Chosen Solution
My Sharp LC-50LBU591U won’t turn on and is showing no standby light so I suspect something is wrong with the power supply. How do I check if it’s getting power though? I have a picture. The AC input is in the bottom left of the power board.
Ok so on the bottom right you have a bridge rectifier. The center pins should have access line voltage and the outer pins should have 1.4x DC line voltage. If there’s nothing on the rectifier then find the burnt fuse. It looks like the board has multiple switch mode power supplies that are “low component count" alias cheap as possible. Difficult to diagnose, especially without a schematic or service manual. A factory tech would either fix it in 15 minutes or change boards when 15 minutes ran out.