I have a Westinghouse VR-3725 that does not turn on with the standby light always on. I took it apart and found that there is a capacitor on the main video board with a black smudge on the top of it. It appears to look like a burn spot but I am certain that it isn't a permanent marker like some capacitors get. There is no bulging or other spots on the capacitor and it looks like the same ones next to it minus the smudge.
It would make sense if the main video board is the culprit but I wanted to be sure that the capacitor is at fault.
Not coming out of standby can be either then Mainboard or the Power Supply, you can never just say it's always just one or the other with this. As far as the Cap, a black dot doesn't mean all that much normally they are bulging or leaking. The only way to check a Cap is to unsolder and pull one leg away from the Circuit and check with a Multimeter, the rating should be labeled on the side of the Cap.