all off suddenly my picture went black but could hear it

Josephine Pagan in a darkened room and with the TV screen black but the sound still playing, shine a flashlight at an angle against the screen. If you can still make out shapes or similar, you know that your backlight is out. Possible the backlight strips. If you do not see anything with the flashlight then it is most likely your T-Con board. Remove the back cover and take some good pictures of your boards. Post those with your question so we can see what you see Adding images to an existing question

Of course you can also try a reset. Unplug everything that is plugged into your TV (BR/DVD, Game Console SAT or Cable box/ Speaker bar etc.). Unplug the TV. Hold the power button down for about a minute. Then connect a local video source, like a DVD/BR player to your TV. Plug your TV. Turn your TV on and see what happens. Let us know.