I realize this is a PNxxf8500 thread, but I had the same symptoms as cardinal4 on a PN63c8000 with very low hours of usage. This was NOT a case of bad capacitors, but a bad transformer on the main power board. When I took the back off the TV and plugged it in, I could actually hear the sound of something frying/fizzing. Looking at one of the transformer from the underside after removing the board, I could see some burned connections. Not burned off, but certainly damaged. Simply a case of another bad/cheap part being used by Samsung, I suppose. Replaced the power board and all is well.