Apple II Floppy Disk Drives

Csa2 FAQs-on-Ground file: Csa2FDRIVE.txt  rev012

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 001- How do I add a write-protect On-Off switch? 
 002- How do I add external speed adjustment to my Disk ][ drive? 
 003- How can I adjust my 5.25" drive for optimum performance? 
 004- How do I clean my disk drive R/W head(s)?
 005- What is the pin-out for a duodisk drive connecting cable?
 006- What DuoDisk mods are necessary?
 007- Will a Duodisk function correctly on my ROM 3 GS?
 008- How do I fix a false Write Protect?
 009- My 3.5 Disk Drives don't work! What should I try?
 010- I added SCSI; now, my 3.5" drives often fail to work. Why?
 011- Both of my Disk ]['s come on when booting! Is there a fix?
 012- In connecting a Disk II I misaligned the connectors. A fix?
 013- A sound like a shotgun going off came from my drive. A fix? 
 014- Uni-disk and Laser drives: neither works with my IIc. Why?
 015- How do I replace a 3.5" drive mechanism with one from a Mac?
 016- I have one 5.25" drive. Sys6 shows two icons!? Is there a fix?
 017- How can I tell a 13-sect interface card from a 16-sect model?
 018- Can a Disk ][ Drive be used on a IIc or GS smartport?
 019- How do I install a bi-color LED R/W indicator in my Disk ][?
 020- What's the scoop on the 3.5" High Density drive?
 021- What is a "UniDisk"?

From: Stephen Buggie

001- How do I add a write-protect On-Off switch
     to my Disk ][ drive?

            Adding an Auto/Manual Write-Protect Switch
     Often, as when doing copying, it is useful to be able to guarantee
that a diskette is Write-Protected whether or not the side is notched.
Other times, it is convenient to defeat Write Protection-- for example,
when you wish to write to a diskette side which is not notched. And,
naturally, you also want a setting which permits Normal,
notch-controlled, Write-Protect.

     Based upon a circuit suggested by David Wilson (Australia), the
A/MWP enhancement offers full user control of Write Protect. The
switch's three positions are

Protect OFF: Writing is allowed regardless of notching.

Protect ON:  Writing is prohibited regardless of notching.

Normal: a diskette side must be notched to permit writing.

A/MWP Step-by-Step

Unplug the drive from the disk controller and remove the case.

Drill a mounting hole. This can be at a convenient spot in the back or
in the plastic front panel. On the front, a good spot is at the lower
left, above and to the left of the "in use" LED. Another open spot is at
the upper right in the space just above the diskette slot; but, we're
saving this place for Part 2's enhancement. (You can't use the lower
right, of course, because this would mess up the "Apple" logo!)

Cut three wires (Brown, Black, and White) long enough to run from the
mounting point to the Large Connector plugged onto the back, middle of
the Disk ][ circuit board.

Solder the leads to a Single-Pole Triple-Throw mini toggle Switch: 
Brown to center, White to one end, Black to other end. Twist the leads
or encase them in tubing.

Mount the Switch. Normally, the Switch handle will point in the White
lead direction for "Protect OFF" and in the Black lead direction for
"Normal". Center is "Protect ON". Route the leads to the area next to
the Large Connector. (Make sure no wires will get in the way of an
inserted diskette.)

Locate the Brown and Black leads coming from the Notch Detect
micro-switch. The leads are the Brown (bottom) and Black (top) pair near
the right end of the Large Connector (as viewed from the front of the

Cut the Notch Detect micro-switch leads about 1" away from the Large

Connect the Black Notch Detect, Black Large Connector, and Black Switch
leads (i.e. strip ends, solder, and cover in heat-shrink tubing or

Connect the Brown Notch Detect lead to the White Switch lead.

Connect the Brown Large Connector lead to the Brown Switch lead.

     Viola! Now you're ready to replace the cover, plug in the drive,
and try out your A/MWP enhanced Disk ][.

     Boot a diskette which is not write-protected and load a program,
say the HELLO program (or STARTUP on a ProDOS diskette). Set the A/MWP
to center and try SAVE HELLO. You should get a "WRITE PROTECTED" error.

     Place a write-protect tab on the diskette. Set A/MWP to the Left or
UP position and try SAVE HELLO again. If the save works, then Left or UP
is the "Protect OFF" position and Right or Down is "Normal". If you get
a "WRITE PROTECTED" error then it's the other way around.

     Now is a good time to mark "Normal" and, if you like, the other
positions. You can use dots punched from self-stick labels.


002- How do I add an external speed adjustment to my Disk ][?

Reference: FAQs Resource file R006SPDKNOB.GIF

          Adding a Speed Control Knob to your Disk ][ Drive

     This article tells how to move speed adjustment from the Disk ]['s 
dark interior to a handy front-panel location and how to  "tune" the
drive for optimal performance.

