Re: IIc Problems!

[dempson@actrix.gen.nz (David Empson)]

Tony Cianfaglione <ab616@chebucto.ns.ca> wrote:

>    A friend has a IIc with a big problem.  If you try to boot a ProDOS
> disk, it renders a "UNABLE TO LOAD PRODOS" message and makes loud 
> grinding noises like it does when it formats; on DOS 3.3, it just keeps
> running and never stops.  However, if you start it with no disk in the
> drive and the door open, it renders the "Check Disk Drive" message.

The "Check Disk Drive" message indicates that the IIc is at least able
to identify that there is no disk in the drive (by detecting an absence
of data for a long enough time).

Failure to boot both DOS 3.3 and ProDOS could be due to any of several
reasons:

1. Something wrong with the drive head movement mechanism, which has
caused it to get stuck on track 0, or to move the wrong amount when
stepping between tracks, or blocked from moving past a certain point.

2. A dirty or damaged head in the drive, which is making disk access
unreliable.

3. A memory fault in the IIc (could be anywhere).  Try the self-test
(assuming this IIc has the UniDisk version of the ROM - the original ROM
didn't do a real self-test).

4. A power supply problem.


Which ROM version does this IIc have?  You can check the ROM version by
getting into BASIC (press Control-Reset if necessary after "Check Disk
Drive" is displayed) and typing PRINT PEEK(64447).

If it says 255, then you have the original IIc firmware, and there is
one option open to you: you can connect an external 5.25" drive and try
booting (ProDOS only) from that.  To boot the external drive, type PR#7
from BASIC.

If it says 0, 3 or 4, then you have a later firmware version, which is
only able to boot from the internal 5.25" drive, or from a UniDisk 3.5
connected to the disk port.  It would be possible (but somewhat tricky,
involving some poking around in the monitor) to boot off an external
5.25" drive.

-- 
David Empson
dempson@actrix.gen.nz
Snail Mail: P.O. Box 27-103, Wellington, New Zealand