So sorry that you have encountered such an issue. But there are many methods that you can try.
1. Check that POWER SAVER/ENERGY SAVE MODE is set to OFF.
2. Turn off SLEEP TIMER.
3. Check that STORE MODE/DEMO MODE is not turned ON.
4. Use a different HDMI port for the component you are using.
5. Connect a different component to the TV or the same component to a another TV.
6. Turn the component (Ex. Blu-Ray/CABLE BOX) you are using OFF and then back ON.
7. Hidden fault within HDMI cable – Replace with new cable.
8. Unplug the TV for 5 minutes to attempt a reset.
9. Factory reset the TV to resolve the issue.
10. Download new software/firmware update.
In many instances this issue is caused by a bad driver board, LEDs, or possibly a faulty T-Con board in the TV. It may also be an issue with bulging capacitors or a loose cable or ribbon connector. You will need to take the TV apart and diagnose the issue. We do not recommend you do the repair yourself unless you know exactly what you are doing.
If the issue of the TV showing a black screen is still not resolved, you can try to claim warranty service or fix the TV yourself.