     One drive-test software vendor states that Disk ][ is good for
about 500 hours of normal use between speed adjustments-- not exactly a
strong argument for placing the control on the front panel! On the other
hand many of today's Disk ][ owners are interested in applications which
go beyond "normal use".

     Some utilities (e.g. DiversiCopy II) report rotational speed during
ongoing applications; so, relocating the speed adjuster to the front
panel is especially helpful. Similarly, users who want to back up their
old, copy-protected wares know that ready access to speed control is

     Finally, there is no question that, whatever your applications,
periodic speed trimming will be required. When it is, you'll be very
glad _your_ Disk ][ has a front panel Speed Knob!

Adding Speed Knob

     To install Speed Knob you will need a good quality, linear taper 5k
Ohm potentiometer, some wires, and a knob with a pointer mark or some
other way to show position (e.g. a ring of numbers).  Most of the work,
really, consists of opening the drive and drilling a hole. There is no
need to disconnect the drive from the controller card.

1. Remove the 4 bottom bolts and slip off the case. Unscrew the 4 bottom
bolts holding the drive to the case bottom, and unplug the main ribbon
cable. The drive can now be moved to your work area.

2. Drill a hole properly sized and centered for mounting your 5k Ohm pot
in the upper right front panel.

3. Place the drive on its face and unscrew the 2 bolts which hold the
small daughter board to the drive. (Be ready to catch loose spacers,
washers, etc..)

4. Turn the small board over to the bottom side. Locate and cut the
traces going to the mini-pot speed adjuster as shown in pic

5. Cut three wires, White, Gray, Black, long enough to reach from the
board to the front panel. Connect these to your 5k Ohm pot and to the
small circuit board as shown in pic R006SPDKNOB.GIF. (In case you cannot
view the pic, what you're doing is substituting the new pot for the
mini-pot. )

6. Re-mount the daughter board. Mount the 5k Ohm pot. Install knob.

7. Bring the drive back to the computer. Slide it onto the case bottom
plate, reconnect main ribbon cable, replace bottom bolts, slide on and
re-fasten case top.

     You can use Copy II Plus, XPS, APEX, or one of several other
utilities to set speed (see next question). A good starting adjustment
will be near the center of Speed Knob's range. Once speed is adjusted,
you can loosen and re-set the knob so that its position indicates a
"correct" speed setting.


003- How can I adjust my 5.25" drive for the best performance?

     The typical 5.25" drive will run for months with no need for
maintenance save an occassional dusting or session with a head-cleaner
disk. When adjustment is required, it will usually be to fine-tune Speed
or, less often, to set track centering.

     If a 5.25" drive has difficuly reading diskettes, including those
it created, and head-cleaning does not help, then, the odds are it's
time to adjust speed. If your drive is a Disk ][ and does not have the
external 'Speed Knob' mod, look for a small hole on the lower right side
near the back-- some owners add this hole to allow easy access to the
Speed Adjustment mini-pot screw. If there is no hole, you will need to
remove the case. (Remove bolts on bottom and slide out the drive through
the front.)  

     On the 5.25" Apple 'Platinum Drive', the Speed Adjustment is
accessed through a small hole on the bottom of the drive near the front
on the right side. Non-Apple 5.25" drives may place the Speed Adjustment
almost anywhere. Look for a small hole through which you can see a screw
head. If you don't fine one, remove the case and look for a mini-pot
labeled "Speed" or something similar.

     The most popular speed adjustment software utility is, probably,
dear old Copy II Plus. From the menu, just select "Verify", then "Drive
Speed". Put a diskette into the drive you want to adjust and, turning
the Speed Knob (or min-pot shaft) use Copy II's numeric speed display to
zero-in on the 'magic' 200ms. number. (Standard Disk ][ rotation speed
is 300 rpm, which comes out to be 0.2 seconds per revolution.)

     Other speed adjustment utilities show an rpm number or a hires
pointer. Whatever, all speed check routines need to read AND write; so,
you will usually need a "scratch diskette" which you do not mind having

     Track-center realignment is needed when a Disk ][ writes and reads
its own disks fine, but does not 'communicate' with many other Apple II
5.25" drives. It generates disk errors when reading disks written by
other drives and other drives have the same problem with its diskettes.

     CALL A.P.P.L.E's APTEST, now in the public domain, tests
track-center alignment. With  this software, the user checks the
alignment of the drive with disks regarded as well aligned --- such as
Apple diskware supplied with the computer or some unprotected, original,
commercial software diskette. (In a pinch, a diskette formatted by any
drive that has no problem reading most other diskettes should be okay.)

