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ModA1010.txt
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1992-06-29
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AMIGA (tm) TECHNICAL NOTE
Modifying an Amiga A1010 Disk Drive for External Power
(C) 1986 by Thad Floryan
For those people who need more on-line disk drive capacity but don't wish
the hassle of "rolling your own", this paper describes one procedure that
modifies an A1010 drive for use with an external power supply so that it may
be connected as DF2: or DF3:. The modification includes special wiring such
that the drive may again be used as DF1: with the Amiga's power supply.
Accompanying this article are schematics and illustrations as IFF ILBM Hi-Res
format, created 640x400 with one bit plane, in the file ModSch.iff-H which is
available on a FAUG Hot Mix disk and on a "Fish Disk" under the name
ModSch.iff-H. Included also is the hi-res digitized photo P6-J6.iff-H which
illustrates the plug and jack used for the external power supply connection.
The IFF images may be displayed on the screen with the "ShowALL" program,
and may also be printed with Deluxe Paint (tm).
This project is not for the faint-of-heart since it requires drilling a
large hole in the A1010's case. The internals of the A1010 drive are
fragile; working on a disk drive is not like working on your car. Also,
opening the disk drive case will void your warranty. It may be worth your
peace of mind to contract an experienced technician for the modifications.
Common sense and a good mechanical aptitude are essential. Take your time
and do not rush.
The modifications have functioned correctly WITH MY DRIVES since March 8,
1986, when I performed the operation. You are responsible for verifying
the arrangement of the connectors and power distribution inside YOUR drive
since there may have been production changes and model variations.
The modification and details described in this technical note are provided
"as is", without warranty of any kind, either expressed or implied,
including, but not limited to, the implied warranties of fitness for a
particular purpose. The entire risk as to the results and performance of the
modification is assumed by you. In no event will I be liable for direct,
indirect, incidental or consequential damages resulting from the use or
(mis-)application of this information.
Prior to starting the modification, you will need to acquire a power supply
capable of supplying 2W at +5 VDC (0.400 Amp) and 2W at +12 VDC (0.200 Amp)
for each disk drive. "Surplus" power supplies from modems are readily
available for approximately $10 each and are ideal for this application; be
sure you get a regulated power supply and not just a simple transformer.
You should also purchase a mating plug and jack for connecting the power to
the A1010's circuitry; hardwiring an external power supply directly to the
A1010 is not advised. The jack should be one that does not extend too far
into the A1010 case since there isn't much room; examination of the interior
of the A1010 will reveal what connectors are suitable. I used some surplus
connectors manufactured by Amphenol; there is no part number on the connector
but the illustration accurately depicts the part I used, which also has a
locking twist-tab to prevent accidental disconnection.
The remainder of this article references the illustrations, so either make a
hard copy of ModSch.iff-H, or display it on your monitor using the ShowALL
program. The drawings may flicker if your monitor does not have a long
persistance phosphor, so adjust the brightness and contrast as suitable.
Opening the A1010 case requires unscrewing the four screws on the underside
at each corner. Inside will be a metal RFI shield covering the back of the
disk drive and the interface printed circuit board.
Remove all screws that fasten all parts to the plastic case, making note of
each screw's location. I find that making a rough sketch of all the parts
on a piece of note paper and pushing the screws into the paper at the proper
location provides an easy and safe way to assure that all parts are restored
to the proper location upon reassembly.
Examine all parts while they are still in the case. Try to find a location,
preferably on the back panel, where your jack can be placed without its pins
shorting against something and, most importantly, where it will fit with
adequate working clearance. Note the location of J6 (the Amphenol 5-pin
jack I chose to use); that was the only location that worked for me. Your
connector may permit other placement. Experiment now, while all the parts
are still in the case and before you drill any holes.
Once you've found a place for the jack, mark the location on the outside of
the case and remove all parts (disk drive, RFI shield, and interface PCB)
from the case. Drill a small pilot hole for the jack at exactly the marked
location, using, for example, a 1/16" bit. Then gradually use larger bits
until the hole is the correct size for your jack; the Amphenol required a
1/2" hole. The case drills cleanly and easily, so there is no need to force
the drill (which might crack the case).
Proceed now to solder wires to the jack per the wiring diagram. It's easier
to wire the jack before fastening it to the case. Note the excessive slack
in the wire which is necessary to provide working room when routing the wires
when re-installing the RFI shield.
Now install the jack in the case and position, but do not fasten, the disk
drive and interface PCB back in the case. Following the wiring diagram,
connect the wires from J6 (the jack) to J3 (on the interface PCB) and to the
disk drive power connector. You should buy or make connectors that will fit
the pins (at J3 and on the disk drive); I re-used parts of the original cable
assembly and also made one connector from a piece of 0.100" spaced socket
material. You will need to be creative when fabricating the new harness.
Be sure to verify the +5 VDC and +12 VDC connect to the original pins on the
disk drive. Also make sure that the ribbon cable to the disk drive from the
interface is firmly connected, and proceed to reassemble the A1010 placing
all screws in their original location. Check all wires to be sure there is
adequate clearance and no inadvertant short circuits.
Now wire the plug (P6) from the power supply, making sure the +5 VDC, +12 VDC
and ground will mate with the proper pins on jack J6; this plug is shown as
P6B in the illustrations. The P6A is an accessory "jumper plug" which, if
inserted in J6, powers the drive as it was originally wired.
Before connecting the modified drive to your Amiga system, power it up
stand-alone and verify the proper voltages are present. If so, then remove
power and put the A1010 case cover back on.
With your Amiga and the modified A1010 powered off, connect the DB-23 cable
from the modified drive to the back of DF1:, power up the system, and enjoy
increased floppy disk capacity. Note that each additional A1010 drive
connected to your system will consume an additional 25K of chip RAM for disk
buffers; this "may" cause problems with some programs, so remove the drive
if necessary.
Comments about this Technical Note are welcome! I can be contacted at the
following computer and net mail addresses:
UUCP: ... {lll-crg, ptsfa, hplabs}!well!thad
ARPA: well!thad@LLL-CRG.ARPA
The WELL: thad [415/332-6106, or Telenet '@c well']
DELPHI: THADF [617/576-0862, or Telenet '@c delphi']
AMIC: Thad Floryan [707/579-0523, 300/1200/2400]
BBS-JC: Thad Floryan [415/961-7250, 300/1200/2400]
FAUG-BBS: Thad Floryan [415/595-2479, 300/1200, First Amiga Users' Group]
BBS-HT: Thad Floryan [408/737-0900, 300/1200, 6P-8A M-F, 5P Sat-8A Mon]
AmigaDevExch: Thad Floryan [408/372-1722, 300/1200, MaxiSoft BBS]
--------------------
Amiga is a trademark of Commodore-Amiga, Inc. / Commodore Business Machines
Deluxe Paint is a trademark of Electronic Arts, Inc.