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Apple II Csa2 FAQs: Floppy Disk Drives, Part 9/25 (2/2)
[continued from previous message]
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
sh
aring 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,
includi
ng 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.
WHAT ABOUT THE APPLE UNIDISK 3.5" DRIVE?
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.
FINDING A USED MAC 3.5" DRIVE MECHANISM
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 discarded.
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.
DISASSEMBLY OF THE APPLE 3.5" PLATINUM DRIVE
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 d
b-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 replacement.
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 pins.
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 inside.
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.
REASSEMBLY
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'
in
sertion 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 = standard).
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 box).
____________________________
From: Neil Parker
017- How does one distinguish between a 13 and 16-sector Disk ][
controller 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: FF if 13-sector; 00 if 16-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.
Parts
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 --- Fruity Dog 6.2