Potter Instrument KDR/KB 3100A (Micro Switch 51RW1-2)

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Noobmaen

24 Aug 2018, 20:27

While procrastinating the restoration of the IBM 4978 due to the mental and physical pain caused by removing the especially tight metal stem inserts, I got this keyboard with the help of a community member: A 1970 Micro Switch magnetic reed keyboard, possibly made for a key punch or early terminal. Thanks again, pngu!

I have been looking to get a Micro Switch keyboard for a long time, but they are rather scarce outside the US, and usually fetch quite high prices. I expected to find a SD board, or maybe even SW, but never would have imagined to find the much rarer RW switch.

ImageIMG_2901 dirty keyboard

The board was very dusty when I got it, yet the switches were relatively smooth with a nice weighting similar to mx black. I will probably desolder a few for further cleaning to see whether it will improve anything. The case is made out of ~1.6mm steel, bent and welded at the edges. I don't have a working scale at the moment, but I guess the weight to be around 4-5kg.

Due to the sensing being conductive, it shouldn't be very difficult to create a replacement controller, or so I thought at least, until I noticed the absence of a traditional sensing matrix; instead, every switch shares a common connection on one pin, and an individual connection each on the other pin. This array of key positions then connects to a PCB with a matrix of diodes (which looks wonderful thanks to the gold plated traces), which appears to translate the one dimensional encoding of the sensing into a matrix. Ideally I would want to convert it in a least destructive way, which might just be handwiring in this case.

For now, here are 45 pictures of the mostly cleaned up keyboard in various states of disassembly on flickr.

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Lanrefni

24 Aug 2018, 21:06

Those keycaps are beautiful.

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Muirium
µ

24 Aug 2018, 23:31

Yup. A real looker in that department. The Futura legended sci-fi going on up top is pretty, too. And then there’s that PCB trace art…

They just don’t make them like this, anywhere, in any way, any more.

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digital_matthew

25 Aug 2018, 00:32

Simply glorious. It looks like it came off of the original Enterprise. Are you sure it's not from the future?

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JP!

25 Aug 2018, 01:32

:o

codemonkeymike

25 Aug 2018, 01:54

oozes 70's class

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Niko1U

26 Aug 2018, 00:33

that thing looks super cool

clickboyclick

26 Aug 2018, 16:00

"MICRO SWITCH" and its the size of 15inch laptop lol. But seriously I can't imagine what its like to use it for data

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Sangdrax

30 Aug 2018, 03:15

Jesus, look at those stepped attenuators attached to the dials. You could run the volume in a balanced amp off something with all those channels.

And the cap colors. Kickass.

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