Dead //c

[gospodin@indigo.ie (Vincent Quinn)]

I have an Apple //c, manufactured Cork, Ireland, 1985. It's the UniDisk
//c - PRINT PEEK (64447) returns '0' - with 128K RAM.

It was working fine until around ten days ago. Then it died mid-way
through a disk access.

Now whenever I try to boot the machine the internal 5.25" drive spins:
then the red light comes on and I get the message "Check Disk Drive".

There is a boot disk in the drive. It's not corrupted (I've checked it on
a IIGS).

The self-test (starting up with both Apple keys down) gives me "System OK".

I've taken out the internal drive and attached it to the IIGS. It reads,
writes and formats perfectly. The drive speed also checks out fine.

I've tried to boot from the external UniDisk 3.5" with #PR5. I get the
message "Check Disk Drive".

I've tried changing the external power supply for a second one (a supply
that I know is good). Again, I get the message "Check Disk Drive".

OK - by a process of elimination, I suspect that the internal power
converter is dead. Am I right? Does anyone have any other diagnoses?

If it is the internal power converter, can anyone suggest/recommend where
I can get a replacement from?

TIA

Vincent Quinn

[I really would appreciate any reply posts being copied to me by e-mail -
I manage to check the group only about once a week :-(   ]