HP 8110A with faulty display GU 256 x 64

[Tracker]

Hello folks,
I have a faulty a HP 8110A 150 MHz Pulse generator.
But its display is blank, it appears someone attempted repair.

On the display board I can see the Power transistor and Ram chip were replaced.
I can measure +5 vcc on the main input.
It also generates -18v, +15v and +125v which all seem appropriate.
But the display docent show any sign of life.


No diagrams seem to be available.
Does anyone have knowledge of these displays, what should I be looking for to see if the actual display tube is faulty?

Thanks

[tagchen]

I have paper for HP 8114A 100V/2A and a defect 8114A, but display is working.
I can some measure for help?