Teletype 40k 103 (magnetic plate switches) USB conversion

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29 Aug 2018, 00:03

A couple of these have popped up over the last few years but I got one in really nice shape and thought I'd share it now that it's alive.

The thing is a steel mammoth. 1/8" plates screwed together holding 6 rows of switch troughs. Copper sheeting around the LED switches, separator made from bent and soldered copper sheet because apparently it was easier than another little piece of molded ABS. All encased in a bent stainless steel pan and switch cover and plastic top case held on with steel levers the size of human fingers. I had to use more gun oil to wipe down the galvanized metal than a long gun. My kind of overkill.






Even the connector bracket is folded 1/16" steel and held on with no less than 8 machine screws with washers and split ring lock washers.


The switches are normally closed so work the inverse of normal switches. The green and orange ones have a second function when you completely bottom them out. The green act as a normally closed switch and the orange as a normally open. This means I was able to swap some of the switches around to where you could get second functions that worked with the greens. Places like Control and Shift were ideal for this.

While the switches were insanely clean and smooth when I got them, I still had to clean a few that seemed to have had their internals gum up a bit with old lube. They would snap and actuate but wouldn't reset right. A bit of alcohol and they got right back in shape.


I handwired the matrix backwards from normal with diodes facing the columns so the multiswitches could get full NKRO while still sharing their common pin and used a Cypress devkit with DMA commonsense in beamspring configuration for the controller.

The LED's were an old 4V type, odd for red, but once I knew what they needed, easy enough to adapt. The Send key flashes with every keypress, highlight shows the caps locklight and clear is numlock. Everything else is lit all the time solely because I think it looks cool and the circuit being completed by springs under the caps is too cool not to use.

All put back together


And a typing test with 100% unadulterated switch racket.

This is probably the only board I've held in my hands that honestly feels like some old mechanical bar typewriter. I think it's a combination of the snap and the long release. The southpaw layout without a numpad drives me nuts though. Might pass it along to someone else now that the project is complete.
Last edited by Sangdrax on 31 Aug 2018, 23:34, edited 1 time in total.

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29 Aug 2018, 14:32

I love it! I was looking for one of these but never found one for a reasonable price.


29 Aug 2018, 16:16

Nice work. Definitely an interesting piece of engineering especially compared to today's disposable keyboards.

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17 Nov 2018, 00:04

Man oh man, you and oldisnew absolutely kill it with these restorations. I can only dream of getting something like this. The 'old mechanical typewriter' feel sounds like right up my alley. Would sooo love it man.

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28 Dec 2018, 03:35

Nice! I missed this one - very cool. I have a similar teletype board but its not as pretty and no case - the normally closed switches are pretty neat. A very nice job for sure!

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