The M series from Vizio has a really good picture but the CPU burns very hot and can, after 4-7 years or so, unsolder itself. So the TV starts by being difficult to turn on and it gets worse until it just doesn't turn on at all. A tale tale sign is the white status light in the lower left hand corner will come on and then gradually fade away to nothing. I am not sure that is your problem but it is more common than a bad power supply. If it is, you need to repair the main board or get a used one somewhere with no guarantee that it is not just as old and also ready to crash.