My TV turns on for a second and then turn off what's wrong?

Carlos Mejia, The very first thing to do is to turn off the light in the room and with a flashlight, shine it at an angle on the screen. If you see shapes and shadows that match what you should be seeing, you have a backlight problem. This isn’t very likely, since you say audio also disappears.

Unplug the TV from the power outlet and unplug any sources. Press and hold the power button for a good 15 seconds, to drain residual power from capacitors. Plug the TV back in to power and plug in one source. Check if situation has changed.

If still same problem, unplug power again and hold the power for 15 seconds. Then take the back of your TV so you can check the boards. Careful as there are some high voltage capacitors in there that could still hold a charge. Inspect boards for obvious damage, like burn marks, blown components, etc. Take some good quality and up close pictures, then update your question with those. Adding images to existing questions. If we can see what you see, we might be able to more accurately identify issues.