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C128D Keyboard for C-64

Project: C128D keyboard as substitute for original C64 keyboard.
Target : C64
Time   : 90-180 min.
Cost   : ~10 US$
Use    : - C-128 keyboard is more ergonomic
         - up to 10 meters cable length without killing the CIA


C-128 keyboard parallel to original C-64 keyboard with a keyboard booster circuit.


Simply replacing the original keyboard by a C-128 D one would be dangerous for the CIA. To save lines, the CIA is wired as a matrix, so that the controlling is dynamic. The CIA has to supply the necessary currents for loading the cable capacities. The longer the cable, the higher the capacity. The maximum output current varies with the manufacturer; overloading the CIA with a capacity exceeding the specified output current will destroy it.



  1. Pull off all cables, then open case.
  2. Build the circuit shown below:

    [Picture of DIN - Sub-D25 connection]
    (Click here for ASCII version)

  3. Now solder the other end of the flat cable to the 25-pin connector according to the following scheme:

    [Picture of connection scheme]
    (Click here for ASCII version)

  4. Close the case again.

Possible failures

Updated: September 30th, 1997
Created: Early 1997
Status : Verified

Site copyright © 1997 by Marc-Jano Knopp
This document is part of MJK's Commodore 64 & LCD Page
Brought back to life by Peter Schepers, Dec 10, 2005 because I really liked this site!