Apple //e keeps Killing Floppy Drives!

[Boot Zero <apple@bidlink.net>]

Hey,

I have an Apple //e enhanced, which has recently been brought back into 
service.  Upon initial use, both floppy drives worked, and I was able to 
copy some disks via ADT.  After a few hours of intermittent copying, 
drive 1 (of a Duo-disk) was throwing errors.  Disks that used to boot 
stopped booting.

Drive 2 in the duo still worked.

I purchased a stand-alone 5 1/4 floppy, that worked fine for a while, 
then had the same problem. First it reads, then it throws errors, then 
it won't boot.

Bought another Duo-disk on E-bay.  Drive 2 was working, so I removed it 
and installed it into my old Duo-disk unit, giving me 2 working drives. 
 After some hours of intermittent use, drive 1 started throwing errors. 
 Moving to drive 2, it worked fine for a while, then the same result.

Before all drives died, I did a speed test using Copy2plus.  On the 
drives that were working, they showed normal speeds (198-202ms).   On 
the failing drives, the speeds are all over the place.  STarting at 
around 225, then dropping to almost zero, then back up to 300 or so.

Any idea what might be causing this?  Any clues as to what was needs to 
be replaced?

Any suggestions welcome

-BZ