IC1 & 2 are what are known as transconductance amplifiers and a discussion of their behavior on here would probably count as a cruel and unusual punishment!
BTW the LM13700 is a slightly more modern replacement for the 13600.
It's interesting that you get nothing on the last stage. It suggests that chip is at fault. However, before accusing it can you check that there is -12V supply on the bottom of that 10k resistor (the other end of which is on pin 9).
Also it's not too clear from the drawing which pin is which. I'm assuming that pin 9 is the one that goes to the LM3080.
In any case, it's clear that you have more than one fault (possibly as a result of those plugs having been in the wrong way round) so it might take a while to get everything sorted.
I deliberately didn't mention the waveshaping section as I wanted to keep to tracing the most direct line until things were a bit clearer.
If you've got some 3080s that could be very helpful
Hmmm, I'm getting more and more suspicious of that -12V generally - could answer a lot of questions.
It wasn't me!
(Well, actually, it probably was)
Edited by Folderol (17/03/12 09:21 PM)