CHATTANOOGA COMMODORE USERS GROUP

KEYBOARD MAINTENANCE

BY: DAN McFARLAN


     In the several years that I have had and used my Commodore 64 I have
experienced only two cases of trouble.  The first was apparently a power
supply connector problem.  This resulted in a complete shutdown of the
computer and output to the then TV monitor, however the red indicating light
on the computer continued to operate.  This case of trouble was at first
intermittant and eventually went away on its own perhaps due to the wiping
action of plugging and unplugging the power supply cable at the computer.
     The second case of trouble was a contact failure of the 'U' on the
keyboard.  The 'U' never did fail completely but required several times the
force required on other keys to make it operate. In normal typing the 'U' just
got left out.  Imagine typing  RUN and getting a SYNTAX ERROR almost every
time.  I finally  broke down and tried cleaning the contact pads of the
keyboard circuit board with plain water.  This helped for a few months but
eventually went back to missing 'U''s again.  The next time the contact pads
were cleaned with alcohol and has been working OK ever since.
     Some members of the club have gotten into the circuitry of their
computers quite deeply but if the idea scares you, the following may help if
you have key contact trouble.
     Unplug all cables and turn the computer over.  Remove the three phillips
head screws on the front edge then holding the two halves of the case together
turn the computer back upright.  Lift the keyboard from the base allowing it
to hinge at the back edge and raise the keyboard to about 90 degrees.  Now
unplug the two cables (a 2-wire and an 18-wire) from the circuit board thus
allowing the keyboard to be turned upside down on the table.  Unsolder the two
wires from the shift lock switch.  Now with a small phillips screw driver
remove the 23 small screws from the brownish orange circuit board of the
keyboard.  The circuit board can now be lifted out and turned over.  Identify
the key contact pads (2 per key) of the key in trouble and clean the pads with
a Q-Tip and rubbing alcohol.  During reassembly align the circuit board on the
alignment pins so the pins just extend through the board and replace the 23
small screws.  Don't over tighten these screws - they are very small and only
need a small amount of torque to secure them.  The rest of the reassembly is
just the reverse of the disassembly.
 
[PRESS RETURN]: