Potter Instrument KDR/KB 3100A (Micro Switch 51RW1-2)
Posted: 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.
IMG_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.
IMG_2980
IMG_2985
IMG_2939
IMG_2951
IMG_2942
IMG_2963
IMG_2964
IMG_2965
IMG_2959
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.
IMG_2901 dirty keyboardThe 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.
IMG_2980IMG_2985IMG_2939IMG_2951IMG_2942IMG_2963IMG_2964IMG_2965IMG_2959