My 50 inch plasma hitachi went black while watching it and now all i have is a blue blinking light (3X's then 5 seconds and then again the blue light) no sound, no picture.

For more info on this set please check out http://www.hometheatershack.com/forums/hitachi/38229-hitachi-p50h401-led-flashes-3-times.html
if will tell you how to trouble shoot this tv. these tv's are known for two caps in the power supply to go bad and they need replaced then you have to test the sdr boards if they are bad you need replacement boards or you can send them off to be repaired. the link for the repair guy is on the page. this guy also sells the repair on ebay but if you contact him directly i beleave the price is lower. just tell him you were send over by home theater shack.

Tries to tv unplug,replug an hour later let the tv reset itself.See,if it work.Not the power supply board is dead.That the board,where the power a/c cord plug into it.Tries websites like Shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.