Re: DuoDisk 5.25 bug (ctrl-oa-reset)

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

In article <15JUN199402153411@vax2.concordia.ca>,
Mitchell Spector <spector@vax2.concordia.ca> wrote:
> 	Was just reading one of my old InCider/A+ magazines and noticed
> a mention of certain flawed Apple DuoDisk 5.25 drives. Notiably, the
> random "eating" of disks triggered by a CTRL-OA-RESET. They said any
> DuoDisk analog boards with the part number '676-X101' or '676-X102' are
> at fault. Seeing that I have two DuoDisk drives here, I opened both and
> found (with my luck) the first had a # '676-101' and the second '676-102'.

There was mention of this in the January 1986 issue of Open-Apple
(later called A2-Central).  I quote:

"Some Apple DuoDisks can erase disks by accident.  It happens during
rebooting with open-apple-control-reset and with some copy protection
schemes.  Drives that have the problem have serial numbers beginning
with 676 and ending with either 101 or 102.  If you have such a drive,
take it to your dealer for a free fix."

There was a letter from Apple in the following issue:

"... The number you published ... is the part number of the DuoDisk
printed circuit board located inside the drive, not the serial number
of the affected units.  The potential exists for problems to occur
with units of almost any serial number.
Apple users who think they have a unit in need of upgrading should
take the DuoDisk unit to an authorised Apple servicing dealer for a
check.  If the circuit board has not been upgraded, the dealer will do
so at no cost to the user.  ..."


I suspect that Incider/A+ abbreviated the description of the number
to "676-X101 or 676-X102", meaning "676-<anything>101 or
676-<anything>102".

> I didn't see any "X" (or any alphabetical marking) within the serial number,
> so I'm not quite sure if I have these faulty drives. I'm also not certain if
> these faulty drives affect only original copy-protected disks, or backups
> as well. I'd like to know before I ruin my software collection... :/

Unclear from the above, but I think it would affect ANY disk which
uses the particular copy protection scheme or schemes.

> 	If I do have two faulty drives, how do I go about fixing the
> problem? The article mentions having to clip two capacitors off the
> analog board, but doesn't mention which (or where they're located).

That isn't mentioned in the Open-Apple article.  I've checked up to
volume 6 for any further mention, but can't see anything in the index.

In a later issue they mention that some DuoDisks have problems being
used on the IIgs disk port unless a couple of resistors are removed,
but this seems to be an unrelated problem.  It doesn't say which
version of the board is affected.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand