I recently acquired a Japanese Super Game Boy adapter and it's not working on my American SNES. My SNES is a SNS-101 and I removed the upper part of its carcass, so Super Famicom games can fit on it (I have a bunch of them and they all work perfectly on this same SNES). If I put in the Super Game Boy, though, it only shows a black screen, with no sound, regardless of the presence of a Game Boy cartridge on the Super Game Boy itself.
Could this be happening because of some kind of region locking? Or perhaps, the Super Game Boy is broken? If it's broken, is there any possible way to fix it?
I took some photos of the Super Game Boy internals: https://www.flickr.com/photos/127415454@N03/albums/72157668405888454