Unplug the tv for 5 minutes, then try this. Keep holding the VOL+ and CH- buttons down while you plug the tv cord back into the wall ac outlet till you get sound and picture for a second or two. You should be able to turn the tv on and off with the power button now. Next turn the power button off and unplug the tv for a few seconds and then plug it back in and turn the power button back on. Watch the screen and see if the sound and picture comes on, best to check in a dark room to see better, if sound stays on and picture comes on a few seconds and back off you have a bad CCFL backlight lamp in the LCD panel. This tv hads (10) CCFL lamps part # RLMPLA029WJN1 cost $15.93 at www.partstore.com
or $19.49 at www.encompassparts.com
in it and if one is burned out it will not let the tv picture be powered on till it is replaced. To check and replace the CCFL lamp you will have to unplug the ac cord from the tv back and remove 10 screws holding the back on. With back removed unplug the wire plug on the power button circuit at top left side of the black LCD screen trim, remove 4 screws holding the top of black trim, lay speakers off it, and release trim clips, (4) at top and (2) at bottom with a flat screw driver, and lower the trim to unclip the LED circuit board at bottom left side on the trim. With trim removed, at top of LCD panel remove the (2) PC ribbon wire clips with thumb nail by lifting up on it to release the flat PC ribbon wire. Lay the tv back on a soft pillow with screen up, and look on the LCD panel front for and remove the (10) silver screws 1/2" long with an arrow mark beside them. Do not remove any gold colored screws or any without marks. The LCD panel screen can now be lifted off, lift the backlight plastic thin sheeting and thick sheet off to see the CCFL lamps. Plug the ac cord back into the power supply inverter circuit board and plug the power button plug wire back in its circuit board on the LCD black trim panel, and power the tv on while looking at the CCFL lamps. If the lamp is dim or burned out, take the (2) white plastic covers off the ends of the lamps with a flat screw driver and unclip the lamp to replace it, Check the lamp socket part # QSOCFA003WJZZ by putting a good lamp in it and if it lights up the sockets are good and the bad lamp was the problem. If all the CCFL lamps do not light up, unclip the top lamps and move them to differant sockets to the center and the center lamps to the top, if the lamps do not light up, then it is a bad power supply inverter circuit board the ac cord plugs into, part # RUNTKA448WJQZ , cost about $160.00 for new one or less if you buy a used one on www.ebay.com
, replace it and the tv should work ok then.