I didn't think of contamination. It's interesting that the channels that are the worst are the ones on the ends, where contamination might be more significant. Contamination makes sense because of the fact that they channels are a bit flaky in their behavior. To be honest, I didn't see anything on the PCB. There was some dust on the keyboard and under the keyboard, but I didn't see much on the PCB... I'll definitely take a can of air the next time.

I'm back home now, but we'll schedule another visit in the future and we'll try again.

I bought a full set of replacement caps for the oscillators, but I didn't know how physically small they were and the ones I bought (in order to get polystyrene) were rated at 100 and 400 volts so they are kinda large. I'm not sure they will fit well or even at all. I'm going to have to go back to the drawing board on those and see if I can find a better source. Robert suggested Silver Mica, do you agree they will work as well, or should I stick with polystyrene?

Thanks for confirming that the non-linearity we are seeing is not normal. We did mess with the sliders for PCM adjust, and to be honest, in retrospect, they might not have been working very well. We'll definitely do the slow slide ADC test next time.

We spent a great deal of time learning how to test various oscillator features. Including turning off one or the other (or both) oscillators which was very strange. The best way to disable them was to load A1 (which contained the test sawtooth) and then set them both to pulse with the sliders set to the middle. That's not what the manual said, it said you had to slide the sliders to the edges to disable the channels. I thought it was odd at the time. Do you know if that's the expected behavior?

It will be some time before we get back to it. We'll be sure to post updates after we come up with a plan and get together again to try to get it to behave itself.

We played with some of the features and even though it was out of tune on the low and high ends, it was really cool to see what it could do.