Reset Macbook Pro LED backlight
Here is the magic key command to reset Macbook Pro Led Backlight:
You can use this key command to (temporary) fix the problem of dark bands showing on the screen. Note that the screen will go black, just press any key to wake it up again.
I had this problem, and it took me a while to find out I didn’t have to replace the led inverter board, but could just hit this key command every now and then when the problem’s there.
Here’s a link to the official Apple page.