Sorry to hear about your problem. I will be happy to help. Your Tv has a failure inside for which parts will need to be replaced. At this point the Tv needs to be opened up and checked inside. A local repair shop will charge $350-$500 total to fix your Tv. You can save a lot by trying to repair it yourself and we can help with that but just be aware that it all depends on your ability to follow instructions precisely, use hand tools, meters, and do soldering on circuit boards. Also working on Plasma Tv's is very complicated and dangerous, it involves working near live high voltage that can seriously shock you. To get started just reply here when you have the full model number of the Tv and back off the Tv with a meter ready.
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Thanks. The Tv still needs to be opened up and checked. It could be something small like capacitors on the power supply (soldering required) or it could be an entire circuit board. Bad capacitors can sometimes be spotted visually. If you don't see any bad capacitors then figuring out which board is bad can be very difficult and dangerous if you don't know what you're doing. Repair shops usually charge a non-refundable $100 diagnostic fee and then if you decide you want to have the part(s) replaced they roll that into the total bill which can be $350-$500 (or more depending).