I've got a (apparently roughly) used GBA SP with a screen light that only wants to work sometimes. The screen itself looks fine (it's not obviously broken in any way, and it looks just fine without the light), but the light only comes on when the screen is tilted all the way back. Also, there appears to be some sort of ding in the screen cover, and when the light is on it appears darker in that spot.
I'm hoping (and I rather suspect) that the dark spot is not actually a screen problem, as the screen does look fine when the light isn't on.
Anyone have any ideas?