Apple II 5 1/4 drive went bad, need help?

[mdickins@brightok.net (md)]

I have two very used drives that I bought on ebay.  I hooked them up
for the first time and they worked fine.  After some time drive 1
wouldn't boot a disk anymore it just spun.  I switched the positions
of drive 1 and drive 2 on the controller and drive 2 did the same
thing.  I then took drive 1 (which is now in the drive 2 position on
the controller) off the controller and the drive 2 (now on the drive 1
position on the controller) worked fine.  I put the old drive 1 back
on by itself and it wouldn't work.  I concluded the drive itself went
bad somehow, but I haven't a clue to what is wrong, any suggestons??
Any diagnostics I can do?