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. This is actually the most common problem with this type of TV, I see it every day, it just happens - sometimes with new TVs and sometimes it takes many years for it to happen.

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.

If you want to attempt the repair yourself please let me know and I will get you the part number and a place you can purchase it from for what you need.

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

Thanks
Tim