Many Texas Instruments TI-99/4A have been cursed by cheap Mitsumi mylar keyboards which are prone to failure with age. Even the NOS replacement keyboards are often in bad shape.

This project aims to provide a drop-in replacement for the Mitsumi keyboard using modern Cherry MX compatible switches, with adapters for the original TI-99/4A keycaps.

This project is intended as an upgrade for an existing Mitsumi mylar "keyboard". As such, you will require one of these (probably non-functioning) "keyboards" to begin. We will be re-using all of the original keycaps, the metal PCB support strips and screws, and (optionally) the space bar support brackets and 15-pin ribbon connector.

Don't feel bad for it. That brown abomination should have been relegated to landfill years ago. It's one of the lucky ones!

There are a number of 3D printed parts, including keycap adapters.

Further documentation can be found on GitHub