This project was inspired by the fact that I thought this was a cool old board and I very much disliked the idea of having a board I could not actually use on my computer. Should you do this with your foam and foil? Probably not. I did it because I wanted to use the board and also largely just for the heck of it to see if it would work - and it did.
I recently bought a Tandem Computers terminal keyboard with vintage Key Tronic foam and foil switches. I like the look of the board and the keys actually feel pretty nice I think. I have not found much on what protocol the board uses and it seemed unlikely that I was going to find a simple existing converter for it. The foam pads were in good shape - so I decided to try modifying the switches from capacitive foam and foil to foam and copper contacts and have a go at hand wiring it. This was a "Lowe's Home Improvement Special" - used copper flashing to make switch contacts for a new "PCB" and for the contacts over the Mylar on the foam switch plungers. 14 AWG solid core wire for switch posts, an acrylic sheet for the "PCB".
And super glue.
I traced out the switch layout on the acrylic sheet (also from Lowe's) then cut out the "PCB" contact pads from the flashing. Drilled holes and used 14 AWG solid wire to make posts for the contacts, used a 7/16" punch for the copper flashing disks for the foam.
Super glued the flashing in place and then spent a lot of time testing and adjusting the switches and contact pads - a major pain in the a** - but they work. Then a matter of soldering the
diodes, rows and columns and hooking up the Teensy. So far so good and I'm typing on the keyboard now.
I cannot feel any noticeable difference in the switches after the mod - and that was also a goal. Plan to wire the board's LEDs next. Why go though all this trouble? I don't know - why not?
