Here's some stuff you should try first: https
1 – Be sure the component you are using (Xbox, Cable, SAT, ROKU) is turned ON.
2 – Check to be sure all cable and cords are securely connected to the TV inputs and component outputs.
3 – Make sure you are on the correct input as some TV’s will show a black screen if there is nothing connected to that input.
4 – Unplug the input you are trying to use from the TV (such as an HDMI Cable) and plug it back in.
5 – Check for signs of damage on all cords and cables from the TV to all components.
6 – Make sure the TV is not in ENERGY SAVE MODE, press the button on the remote control to go back to normal mode.
7 – Unplug the TV for 10 minutes to see if there was a temporary one time issue with the TV.
8 – Disconnect the TV from power for 2 minutes, then when plugging it back in PRESS AND HOLD THE POWER BUTTON ON THE TV FOR 10 to 20 SECONDS to try and force the TV to reset.
9 – If after checking all these different issues, you may have a Faulty Power Supply Board, A Bad Capacitor on the Power Supply Board, Loose Wire Harness, or Loose Ribbon Connector in the TV itself.
10 – Most likely when a TV has the power light ON but NO PICTURE and NO SOUND, it is the Power Supply Board that has failed.