     Basically, a track-centering test tries to step your head between
two tracks of the 'standard' diskette and read the tracks on either
side. If the number of successful reads from each track is about equal,
the head is "centered" and your drive is well-aligned with the standard

     The test may indicate serious misalignment. ("Aha! That explains
why my IIgs and II+ have problems reading each other's diskettes!") 
Centering adjustment is done by slightly repositioning the stepper motor
(mounted on the underside of the drive). This requires loosening the two
bolts holding the stepper-motor, rotating it clockwise or
counter-clockwise, and retightening.

     The adjustment/test process may require several repetitions. Each
time, the program will report "differential fractions". The smaller
these numbers, the closer you are to near perfect alignment with tracks
on the diskette.


From: Rubywand

004- How do I clean my disk drive R/W head(s)?

     The easiest way to clean a drive's R/W head(s) is with a Cleaner
Diskette. This is a diskette with a paper disk such as the 5.25" and
3.5" Cleaner Diskettes available in Radio Shack's Disk Drive Head
Cleaner Kits. These kits usually include "Cleaning Fluid" (isopropyl
alcohol), too.

     The 5.25" Cleaner Diskette has panels you pop out to expose the
cleaning surface. Apple II 5.25" drives have a single head which
contacts the disk from the bottom and a pressure pad which presses
against the top side. So, pop out the panel on the bottom side of the
Cleaner Diskette and leave the top panel in place. When cleaning, insert
the diskette with the bottom side facing down. This lets the paper disk
rub against the head and avoids wear on the pressure pad.

     The 3.5" diskette has a small plastic panel you can snap out for
cleaning two-head drives. Since the standard 3.5" 800k Apple II drive
has two heads, snap out the panel so that both the top and bottom heads
get wiped.

     To clean your drive head(s), you sqirt a few drops of Cleaning
Fluid onto the Cleaner Diskette disk, insert it into the drive, and get
the disk spinning for 20 seconds. (Booting the Cleaner Diskette is one
way to get it spinning. If DOS or ProDOS is installed, doing a CATALOG
is another way. For example: CATALOG,S6,D2 would get your 5.25" Drive 2

     If you think it has been several months since the drive was last
cleaned, repeat the procedure-- i.e remove the Cleaner Diskette, add
more fluid, etc.. As a rule, do not let the disk spin more than 20
seconds for any cleaning cycle. This is especially a concern with 3.5"
drives where the heads are mounted on springs and much more subject to
snagging and being pulled out of alignment. 


From: Steve Jensen

005- I picked up an apple IIe and a duodisk drive at a thrift
     store. Could someone describe the connecting cable?

     I just checked the pinout on a Duodisk cable.  The numbers for the
pins are inside the plug by the pins, but I'll draw them for you.

DB 19 looking at the end of the cable:
    1   2   3   4   5   6   7   8   9  10
    o   o   o   o   o   o   o   o   o   o
      o   o   o   o   o   o   o   o   o
     11   12  13  14  15  16  17  18  19

DB 25 looking at the end of the cable:  (x = no pin)
     1   2   3   4   5   6   7   8   9   10  11  12  13
     x   o   o   o   o   o   o   o   o   o   o   o   x
       o   o   o   o   o   o   o   o   x   o   o   x
      14  15   16  17  18  19  20  21  22  23  24  25


DB 19   DB 25
1       2
2       4
3       9  & 21
4       10 & 14
5       23
6       7
7       19
8       20
9       8
10      12
11      15
12      16
13      17
14      18
15      5
16      24
17      11
18      3
19      6


From: Steve Jensen

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

     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.


     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,


     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
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).


From: 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.


From: 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.


From: Steve Buggie

007- Will a Duodisk function correctly on my ROM 3 GS?

     I have three Duodisks.  The one connected to my flagship Rom 3 IIgs
has had the resistor and capacitors clipped out as recommended in a memo
from Mitch Spector. It works perfectly!


From: John L. Graham

008- How do I fix a false Write Protect?

     I recently ran into this problem with a Disk II. It insisted the
disk was write protected. I checked the write protect switch, but it was
okay. I pulled all the chips out of the analog board inside the drive,
cleaned the contacts with a clean pencil eraser (one was _really_ dirty,
almost looked burnt) and re-installed them. Voila! The problem went


from Rubywand

009- My 800K, 3.5 Disk Drive is no longer working on my IIGS.
     When a disk is inserted the drive tries to read it and then
     locks up the entire system forcing me to do a 3 finger reboot.
     Any suggestions on where to start troubleshooting?

     If you have a SCSI interface card plugged into your GS, you may
have run into a bug which seems to affect setting up of the diskette
port. (See the next question and answer.)

     Try cleaning the heads using a Cleaner Diskette (e.g. a paper
diskette + cleaning solution kit from Radio Shack).
     If cleaning does not seem to help, try wiggling the drive cable
while attempting to CAT a known-good, unprotected diskette in the drive.
If wiggling helps, you are likely to have a bad cable or a GS plug with
a loose connection to the motherboard.

