The motherboard is working fine 8 years since last testing but more work remains to be done.
Ian P says:
"...The 128 uses a pair of discrete transistors for it's vertical driver.
If one of the caps in that circuit has failed/is failing, I'm guessing
it's C6. Or it's either C5 or C11. While you're in there,
be sure to resolder the yoke connector, it's a very common point for
cold solder joints (will cause total loss of deflection)
If it's intermittent (i.e., you can hit it and it pops back), it's
probably just a bad solder joint. Resolder Q1 and Q2, and nearby
components, as well as the yoke connector. If it starts out bad and
gets better as it heats up, or starts good and gets worse as it heats
up, and hitting it doesn't affect it, then, it's definitely one of