Hi :-)

First disconnect all input connections too the TV, then unplug the TV for an hour. After an hour plug the TV in, wait for about 10 seconds, then press the power button for 2 seconds. Does the TV come on? if yes then there's a reset problem on the interface board may be caused by bad passive or linear components around the logic section. If the tv still has no video/audio after an hour then the interface board has a DC switching failure and/or the power supply has DC output problem. Either case the TV needs some servicing, if you have an electronics background and some test equipment I'll show you how to fix this. Or have your local TV shop fix it for you.

Please let me know if this helps you some:-)