Removing the mica cap had no obvious effect so I tried replacing the HV cap. All I had on hand was 1000pF rather than 500pF like the original. That seemed to help a little and I'm up to 5.5 kV now.
I figure that should be enough to see some glow on the CRT. Then I remembered that the ion trap electromagnet would mess up these test CRTs and removed it from the neck.
Still nothing until I rotated the focus control fully CCW. Finally, a trace!
Swapping out the 6J5 vertical oscillator tube got me some height.
Finally, I feed in a signal and after a lot of tweaking got stable image and decent sound
