Desktop Calculator Keyboard with Clare Pendar S830 Switches

[Ratfink]

Hey all,

Today for your viewing pleasure I present what I believe to be a very rare specimen. To the best of my web searching ability, I have found no record of the switches on this keyboard. I know that the keyboard itself came from an old desktop calculator, but exactly what model I don't know as I obtained this as just the keyboard PCB.

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It has some pretty nice spherical doubleshot caps with lots of fun math symbols. By the look of it, it was a programmable scientific calculator.

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As for the switches themselves, they appear to be Clare Pendar S830 switches. They're magnetic reed switches, around as tall as beam springs. They're linear, and fairly scratchy. Spraying them with some dry lubricant helps immensely with the scratchiness, and I'll probably do it all of them if I find a way to actually use the board. All the switches have date codes 7218 or 7227, making this the oldest keyboard I own by about a decade.

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There are also five toggle switches on the board. I don't know what function they had, as I haven't seen the case of the calculator.

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Interestingly, the rows and columns of the board are set up so that almost no traces run through the switch area on the back of the PCB. Each switch is held firmly in place by an embedded machine screw.

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Three of the switches have no stem, and were zip-tied together so none of them could be pressed. This piqued my interest, so I just had to take a more detailed look at them.

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Looking through a hole in the top of the slider, it's possible to make out one of the leads of the magnetic reed switch. When the switch is pressed, you can barely make out the end of the glass capsule itself.

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[Ratfink]

Replacing that switch and pulling a cap, we can see that they're pretty substantial doubleshots.

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As can be seen more clearly on the bottom of the dark cap, the tops and sides have yellowed significantly over the board's four decades. They also have a lovely squared font on the keys that aren't just mathematical symbols.

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When I said they were doubleshots, I spoke of everyone except this guy:

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Apparently he skipped on Beige Day.

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The 2u caps sport an interesting stabilizer mechanism: a simple post that slides through the screw hole for the next switch in the matrix.

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[snuci]

These are pretty cool switches. Thanks for posting.

[terrycherry]

IThis old calculator always having the interesting inside.

Glad to know this rare one. Thank you for share.

[Redmaus]

I have a neat gas station module that reminds of this. I wonder where this would be used. Maybe in some mathematician's profession? Or a theoretic physicists?

[Abstractions]

I just got word from an expert on vintage calculators. He said:

It is my belief that this keyboard was originally installed in a Monroe 1880 programmable advanced scientific calculator. Unfortunately, I do not have one of these documented yet in the Old Calculator Museum website, however, I do have a very close relative of the 1880, the Monroe 1860(made in the same timeframe), which you can see at http://oldcalculatormuseum.com/monroe1860.html . The only difference between the 1860 and the 1880 are the functions on the right-most group of keys.

From the keyboard standpoint, the only real difference is the keycaps placed on the keys. The 1860 has more statistical math functions on these keys, while the 1880 has more scientific/engineering functions on the keys.

It is also possible that this keyboard could have been used on a Computer Design Corporation (also known as Compucorp) calculator. Computer Design Corporation built the calculators for Monroe, and Monroe just sold them under the Monroe label. Computer Design Corporation built the same machine, and marketed it under the Compucorp brand, but at this point, I don’t know the specific model number of the Compucorp machine that matched the Monroe 1880.


You can learn more about Computer Design Corporation via my essay at http://oldcalculatormuseum.com/d-compucorp.html

[Ratfink]

Wow, thanks for finding that! It does definitely appear to be from a Monroe 1880. Here's a video I found of one working:

I'm only a little jealous of those relegendable caps.

[seebart]

Quite impressive find thanks for sharing. Beautiful.