Looking for CRT monitor advice GDM-FW900

[andym8]

Greetings, I have come from Dave's excellent youtube channel.

I'm hoping to get some information on the workings of my Sun GDM-FW9010 (essentially the same as the more common FW900) and possibly some repair tips.
The service manual is available here for those interested.
I'm aware of the dangers messing with CRTs, please preach of them elsewhere.

A little background on it:
Currently it does absolutely nothing when powered on.

However, originally it would work fine for a period of time but then the screen would go blank. No errors would show and it appeared to continue running as normal albeit without the picture.
I measured the voltages from the outputs on the power supply board, G, and found the heater supply falling off after some time. From this I assumed the tube was ok and the problem was on the G board?

That's when this tale takes a turn for the worse. Poking around trying to measure voltages I shorted some part of the G board with one of the test leads, I forget where, it was possibly one of the big regulators (it was years ago when I did this), it was certainly in that area anyway.

What I would like to know:
What parameters control the main power on of the G board? I had assumed IC001 on the N board had ultimate control, but what does it look for inorder to activate it? Should only the 5v standby rail be available otherwise?


Many Thanks for any help,  Andy.