Apple //c , hardware(?) problem

[RKE <gardnern@ats4.colorado.edu>]

I have a //c that has been on a shelf for awhile and I wanted to get get
it back up and running.  Whenever I turn the computer on, I encounter the
following: 

1) With no disk in the drive - The computer gives it's "Apple //c" and
"Check Disk Drive." messages.  It also put's a "`" (backwards accent) on
the middle of the screen.  If I press Control-Reset to get into AppleSoft,
the computer will always place an accent in the middle of the display. 
All of Basic's commands seem to work fine. 

2) With a ProDOS disk in the drive - No matter what, with or sans the
PRODOS system file, the computer shows "UNABLE TO LOAD PRODOS".  I have
the same accent problem as described above. 

3) With a DOS 3.3 disk - The computer seems to boot fine and it even tries
to read the disk but after a moment, it drops into the system monitor at
$9D86.  Once again, I still have that stupid accent problem. 

4) When I try the self-test - There is a "!" (on the graphics screen) for
a moment.  Periodically, The external drive comes active and the speaker
clicks, sometimes independent of the drive.  The testing cycle never ends. 

I have a copy of Apple Diagnostics 2.0 but because of the ProDOS problem,
I can't run the program.  There doesn't seem to be anyone who will service
the computer either (I find it ironic that I can still get my old IBM
PCjr. serviced but once someone hears "Apple 2" forget it - and I don't
even like IBM's).  If there are any hardware gurus lurking about that
could offer some advice, I would be thankful.