     Try formatting a diskette. A drive which can format and R/W
diskettes it has recently formatted but cannot read most other diskettes
probably has heads which have become misaligned.

     Set your boot Slot to Slot 5 and try power-up booting a couple
bootable ProDOS diskettes known to be in good condition. If you can boot
a variety of disketts, including commercial game, etc. diskettes, the
odds are pretty good that your drive is okay.

     A 3.5" drive that, after cleaning, cannot boot known-good diskettes
is likely to have screwed-up heads. However, it's a good idea to try
unplugging and re-plugging the drive (with the computer OFF) and, then,
try another boot.

     If you have a 5.25" drive attached, boot ProDOS from the 5.25"
drive and try some CAT's of non-protected known good 3.5" diskettes in
the 3.5" drive. As earlier, do the cable wiggling test while attempting
the CAT's.

     A very good test is to try out the drive on a friend's IIgs or
IIc+. If it continues to bomb, it is likely to have R/W heads which have
become badly misaligned, heads which are badly worn, or heads which have
been partially dislodged from the mountings. (The 3.5" drive's heads are
held in place by springy metal sheets. Unlike the mounting for the 5.25"
Disk ][ head, these are fairly delicate. If anyone has tried cleaning
the heads by sticking in an alcohol swab and 'swishing around', there is
a good chance the head mountings are messed up.)

     Shops which replace heads are fairly rare. I had this done a few
years ago and the drive still works fine. However the charge is around
$80. It is cheaper and easier to get a good 2nd-hand drive at a
swap-meet. You can, also, look for a bargain Mac drive and do a
"transplant" as described by Steve Buggie in the Winter issue of II

     Steve Buggie is a good source of information on drive repairs.
Check out some of his recent posts to this newsgroup.


010- Sometimes the 3.5" drives on my GS do not function correctly.
     This started after adding a SCSI interface card.
     Is there a fix?

     This problem seems to crop up from time to time when a SCSI
interface is present, especially when no device is connected and
recognized on the SCSI chain. (For example, you may have only a Zip
Drive connected to your SCSI interface; but, it is not powered ON or no
Zip disk is inserted.)

     Evidently, something (e.g. a register or softswitch) in the usual
GS power-up routine relating to on-line devices gets messed up.
Arranging to have some active, on-line device on the SCSI chain (or
removing the SCSI card) seems to eliminate the problem.

     Otherwise; inserting a 3.5" diskette into Drive 1 before or just
after power-up usually forces recognition of 3.5" diskette drives and
enables correct functioning.


011- Both of my Disk ]['s come on when booting! How can I
     fix this?

     Basically, it sounds like Drive 2 does not know when to stay OFF.
There are three fairly high-probability places where a glitch may cause
this to happen:

 1. The 74LS132 on the Disk ][ Controller card may have a blown gate or
some pins may be making poor or no contact. Try unplugging and
re-socketing the IC. This usually takes care of bad contact problems.
(Or, you can replace the 74LS132 IC with another 74LS132 or 74132. A
74LS00 or 7400 may work, too.) Also unplug and re-socket the 9334 and

 2. The ULN2003 IC on the Drive 2 main circuit board may have a bad gate
or may have developed some poor pin-to-socket contacts. Remove the drive
cover. Unplug and re-socket the ULN2003 IC. (Replacing a blown ULN2003
should not be too difficult. Both Mouser and Newark carry the IC.)

 3. Drive 2's cable may have developed a short between pins 14 and 16.
Mark the position of the cable at the Controller card and at the Drive 2
circuit board and unplug the cable at each end. Use an Ohm meter to
check for shorts between adjacent pins. If you find a short between 14
and any other pin you can try repairing the cable or cutting out line 14
and running a new lead; or you can get a replacement cable.


012- In connecting a second Disk II drive to my Disk II card I
     misaligned the connectors. The result upon turning it on was a
     static-like clicking noise. Now I can't load anything from
     disk. Is the Disk II card dead? Are the IIe and Drives all

     Try removing the drive which was connected incorrectly. If your
system boots from the remaining drive (connected in the Drive One
position), this is a fairly good indication that the Disk II card and
IIe are okay and that the removed drive is messed up.

     If it looks like a drive is bad, remove the cover and inspect the
drive's main circuit board for blown components. If nothing obvious
shows up, a decent fix try is to replace the 74LS125 IC on the drive's
main circuit board. (Also, see Question 023.)


013- Last night a sound like a shotgun going off came from my 5.25"
     Disk ][ drive. Now it doesn't work. How can I fix it?

     The noise was probably an electrolytic capacitor exploding.
Sometimes, these develop internal shorts, heat up, and blow (kind of
like a sealed can of beans on a campfire).

