This is my IBM 4979 terminal. It's part of the IBM Series/1 minicomputer ecosystem which launched in 1976 although my terminal was made 1979 or 1980. It features a 66 key IBM beamspring that was unfortunately suffering from the usual material degradation. The CRT was also non-functional with an apparent HV issue.
The terminal was available in a number of different languages with many of them having extra keys for an extended alphabet. Mine being a boring US English model had several blank caps with blockers underneath the switch to prevent actuation. Fortunately the blockers can be removed and the switches are fully functional.
I went about the cleaning and rebuild as normal for a beamspring.
Plastic degradation with glass fiber exposed
I won't go into too much detail about troubleshooting and repairing the CRT unless anyone asks. Short story is that some resistors didn't age well. Some fresh modern ones and it's good to go.
The protocol is a pretty basic parallel bus with a secretarial caps lock handled by the keyboard logic. I was able to whip up some QMK code and a converter to speak to it.
Absolutely no modifications were made to the terminal other than cleaning, repairing, and replacing aged materials with archival grade equivalents. Conversion was done entirely with a plug and play connector that interfaces with the terminal as if it were a real Series/1.
Right now it's plugged into a Raspberry Pi, boots up to a login prompt, and works perfectly! This is without a doubt the best way to experience a text adventure game if you ask me.
Nice work - a cool looking machine you got there :-)