Micro Switch 58SW5-9

SOTGO

15 Jan 2021, 20:00

I recently purchased this Micro Switch SW series keyboard model number 58SW5-9 and I am having trouble figuring out exactly what it is.

Superficially the layout looks quite a lot like the IBM 3277 that sometimes came with the same switches that are documented in these Deskthority posts: [1], [2], so I thought it might be related. However, the layout is different, the model number is different, and there is no IBM branding anywhere, and this keyboard uses different colored sliders than the ones in those posts.

It appears that this board was made in 1977, and I’m not sure what the other part of the date code means. Using this wonderful catalog entry from 1973. The board does appear similar to other communications keyboards, but I don't know for sure. If anyone knows anything about this model number I would be very excited, because I haven’t been able to find a reference to this model number anywhere.

Unfortunately most of the switches are unlabeled and so I can’t figure out which model most of the switches are. Almost all of the switches use red sliders, with a couple using green sliders. The right shift has a dummy switch to help stabilize, and the spacebar uses a wire stabilizer, and funnily enough the keycap doesn’t have a mount at all it simply presses on the top of the slider which has a fuzzy pad on it. Finally there is an alternate action lock switch which does have the label: 1SW13-R. The sensor die for the switches are labeled 298A for the red slider variant and 65C for the green. Using the wonderful chart I think the red switches are possibly1SW43-R or 1SW51-R and the greens 1SW31-R, 1SW41-R, or 1SW45-R, but I am not sure if this is even the switches in this board.

The switches and board are in good condition and so I do have some desire to convert it to USB, although I’m not sure how hard it will be. If anyone has resources or knowledge about converting SW keyboards I would appreciate it. Even without being about to use the board for now it is still a lot of fun to play with. The switches are Micro Switch SW, most of what I know about them came from this website and this video from Chyrosran22. They are extremely smooth, fairly stiff linear switches with a long travel distance, and are super fun to use. Watch the video if you want a full review.
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pcb2.JPEG (1.66 MiB) Viewed 1968 times
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sliders.JPEG
sliders.JPEG (598.3 KiB) Viewed 1968 times
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red_slider.JPEG (1.26 MiB) Viewed 1968 times
green_slider.JPEG
green_slider.JPEG (1.23 MiB) Viewed 1968 times
spacebar.JPEG
spacebar.JPEG (1.55 MiB) Viewed 1968 times
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dummy_switch.JPEG (1.52 MiB) Viewed 1968 times
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alternate_action_switch.JPEG (1.27 MiB) Viewed 1968 times
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alternate_action_echanism.JPEG (32.68 KiB) Viewed 1968 times

John Doe

16 Jan 2021, 05:51

Micro Switch SW series keyboards always have a comfortable type feeling, probably one of the best linear kinds I personally think. However I'm also confused about its convertibility to USB interface, as my digging of the PCB, there's no rows&cols conception like common contact switches working mechanism. Perhaps the best result is 1KRO if there's indeed a solution but let me know if you could figure it out. :D

Spoiler:

I have one sadly not in great shape.

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SOTGO

16 Jan 2021, 18:59

I guess I intended to get it to work on a modern PC at all, because even when new it likely never had more than 1 key rollover. In the catalog the similar boards have "N-key" rollover, which means that hitting keys in quick succession will register.

MMcM

16 Jan 2021, 22:33

John Doe wrote:
16 Jan 2021, 05:51
there's no rows&cols conception like common contact switches working mechanism
Many SW series boards and some early SD series are "two-of-n."

MMcM

18 Apr 2021, 20:41

Someone asked privately about getting a board like this to work, so here is my guess for getting parallel ASCII output using the existing encoder. Note that working for real with a modern PC will likely mean taking that out and wiring directly, which others can give better advice on.

The AMI CMOS encoders used on Micro Switch boards are (as far as I have found) pretty close to one another. An abbreviated datasheet for the one in the Diablo is here: https://archive.org/details/bitsavers_d ... 2/mode/1up. Call the edge connector solder side 1-12 right-to-left and the component side A-N left-to-right. I can see that pins 1-13 from the chip go across on the component side and down on the solder side to implement the scan “matrix” (quotes because of that two-of-n layout). The strobe output pins on the other side of the chip go to pull-up resistors and pins 4-12 on the edge connector (starting after the key cut). Ground looks to be 1&2; +5V A&B. -12V E. Some special keys – likely shifts and CLEAR -- are output directly on C,D,M,N. It's possible one or more of those are actually jumpers, though those look to affect shift / lock handling.

12V is the scary part, so try to be absolutely sure it's connected properly (and maybe keep hunting for confirmation if a schematic can be found) before powering on.

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