     The fix is to remove the drive cover and replace the blown
capacitor. (Look for a small can-like component with goo and/or shredded
foil coming from it.) Circuit board markings should help identify the
component. Here are some suggested replacement values:

C2 (on +12V line):  220uF-500uF at 20V-50V
C4 (on +5V line):    470uF-500uF at 10V-25V
C5 (on -12V line):  10uF-50uF at 20V-50V

     If there is some difficulty identifying the blown capacitor,
replace it with a 500uF unit rated at 20V-50V.

     Before removing the bad capacitor, note which lead is connected to
the outside 'can' part and mark the circuit board where this lead is
connected. This is the Negative side of the capacitor. When installing
the new capacitor make sure its negative lead goes to the marked point
on the circuit board.


From:  Wayne Stewart

014- Recently I picked up two 3.5" drives at a swap meet-- a
     Uni-disk and a Laser 128 drive. I've tried cleaning the
     heads; but, neither works with my IIc. What's the problem?

     The 3.5 unidisk won't work on the earlier IIc unless the IIc has
had a ROM upgrade. The Laser 3.5 is actually a Macintosh drive with the
addition of an eject button. It isn't compatible with any Apple II
unless it has a special controller card, which of course a IIc doesn't.


From: Stephen Buggie

015- Can I replace a bombed Apple II 3.5" drive mechanism with
     one from a Mac?

     Yes. 3.5" drive mechanisms are cheaply and abundantly available
from the Macintosh world. Although Apple II users have increased their
interest in 3.5" drives, these drives have declined in their utility for
Mac users who have shifted to hard drives, CD-ROM, and flopticals.  Few
Mac owners have use for the external 3.5" drive any more; if they have
not yet discarded their external 3.5" drive, it is now in storage.


     The basic Sony 3.5" mechanism is shared by Mac and Apple II.  It
stores 800K of data on a two-sided disk.  Unlike the IBM version with
its constant rotational speed, Mac/Apple II drives maintain constant
head velocity by varying the rotational speed as the head assembly
approaches towards or moves away from the disk hub.  Mac and Apple II
drives differ in their track sectoring arrangements, so disks cannot be
read directly without special translational software.  The opportunity
for compatible disk sharing was lost during development, because rival
teams working on Mac/Apple II drives went their separate ways (Steve
Weyhrich, APPLE II HISTORY, Pt. 9, 1992).

     The platinum 3.5" drive supplied with the IIgs is directly
compatible with the Mac, although the Mac ignores its front panel manual
eject button; Mac disk ejection is handled strictly by the desktop trash
icon command.  An older version of the external Mac 3.5" drive lacks the
manual eject button and, in its casing, is plug-incompatible with Apple
II.  Thanks to advice provided by Ken Watanabe, I learned that the inner
mechanism is identical  among all versions of 800K Mac and Apple II
drives, including the internal drive mechanism in the Mac CPU.  This is
good news for Apple II users who wish to transplant the abundantly
available Mac mechanism into their platinum 3.5" drive casing.


     The classic white Unidisk drive was released in 1985 as a 3.5"
platform for the IIe and IIc.  This release date was 18 months prior to
the introduction of the IIgs.  Disks written by the Unidisk 3.5 and
Platinum 3.5 drives are fully interchangeable; the two models differed
because the earlier Unidisk 3.5 used an intelligent
microprocessor-controlled analog board to slow the data transfer rate to
match the IIe/IIc parameters.  This slowdown was not needed for the
popular platinum  3.5 drive used by the IIgs.

     Can the Mac mechanism be transplanted to the Unidisk 3.5 casing?
Probably yes, but this has not yet been verified.  I am reluctant tohack
with the working Unidisk 3.5's attached to my IIC's.  I now seek a
mechanically jammed Unidisk 3.5 drive to verify whether its life can be
resurrected with a Mac transplant.


     The internall DSDD 800k drive mechanism can be salvaged from any
mid-vintage Mac except for early models (Mac 128, Fat Mac 512) ----
those two models used a quaint single-sided 400k drive.  Suitable models
include the Mac Plus, Mac SE, Mac II, or other Macs that have the
standard DSDD 800K mechanism --- newer Macs have incompatible high
density drives.  Get a genuine Mac Sony drive mechanism, not a clone;
the suitability of non-Sony clones is uncertain.

     Salvaged internal drives must be removed from the Mac internal
mounting bracket --- take out the four side-mounted bolts, and slide the
mechanism forward.  The early version of the external Mac mechanism is
mounted in a plastic casing that resembles the Apple II platinum drive
except that the manual eject button is absent.

     Remove the mechanism from the casing, but save its round external
cable and db-19 plug --- that cable/plug can be used later to adapt
flat-ribbon Apple II drives for use with the IIgs or IIIc!  The Mac
externaldrive's plastic casing can be saved for use as a coin bank, or

     You should anticipate  that the older Mac drive has had plenty of
use; most Mac users have fewer drives attached to their computer than is
common for the Apple II.

