Shift Lock Circuit
The original Shift Lock key uses a latching/locking type switch. Cherry used to make these but have since discontinued making them. Thus, I had to come up with another solution. I therefore made a small circuit which adds a push on push off functionality. This way a standard non-latching microswitch can be used to turn on the Shift Lock and when pressed again, turn it off. In order to get a visual indication of the state of the switch (on or off) a red 3 mm LED is placed underneath the keycap which lights up whenever the switch is activated. The circuit is made from a few standard components including a NE555 timer, a 4066 analog switch, some resistors and two capacitors.
Before transferring the circuit onto the PCB, the Shift Lock circuit was tested with a simple breadboard connected to a Commodore 64. The Shift Lock circuit is powered using the 5V line going to the keyboard. This 5V line is not used on the original C64 keyboards, so it came in handy for powering the Shift Lock circuit on my keyboards. The 5V line is also present on the C64 Reloaded boards and Gideon has confirmed that it is also present on his Ultimate64 boards (thanks Gideon!).
Two SIP sockets have been added to the Shift Lock microswitch. This way the color of the 3mm LED can easily be exchanged to match the color of the power LED of the machine.
It is also possible to exchange the standard non-latching microswitch with a locking type switch like the Cherry Locking switch. To do this, the momentary microswitch obviously needs to be de-soldered and replaced. In that case the small Shift Lock circuit is no longer needed and must be bypassed in order for the locking switch to work properly. This is simply done by moving the two header caps inside the Shift Lock Circuit area of the PCB as indicated by the text on the board. Easy peasy!
NOTE: Using the MechBoard64 with a Keyrah from Individual Computers (link) should be possible. However, as the 5V line of the Keyrah is not connected, neither the Shift Lock circuit nor the LED will function. In this case, a Cherry Locking switch may be used instead.
Wiring the MechBoard64
The keyboard is connected to the motherboard using a 20 cm ribbon cable. Below are images from installation in a long board (Assy 250425) and a short board (Assy 250469).
One of my C64C slim cases has an Assy 250466 long board installed as Commodore basically assembled machines depending on what they had in stock. The combination of a long board and a C64C slim case places the keyboard pins on the C64 motherboard quite far from the keyboard pins on the PCB and the 20 cm ribbon cable is simply too short. I therefore had to use a 10 cm extension cable to make it work. I have also seen Assy 250425 long boards installed in C64C slim cases. That combination will also need an extension cable…
Keyboard Case & Mount Compatibility
I wanted to make sure that the keyboard is as universal as possible. I therefore tested it in all the different machines that I have in my possession. I found that the MechBoard64 fits perfectly in all of my machines regardless of the internal hardware and cases (breadbox and C64C slim cases). The only combination that caused some trouble was long boards (e.g. Assy 250425 and Assy 250466) installed in a C64C slim case. This combination needs a longer ribbon cable in order to make the connection as described previously!
Adding the MechBoard64 to Real Hardware
Well, there is not much to report as the MechBoard64 simply does what it is supposed to do – give inputs to the Commodore 64 regardless of motherboard version. The Shift Lock circuit works like a charm and turns on and off as it is supposed to. The MechBoard64 fits perfectly in both C64C slim cases and the old breadbox cases.
If looking closely at the images below of the keyboard inside a C64C case, it’s possible to see the wider Gateron microswitches underneath the keycaps. This is of course not possible on the old keyboard as it has, well no microswitches. All that is visible is the springs…
…and after waiting for more than two years, my C64 Reloaded machines have finally gotten their new keyboards… Now I just need need some keycaps. Please hurry up Phase5!
My little keyboard project has finally come to an end! I’ve spend 350+ hours on the project and the total cost of making the two keyboards exceeds reason by a very large margin… But it has been sooo much fun creating something usefull for my machines that I couldn’t just order somewhere. Hopefully they will last for at least 30 years! The final looks of the keyboard also exceeded my expectations by far and I’m really glad I abandoned the acrylic plate bracket and went for an aluminum version instead. The final version is very stiff and should be able to take some serious pounding…
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