Cant find the short - JMK PCB Engineer's Thumb (no sound)

[jfrabat]

Hi, guys.  Need some help.  I just populated a JMK PCB for the Engineer's Thumb (already have one with the 5 knobs version working, really liked it, and decided to build a 2 knob version for my acoustic setup), but I am getting no sound. 

Diagram and instructions are here.

Issue is I get no sound at all when I activate the switch (like when it shorts; nothing is coming out).  I am repurposing an old 5 effect pedal  I had for acoustic duties (used to be overdrive, Rat, booster, Little Angel Chorus, Deep Blue Delay with Tap Tempo; will now be Engineer's Thumb, Blue Warble, Booster, Little Angel Chorus and Deep Blue Delay with Tap Tempo - Booster may be replaced later for a Reverb), so I took out the first overdrive (it was also a 2 knob design, so other than using cables for the 2nd pot to fit in the holes, the compressor fits fine in the space).  Stomp switch is the same one I already had, and 9V and GND also I am re-using what the overdrive was already using, so I know the switch (has not been touched) and 9V source are not the issue.

Everything used is as per spec except for using a TL084 instead of a TL074 (should be the same, except a bit more noise until I get TL074 to replace it).  Only hillbilly McGiver things I did was (1) use 3 resistors in series (4.7M+4.7M+470K) because I did not have 10M resistors, but I measured that and it was 10.08M, hence I am confident that is not the root cause either; and (2) wire the 2nd PCB off board so that I could get the pots in the holes already drilled in the box.





I checked the connections that appear to be contacting (above image) with the voltmeter, but the only ones with continuity are meant to have it (like R2 to GND).

Here are my voltage readings so far:

Q1: 2N3906
E: 4.55V
B: 4.25~4.75V
C: 0V

IC1: TL084 used (supposed to be TL074)
1: 4.56V
2: 4.56V
3: 4.14V
4: 9.09V
5: 4.14V
6: 4.56V
7: 4.56V
8: 4.08~4.74V
9: 4.56V
10: 4.30V
11: 0V
12: 4.34V
13: 4.56V
14: 4.56V

IC2: CA3080 (last one I had!)
1: 19.8~35.5mV
2: 4.56V
3: 4.56V
4: 0
5: 0.56V
6: 4.56V
7: 9.09V
8: 39~44mV

Any ideas?

[MikeA]

Where does your DC ground connect to the PCB?  I see a black wire on the "G" terminal, presumably going to lug 5 of the foot switch, but shouldn't there be a DC ground lead on one of the "-" terminals beside the "+" 9V terminal at the top of the PCB?

[merlinb]

I did was (1) use 3 resistors in series (4.7M+4.7M+470K) because I did not have 10M resistors,

It doesn't need to be 10M, just use 4.7M, it makes things neater and simpler.

[jfrabat]

Where does your DC ground connect to the PCB?  I see a black wire on the "G" terminal, presumably going to lug 5 of the foot switch, but shouldn't there be a DC ground lead on one of the "-" terminals beside the "+" 9V terminal at the top of the PCB?

Not on this pedal, no.  All the grounds in the pedal (stomp switches, boards, plugs) go to a star ground.

I did was (1) use 3 resistors in series (4.7M+4.7M+470K) because I did not have 10M resistors,

It doesn't need to be 10M, just use 4.7M, it makes things neater and simpler.

Ah, thanks!  Just took out my hillbilly 10M and changed it to a 4.7M. 

While at it, I decided to re-solder all the components, taking special attention to cut and severe any possible shorts.  I cannot say I now know where the short was (was it the 3 resistors touching something?  Or was it a solder bridge somewhere?  God only knows!), but what I CAN say is that I found it and it is not working!  On to the Blue Warbler now!