Toshiba Chromebook 2 Screen backlight too dark and the bar is high

My Toshiba Chromebook 2 Screen backlight is too dark.

I have turned the brightness up.

I have plugged it into the tv and the laptop still works fine.

I have taken it to get looked at and they said that they tried a screen replacement and it didn't work.

I have seen videos of people fixing it and even read a guide on here about it.

My question is, Is it possible that something may have burned out on the motherboard? would that effect the screen in anyway? I would have thought if the mother board was damaged it would have not turned on or charge.

If anyone can help, I'd really appretiate it:)