84542 packages online


No screenshot available
Short:easiest A1200 tower keyboard solution
Author:jeff at
Uploader:jeff unitechelectronics com
Requires:care and about 1 hour fitting.
Download: - View contents

Hi Folks......

Welcome to the simplest logical solution to the dilemma of the A1200 tower

This project was first researched in May 1993, due to the requirements of
fitting an A1200 into a tower at the minimal cost to the client/customer.

It was discovered by myself (Jeff Rose) that most models of A500 keyboard
could in fact be utilised in the same way as the A1200 keyboard connects to
the A1200 motherboard.

The connectors are the same width, 31 connections, so if it worked on a
A500, it was expected that the Commodore engineers would use logic and
simply have moved the connectiom to the centre of the A1200 keyboard, thus
connecting to the A1200 motherboard.

After carefully studying the circuit diagrams of both keyboards, with
confidence, I wired up the keyboard as per these attached diagrams and it
worked first go, complete with reset.

This was then tested on and it worked on Rev 1D4 up to Rev 2B A22200
Motherboards. A logical solution was born to solve the A1200 tower
conversion problem. This information was classified up till now by myself.

Making the small circuit sitting over the ram is simple.

Cut a small copper clad circuit board to fit just over the 4 chips, score
out teh five dividing spaces witha small sharp knife. heat up the  small
cut out pieces and they will lift off the printed circuit board leaving
five solder rectangular pads on which to connect via soldering,  do not
overheat as they too will lift.

Parts Required:

the small copper clad board, a ferrite bead, (A500 has many)
a 15µF ~ 22µF  capacitor and some colored wires per the drawings.

Doing it:

The most complex part is the lifting of pins 12 & 13 of the keyboard chip.
this will require an amount of skill, not to get it too hot and not to
the pads on the 12 & 13 chip legs pads.

I would suggest using a very thin rigid knife sliding it under just as the 
solder melts, this will do three things, 

(1) this will separate the leg from the pad.
(2) it will lift the leg off the pad due to the thickness of the knife.
(3) finally it will assist in cooling the pad and legs after heating.

Follow the pictures (in color) no black & white diagrams to confuse.
Try to stick to the color wiring patterns I have outlined, this will 
aid fault finding.

Be sure to check your work before you power it up, a good digital multimeter
is a good start, the range in price from el-cheapo to really expensive. 

The el-cheapo as long as it has a continuity piezo buzzer or similar in it is
fine to use.

It is now for everyone to enjoy !


Comments to me, Jeff Rose, Managing Director CEO, Unitech Electronics
Pty.Ltd. Est. 1978.

email: jeff at  web:


Cheers, Jeff

Kindest Regards, Jeffrey. G. Rose. JP        C.E.O. and President.
Unitech Electronics P.L. 1978-2002   Dare to be different ! Just do it!
Designers and Manufacturers of Hi-Standard Quality Electronic Equipment
jeff at 195 Pages
Showroom: 9am-5pm. 8B Tummul Place, St Andrews. Sydney. Australia. 2566
          Fax : +61 2 9603 8685          Phone : +61 2 9820 3555

"There is one thing stronger than all the armies of the world, 
                    and that is an idea whose time has come...Neways"  

"This communication, including any attachments, is strictly confidential.
Dissemination of the contents without permission is a breach of Federal Law.
If you are not the intended recipient, you are not permitted to read it - 
please contact me immediately and in doing so destroy it, and do not copy 
or use any part of this communication or disclose anything about it to any
unauthorised persons whatsoever, only the recipient mentioned. Thank you."

Contents of docs/hard/a1200kbpcb.lha
---------- ----------- ------- ------- ------ ---------- ------------ ----------
[generic]                 1366    2833  48.2% -lh5- 4116 Apr 19  2002 a1200kbmods0.text
[generic]                13345   13345 100.0% -lh0- 7669 Apr 19  2002 a1200kbmods1.gif
[generic]                 7746    7746 100.0% -lh0- 31d1 Apr 19  2002 a1200kbmods2.gif
[generic]                 7860    7860 100.0% -lh0- 7320 Apr 19  2002 a1200kbmods3.gif
[generic]                 9016    9016 100.0% -lh0- bfab Apr 19  2002 a1200kbmods4.gif
[generic]                27034   27034 100.0% -lh0- b53f Apr 19  2002 a1200kbmods5.gif
[generic]                31044   31044 100.0% -lh0- e427 Apr 19  2002 a1200kbmods6.gif
---------- ----------- ------- ------- ------ ---------- ------------ ----------
 Total         7 files   97411   98878  98.5%            Apr 22  2002

Aminet © 1992-2024 Urban Müller and the Aminet team. Aminet contact address: <aminetaminet net>