bad inputs?

[jhall]

I have a Hitachi 61SDX01B and have been having some issues lately. With either the cable set top box or my xbox 360 the tv will display fine for a few minutes then the screen just goes blank. I hit the menu key and the menu displays fine. I removed the front and back covers and dusted everything off. I then removed the card that the inputs go into and dusted it then reseating it. The tv still does the same thing. The tv does this with all inputs 480i -1080i. I spoke with Hitachi and the tech said they have two bulletins out on this issue ptv00-17 ptv01-12a. I replaced the suggested capacitors but still have the same problem. I also removed the high voltage unit for the crts and re soldered the connections with a high silver content solder.... If anyone knows what is causing this I would really appreciate it. Thanks

[torbjorn]

Check out more caryfully what happens when the screen goes blank.
Is there still high voltage for the CRTs?
Are the CRT heaters still lit?
Are all other major supply voltages still there?
Seems the horizontal and vertical deflection circuitry to work? Else, probably some protection circuit blanks the screen to prevent burning-in.
Can you get a raster by turning up the screen voltage? (but don't touch that control unless you know from the service manual how to reset it).