I'm sorry to hear that you're having problems with your set.
Our support line at 800-SAMSUNG can set up a ticket to see if it's worth fixing. The best determination of cost analysis is best done by you.
I have a TXM2798HF TV. It is 5 years old and just started to turn itself off. The screen goes to a single line running from top to bottome and then off. The red light comes on after about 5 seconds and blinks several times and then goes to a solid red indicating stand by. I think it may be a power supply problem.
Is it worth fixing?