Diagnosing faulty 1571

[Digitalman]

I have a 1571 that won't read or format. It resets with the computer and when you issue a command it attempts to do something but always comes back with an error. It doesn't move the head, it does a little bit but never resets to track 0. The drive mechanism is ok, I tested it on a working board. I don't think its the DOS ROM as I swapped that out. Not the power supply either. The board looks ok, but the ceramic caps are green with some fading on them. What kinds of tests might you perform? Same results in C64 mode.

Thanks.