I have a TN55x81. the picture will just stop working (goes black). I will shut it off for about 5 minutes and then it will work fine. Some times for 2-3 days and other times just 10-15 minutes. Any ideas??

Intermittent problems on this type of TV are often because of cracked solder joints on the circuit board. They can be hard to see. When the TV gets warm, parts on the board expand and move by tiny amounts, sometimes with the right amount of expansion or vibration from the speakers, the broken solder joint looses connection and the unit shuts down. When things cool-off, the contact can be made again all by itself and everything fine until it happens again. Given the random nature of your problem, this is a suspected problem. Often it is the solder around the lead of a large component which is mounted to a heatsink.