Re: DuoDisk-Disk II problem

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

In article <Z04YFcn.rogtha@delphi.com>,  <rogtha@delphi.com> wrote:
> I have a DuoDisk hooked up to a IIe, and a Disk II hooked up to a II.
> Whenever I run a program using the DuoDisk, it won't work afterwards
> with the Disk II. 

I wonder if this is the old "erasing track 0" problem that was
reported in Open-Apple (R.I.P., sniff) back in 1986/1987.  From a
quick scan through the articles, there were two possible causes:

- Some versions of the DuoDisk could erase part of the disk.  This
mainly affected copy-protected disks.  It is dependent on a particular
board revision in the drive, and can be corrected.

- There may be a problem with the power supplies in some Apple IIes
that can cause track 0 to be erased, but this only happens with ProDOS
disks, and possibly only with older versions of ProDOS.  You can easily
check for this one: try installing the DuoDisk in the II+ and see if
the problem still occurs.

There is a bug in ProDOS-8 1.1.1 which can make this problem appear.
This was fixed in 1.3, but there are even more serious bugs in that
version.  Using 1.4 or later should avoid the problem.  Ideally, use
1.9 to get even more bugs fixed, or 2.0.3 if you have a 65C02.


Neither of these possible solutions explain why you are getting damaged
DOS 3.3 disks.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand