The screen is black and no sound

@saiddahroug you have not told us what you have checked. The no video issue can be related to a bad backlight inverter circuitry. A simple check for that would be to darken the room and turn the TV on. Then use a flashlight and angle the light at the screen on different areas. you might make out some shadows or see s slight grey color.

After that, remove the back cover and take a look at all the boards to check for any obviously missing or damaged looking components. Take a couple of well focused pictures of the boards and post this with your Question. That way we can see what you see.

You will need a voltmeter to check a few things once we can see your boards. We need to determine if your main board tells your power board to turn certain circuits on. For now the prime suspects (in order of possibility ;-) are backlight strips. main board, power board, T-con board (if separate from main board) and the panel.

Adding images to an existing question