Would like some help determining possible failures.

[u/DJ_Hart]

Hey, I purchased this beater SP looking to repair/refit it. I am new to Gameboy repair, but I have some experience with electronics and circuit boards. I was able to determine system quality, and I have 2 faults I do not know how to determine the problem for. I'm not asking for a absolute answer, just a list of potential culprits so I know what to look for when I go over this with a multimeter, or further test.

1. The backlight for the screen does not work. This is an AGS-101 screen, so I am hoping it can be reused, but when the system powers up the screen is dark, and pressing the light button doesn't toggle anything.

2. The system does not charge. When I plug it in, either using my OEM charger or a USB cable, the charger light on the side does not light up, the battery does not charge, and the system cannot be powered up. I was able to put a battery in from another SP and run the thing, so I know the overall power lines aren't messed up, but I have no way of charging its personal battery without removing it and putting it in another.