I'm back finally to work on this. I got a refurbished CCPU from @Matty-t (TY!!) and same issue. Going to revisit this thread, and re-read the faq then get to work.
But at least, that leads me to believe the problem is on the monitor (deflection board, HV Unit, or tube)
My probe here is at the yellow wire by the brightness pot. This is saying that at 50v/div I have a reading at the highest of 93.4, and the lowest at 42ish? So that's about perfect, in attract mode, with the drawing of the hi and lo intensity vectors.
I am hoping, but not going to hold my breath, that the game board is ok (obviously) and the monitor board is ok also. Which leaves the HV unit or the tube, or am I thinking about this wrong?
Years ago I had an asteroids monitor with a bright dot in the middle of the screen also, and it was fixed with a rejuvenator.