Had a 230MB Quantum that would make a short "skrrrk" sound, then sit there, spinning away. Turned out that the board had become fried. Replaced it with another board, and the drive works again. Now is an Apple ROM'ed 230MB, too.
The ProDrive LPS drives usually suffer from sticky rubber bumpers that prevent the heads from moving. I believe there are some threads with pictures on how to fix this.
Not joking. I had the same issue after my drive sat for about 8 or 9 years. One bump and it's been working since December.
Hold it so that it is 1" above the surface of a solid tabletop with the SCSI pins facing directly upward. Drop it and brace it so it doesn't fall over. If it doesn't work the first time, give it just one more bump.
Isn't the first time it's worked for me. It's just unsticking the arm.