Commodore 64 / 128 latching Key Adapter

by Pippowicz Feb 13, 2018
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Hello Pippowicz.

I like this idea very much.

I have a C64. It's an early model. The shift lock won't stay down.

When I looked at the contact circuit board it had VIC 20 printed on it.

The Shift lock is an unusual round style. Similar to the regular square one that is most common. I can't seem to source the original one anywhere.

This project looks perfect for my needs.

I will get back to let you know how it goes.

Thanks for sharing!

Could you take some Photos from the original Key / Keycap please? I am always interested in
uncommon parts.

Hi Pippowicz,

Apologies for the delayed reply. I got a little busy.

Here are the photos of the original latching switch.

You will note that the unit is aprox 15mm x 15mm in size.

The plunger shaft is a precision fit into the switch assembly. When it is all inserted it has negligible side movement.

On the plunger shaft one can see a small bent metal wire. I had made this in an attempt to replace the original plastic one. The plastic one had a little pin on one end which had broken off. This is the means by which the switch "latched" into the white nylon piece.

The back cover was fastened by the 2 metal contact pins. These pins were twisted into the main body of the switch. One can see the spiral thread on one side of the pin.

I had made a mess of the electrical contacts when I mistakenly thought the the back cover was friction fitted. I inserted a thin edged screwdriver along the seam breaking the wire contacts.

The internals were very small. The aging plastic was not up to the task any more unfortunately.

If you happen to see a latching switch with a nice sturdy plunger please don't hesitate to let me know. I will be more than willing to try it out.

Ok, i see. Let me sort that out:

  • You want some longer travel of the Switch
  • You want to "latch" the switch more "sturdy" and a more "sturdy" Shaft
  • The Switch needs to go in the Round Hole of your Keyboard, eventually with some printed Adapter
  • The Switch has to be small enough to have clearance under the Keyboard.

Let me tell you that i found it nearly impossible to find a latching switch matching all criteria.

I even searched Aliexpress and found nothing - except some Keys with the right measurements in a pack
of 100 - but after asking the Seller they turned out as no latching Versions.

I personally have never seen the round version before.

I know that my Chinese Switch isnt the best but it turned out the most obtainable version.

Hi Pippowicz,

Thanks so much for taking the time to read and reply to my post.

Yes, that's it.

Main upgrades would be

~ some longer travel of the Switch

~ the switch with a more "sturdy" Shaft

I found your 3d printed adapter design to be perfect for fitting into the square hole of the Key Board frame.

I think the PCB has a round hole (this is what can be seen in the photos). The Keyboard Frame is actually square and the same dimensions as your great adapter design. There were no issues at all in installing your 3d printed adapter (i think my 3d printer is not calibrated correctly, hence the duct tape).

The adapter with the switch assembly did not go past the PCB's round hole. I think the hole has a diameter if 15mm.

Later model C64's used a latching switch with a square body 15mm x 15mm and the PCB also had a square body to suit.

The PCB is exclusively used for every other key except the latching switch. The latching switch is "independent" of the keyboard. I think that's why there is a round hole, just to make clearance for the latching switch. It just seems to slot into the Key Board Frame and is not attached to this PCB.

If a much longer switch were to be used it would need to fit thru this 15mm diameter hole. There is quite a bit of room to maneuver between the underside of the Keyboard and the top of the circuit board.

What I will do is take some more photos and measurements of the PCB round hole and the Keyboard frame square hole.

I too couldn't find anything suitable in the latching switches.

I did find this :


And this:


I am not sure if the shaft is stable laterally or not. So too the external dimensions of the foot peddle switch.

The original latching switch is 36 years old. Technology and keyboard designs have moved on since then.

I find your design great and the switch I used does work.

I would like to get a switch that had a little more lateral stability and travel distance.

Your Number one Link has the Connectors on the Side, i got one of these
and it wont fit nice to the hole.

Number two link is difficult to adapt to the Keycaps.

Hi Pippowicz ,

Thanks for investigating these other switches. It is shame they are not suitable.

Here are some more pictures from a later model C64 keyboard.The shift lock is slightly different from the earlier round model.

The shift lock switch is quite independent of the rest of the keyboard save the 2 wires used to connect the shift lock switch to the main keyboard harness.

The round switch and the square style switch are not interchangeable due to the hole in the pcb.The switches protrude a little at the back.

Would it be possible to modify your design so that the key adapter sort of slid inside the square mounting bracket maybe touching the sides for the key's entire travel cycle?

That would definitely eliminate any side movement in the key. Just a thought.

I like your design very much:-)

I have only limited time atm and thats really not a complex Design,
so perhaps someone other can do it.

If you have time to wait i could look into it but it will take some time.

Hi Pippowicz,

I totally understand.

I appreciate the time and efforts you have already put into this project and replying to me.

Take care.:-)