Debug: no distortion from Dist +

[rockhorst]

I decided to finish up a Distortion + board that had been lying around for a year. Surprise: it doesn't work the first time I fire it up . With both pots turned fully clockwise, I get a clean, unity gain signal with a slight loss of high end (could be cable capacitance). No distortion. So if anybody has any suggestions, please share.

The particulars:
Using this board/layout from Newtone, including the asym clipping diode D3.
I used a OPA134 opamp, which has a slightly different pinout than for instance a TL071, with pins 5 and 8 'swapped'. Since these pins are not used in the design, it shouldn't be a problem.

On 9.3V from a wallwart, without a guitar signal, all the diodes register 0V at both ends.

IC values:
IC1 = 9.3 V
IC2 = 4.7 V
IC3 = 4.1 V
IC4 = 0V
IC5 = 0 V
IC6 = 4.6 V
IC7 = 9.3 V
IC8 = 9.2 V

[slacker]

If it's passing signal but turning the gain pot does nothing then you've probably either got a short between pins 2 and 6 of the opamp or a break somewhere between pin 2 and ground, either of those things would basically make it into a buffer.
Also check the values of R3 and R4 if they were wrong that could give little or no gain.

[rockhorst]

Gotta love this place. R3 was the culprit.

NOW all that's left to be done is to see if we can actually make it sound GOOD

[Quackzed]

     ,---si'<---si<----,
----l--->si'--->si----l-----
for overdrive/dist vibe...
     ,---si'<---ge<---,
----l-------->si'------l-----
for heavier asym distortion...

the dist + doesn't get enough credit imho...
its a straight up clipping stage without alot of frills, but thats whats good about it in my book.