ggibeau@ucqais.uc.edu (AMOEBOID) (01/19/90)
Here is a slightly modified version of the article that was
submitted (and tentatively accepted) to Amazing Computing.
It is for the modification of your A1000 into a ROM based machine.
Duplication of this article without express written permission of
the authors will probably result in your not winning the
Publishers Clearing House sweepstakes (and you thought you were
going to meet Ed himself :-)).
---------------------------------clip here--------------------------
How to turn your A1000 into a ROM based machine
by
Dwight Blubaugh and George Gibeau, Jr.
Ohio Valley Amiga Users Group (OVAUG)
WARNING - This hardware modification will VOID your warranty
(GRIN). It requires some electrical component assembly experience,
such as soldering and desoldering printed circuit boards. Do not try
it if you do not feel comfortable disassembling your computer and
working inside your machine. Please read this entire article before
actually starting any of the described work.
Are you tired of spending extra time looking for that misplaced
Kickstart disk in order to get your A1000 up and running? Do you want
to run a BBS but don't want to deal with the infamous Kickstart "hand"
screen after a power outage? Would you like to get rid of the
daughterboard and eliminate a potential source of GURU visits? If you
answered yes to any of the above questions, then this hardware
modification will be of interest to you. With a little bit of work and
the following information, you can make your A1000 a ROM based machine.
The first choice you have to make is to decide which version of
the Amiga ROM you want to use. When deciding which ROM version to run,
carefully consider whether you will be running an autoboot hard drive
or not. If you are not going to run an autoboot harddrive, then you
can probably go down to your friendly local dealer and talk them out of
a 1.2 ROM that they acquired during an upgrade to 1.3 for a 500/2000
owner. If you will be running an autoboot hard drive, then you can buy
the 1.3 ROM for about $35.
You will need to gather the following tools before you begin:
25 watt soldering iron, desolderer (vacuum type - piston, not bulb -
works best), thin electronic solder, small pair of wire snips, small
needle nose pliers, Phillips screwdriver, flathead screwdriver,and a
good volt/ohm meter.
parts list
QTY PART TYPE
2 74F257
2 74LS244
2 20 pin IC machine socket
1 40 pin IC machine socket
1 piece 30-22 gauge wire
1 1.2 or 1.3 ROM (or 1.4 - grin)
36 gold posts (use the ones removed from the motherboard).
1 16L8 PAL (CAS)
1 16L8 PAL (EN) (for engineers, we can supply JADEC file
for these, or the PAL equations
- *** The CA A1000 docs have wrong equations!!
The TTL's can be obtained from any electronics supply house
such as Digi-Key Corp.. PALs can be obtained from several different
sources; Commodore, Spirit, or if needed, we can supply them. If
possible, order 15ns PALs instead of the 25ns, as these will perform
better.
Disassembly of the machine.
Find a large, clean work area with plenty of light and
electrical outlets. Cover the work area with some sort of static-proof
material to keep from damaging the parts. Unplug the power cord to
your machine and disconnect all external devices from the computer
(drives, monitor, mouse, etc..). Turn the computer upside down and
remove the 5 Phillips screws holding the top and bottom parts of the
case together (it will greatly facilitate reassembly if you organize
the screws into groups based on their origin within the machine as you
remove them). Carefully turn the computer back to its normal position
and remove the front 256K memory cartridge (if installed) and then the
entire front faceplate. Next, GENTLY separate the case halves (if you
start on one side at a time, and pry the top away from the bottom, you
will get better results). The case is connected by 2 small hooks on
each side, be careful not to pry too hard or you will break them. Set
the top of the case off to the side where it will not get in the way.
Next, remove the metal RF shield which is held in place by 14 screws
and 2 metal tabs (tabs can be straightened with a small pair of needle
nose pliers). Remove the screws and posts securing the disk
drive and remove the drive, including power and data cables. The
floppy LED must be removed from the front panel or disconnected at
in-line coupling, depending on the model. Disconnect the power supply
cable (a screwdriver may be needed to get the plastic tab to unhinge
enough) as well as the power LED.
You should now have just the mother and daughter boards
remaining. To remove the daughterboard, unscrew the 3 small screws
holding the board down. The daughterboard is now held in
place by numerous gold posts. In order to separate the daughterboard,
begin on one side and gently pry up while moving around the board (do
not apply too much pressure as you do not want to break the board).
After removing the daughterboard, grasp the motherboard near the side
where the mouse and joystick plug in, slightly pulling the side of the
case away from the board, and remove it from the case. It will come
away with the bottom RF shield attached. To remove this, straighten
out the remaining metal tabs securing the shield to the board. Finally,
remove the 3 plastic stand-offs that support the daughterboard, they
are secured from the bottom of the motherboard by 3 small screws.
