Repairing a broken C64 key

2019-03-10

(C64,3DPrinting)

A while back I pulled my C64 out of a box and the escape key caught on something and snapped off, sending the key and the spring into outer space (or somewhere behind a cupboard). Unfortunately the key plunger also broke. I found a model on thingiverse for a new plunger so time to take my keyboard apart and also give it some much needed cleaning. This is my setup:

Remove the three case screws underneath the front of the C64. You can then hinge the top off. Take a photo of the connectors just in case.

Unscrew the keyboard from the top of the case. I also took a photo of the keys so I knew what went where later on (I know the Internet, but just in case). You then need to de-solder the two wires connected to the shift-lock key.

Pop all the keys off and don't loose them springs!

You can now unscrew all the tiny little screws holding the keyboard circuit board to the plastic key plunger mount.

It took me a few failed tries to print the plunger. First because I was trying to print the model as-is rotated on it's side - I used Slic3r to rotate it around the X axis so it was vertical. Secondly the print game unstuck as the model has very little footprint on the hotbed - I used a lot of glue.

The keycap is really cool. The model is here. I haven't painted it yet and I think I will just leave it as-is rather than try to make it look original.

Here is the plunger installed:

Screw the circuit board back onto the plate and prepare to put the keys back on. I made sure to clean each keycap nicely and also rub the circuit board contacts with alcohol to get it all noce and new.

I then made a shitty spring by breaking open a ball point pen, straightening the spring and re-wrapping it around some else. I am not super happy with the spring but it's good enough for now. The printed keycap and the printed key plunger had a loose fairly fit so I put a blob of wood glue to attach it and held the key down with a weight while it dried. I hope the glue is enough to hold it, but not so strong that I won't be able to leaver it off if I need to do another repair later on. Here is what it looks like: