Ok. Finally had a chance to pop the lid off this thing and get some probes on it.
1: The keyboard circuit works.
2: The oscillators appear to not work.
3: This could be because I think something flaked out on the power supply while I was trying to get at the oscillator boards. Some of the voltages are wrong now.
I’ve decided to pull the whole thing apart, clean it up and plug-ify each module – it’s way too hard to get at anything, and there’s cruft everywhere.