You should now have nothing in front of you but the
motherboard. Now comes the fun part :-), this will go faster if you
have a friend handy, but it can be done by one person. You will need
to desolder and remove ALL of the gold posts. This is best
accomplished by sucking the solder from the holes first, then gently
pulling on the post with the needlenose pliers from the component side
while heating it up from the solder side. Try not to bend the gold
posts during removal as they will be used later. Also, do not apply
too much pressure so as to damage the plate though holes. There are a
total of 124 gold posts to remove, so take your time, and be careful
not to gouge into the board with the soldering iron or you may
inadvertently cut traces. After all posts have been removed, you will
need to clean the old solder from the holes. This can best be done
with a vacuum type desolderer. To facilitate solder removal, fill the
holes with new solder, then heat up the solder and suck it out. This
works better than trying to remove the old solder by itself. A final
cleaning of the area around the holes can be done with the aid of
solder wick, this will help remove any splashes or flakes of solder
that may cause problems.
Next, carefully desolder the capacitor located at C137 and save
this, it will be used later. Solder the 4 TTL chips into the following
locations (machine pin sockets are optional): the 74F257's into U2I and
U2J (**NOTE** the board is silk screened at these spots with the label
S257, however F series chips are used on the daughterboard. The F
series is a better chip than the S series), the 74LS244's into U3G and
U3I. The 20 pin IC sockets go into U5L and U5M, these will be where
the PALs go. Remove the 2 socketed ROMS (but leave sockets
for now) located at U5N and U5P and keep these as a memento of your
prehistoric machine days.
Next you will have to cut 2 traces and solder 2 jumpers on the
motherboard, this will vary depending on which board revision you have.
If you look on the motherboard under the floppy drive you should be
able to determine the board revision. It will be one of the following,
either Revision 6 or Revision A.
Cut the appropriate traces and add appropriate jumpers (a small
piece of 30/24 gauge copper wire, bent over, makes a perfect jumper)
dependant upon the motherboard revision: (for correct directions
on which cuts to make, send lots of small, unmarked bills... :-),
actually I will put together a IFF file of the diagram and send it up.
If you do buy the board, it will come with complete directions and
pictures).
You are finished with the motherboard for the moment, set it
aside and concentrate on the Kickstart ROM adapter board.
Kickstart ROM Adapter Board
The following instructions are for a printed circuit card
available from us, if you wish to wire wrap one or etch your own, then
it is assumed that you know what you are doing and will be able to
follow the provided pin list.
Refer to Figure 5 for components and locations described in the
following steps. Using the gold posts previously removed from the
motherboard, place them into the proper holes, extending just above the
surface of the board. This works easier if you seat them from the
bottom. Once in place, press down on the card (top side down) to
ensure that the pins are flush with the top of the card. When you are
sure all pins are even, solder them in place. Next, place the 40 pin
socket in the card making sure that all pins are aligned into the
proper holes, as well as proper orientation (pin 1 of socket in pin 1
hole), then solder it in place. The last item to solder is the
capacitor that was removed from the motherboard (orientation of
capacitor is not important).
Provisions have been made on the card for a 512K ROM if CBM
ever uses this part. This is accomplished by a trace cut on the
adapter board and a jumper to A18 on the motherboard. This signal is
NOT available on the ROM sockets in a stock A1000.
Trouble Shooting
Before powering up your machine, it is a good idea to check for
potential errors. One of the first items to check is the adapter
board. Visually inspect it for any solder bridges (solder making a
connection between two spots where it should not be) or solder flakes
that may have occurred during the assembly process. If you find any,
carefully scrape them away ensuring that you do not do any damage to
the card in the process. Next, test the ROM chip for shorts using a
volt/ohm meter. Place 1 probe on pin 1 and run the 2nd probe along the
rest of the pins, then move the 1st probe to pin 2 and repeat.
Continue this until all pins have been checked. The only pins that
should be connected are pins 10, 11, 30, and 31 (all of them are
ground). If you find any shorts, you will have to determine where the
problem originates. This may take a bit of work, but if you were
careful during the initial assembly this should not be necessary.
Another potential source of error can be caused by heat damage causing
the separation of pads and/or traces from the motherboard during the
desoldering process. You will need to both visually and electronically
test the circuitry. Start testing the traces as they leave the ROM
sockets and make sure they are making the proper connections.
The big moment :-)
Your computer should now be ready to test. Temporarily replace
the motherboard in the case, hook up the power supply, disk drive (can
fit in loose) and the monitor. The card that you just finished
assembling will fit into the existing sockets (U5N and U5P). Make sure
it is oriented in the proper manner (Figure 6). Press it into place,
making sure that all pins are in the proper receptacles. Making sure
nothing else is loose on the motherboard, turn on the power. If all
went well, you should see the familiar gray to white cycle and in a few
seconds the assuring "Insert Workbench" screen. If this is what you
see, then congratulations are in order, you have successfully completed
this project, if not, then some additional error checking has to be
performed. To explain fully what additional checking has to be
performed is beyond the scope of this article, but basically obtain an
A1000 schematic and verify connections to all new chips.
