So... My IIGS was working just fine and I plugged a ADB cable I'd never used before into it and became distracted momentarily by something else. I soon, however, noticed a bad smell, and reached down to find that the ADB cable I'd plugged in was quite warm, almost hot to the touch. I shut the IIGS off and unplugged the new cable, and I tried one that I knew worked (and had just tested with my Performa 6200CD), but to my significant dismay, the ADB port no longer responded.
A quick Google search yielded some clues, including a forum that said I might be able to fix a fried ADB bus in a IIGS by replacing the chip that's connected directly to the ADB port. On my IIGS there's a little 8 pin chip that says, "Tokin D-16C" on top. More googling led me to the Tokin.com data sheet that tells me the D-16C is a "Dip Noise Filter". The only place I could find online that sells them was a fairly shady looking Chinese website that was charging quite a lot for shipping. When I put my nose up to this chip it does have that same bad smell I was smelling when I had the bad ADB cable plugged in, which makes me hope that it could be it. But I don't want to spend the money without more info.
So.. Anyone have any experience repairing a fried ADB port on a IIGS? Anyone know where I can find one of these chips or a reasonable substitute (if it is, in fact the burnt out culprit)?