In my case, it was a bad LED or LED strip. The TV is going into a mode that shuts everything off when the LEDs fail. The ones in the TV I salvaged were five years old and were dim or burned out.
You can get the parts at a site like ShopJimmy.com for the make and model of the TV. I bought a full replacement set for $60, double sided tape, and shipping, for a total of $75 spent. However, it’s a time consuming process to repair. I spent four hours just getting the TV apart and putting the new strips in, and in the correct order. There are also a lot of screws holding everything together, and holding the strips down to the back of the TV. I’m on the second afternoon of trying to put it all back together.
If you decide to tackle this repair, you should also wear nitrile gloves. Fingerprints on the diffusing layers will ruin them. There are at least four, and they can’t get out of order. You also don’t want to bend them. You also run the risk of cracking the LCD screen if you don’t support it properly when removing it.
I honestly wouldn’t do this again. It’s a TV I salvaged though, and I figured I’d give it a shot.