I have a Zenith Flat Screen TV. After the TV is on

To isolate the problem...you will need to replace the power board and see if it keeps on happening and then replace the Y-sustain board and see if it keeps happening.

It could be either of those; it could sure be other things too, but those two are the primary candidates.

Note: I do not have experience with your particular model; someone more specialized or who had come accross it before may know upfront which of the two is the more likely candidate.

If I were to take a pick I'd choose the Y-sustain first.

Unfortunately I don't think there's an easy and elegant way to determine which is it; you either have to know from experience or you just try and see.

Hope this helps. If it does, please rate it or comment - I need your feedback!