OK - it is most likely out of warranty. It could be the inverter board that runs the back-lite. There is a master and a slave. One one of those boards, usually they are on the right and left sides if you take the back cover off (unplug electric cord first) will have a chip in the middle that will have silver prongs except for a black one that means it is burnt out. The replacement board is about $50-60 compared to a new TV. It is a simple replacement if you are comfortable doing things like that. I can send you a link to a video that explains the fix, if you wish.