The screen began to show dark, because of what?

Question

Windows

Good afternoon, I had an unusual case with a computer. Yesterday, at night, the screen became dark for no reason at all (the brightness of the screen somewhere from 100% dropped to 5%), but looking into the screen settings, I could barely see how everything was in its place. I thought the video card was burned out. I pulled out the video card, put it on a standard video card. Still a dark screen. Pulled the battery out of the mat. boards, I think maybe something with the BIOS, yeah, I turn on the computer, it shows me like press F1 and F2, well, as usual, but without having time to press the computer beeps and seems to skip this steps. In general, the BIOS guys can’t be viewed in any way, the BIOS starts literally for 1-2 seconds. and changed the cable, and disconnected the hard DVD, still the same garbage.
But one more not unimportant moment, if you turn on the computer, then it works, the sounds go on, if you close your eyes directly with the screen, you can see something. Maybe someone had this? Tell me
YES I forgot to add it, when you turn it on everything is displayed well, after Windows loads everything, the screen is dark.

Answer 1

the backlight of the matrix died in the monitor