     The 3.5" drives are sturdier than hard drives, but to protect the
drive's head assembly from damage during rough shipment, the seller
should be asked to ship the unit with a disk inserted.


     Use a well-light work area that gives you plenty of elbow room,
with containers to hold bolts and other small parts  All dimensions
(left/right/top/bottom/front/rear) refer to the unit's own dimensions,
NOT to your own egocentric viewpoint as the observer.  Standard
precautions against static or other electrical damage must be followed:
Discharge static frequently by touching grounded metal, wear a grounded
wrist strap, hand all power  OFF when attaching/removing drives, put
insulating tape over the db-19 drive plug when not in use.

     Move slowly and patiently when removing or inserting the mechanism
from its housing ---- metal parts must not be forced or bent.  These
tools areneeded: (a) medium and small Phillips-head screwdrivers, (b) a
small pliers, and (c) a fine-tipped felt marker.  This procedure was
outlined in an essay by Lorne Walton (Apples BC, 1992), but many further
details have been added here to facilitate disassembly and drive

     The first step is to remove the worn/defective mechanism from its
Apple II platinum casing.  Flip the casing on its back and rest it on
soft cloth.  Re,ove the four shiny bolts from the bottom of the casing.
With the unit inverted, slowly lift the bottom half-shell of the plastic
casing upward and push the external cable's attached grommet towards the
upper casing.  The unit's bottom casing should come off cleany.

     Use the felt marker to label the unit's own main dimensions,
writing on the metal internal shroud: front-bottom, rear-bottom, left
side, right side. Examine the metal innards as they lie upside down in
the upper casing. Note that a red and black wire pair are tucked on the
inner edge of each side --- These two wires go to the eject switch
(right front) and to the red in-use LED lamp (left front).

     At the unit's rear, observe that the wire pairs terminate in RED
and BLACK plugs.  Use the felt-tipped marker to write "R" and "B" on
nearby metal surfaces to identifythe positions of these two plugs. These
letters will help during reassembly when reinsterting the two plugs onto
their proper pins.  Next, use the small pliers to grasp each plug,
slowly and carefully pulling it backwards to remove it from its mounting

     With the black and red plugs each removed, slide the top plastic
cover in a rear-to-front direction, past the metal-enshrouded mechanism.
The wire-pairs from the eject-button and also from the in-use LED lamp
should remain tucked into their plastic side-braces.

     You now hold the mechanism, enshrouded in its grey metal shielding,
with the external db-19 cable protruding from the rear. Remove the two
medium Phillips mounting bolts (with flat washers) from each side. 
Remove the single medium Phillips bolt/washer that is centered on the
upper-rear metal shroud. Then lift off the upper-rear should and look

     Note that the round external cable terminates in a familiar IDE-20
flat-ribbon connector that plugs into the inner mechanism.  Unplug that
inner connector --- the small pliers can be used to rock and pull the
connector towards the rear.  With the IDE-20ribbon connector unplugged,
the inner mechanism can be slid forward and out.

     As you hold the inner mechanism in your hand, observe that a shiny
thin metal shroud covers its to and sides.  Use the felt-tipped pen to
label this shrou's dimension: TOP-FRONT and TOP-REAR.  This thin shroud
should be removed by rocking it and spreading its thin side-tabs.  At
this point, you have the bare mechanism in your hand, with heads visible
from its top perspective, and with pancake motor visible underneath.

     You are now ready to begin reassembly, but pause to appreciate what
is before you.  Hold the old mechanism and its Mac replacement
side-by-side --- they should appear identical.  The date of manufacture
is coded on a sticker on the pancake motor (e.g., 8809 = September
1989).  Apply rubbing alcohol with a cotton swab to clean the surfaces
of both read/write heads.


     Remount the innermost top-and-sides metal shroud, taking care that
its "fingers" have clicked into place on the mechanism's sides. When
properly fited, both bolt-holes on each side will be visible through the
shroud's thin metal. If the shroud does not fit, or if the bolt-holes
are not seen, check with your dimensional labels to verify that the
front and rear have not been reversed.

     With the top/side inner shroud correctly in place, then reverse the
disassembly steps: Slide the mechanism through the front of the metal
shroud. Reattach the IDE-20 internal ribbon connector, align the two
bolt holes on each side of the outer shroud with the mechanism and
reinstall the four medium Phillips bolts and their washers.  Then
reattach the rear-upper shroud with its centered bolt and washer.
Reassembly of the outer metal shroud is now finished!

     The final reassembly task is to refit the enshrouded mechanism into
the plastic outer casing.  Lay the inverted UPPER plastic half-shell on
the bench,with its front facing away from you.

     Observe the small red or black wires tucked along the sides of the
upper plastic half-shell. With the metal enshrouded drive mechanism
upside down, it should be slid into the plastic top-shell, from  its
rear to its front.  Check that the red-black wires remain tucked along
the inner edge between the plastic casing and the metal shroud.  Insert
the black and red plugs into their respective connectors.  Note the "R"
and "B" markings you wrote on the metal shroud; those markings will
guide the plugs' insertion into their proper connectors.

