Chosen Solution
Backlight comes on when disconnecting main power board. Is it the t con board or the other one? Or most likely the fuse ? Model #UN55F6400AF.
@benjer clarify the not coming on park. The only thing you know thus far is that the power board supplies power to the backlight LED’s. You need to check the voltages from the power board to the main board. Only if those voltages are correct can you essentially rule out the power board. Next suspects would be your main board or the T-con board (a failed t-con board can prevent your TV from turning on). Post some pictures of all of your boards etc., with your question. That way we can see what you see. Adding images to an existing question
