Chosen Solution
One normal day I turned on my Macbook and my screen was completely dark, as if it had given problems in the backlight. Today after some time with it turned off, I turned on HDMI and it worked on a second monitor When I unplugged the HDMI, the Macbook screen turned on again, but if I increase the brightness to a certain extent, the screen turns black again. What can it be?
Try zapping the PRAM. Restart holding down the par, command and option key. Let it tone three times then lift you fingers and allow it to boot and see if the problem persists. UPDATE There are several things to try as, listed on this Apple discussion: https://discussions.apple.com/thread/350…
