I've been tearing apart one of the non-SP GBA's for a project I'm working on. It requires that I relocate the cartridge slot (Which is about as painful as just shoving a soldering iron directly into your eye). I have done this - And I can get it to recognize that I've placed a CGB/GBA game in the slot, HOWEVER, it is just hanging on the screen now. I know that this GBA worked prior to screwing with it; I have gone through and done continuity checks between each pin, and done my best to get the contacts clean (This may still be the issue, if anyone has any suggestions on how to clean it better I'm all ears) where the games touch.

Like I said, it recognizes that there is a CGB game in there, but hangs right after; no splash/title screens, just GAMEBOY or GAMEBOY + nintendo. I have tested my test game on a CGB, GB pocket, and another GBA, it works fine on them.

What am I missing, and what can I check (or check again) to figure out why it's not starting up the games? I'm stuck at this step of my project until I can figure it out.

When you put a CGB game in there, does it display the GBA boot screen or the CGB boot screen?

It shows the CGB boot screen. I managed to track down what I think is the problem - there is a short between pins 16 & 18, at least, my continuity tester thinks so. I cannot physically locate the cross, however.

I've relocated the cart slot of a GBA twice. A few good pictures of what you've done would help.

If you used long wires between the cartridge slot and the MOBO they may be lowering the voltage coming from the cartridge. Perhaps use thicker and/or shorter wires?

there is 32 pins total ( if i remember corectly) try bending one pin down and the next pin up, makes it a lot easyer to soldier, although don't bend "up" pins on the sp motherboard, they can easily come off and rip the trace off, just on the cartrige slot.I used 30 gauge wire and it worked for me, i extended wires at almost 3'' long..good luck, also make sure they are not reverse, that when you extended it you didnt flip it,would be like putting game in backwards.