Give the vents and such a going over with canned air. Try a small fan blowing at the back of the unit.
I Have a un46eh6000f TV that will not power on sometimes. If you leave it unplugged for an hour and plug it in the ir red light will come on and the TV will power on with the remote. Unplug and then plug the TV in and the ir red light briefly flashes and goes out and the TV will not power on. As you unplug the TV the ir red light will briefly come on. you say well just leave it plugged in, but at some point the TV quits working without unplugging it. could it be the ir/remote sensor board or the main board?

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