Akai pdp5016h 50 inch

Thats a real tough call on your problem as the set acts like its working normal and then gives out. It could be any number of things, but mostlikely somthing is drawing too much power causing a protection fault hence the power off. These types of problems are very hard to diagnose as the stuff your looking at looks good, its not until it warms up (even being a few seconds or so) that they go bad. You can allways put a meter on the VA and VS to see if there is a flucuation in voltage or even a spike and that could tell you possibly which board is the culpret, but the best is to replace and not repair as switching supplys can be a pain.