If your computer is properly functioning, turn off the power,
disconnect all external devices, and remove the adapter board. Remove
the motherboard from the case and unsolder the sockets at U5N and U5P
and clean the holes as before. The sockets must be removed and the
board soldered in place to ensure the proper fitting of the floppy disk
drive. If the adapter board is too high off the motherboard, it will
interfere with the floppy chassis. Insert the adapter board into the
proper location (maintain proper hole alignment) and solder it in
place. After you are finished soldering, trim the gold posts even with
the solder.
Reassembly
Since you already have the computer apart, you may as well take
this opportunity to clean it. For optimal results use Flux-offtm or
alcohol to clean off the solder side of the board, if nothing else,
blow the dust off all the components with a clean source of air and
make sure all chips are seated securely on the motherboard. Now you
are ready to reassemble your machine. Replace the RF shield on the
bottom of the motherboard and secure it in place with the metal tabs
that are not used to hold down the top shield (a half twist with the
pliers will do the job). Next, place the motherboard back into the
bottom of the plastic case and replace the 2 screws that will be under
the drive. Reconnect the power supply cable, power LED, floppy drive
ribbon cable, and floppy drive power cable. Re-seat the floppy drive
into its appropriate place (make sure the ribbon cable does not come
off the drive) and refasten the screws and posts that hold it to the
motherboard. Replace the top RF shield and secure it with the screws
(make sure the correct screws go back into the proper locations).
Next, replace the backplate and the faceplate, be careful not to break
them (the backplate can be bent, but do not overbend). After the front
and back plates are in location, replace the top of the case and ensure
that it latches into place, secure it with the 5 screws from the
bottom. After replacing the front memory module (if present) as well
as the small front cover, your machine should now be ready for normal
operation.
You will have a few parts left over after reassembly. They
will include; 1 daughterboard, 3 plastic standoffs, 2 ROMS, and 6 small
screws. These parts should be saved just in case you have need of them
in the future, besides, the daughterboard is a valuable commodity as
CBM does not sell them as spare parts.
This project has been successfully tested with the following
combinations of system configurations; Spirit Technologies IN1000
memory card with 1.5 megs installed, the Palomax hard drive interface
kit, a Ronin Hurricane Accelerator card (with and without memory card),
and an ASDG memory box.
For those of you who do not feel comfortable etching or wire
wrapping your own boards, we have a printed circuit cards, PALs and the
other components available. The bare card is $15, a kit containing 1
bare card and all necessary components (except for PALs and ROM) is
$30, and an assembled, tested card plus other needed parts (no PALs or ROM)
is $40. For JADEC file or PAL equations, send SASE. Inquire about user
club quantity discounts. You can order from:
George Gibeau, Jr. Dwight Blubaugh
Dept. of Biology - ML06 Dept. of Chemistry - ML 172
University of Cincinnati University of Cincinnati
Cincinnati, Ohio 45221-0006 Cincinnati, Ohio 45221-0172
UseNet ggibeau@uccba!ucqais.EDU blubaugh@uccba!ucqais.EDU
BitNET pbior4w.ucccvm1
On various Amiga BBS's as Ni-Lach
If you do not feel comfortable performing this modification
yourself, we can do it for you for a small fee (GRIN), or get together
with your local user group for a group "hack".
Parts sources:
Digi-Key Corporation
P.O. Box 677
Thief River Falls, MN
56701-9988
1-(800) 344-4539
Kickstart, Amiga, and A1000 are trademarks of Commodore Business Machines
Flux-Off is a trademark of Chemtronics
Palomax is a trademark of Mr. Jack Koehler
PIN LIST FROM ROMS ON ADAPTER BOARD TO SOCKETS ON MOTHERBOARD.
ROM PIN U5P PIN U5N PIN SIGNAL
1 14 or 14 GND (A18* for future 512K ROMs)
2 3 or 3 A8
3 4 or 4 A7
4 5 or 5 A6
5 6 or 6 A5
6 7 or 7 A4
7 8 or 8 A3
8 9 or 9 A2
9 10 or 10 A1
10 14 or 14 GND
11 14 or 14 GND
12 22 or 22 ROM*
13 11 -- D0
14 -- 11 D8
15 12 -- D1
16 -- 12 D9
17 13 -- D2
18 -- 13 D10
19 15 -- D3
20 -- 15 D11
21 28 or 28 +5 VOLTS
22 16 -- D4
23 -- 16 D12
24 17 -- D5
25 -- 17 D13
26 18 -- D6
27 -- 18 D14
28 19 -- D7
29 -- 19 D15
30 14 or 14 GND
31 14 or 14 GND (A18* for future 512K ROMs)
32 20 or 20 A17
33 1 or 1 A16
34 27 or 27 A15
35 26 or 26 A14
36 2 or 2 A13
37 23 or 23 A12
38 21 or 21 A11
39 24 or 24 A10
40 25 or 25 A9
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Hopefully this will make using your A1000 a tad bit easier, it is always
good to give something back to the Amiga community.
Regards,
George
--
UUCP: ucqais.uc.edu!ggibeau BBS: (513) 721-7977 GT NODE: 006/005
US Snail-Dept of Biology ML 06, University of Cincinnati, Ohio 45221
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