Research help needed !

[burann]

Hello !

I have a keyboard where a number of keys have stopped working, pretty sure its not mechanical issues but electronics in the board. The keyboard in question is a OEM Key Tronic "foam and foil" keyboard from the early 80s, it was manufactured by a Swedish company called Luxor for a computer called ABC 806. I have in total of 3 keyboards where different pads have stopped working and I cant figure out why, here is an image of the keyboard:

2018-11-11 12.46.09.jpg (2.67 MiB) Viewed 1367 times

The keyboard uses the Intel 8049H keyboard controller and a XR 950-3B scan driver and something like a 3 pin 7805 voltage regulator.

Any tips, comments or ideas are very welcome, I love to get this board working so I can use my computer.

[Chyros]

Is the foam in the switches still okay? Over time, it can disintegrate and interfere with switch operation.

[green-squid]

The foam in the 'foam and foil' has disintegrated, so the foil doesn't make contact with the pads anymore. You can make new ones yourself (workshop-f7/1983-general-radio-genrad-l ... 19531.html) or buy pre-made ones (https://texelec.com/product/foam-capaci ... keytronic/), but I don't recommend that, it's way cheaper to do it yourself. Good luck with the project!

[burann]

Hi guys, thanks for the quick reply.

All foam is replaced with the ones from Texelc, the reason I suspect the electronics is that I switched between 2 different circuit boards and the keys not working was different on both boards, despite using the same switches.