Lets try this again. Cmon, google, post!

I have a little 4.5" monochrome CRT Display in a deposition controller I have. It runs on 12v and uses NTSC. Pretty generic.

Its Dead.

I have high voltage, getting about 260v to the screen grid, filament is glowing. Scope shows activity on horizontal and vertical deflection. I can see the amplified video signal at the cathode on the tube.

What am I missing? Not enough HV? Poisoned cathode?

Checked the video output with another display and the video is good. If all else fails I will just run an external display.