“TV keeps shutting off and on then stays off. My TV is 15 months old. It shuts off and then comes back on. It does this about three times and then shuts off. When I turn it on it shuts off again. I unplugged it and pushed the power button for 30 seconds and it works for about a half an hour and shuts off again. Is there a way I can tell if there is a problem with the main board or the power board? Is there a way to run a test on it? Thanks”