Tv won't power up

@darrenphil96449 this "very faint blue screen for a second then turns off the blue screen" would mean that your backlight turns on as it should. That could mean that your display either does not turn on or that it does not get the signal to turn on.

Remove the back cover. Then verify your backlights turning on. Unplug you power cord, unplug your mainboard from the power board, plug your power cable back in. Your TV should now turn on with only the back lights showing. There are holes in the back of the screen through which you can see the lights turn on. Even so the backlight turns on briefly, it will turn back off if there are issues with the backlight strips. That will turn your TV off but should also generate a blink code on the power LED. If yours does not blink, it is possible that the error is with the panel or with the main board as well as the power board.

Take a pictures of all of your boards and post those with your question. That way we can see what you see. Check all of the ribbon cables and makes sure there are no tears, no corrosion, no frayed ends and that the cables are properly seated.

Adding images to an existing question