Like many of you, I have a couple of Atari 800s with keyboards that aren't working for various reasons. I didn't like the idea of buying a NOS one from ebay and having it fail for the same reasons as the ones I have, but there weren't any other available options. Then it occurred to me that since mechanical keyboards are now a hobby, maybe I could make my own. My goal was to make a drop-in replacement keyboard that didn't require any modifications to the Atari, used the original key caps to maintain the original look, and should be easy enough for most maker types to reproduce.
Luckily, the 800 keyboard is pretty simple. Its just a matrix of switches with no diodes or microcontrollers needed. So I mapped out the matrix using a multimeter and got to work in KiCad designing the PCB. A few weeks later, my newly designed board was delivered from the board house in China.
After soldering in 57 Cherry MX black switches and a pin header, I hooked the new keyboard up to the Atari with an IDE cable for testing, and success! The PCB worked first try!
The original keyboard mounts at an angle and is very recessed compared to modern keyboards. As I had a Stackpole keyboard to use as a template, designing 3d printable mounting brackets was pretty easy. I also integrated a support to run along the top edge of the PCB and limit the amount of flex it had when typing.
The adapters to use the original keys, however, were much more challenging. The dimensions of both the original keycaps and the Chery MX switches required pretty tight tolerances, and since I needed an adapter for every key, I wanted them to print without supports and without needing tedious cleanup. After dozens of failed attempts, I finally got something that would fit snugly and could be printed in bulk on my 3D printer.
Here's the finished installation:
The keys have a little bit of wiggle, because of the extended height of the keycap/adapter/switch combination, but it's very usable and the modern switches should last a very long time.
For those of you who'd like your own, I've uploaded all the files for the PCB and 3D prints to github and have included some instructions. https://github.com/multifariousindustries/Atari800Keyboard
If you make one, please let me know what you think!