It could be a few things. But you can try checking and adjusting the for the correct voltages; there's three that need to be correct and are adjusted with pot's on the PSU board, they supply the PDP engine boards. I don't have the info right now on the lappy but a few 50" plasma's that i've worked on had the voltage settings displayed on labels inside the unit. This might fix the issue although if it's temporary then the problem is elsewhere.
Oh and while the cover is off check the PSU board for bad caps, I had to replace 9 on the PSU of the current TV i'm looking at, although this is less likely to be the problem.
If the voltages are correct, 190V, 5V, 18V, I think(?), then i'd suspect the 'Y' or 'Z' sustain boards.
I don't think it's the Main/AV Board or the Control Board basically cause these are pretty reliable parts of a plasma TV and i'll rule out the upper and lower 'Y' buffer boards cause the chances of both failing at the same time are low.
I'll be on the main rig later so i'll post up some pictures of the current set i'm looking at to help you out.
EDIT:
Does anyone know how to set the forum to automatically display the last post in a thread?
