Disconnect the power from the TV and then inspect the boards, especially the power board for any obvious damage such as heat stressed or burnt out components or blown or bulging capacitors.
Post some close up images of the boards, the power board in particular so that others can see and maybe spot something. Here’s how to do this. 기존 질문에 이미지 추가하기
Other things that you can try:
Disconnect the power from the TV, remove the back cover and then disconnect the cable that connects the power board to the mainboard. Reconnect the power to the TV and switch on the TV.
Be safety aware as there is potentially lethal voltage in the back of a TV so stay focussed on what you’re doing. Always turn off the power before working in the back of a TV and then turn it on again when you need to check what occurs and you are safely away from any harm
The TV screen’s backlights should come on and stay on as long as power is supplied to the TV. There will be no picture on the screen as the mainboard is disconnected.
If the TV backlights do come on, measure the voltages at the connector where the cable goes to the mainboard (cable should be removed from here before) and verify that their values are as shown printed on the board close by.
If the voltages are OK it may be a mainboard problem.
If you don’t know how to use a DMM especially when lethal voltage is present on the board, then leave it for the experts. It’s not worth endangering yourself
If the backlights don’t come on it may be a power board problem