Hello Tom,
Am 21.09.2020 um 13:41 schrieb Tom Hunter via cctalk <cctalk at classiccmp.org>:
Has anyone got experience repairing or restoring this
type of membrane keyboard mechanism used in the Osborne 1 and probably in other keyboards
too?
Not with the Osbornes, but with others. This kind is cheaper to manufacture than the ones
with "true switches".
Anyway, to get rid of the problem, carefully heat the ground plate to "does not hurt
if I touch it for 10 seconds" and remove all the spring housings. Punctual further
heating is most likely needed. This enables you to separate the sheets, and clean them.
This should remove remains of soft drink spills (possibly explaining your particular
problem), as well as insulating black silver sulphide layers.
I Germany we have a very mild solvent for electronics, proved to do wonders to this type
of partly-conductive foils.
https://www.amazon.de/KONTAKT-CHEMIE-71809-Tuner-Kontaktreiniger/dp/B000NI2…
Maybe there's something similar where you live?
Also, carefully inspect the foils if there's some mechanical damage, like dents on the
actual contact spots, providing a contact all the time. If there are, there's some
creativity needed to even them out. I never needed to do that.
Here are some good and detailed photos of keyboard
mechanism:
https://www.flickr.com/photos/123564336 at N03/sets/72157644113347562/
Thanks, this helped a lot!
:wq! PoC
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