{"id":13992826,"url":"https://github.com/visrealm/keyboard4a99","last_synced_at":"2026-01-08T05:52:03.428Z","repository":{"id":231469087,"uuid":"778106418","full_name":"visrealm/keyboard4a99","owner":"visrealm","description":"Cherry MX compatible upgrade for your Texas Instruments TI-99/4A Mitsumi mylar keyboard","archived":false,"fork":false,"pushed_at":"2024-04-13T05:56:25.000Z","size":15536,"stargazers_count":4,"open_issues_count":0,"forks_count":0,"subscribers_count":4,"default_branch":"main","last_synced_at":"2024-04-14T04:08:01.087Z","etag":null,"topics":["cherrymx","keyboard","mitsumi","pcb","texas-instruments","ti-99","ti-994a"],"latest_commit_sha":null,"homepage":"https://hackaday.io/project/195508-keyboard4a-99","language":null,"has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"cern-ohl-w-2.0","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/visrealm.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":null,"code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null}},"created_at":"2024-03-27T04:52:31.000Z","updated_at":"2024-04-15T05:29:51.842Z","dependencies_parsed_at":"2024-04-15T05:29:51.566Z","dependency_job_id":"5d68618a-b3de-4b5a-a17e-b7ffcb1b26bb","html_url":"https://github.com/visrealm/keyboard4a99","commit_stats":null,"previous_names":["visrealm/keyboard4a99"],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/visrealm%2Fkeyboard4a99","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/visrealm%2Fkeyboard4a99/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/visrealm%2Fkeyboard4a99/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/visrealm%2Fkeyboard4a99/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/visrealm","download_url":"https://codeload.github.com/visrealm/keyboard4a99/tar.gz/refs/heads/main","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":246413244,"owners_count":20773053,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["cherrymx","keyboard","mitsumi","pcb","texas-instruments","ti-99","ti-994a"],"created_at":"2024-08-09T14:02:08.924Z","updated_at":"2026-01-08T05:52:03.423Z","avatar_url":"https://github.com/visrealm.png","language":null,"funding_links":[],"categories":["Others"],"sub_categories":[],"readme":"![KEYBOARD/4A-99](img/logo.png)\n\n# Introduction\n\nFinally! a Cherry MX compatible upgrade for the infamous Mitsumi mylar keyboards that plague many unfortunate Texas Instruments TI-99/4A computers.\n\n![](img/black-and-beige.jpg)\n\n![](img/drake.jpg)\n\nThe 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.\n\n![](img/keycap-adapter.jpg)\n\n## Only Mitsumi boards?\n\nCurrently, 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.\n\n## The hardware\n\nThe Gerber file for the KEYBOARD/4A-99 PCB is available in the [/pcb](pcb) directory. I recommend the PCB is ordered in black.\n\n#### New version: v1.1\n\nVerion 1.1 adds support for re-using the original alpha-lock switch. The original switch provides much greater throw than the replacement I used in v1.0. As a result, the keycap adapters for v1.1 are slightly taller to match the taller alpha lock key. Also, the mounts are slightly slimmer.\n\nSTLs for all 3D printed items are located under [/stl](stl). \n\n**Note:** Not all STLs are required.\n\nCheck out the [documentation](doc) for more details, including a [bill of materials](doc#bill-of-materials) and full build process.\n\n## Purchasing options\n\nKEYBOARD/4A-99 PCBs and kits are available on my Tindie store:\n\n\u003ca href=\"https://www.tindie.com/products/visrealm/keyboard4a-99\"\u003e\u003cimg src=\"https://d2ss6ovg47m0r5.cloudfront.net/badges/tindie-larges.png\" alt=\"I sell on Tindie\" width=\"200\" height=\"104\"\u003e\u003c/a\u003e\n\nAlso (more convenient for North America)\n\n\u003ca href=\"https://www.arcadeshopper.com/wp/store/#!/Keyboard99-Mitsumi-membrane-replacement-PCB-only/p/648592668\"\u003e\u003cimg width=\"640\" src=\"https://www.arcadeshopper.com/wp/wp-content/uploads/2016/01/Arcadeshopper-horizontal-Web-logo-1024x147.jpg\"\u003e\u003c/img\u003e\u003c/a\u003e\n\nFor 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). \n\n## Detailed build instructions\n\n[![KEYBOARD/4A-99 Cherry MX compatible upgrade procedure](https://img.visualrealmsoftware.com/youtube/thumb/9g29EfUJuLM)](https://youtu.be/9g29EfUJuLM \"KEYBOARD/4A-99 Cherry MX compatible upgrade procedure\")\n\nAlso check out the [documentation](doc) for more details.\n\n### Thanks\n\nThanks to [PCBWay](https://pcbway.com/g/186WQ9) for supporting this project.\n\n[![PCBWay](/img/pcbway_sm.png)](https://pcbway.com/g/186WQ9)\n\n### Gallery\n\n![](img/keyboard-populated.jpg)\n\n![](img/keyboard-nocaps.jpg)\n\n![](img/pcb-v1_0.jpg)\n\n### Licence\n\nAll hardware designs and products you can find in this repository is licensed under [CERN Open Hardware Licence Version 2 - Weakly Reciprocal](/LICENCE.txt)\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fvisrealm%2Fkeyboard4a99","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fvisrealm%2Fkeyboard4a99","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fvisrealm%2Fkeyboard4a99/lists"}