I am currently refurbishing an Apple IIe I recently purchased and the keyboard is giving me quite a bit of trouble. It's an Alps keyboard, the one with the tall white stems on the keyswitches. One switch was busted, which I replaced and now works correctly, however there are about 6 keys that strike repeatedly on powering on the computer, like space and a few letters and numbers. I tested this broken keyboard on a working Apple IIe and the same problem happens there (plus tested a known working keyboard on the broken computer, which worked successfully), so I don't think it's a capacitor or the keyboard ROM.
So far I've cleaned all the switches with Simple Green, 99% alcohol, and Deoxit, done continuity checks on all the switches which are all working fine as far as I can tell. I looked over the traces with a magnifying glass and don't see anything unusual there, the solder joints look fine for the most part, but they are pretty old so its hard to tell if there are any cold solder joints. I haven't actually disassembled an entire keyboard before, but I'm not sure what else to check at this point. Replacing the switches is about $10 each on Ebay, but for that price I might as well just get a new (to me) keyboard altogether. Does anyone have any ideas on what else I can check before I throw in the towel? I'm somewhat new to doing this level of repair on these machines, so it might be something simple I'm overlooking. I did notice that someone had replaced the CPU with a 6502 instead of a 65C02, so I'm not sure what other shenanigans previous owners might have done. I'll upload a motherboard pic just for reference just in case something goofy is going on there, but the keyboard did cause issues on another computer so I doubt it.