     The oblong-shaped grommet attached to the round external cable
should be fitted first to the bottom plastic half-shell casing, which is
then mated to the top casing.  Reattach the four small shiny Phillips
bolts through the bottom plastic half-shell, and you're done!


From: David Empson

016- I have one 5.25" drive connected to my GS, but the System 6.0.1
     Finder display shows two 5.25" icons!? How can I fix this?

     You need to change the AppleDisk5.25 driver file's auxilary
filetype from $010E to $0101. You can use File Manager (an NDA utility)
to make the change.

     For a standard GS/OS device driver, the lower six bits specify the
number of devices supported by the driver (see the file type note on
GS/OS drivers: FTN.BB.XXXX), so the maximum number of devices that can
be supported by a single driver is 63.  You should NEVER increase this
higher than the original value, because the driver probably doesn't have
space in its device tables to support more drivers than it originally
claimed to.

     The AppleDisk5.25 driver supports a maximum of 14 devices - two
5.25" drives for each available slot.  (In theory, it should be able to
support 16: all seven real slots, plus the built-in disk port, but Apple
never completed the implementation of dynamic slot switching for
drivers, probably for compatibility reasons.)

     Don't change any of the higher order bits.  The high order byte
specifies the type of driver ($01 = GS/OS device driver), and the top
two bits of the low order byte specify the type of GS/OS driver (00 =

NOTE: All of the above applies ONLY to GS/OS standard device drivers,
not to GS/OS supervisory drivers, printer drivers, or anything else. See
the filetype note for further information.

     There is one bit in the auxiliary type which is the same for all
types of drivers: bit 15 set ($8000) indicates the driver is inactive
(this is what Finder toggles when you click on the "Inactive" check


From: Neil Parker

017- How does one distinguish between a 13 and 16-sector Disk ][
     interface card?

     For a while at least, new 16-sector Disk II cards shipped with a
little white circular sticker depicting a red Apple with the number "16"
in the middle.

     But the sticker is hardly a reliable test.  A better test is to
look look at the part numbers of the P5 PROM (the lower left chip on the
card) and the P6 PROM (left column, second from the top).

          13-sector    16-sector
          ---------    ---------
     P5   341-0009-xx  341-0027-xx
     P6   341-0010-xx  341-0028-xx

The 16-sector PROMs may also be labelled "P5A" and "P6A".

A program can test the card type by looking at its slot ROM space.  The
signature bytes are as follows:

     $Cn01: 20
     $Cn03: 00
     $Cn05: 03
     $Cn07: 3C
     $CnFF: 00 if 16-sector, FF if 13-sector

For example,

     1  REM Scan the slots for Disk II interfaces
     2  REM By Neil Parker
     10  FOR S = 1 TO 7
     20 A = 49152 + 256 * S
     30  IF  PEEK (A + 1) <  > 32 OR  PEEK (A + 3) <  > 0 OR
        PEEK (A + 5) <  > 3 OR  PEEK (A + 7) <  > 60 THEN 100
     40  PRINT "Disk II (";
     50 T =  PEEK (A + 255)
     60  IF T = 0 THEN  PRINT "16-sector";: GOTO 90
     70  IF T = 255 THEN  PRINT "13-sector";: GOTO 90
     80  PRINT "other";
     90  PRINT ") in slot "S
     100  NEXT


From: Dan DeMaggio

018- Can a Disk ][ Drive be used on a IIc or GS smartport?

     Yes. Call Jameco Electronics. Get the S20-pin header- to -DB19-pin
connector module. It is intended for adapting II/II+ drives for IIc.
(Part# 10022; Product name: AAM APPLE IIC ADAPTER; price: $3.95)


From: Rubywand

019- I would like to add a Read/Write indicator to my Disk ][
     drive. How can I do this with a bi-color LED? 

     The circuit described below works well. It shows Red for Drive
Enabled + Write and Green for Drive Enabled + not Write. That is, a Read
is assumed if the drive is ON and no Write is occurring. The advantage
of this approach is that you always have a lighted LED 'drive ON'
indicator and, so, there is no need to drill a new hole in your drive
panel. The new LED can use the hole occupied by the old "in Use"
indicator LED.


