In search of 4B3A Microswitch Keyswitches (for a system restoration, not keyboarding)

Ian Finder ian.finder at
Thu Jul 9 23:39:29 CDT 2020

I know what you guys are thinking- no, this isn't for a keyboard collection
or some modern build or some other nonsense like that.

I have a friend who is restoring a fairly interesting and historically
significant vintage computer-
The correct SD-series replacement switch would be the 4B3A-

*** These can allegedly be found on some of the Diablo printing

Subject to what /appears/ to be a batch-related encapsulation failure in
the glue on the proprietary hall effect sensors, around a little over half
of the switches on the current keyboard are bad.

It is possible other switches ending in ***A could be made to work with a
bit of labor and disassembly (swapping the fairly brittle sensors).

I am not a keyboard expert but I have learned that you can remove a key on
some of these microswitch keyboards and read the model fairly easily on
each switch.

Please let me know if you have a lead on a donor for these switches. They
will be put to good use, and you can reply to me off-list for more details.


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