North
Well-known member
That connector that connects the attack/release to the main PCB. Check all those pads/solder joints and connections.
We're close.
We're close.
Hairball Audio said:
UPDATE !
It was Q1 .. I was lucky enough to have extra 2N5457's that I had order from Studio electronics of Burbank for our 4 Vintage D and E lots .
So , I replaces Q1 and Q11 , and its working great !
thanks again for all your help, You guys have A LOT of patience ! haha thanks again.
-Chris
Echo North
Well-known member
ccommon said:
Well damn!
There you go. Glad you got it sorted.
Echo North
Well-known member
mixmasta said:
What is your DC at each of the 3 release Pads?
Echo North
Well-known member
mixmasta said:
That ain't right. R57 is the correct value?
I think your release pot is messed up. Can you remove it and test it?
Echo North
Well-known member
mixmasta said:
Hmmmmm. What about between both outside pins? About 5M?
Mike
Echo North
Well-known member
mixmasta said:
I'll have to look at the schematic this weekend. Something is happening right below.
You have the proper DC at 18 and you have no DC after the release. It should be on the other side of the release. Your PAD 21 is fine.
On the side of the release with no voltage...what is the resistance to ground? Maybe there is a short there killing the DC.
Mike
Attachments
Echo North
Well-known member
ccommon said:
Ya I figured.
I really think your Signal Preamp is too hot which will only be made worse in the Line Amp.
If you're sure all of the Signal Preamp resistors/caps are correct, you could try replacing Q2 and Q3.
Mike
Hairball Audio said:
Yup .. I think I'll order those to be on the safe side.
It was odd the kit was Missing all 4x 8.2k resistors , So i got some 8.2k metal film at this electronics store here in El paso , but i think they are not correct . The color code is correct but they test high at 8.8k .. I order some high quality replacements from digikey to be safe
-c
Echo North
Well-known member
mixmasta said:
You can see them labeled in the schematic:
http://mnats.net/files/fetrack/fet_rack_a_doc_v1.12.pdf
Pin 1: Ground
Pin 2: When GR is ON and you have input signal, you'll have some AC here depending on your ratio setting. Low AC at 4:1 then higher as you move to 2:1. When GR is OFF it'll be grounded.
Pin 3: If you have input signal, you'll have some AC here depending on your ratio setting. Pin 1, 2 , and 3 are the attack switch. I think this is fine in your unit.
Pin 4: Tied to TP19 they should be the same. It's after the FH333 diode so you should have DC here as long as the DC is higher than the diode forward voltage.
Pin 5: This is where the bias DC V leaves the attack/release PCB. It should have very HIGH resistance to ground. This is your problem.
Pin 6: This is where the bias DC V enters the attack/release PCB. Yours seems fine.
So what's happening at pin 5? It's getting grounded somewhere. Thoughts looking at the schematic:
- Bad solder at your RCA connector has pin 7 shorted to ground. If you can, you can try removing the RCA and see if that fixes it.
- Bad C22 or bad solder. If you can, you can try removing it and see if that fixes it.
- Bad Q1 or bad solder. If you can, you can try removing it and see if that fixes it.
That would be the easiest paths to ground that I can see with a quick look.
I'll be off line most of the weekend, but will pop on when I can.
Good luck!
Mike
Hairball Audio said:
Hi Mike,
I found it! I had the legs of the RCA bent to hold it better to the board but completely forgot that they were touching and shorting the middle pin to ground. Clipped the middle leg and voltages look good now. Have to check the other (working) unit now because I probably did a similar thing there.
Thank you so much for your help and good troubleshooting advice!
RR25
Member
Thanks for your help in the previous posts Mike and mnats. I'm back from a quick break and getting closer to finishing this rev A.
I fixed the issue i was having with a low amount of signal and not being able to compress 10dB to finish the calibration steps that I mentioned in previous posts.
(turns out I just wasn't paying enough attention and I had two resistors in each others places in the signal preamp section)
I have now finished the calibration and everything went great, although when I try and run audio through it I get a very weak and filtered signal, almost sounds like a bandpass at about 1KHz.
I have checked all of the resistors again and they are all correct (now). All of the voltages checked out too.
Any help in narrowing down what might be the culprit would be great.
Thanks again
I fixed the issue i was having with a low amount of signal and not being able to compress 10dB to finish the calibration steps that I mentioned in previous posts.
(turns out I just wasn't paying enough attention and I had two resistors in each others places in the signal preamp section)
I have now finished the calibration and everything went great, although when I try and run audio through it I get a very weak and filtered signal, almost sounds like a bandpass at about 1KHz.
I have checked all of the resistors again and they are all correct (now). All of the voltages checked out too.
Any help in narrowing down what might be the culprit would be great.
Thanks again
I recently purchased a partial kit and the corresponding mousser cart of components. During calibration I have run into a problem with the attack and meter adjustments. I have gone back several times to make sure I have not missed a step and when it comes to the attack calibration with the trimmer R44 I just can not get any results.
With the attack cw to fully on I make the adjustments according to the hairball cal. guide, but I get no meter jump when the attack is switched off and no difference on my DMM reading.
Ive read that this version of the unit has very little possibility of wiring issues since the harnesses are premade and pretty dummy proof.
I did have a slight issue with a pad on the front of the board at Q3, the pad on the back was fine, could the copper pad on one side have caused the issue even if the pad on the back had a good joint?
Is there anyway to trouble shoot my transistors with a multimeter? My solder joints look good, I have touched up a few.
EDIT: I am working on a REV D v1.11 build
With the attack cw to fully on I make the adjustments according to the hairball cal. guide, but I get no meter jump when the attack is switched off and no difference on my DMM reading.
Ive read that this version of the unit has very little possibility of wiring issues since the harnesses are premade and pretty dummy proof.
I did have a slight issue with a pad on the front of the board at Q3, the pad on the back was fine, could the copper pad on one side have caused the issue even if the pad on the back had a good joint?
Is there anyway to trouble shoot my transistors with a multimeter? My solder joints look good, I have touched up a few.
EDIT: I am working on a REV D v1.11 build
