Sounds like a failed or at least failing power supply / power board inside the TV. Unfortunately this is a very difficult repair, and unless you are an electrician I would not recommend attempting it. You will need to contact a local TV repair person in your area. If you think it may still be under warranty please contact the manufacturer to file an RMA. If you happened to purchase the TV with a major credit card (not a debit card) there is a good chance it may still be under the free extended warranty most credit cards place on electronics. Please contact your credit card company to inquire if they do this, and they will be able to file the claim and get you a refund for the TV.

So sorry that I don't have better news but it is definitely a power issue internally.

Thanks
Tim