IC-     74121 or 74LS121 1-Shot multi-vibrator
Qgreen- 2N2222A gen purpose NPN transistor
Qred-   2N2222A gen purpose NPN transistor
Rcath-  120 Ohm 5% 1/4 watt resistor
Rgreen- 3.3k 5% 1/8 watt resistor
Rred-   3.3k 5% 1/8 watt resistor
Rp-     20k 5% 1/8 watt resistor
Cp-     10uF/10v 10% "dipped tantalum" capacitor
LED-    2.2V 20ma 3-lead (common cathode) Green/Red bi-color LED

Building the Circuit

IC- locate pin-1 and mark it on bottom side with white-out.
 'Dead-bug' mount the IC using epoxy in the open area near
  top-middle of board with pin-1 end pointing to the right.

connect Rcath to solder pad at - (minus) end of C2
connect #20 wire from IC pin-7 to solder pat at - end of C2

connect Rp from IC pin-11 to IC pin-14
connect Cp + to IC pin-10 and Cp - to IC pin-11 

connect #20 wire from IC pin-14 to solder pat at + end of C4

connect a wire from IC pin-3 to end of R16 closest to 74LS125

connect Rgreen to IC pin-1 (74121 "/Q" output)
connect Rred to IC pin-6 (74121 "Q" output)

solder transistor Qred Collector to Q1 power transistor Collector
 (solder pad area at left front of circuit board just to left of
  the power transistor). Position toward left edge of pad.

solder transistor Qgreen Collector to Q1 power transistor Collector
  solder pad to the right of Qred. 

LED- connect a 3-wire 11" cable to the LED (black to center, red to
  to lead with right-angle bend, green to lead with slant bend).
Old "in Use" LED- pop off the retainer ring and push through the
  LED. Leave the LED mount in the hole. Cut off the LED, spread
  cable ends and tab over with cellophane tape. (Put old LED and
  ring into parts box.

Spread apart retainer 'leaves' of LED mount (at back side of panel)
  to permit easier insertion of new 3-lead LED.

Run LED + cable over back of board and along bottom toward the
  hole in the front panel. Push through hole. (If hole is too small,
  use a Dremel tool and steel 'bulb bit' to slightly enlarge front
  part of hole.)

connect LED cable black to free end of Rcath
connect LED cable green to Emitter of Qgreen (right transistor)
connect LED cable red to Emitter of Qred.

position old LED cable beneath new LED cable. 

connect a wire from the free end or Rgreen (on IC pin-1) to the
  Base lead of transistor Qgreen. 

connect a wire from the free end or Rred (on IC pin-6) to the
  Base lead of transistor Qred.

Add epoxy to the back of the LED and holder to secure the LED.

How it Works

     When /Enable goes low to select the Drive, the power transistor
(Q1) switches ON and supplies +12V at its Collector. If there is no
Write, 74121 output /Q is high, Qgreen conducts, and the LED shows
Green. That is: the Green LED will light during boots and for any READs.

     If the Drive is selected (/Enabled is low) and there is a Write
operation and Write Protect is not ON, then, the /Write Request signal
at 74LS125 pin 8 will go low. This triggers the 74121 One-Shot (at pin
3) producing an aprox. 160ms pulse at 74121 output Q. For the duration
of the pulse, /Q is low and Q is high. Qred conducts, and the LED shows
RED to indicate WRITE.


From: Dan DeMaggio

020- What's the scoop on the 3.5" High Density drive?

     In order to do High Density on the Apple II, you will need both the
High Density 3.5" drive and the Apple 3.5" HD controller. If you don't
have both, you will only be able to do regular density. Of course, you
will also need High Density diskettes.

     Once you have collected the above items, you are in for a pleasant
surprise. ProDos 8 programs not only recognize it, but most programs
format and recognize HD disks just fine. You can even boot off of a HD
disk, allowing plenty of room for GS/OS Desk Accessories and such.

     There are a few drawbacks: You cannot boot copy-protected software
or some FTA demos. You can't daisy-chain a 5.25" on an HD card. Also, it
takes up a slot, even on the GS.


From: Benjamin Summers

021- What is a "UniDisk"?

     The UniDisk 5.25 was Apple's replacement for the venerable Disk ][.
It featured an updated design, tan color plastic case, a DB-19 cable,
and daisy-chain port on the back to which other drives could be
connected. The case color was later changed to platinum and the drive
was rechristened to the "Apple 5.25 Drive".

     The UniDisk 3.5 was Apple's first 3.5" drive for the Apple II line.
Like the Unidisk 5.25, it had the DB-19 cable and daisy chain port on
back. UniDisk 3.5 was dropped in favor of the Apple Disk 3.5, a
different design, at the time of the launch of the IIgs.


From: Mitchell Spector

     One important difference you forgot to mention: The UniDisk 3.5 was
an "intelligent" drive, whereas the Apple 3.5 was a "dumb" drive. There
was a specialized circuit board inside the UniDisk 3.5 drive which had
its own processor, memory, IWM controller and firmware. This was needed
for the //c, in order for the drive to process data before sending it on
to the machine (which was too slow to do the job by itself). You can
easily spot a UniDisk 3.5 as it matched the snow-white color of the //c
and had its access LED and eject button _above_ the disk insert slot
(the Apple 3.5 has them in-line).