Television and Home Theater

ok i have a 56" samsung rear projection HDTV. Model No. PCN5425RX/XAA. The problem is that the power turns on and the timer light blinks but there is no audio or video. I called a samsung authorized repair guy. The guy was chinese and basically came for 10 mins told me there was something wrong with the power circuit board and didnt tell me wut part was broken and took $65 from me for the estimate and said it was gonna cost $450 to fix the tv. I need some help maybe some1 knows wut kind of problems occur in samsng tv's. any adive will be appreciated

I don't know what to do. My 20" Sharp LCD flatpanel TV shut off one day while I was watching it.  I couldn't get it to power back up.  A few days later I plugged it back in and it powered up and lasted a few days.  I can't get it going again.  I don't know what to do.  I know the AC power supply is working fine because I had it checked.  I also tried plugging it in several different outlets and that didn't work.  Can anyone shed some light on the possible problem?

my 21 inch magnavox turned on in the middle of the night, This set is 2 months old have had no trouble before this. Just wondering if something is going bad while it is still in warrenty. thanks charlie32