Hello, I'm Shahid. Sorry to hear that you're having trouble with this but I'll do my best to help.
1- Could you please get me the model number written on back of TV?2- What video devices/ sources (such as cable box DVD player etc) are connected to TV and does the problem occur on all video input sources?
3- Does screen glow/ show backlight when power On the TV?
I understand, please shine a good flashlight on TV screen bit closely while having channel sound, do you observe any dim/ faint image inside screen with help of flashlight?
No problem, turn On the TV, press Menu button and shine the light on area where you usually get menu graphics screen.
Do you get any thing there?
OK, it seems main board internal failure that provide video data to screen and also controls backlight system in TV to lit the screen. I am really sorry about this and you are going to have to return the TV to have it replaced. It will be covered by the warranty if this has not expired, and the replacement will be done at no cost to you. If TV is out of warranty then main board replacement should be done by qualified TV tech to avoid any further damage to TV.
I'm sorry there is no easy or quick fix for this problem and it is definitely hardware failure that needs defective board replacement to resolve the issue. I trust my input will help you out to make decision about this TV repair or invest that money on new replacement TV. I hope these info will help. If you have any additional questions, feel free to ask. If you're satisfied, please rate me a 5-star at the top of your page. Thank you.
No, you would need to take it in local TV repair shop for main board replacement.
I wish if it was not hardware related failure that needs real hands on TV to replace the bad board in TV. I diagnosed the problem and gave you required info that you will get from TV repair shop after paying up front good money.
Rating my service is appreciation if you feel I help you out.