Re: DuoDisk-Disk II problem

[pbauer@ATHENA.MIT.EDU (Paul H Bauer)]

Here are a couple of posts that seem to address this problem!

 <
 <Subj: Duodisk Modifications
 <
 <There are TWO modifications that should be made to Duodisk drives.
 <
 <The first one was recommended by Apple perhaps 5-6 years ago, to solve
 <occasional problems with trashing diskettes by Duodisks.  The solution
 <is to
 <remove 2 capacitors.
 <The 2nd modification is only required for Duodisks to be used on Apple
 <IIGS's
 <(though the modified Duodisk will still work fine on older Apple II's).
 < It
 <requires removing a resistor.  The problem is that the Duodisk draws
 <just a
 <little too much current. This problem is especially apparent when
 <several
 <drives are daisy-chained from the GS Smartport. Problems are MOST
 <likely to
 <occur when the Duodisk is daisy-chained from a Unidisk 3.5 Drive.
 <
 <DUODISK MODIFICATION - REMOVAL OF CAPACITORS
 <
 <OK, here's the first modification for the Duodisk drive.  This mod
 <should be
 <done on ALL Duodisks, no matter whether they're used on //e's, IIGS's,
 <etc.
 <The problem was that diskettes would sometimes be damaged when doing an
 <Open-Apple-CTL-Reset, or when using disks with certain kinds of copy
 <protection.  The mod was in an Apple dealer service bulletin several
 <years
 <ago.
 <
 <Here's an excerpt from the bulletin, describing the problem:
 <
 <  "Data on disk is damaged when using "Open-Apple-CTL-Reset" for
 <rebooting,
 <  or when using software with certain copyright protection schemes.
 <  Analog board PN is 676-[]101 or 676-[]102."
 <
 <The Analog board is the one inside Drive 1 in the Duodisk.  You may
 <have to
 <unplug the cable near the back right of the board to see the board's
 <model
 <number.  Anyway, if you have the -101 or -102 board, just break off or
 <cut
 <out Capacitors C29 and C30 (at board locations A1 and B1,
 <respectively).
 <
 <I've done this on all 3 of my Duodisk drives, so I can vouch for the
 <safety
 <of the procedure.
 <
 <DUODISK MODIFICATION - RESISTOR REMOVAL
 <
 <Here's the second modification for your Duodisk drive.  This is the
 <exact
 <message as posted on Compuserve in 11/86 by an Apple Computer employee:
 <
 <**********************************************************************
 <
 <Duodisk Mod                13-Nov-86 1150               Accesses: 12
 <    This file describes how to modify your duodisk for safe use on the
 <GS.
 <    Obviously, it is preferable that you have it done by the dealer,
 <but if
 <    you want to do it yourself here's the info... Questions/problems to
 <    76703,3030, PM
 <
 <Using the DuoDisk with the Apple IIGS
 <
 <The DuoDisk can not be used as the last daisy chained device on the
 <built-in IWM disk port of the Apple IIGS. For instance, a UniDisk 3.5
 <will be rendered inoperable when the DuoDisk is installed in the above
 <manner - although using the DuoDisk by itself is not a problem.
 <
 <A qualified technician will have to modify the DuoDisk analog
 <board if the DuoDisk is to be used as the last device on the
 <chain. Please use the following procedure to determine how to
 <modify the analog board.
 <
 <IDENTIFYING WHICH ANALOG BOARD YOU HAVE
 <
 <Remove the top cover as documented in Technical Procedures. Turn
 <the drive so that the identifying number will be at the bottom left
 <of the analog board. The number might read 676-[]101, 676-[]102 or
 <676-[]107.
 <
 <PERFORMING THE MODIFICATION
 <
 <If the I.D.# for the analog board is 676-[]101 or  676-[]102, use
 <a pair of nippers and cut out resistor R8 (located at position A2).
 <
 <If the I.D.# for the analog board is 676-[]107, use a pair of
 <nippers and cut out resistor R39 (located at position A1).
 <
 <******************************************************************
 <
 <I don't know who to credit this info to and I don't have a Duodrive,
 <so take it for what it's worth.
 <--


Hope this helps.


	pbauer@mit.edu