https://github.com/visrealm/keyboard4a99

Cherry MX compatible upgrade for your Texas Instruments TI-99/4A Mitsumi mylar keyboard
https://github.com/visrealm/keyboard4a99

cherrymx keyboard mitsumi pcb texas-instruments ti-99 ti-994a

Last synced: about 2 months ago
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Cherry MX compatible upgrade for your Texas Instruments TI-99/4A Mitsumi mylar keyboard

• Host: GitHub
• URL: https://github.com/visrealm/keyboard4a99
• Owner: visrealm
• License: cern-ohl-w-2.0
• Created: 2024-03-27T04:52:31.000Z (6 months ago)
• Default Branch: main
• Last Pushed: 2024-04-13T05:56:25.000Z (6 months ago)
• Last Synced: 2024-04-14T04:08:01.087Z (6 months ago)
• Topics: cherrymx, keyboard, mitsumi, pcb, texas-instruments, ti-99, ti-994a
• Homepage: https://hackaday.io/project/195508-keyboard4a-99
• Size: 14.8 MB
• Stars: 4
• Watchers: 4
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
![KEYBOARD/4A-99](img/logo.png)

# Introduction

Finally! a Cherry MX compatible upgrade for the infamous Mitsumi mylar keyboards that plague many unfortunate Texas Instruments TI-99/4A computers.

![](img/drake.jpg)

The upgrade consists of a new PCB and a handful of 3D printed parts. The original look is maintained by re-using the original key caps (and some other original parts). Add the switches of your choice and you're set! A brand new keyboard for your TI-99/4A.

![](img/keycap-adapter.jpg)

## Only Mitsumi boards?

Currently, the upgrade is designed for the Mitsumi keyboards since their mylar innards gives the most grief to TI-99 users. It is possible other TI-99/4A keyboard brands could be adapted to use this upgrade in the future, hower that would rely on community input.

## The hardware

The Gerber file for the KEYBOARD/4A-99 PCB is available in the [/pcb](pcb) directory. I recommend the PCB is ordered in black.

STLs for all 3D printed items are located under [/stl](stl). 

**Note:** Not all STLs are required.

Check out the [documentation](doc) for more details, including a [bill of materials](doc#bill-of-materials) and full build process.

## Purchasing options

These are now available at:



For those outside the US, you can support the project by purchasing direct from my [PCBWay project page](https://www.pcbway.com/project/shareproject/KEYBOARD_4A_99_0361cd65.html). 

### Thanks

Thanks to [PCBWay](https://pcbway.com/g/186WQ9) for supporting this project.

[![PCBWay](/img/pcbway_sm.png)](https://pcbway.com/g/186WQ9)

### Gallery

![](img/keyboard-populated.jpg)

![](img/keyboard-nocaps.jpg)

![](img/pcb-v1_0.jpg)

### Licence

All hardware designs and products you can find in this repository is licensed under [CERN Open Hardware Licence Version 2 - Weakly Reciprocal](/LICENCE.txt)