The Sol-20 Keyboard

A project log for Sol-20 Reproduction

I am making a full sized Sol-20 reproduction, the first fully assembled microcomputer with a built-in keyboard and television output.

Michael GardiMichael Gardi 10/14/2021 at 02:184 Comments

The keyboard in the Sol-20 was a capacitive keyboard made by Keytronic. These keyboards had a great feel, but unfortunately, the foam pad present in each key deteriorated over time and virtually all keyboards of this type failed. To be fair it has been 45 years since the Sol-20 was introduced.

If you are lucky enough to find a vintage Sol-20 for sale (and can afford to buy it) you will probably be faced with this keyboard issue. Fortunately all is not lost. One option is repair. Geoff Harrison has figured out a way to make his own foam pads, and has a nice write-up on how he did it. Please see Geoff's web page on how to repair a Sol-20 Keyboard. Also Texelec has a 105 key replacement pad set at a reasonable price.

The second option is to replace the keyboard. I have already mentioned Dave from who has designed a complete replacement keyboard for the Sol-20 using modern Cherry key switches. While not an exact replica, Dave has gone to great lengths to reproduce the look of the original keyboard, including having a set of custom Sol-20 specific keycaps manufactured. Dave's keyboard will drop right into an original Sol-20. So cool.

Fortunately Dave's keyboard is also perfect for someone trying to make a Sol-20 reproduction. I received Dave's keyboard kit yesterday. Dave offered to ship me an assembled keyboard, but I didn't want to deprive myself the fun of soldering one up myself.

You can see above the keyboard PCB and aligner for Futaba MD-4PCS switches. The bag to the right is a set of "standard" keycaps. The keycaps below the PCBs are Sol-20 specific keycaps that Dave had manufactured, and the smaller PCB to the right of that is the PCB for a very flexible encoder with the following capabilities (from Dave's GitHub repository):

I'm chomping at the bit to get started on this but the actual Futaba key switches and some of the other components I need to populate the encoder are still in transit. Patience Michael, patience. 


redjr16 wrote 10/15/2021 at 15:20 point


You can follow my progress over at the VCF forum here.

I'm trying to document what I can as I go along.  There's a lot of useful information from a small group of Sol aficionados there.

BTW, how do you post a link here?  I don't see all the normal thread icons for such stuff when replying. 


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Michael Gardi wrote 10/15/2021 at 16:12 point

Thanks for the URL. That's a great thread. I'm going to join and subscribe to it. I have not found a way to link either ;-(

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redjr16 wrote 10/15/2021 at 14:40 point


That looks like a very cool alternative to the original Sol keyboard.  Special keycaps and all.  I'll be curious how the build goes and how it works out in your Sol replica.  I just finished up refoaming my old keyboard with pads harvested from a Sun 4 KB.  That was a process I don't care to do again!  Too much tedious labor for me where I had to take off and on my glasses several hundred types during the whole process.  But it's done and all the keys work.  So success.

Before I could really finish up the keyboard reconditioning for testing, I had a bit more testing to do on the Sol PSU and mobo.  So I let the PSU run for about an hour, monitoring the stability of the voltages and any magic smoke.  Luckily there was none.  :)

Now came time to power up the mobo.  Using my trusty variac again, I brought the voltage up to mains level (120VAC) slowly, wore some eye protectors just in case.  Good news.  No smoke, minor explosions, or other interesting, unwanted events.

I then plugged in a small LCD screen that had composite-IN, and voila.  I had a familar > prompt from 45 yrs ago!  So in all, a good day yesterday with bring back to life an old trusty friend, my first computer.  :)


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Michael Gardi wrote 10/15/2021 at 14:56 point

Man that is great news about the keyboard and your Sol-20 in general. I hear you about the glasses thing. Not looking forward to soldering in 100+ diodes and 85 key switches. What personality module do you have plugged into your machine? Can you execute commands? You should do a little writeup about your restoration. I'll definitely be posting a log about the keyboard construction soon.

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