Taqueria Overdrive weak signal

F

fav13andacdc

Member
Hello,

I'm having some trouble with my taqueria build. When the pedal is engaged, the signal is very weak. With all 3 knobs turned up to the max, the signal is barely at unity gain. All 3 knobs are reactive, though. At 50%, the signal is extremely weak, very much a cut. What are some causes of a weak output signal? What other troubleshooting measures can I try? Thank you! Posting some voltages below:

Trimmers 1A-3A
9.46, 9.50, and 9.51 respectively

Trimmers 1B-3B
7.43, 9.45, 1.65 respectively (I am unable to go lower than 1.65 on 3B.)

IC pin voltages
1 - 9.03
2 - 4.65
3 - 0
4 - .13
5 - 0.13
6 - 4.22
7 - 5.72
8 - 9.04

D102 - 17.66 IMG_8887.jpeg
 
Sort by date Sort by votes
Question, can Trimmer 3B go to 0V? I can't turn it below 1.43v. I reflowed all of the ground joints and that was the new minimum. I'm also attempting to use Gemini with a wary eye on the side trying to solve this.
 
Upvote 0 Downvote
Update for those of the future researching a weak output signal: Found a short. The output wire is grounding out. I think it's at the footswitch based on my multimeter. May be some solder connecting lugs 5, 7, and maybe 8 underneath the breakout board. Will update when I can get it undone.

That would explain why it works fine in bypass.
 
Upvote 0 Downvote
Are you using sockets on the 201s? May have a bad connection. Press and jiggle with a looper going.
If you have an audio probe, probe pin 1/Drain/left and 3/Gate/right of each 201. 1 should be louder than 3.
 
Upvote 0 Downvote
jwin615 said:
Are you using sockets on the 201s? May have a bad connection. Press and jiggle with a looper going.
If you have an audio probe, probe pin 1/Drain/left and 3/Gate/right of each 201. 1 should be louder than 3.
Click to expand...
Thanks for the reply. I’m using presoldered SMD J201s from PedalPCB soldered in with electrolytic leg clippings. I will probably be using sockets on new builds, though!

I don’t have an audio probe but I’ll try rigging one up.
 
Upvote 0 Downvote
fav13andacdc said:
Thanks for the reply. I’m using presoldered SMD J201s from PedalPCB soldered in with electrolytic leg clippings. I will probably be using sockets on new builds, though!

I don’t have an audio probe but I’ll try rigging one up.
Click to expand...
I think where @jwin615 was pointing is that sockets are sometimes a connectivity issue..... Sometimes they are not a good idea... for jfets I normally solder them in as you have done... for fuzz circuits and germanium trannies I will socket... My $.02
 
Upvote 0 Downvote
swelchy said:
I think where @jwin615 was pointing is that sockets are sometimes a connectivity issue..... Sometimes they are not a good idea... for jfets I normally solder them in as you have done... for fuzz circuits and germanium trannies I will socket... My $.02
Click to expand...
Thanks for the further insight. At this point I’ve desoldered a couple of them from the PCB and I am rigging up a JFET tester (https://www.runoffgroove.com/fetzervalve.html) to try and see what else I can find out before I move on to the next possibility. If they’re dead that makes this an easy fix.
 
Upvote 0 Downvote
J201s are notoriously difficult. Triple check all the biases for each transistor, as it can get confusing due to the bias switch. This is not a quiet pedal, and unity gain is on the bottom third of the volume pot usually. It looks like all values are correct at first glance, but I might be missing something. You can also check to see if you accidentally swapped the volume and drive pots, (A50k vs A500k) and have the A500k in the volume spot. Even still, with the volume knob maxed at zero resistance, this thing would be screaming.

The most likely culprit is one of the J201s, although if the bias voltage is getting within range, maybe not. Could be a short on the underside of the board (pics might be helpful there). An audio probe is your friend here though, and will help you pinpoint exactly where the volume drop off is.
 
Upvote 0 Downvote
Thanks for the reply Lytt. Running a test on desoldered JFETs Q2 and Q3 yielded the following results, in no particular order, mainly because I forgot which one was which:

.022v Idss side (0.22 mA)
.435v Vp side (-.435 Vp)

.034v Idss side (0.34 mA)
.539v Vp side (-.539 Vp)

Seems to be in spec, right? At the very least, not dead.

Just triple-checked the pots, and they are in the right spots. At this point, I'm rigging up an audio probe, which will take me a minute to get the parts together. This is turning into quite the educational experience!
 
Upvote 0 Downvote
I would definitely audio probe this one. Watch a vid on how to make one. Basically you use another audio jack that connects to the input of your guitar amp and on the other end is a wire with a bare lead on the end that you insert into the circuit along the audio path starting from the input of the circuit. Play thru the pedal with your guitar or a looper pedal etc. You're looking for the exact point the signal drops out, then you've found the component you need to focus on
 
Upvote 0 Downvote
You must log in or register to reply here.
Back
Top