Please diagnose my farty Easy Vibe

[pbrommer]

Hey guys-
I've got an Easy Vibe that's working, sort of. I can hear the effect but it's not real pronounced. Also, it's horribly horribly farty.
Here's the breakdown What To Do ...!

Here is the checklist to fill out:
1.What does it do, not do, and sound like? Can hear the effect, but sounds farty. TIcks with the LFO when the pot is turned. Likes to pick up RF frequency and sometimes sounds like a wierd alien theremin
2.Name of the circuit = EasyVibe by John Hollis
3.Source of the circuit (URL of schematic or project) = http://www.hollis.co.uk/john/easyvibe.jpg
Layout: http://www.geofex.com/PCB_layouts/Layouts/easyvibe.pdf
4.Any modifications to the circuit? N
5.Any parts substitutions? N
6.Positive ground to negative ground conversion?N
7. Voltage at 8.31 (yes, I know, but this thing eats batteries for breakfast)

IC1
1 3.53V
2 3.57V
3 1.76V
4 0.00V
5 3.56V
6 3.50V
7 3.60V
8 8.31V

IC2
1 3.43-3.47V
2 3.55V
3 3.55V
4 0.00V
5 3.49V
6 3.55V
7 3.46V
8 8.31V

IC3
1 3.53V
2 3.53V
3 3.51V
4 0.00V
5 3.51V
6 3.31V
7 3.23V
8 8.31V

IC4
1 3.53V
2 3.54V
3 3.50V
4 0.00V
5 3.52V
6 3.15V
7 3.10V
8 8.31V

I have good flashing LEDs signifying something's working, but just need to find this circuit flatulence. Thanks guys for the help. I really do appreciate it (even though I can't show it on the internet). 

[R.G.]

What layout are you using? I can't relate your U-numbers to the schematic?

[pbrommer]

Oh carp!.

Sorry R.G. I'm using your PCB layout. My bad. Will edit.

Patrick

[R.G.]

No problem, just couldn't relate. I'm guessing that your IC numbers are correct, the U numbers are not really all 1.

hmmm...

It's passing odd that you measure 1.76V on the + input of U1 but the output is at 3.5V. I suspect that is because we're using 10M bias resistors and the meter itself loads down the bias resistor. Could be a bum input cap, but likely it's the 10M resistor.

There is nothing that really stands out, unfortunately. The phase stage voltages on IC3 and IC4 seem odd. They're lower than you'd think offse voltages would cause. The reference voltage is about 3.55V, and you'd think that the outputs of all the linear opamps would be within +/-10mv of that. They generally are except for the B sides of IC3 and IC4. It's almost like the + inputs are following the prevous output but not the reference voltage.

Can you run a quick measure on the resistor values on those sections?

[pbrommer]

Yeah. Let me check them. I must add I used 2 5.1M resistors in series to equal the 10M  Sorry. Also, it's a little difficult to measure those voltages as the circuit was chewing through the battery (went from 8.31V to 7.5V by the time I finished in 2 minutes).

R1 (leftmost at top) reads at 10.15M and R2 (next resistor at top left) is about 3.52M (but there's the 100k attached in there). I may pull that pair. The cap reads right at 12nF. So, I don't think that's a big problem (can always change that). All LED/LDRs are heat shrunk together. Maybe there's some gremlins in there. You don't think it's a bad opamp or an incorrect one? Pinouts are correct, etc. Gosh.

[pbrommer]

I got it figured out.

I think I had some wiring gremilins. I used some wire pulled from a printer, and it must not have been top quality. I switched it out with SmallBear's pretinned wire: fired up and sounded beautiful. Nice warbly univibe-ish sound..... I like it!

Thanks for your help R.G. and a awesome layout. Again, thanks.

Patrick