I recently bought an Apple /// (256k model), Monitor ///, Disk /// external drive, manuals, and software. All of the units are cosmetically in amazing condition (no yellowing, no keys missing, etc). However, the /// itself doesn't work. What's strange is when I first turned it on, the computer started perfectly (it said something on the screen, maybe "retry"? I can't remember). After turning it off and coming back to it only about five minutes later, I flipped the switch only to find a screen full of garbled, flashing pixels. The internal drive's light comes on for a split second before turning back off, and the speaker emits a faint buzzing noise that changes pitch slightly when the pixels on the screen do (about three times a second). Sometimes when I turn on the machine, the screen is dark and the speaker is quiet until I hold control-reset; other times it goes straight to the garbled screen and buzzing noise. I tested the /// with another monitor I knew was working correctly, and the same flashing pattern was displayed.
I then set out to try to fix the problem. I took off the top case and found a heavily corroded battery pack clamped to the case (for the clock add-on). I removed the pack and disconnected it from the motherboard, since I wasn't planning on using the clock anyways. I examined the power supply, which is in full working order. I then took out the motherboard and everything seemed fine at first (no corrosion from the batteries in the clock battery pack had touched the motherboard, luckily). No capacitors on the motherboard or power supply looked like they were bulging or exploded. However, I noticed after a while that some chips on the board (around 7-8 of them) had a sort of black tarnish-like material coating the legs which could be scraped off by a screwdriver. I then took the time and painstakingly removed every chip on the motherboard, cleaned the legs with an eraser (or, if it was a tarnished chip, an emery board), dusted off the socket and reseated them. I also cleaned and reseated all of the chips on the RAM daughterboard (and the daughterboard itself). After doing this, I plugged everything back in and tested the system. Nothing had changed since my last attempt, sadly.
I'm at a bit of a loss of what to do next here. I'd really like to get this /// up and running soon, so if anyone has any ideas of what's going on or how to fix it, please let me know!
Pictures available upon request.