water has penetrated the LED screen

alimosavi450 this will depend on where the water created short circuits. For now, do not turn your TV on. Unplug it and remove the back cover from it. Take a look at tall the boards. Check for corrosion and damaged components. Post some pictures of all of your boads, with your Question. Use this guide Adding images to an existing question for that. Also, let us know what happened the last time you ruend it in. If you had a white screen, the issue could very well be that the LCD driver board, which sits on the bottom of the LCD panel, has either shorted out or is corroded. We will need to see that board too. It is attached via some fine ribbon cables to the LCD panel and can't be remove. So be careful around that you do not tear those cables etc. For now, it could be any board that has failed. Most likely it's the driver board or the T-Con board. Missing VGL or VDD voltages on those boards can cause a white screen. Without seeing your boards and eventually having you check them, will only allow us to guess.