🇸🇰 Tesla PMD 85: Part 7 (Keyboard Issues?) [TCE #0447]

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Australia The Clueless Engineer
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Published on ● Video Link: https://www.youtube.com/watch?v=Hu5mys5Eccw


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Continuing on from yesterday's video [TCE #0446], I replaced the Tesla programmable peripheral interface (PPI) chip for the keyboard, MHB8225A, with a Western CMOS equivalent. It seems to have stopped the "key stuck on repeat" issue.

However I think I still have keyboard issues. Thanks again to Jakub@jjermar1 and Yura @yurasergienko6890 for their advice.

Jura pointed to a Hungarian video by@ATLAB where he details about replacing the rubber domes, and also identifies a replacement from Aliexpress:
https://youtu.be/SZ3X2oSUivU?si=S5t4uMJRMcQf75sG&t=1089

On Aliexpress they are described as ... "Φ12*Φ7*H6mm silicone conductive single keypads silicone buttons" ... so I'm thinking 12mm outer diameter, 7mm inner diameter and 6mm height ... ? This one page (that exists as of May 2024) they are "model DGQSDZ-KP58" ...
https://www.aliexpress.com/item/1005003193328919.html

https://archive.is/0Sk09#selection-2037.0-2037.11

I'm really wondering if designing a replacement keyboard might be a better solution ... ?

Time to have a look at the Robotron Kleincomputer KC 85 again I think ...



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