screen goes black and the sound is still on

@kphat verify that you have no image on all inputs. If it remains dark, unplug it and push the power button for about one minute, then plug it back in. See if that resets your TV.

If it remains dark, use a flashlight and angle it against the screen with the TV at a station where you can hear the sound See if you can make out shadows or shapes. If you do, then it is your backlight that has failed. If you do not see anything, unplug your set and remove the back. then visually check the boards for any obvious damage