I was recently working on fixing up my Mac Plus (new MoBo, RAM, etc.), and I was testing it with the case off and the FDD outside of the case, just sitting on top of its mount; it'd had problems ejecting and it was just easier for me to be able to push the manual eject. It read a disk perfectly well a couple times, but after a boot attempt, the drive started producing magic smoke, then stopped working. I'm unsure if it was the main motor burning out/getting stuck or something else, but I now have a dead floppy drive. Any ideas? Is the main drive motor replaceable?

