90 percent chance it is the electrolytic capacitors on the power supply board. Unplug the set and remove the back, find the main power cord receptical and follow the wires to the power supply board. The capacitors look like little beer cans with a flat aluminum surface on top. If any of them are domed up (not flat) or leaking they are bad (althought some can be out of limits without any physical symptoms). I buy mine in kits from lcdsolutions dot com, or a local electronics supply as radio shack doesn't have them all. Easy and cheap fix if you can do some basic soldering. Just youtube "tv capacitor replacement".