Had nearly all the parts lying around, so I put this thing together.

I wanted to add stereo speakers, but it’s hard to find good wiring diagrams for such a niche thing. So, mono for now.

The motherboard has a bad cartridge slot. So I designed and printed a custom speaker holder that fits into the cartridge slot. All pressure fitted, no glue.

Everything works so far. Just waiting for a new shoulder button/SD slot cable, so I can finish it up and load up some GBA games. :)