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09.006 What DuoDisk mods are necessary?




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This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.

09.006 What DuoDisk mods are necessary?

         The following is excerpted from an info file from my old bbs ...

     There are TWO modifications that should be made to Duodisk drives:

     The First one was recommended by Apple several ago to solve occasional
problems with trashing diskettes. The solution is to remove 2 capacitors.

     The Second modification is only required to solve a problem with daisy-
chaining on the GS Smartport, though the modified Duodisk will still work fine
on older Apple II's. It requires removing a resistor.

DUODISK MODIFICATION #1- REMOVAL OF TWO CAPACITORS

     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 for "analog board  PN 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 snip out Capacitors
C29 and C30 at board locations A1 and B1, respectively.

DUODISK MODIFICATION #2- REMOVAL OF A RESISTOR

     This mod should be done for Duodisks used with a GS; otherwise, it is
optional. The problem is that the Duodisk draws just a little too much current
when connected to the GS Smartport. This can render other drives on the chain
inoperable. Problems are MOST likely to occur when the Duodisk is daisy-chained
from a Unidisk 3.5 Drive.

     Remove the top cover and 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. (ROM 3 GS users should check Q&A 007.)

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 C3).

----------------------------

By:  Dave Althoff

     There are two capacitors which must be clipped from the board on the
DuoDisk regardless of what machine you intend to use them on.  Failure to do
this can lead to very nasty failures. For instance, some copy-protection
schemes can cause the drive to start writing unexpectedly-- say, during a re-
boot-- thus trashing the disk without regard to the write-protect switch.

----------------------------

By:  Chet Gerhardt

     I have done the capacitor removal mod with all DuoDisks I have sold and my
own DuoDisks. It is amazing that after all of this time most still have not had
the mod done.

By:  Steve Buggie
    

 

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previous page: 09.005 I picked up an apple IIe and a duodisk drive at a thrift store. Could someone describe the connecting cable?
  
page up: Apple II Csa2 FAQs
  
next page: 09.007 Will a Duodisk function correctly on my ROM 3 GS?