Screen went blank sound still

Before diving into the TV, make a simple check.
Take a flash light and shine close up onto the TV while it is running, if you can see picture then that tells you the inverter board is bad. If your backlight comes on and you can't see any picture then your video board has failed. If neither your backlight or video work then your power supply isn't feeding the proper voltages to those boards.
Since you have sound it most likely isn't the power supply, although stranger things have happened. Check the power supply last in this case.
From these checks you can isolate your problem and then dive into the TV.