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

null ian.finder at
Fri Jul 10 00:12:11 CDT 2020

No, as I understand it that is the predecessor

> On Jul 9, 2020, at 21:58, Brent Hilpert <bhilpert at> wrote:
> On 2020-Jul-09, at 9:39 PM, Ian Finder via cctalk wrote:
>> 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
>> terminals.***
>> 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.
> Are these the key-switch model which snap into a thin-gauge springy stainless-steel U-channel to form the rows of the keyboard?

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