Resurrecting an Apple Disk II

I had an Apple IIc growing up. I still have it, along with a big stack of floppy disks. It still works, even after enough years that you kids need to get off my lawn. I decided I wanted something a bit more hackable, so I got a IIe from Ebay along with two 5.25″ floppy drives and a Super Serial card. So, I powered it all up and tested it out and… one nonfunctional drive. Not too bad considering the drive is over 30 years old. (did I mention my lawn?)

Inside the Disk II

The symptom: On power up, the drive head hits the back stop making that characteristic floppy drive noise but refuses to seek the first track. The access light stays on, and the main motor spins the disk. It just sits there like that without moving the head again. According to the Disk ][ Technical Procedures (found here), the first thing to look for is burned components. Opening things up, we see this:

Ouch!

Looks like capacitor C4 is toast. According to the docs, this means the 74LS125 is also likely dead. Those are both easy fixes, but… no such luck. The symptoms remain. I have a working drive, so I tried swapping the good board to the bad drive. That worked. Since nothing else looked damaged, I tried swapping the rest of the chips one by one into the damaged board. It turns out the MC3470, the floppy disk read amplifier, was the culprit. That’s the farthest chip to the right in the picture. This chip is a little harder to source than the other two. I ended up getting a couple from Newark, though it turns out I should have checked Ebay first. In any case, I now have two working floppy drives. Now the question is, what to do with them…

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One Response to Resurrecting an Apple Disk II

  1. Tony says:

    Now that you have two drives- get a copy of LockSmith 6.0 and Fast Copy a bunch of disks …

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