the power supply inside the tv, is what it sounds like to me. I fixed a 50 plasma about a year ago that all it needed was a 20 cent capacitor. but you might find the power supply for yours on ebay for kit 20 bucks or a used board about 50. this is not a for-sure fix, but if you can fix it saves you about $300+ just be careful when working on it you dont crack the screen.
the one I fixed was a first generation plasma flat screen tv and it price was about 10 grand. I love it it still works good and has a nice picture.I have the most expensive TV on the block ! it likes it's power though 500 watts .
So in summery, the two things I have found over the years in my "look what I found honey" tv projects is that the power supply has failed or the screen light driver needs to be replaced. in the last 30 years I have only purchased 2 new TV's and fixed and gave away to friends about a 100. and that was before I had internet and parts had to be hunted down by catalogs and phone,
SO go ahead and try fixing it, if you cant fix it Give it to your local TV repair shop for parts, he might help you out in the future if you need parts, to fix another stray you bring home ?
Jay... The Pool Pump Repair Guy in Longwood Florida 32750
on Feb 11, 2014