[vtech]

Sounds like a thermal issue, perhaps the capacitor(s) in the vertical circuit? Using a can of freeze spray can be handy in pinpointing the culprit.

[old guy arcade]

I am trying to fix a monitor problem on a Nintendo early 1980's donkey kong cocktail table. The model is tkg3-tbl. I have the original manual and wiring diagrams. I need a schematic of the monitor and the video boards to find out what components are the cause of an intermittent video failure. The system works perfect for 30 to 60 minutes and then the vertical hold goes out. This old guy could sure use some help with this old monitor. Thanks