I just purchased a damaged second hand a-136 Waveshaper. Looking at the PCB I think the module has had it's power conection hooked up the wrong way around at some point in it's life. The chip (75H21EK LM324n) that is hooked up to the amp knob via a yellow wire has a black burn mark under it and on the reverse side the solder is slightly blackened, as is the PCB.

I guess the chip could be blown The rest of the module looks fine.

How it sounds All of the knobs still have an effect although the module only seems to produce sound in the negative range and the ext.level CV inputs don't seem to do anything. It only cost £20 and still produces some nasty sounds!

Any help would be great :)