On 2020-Jul-09, at 10:12 PM, Ian Finder wrote: >> On Jul 9, 2020, at 21:58, Brent Hilpert <[email protected]> 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?
> No, as I understand it that is the predecessor OK, too bad, in my parts stash I have an orphan (caseless) made-by-Microswitch keyboard from 1975, using the key-switch type as I described. I had a couple of the key-switches open years ago. According to my notes there are two types of key-switch, one for characters (black plunger) and one for modifiers (shift,ctl) (green plunger), the chip IDs (inside the key-switches) are 42B and 40H respectively.
