Been working on this for a few days.

[pito]

-4V Leave as is for now.
check how the voltages are change on both sides R62, and how +93V is changing on the Q20 collector.

press GND buttons on A and B channels, what's is happening with dot when you rotate each of position potentiometers ?

[Mark-VA]

Thought I would back up and start with known problems. Reference voltage should be 210 but measured 256. Checked R23 and it was 27k ohms. Replaced with a 200 k but after installing I still get 27k. I missed something, there are a lot of components referencing to ground. But one thing for sure, even if I never repair the scope, I'll have plenty of good parts.