deskthority

Okay, this is my first post here. I've been a mechanical keyboard lover ever since I discovered an IBM model F XT in a pile of junk at a friend's house. I started doing tons of research into mechanical keyboards, and bought my first keyboard with MX Blues manufactured by a certain black and green-themed company that shall go unnamed.

One day I was wandering GoodWill and I saw a giant Alpha 2015 typewriter for $13. I popped off one of the caps as I usually do on these things (to see if the caps are worth harvesting) and saw that it looked like a cherry MX mount. I bought the thing and brought it home and later found out from your Wiki that it was a Type 1 Mitsumi Standard Mechanical board. I knew I had something interesting when I realized some of them were different colors from the ones on the Wiki, so i went ahead and disassembled the typewriter.

Inside, serving as the sensor switch for the swing bar that holds the paper to the roller was a Mitsumi switch very different from the others. It was mounted to the plate, with 4 wires coming off of it. I recalled from the wiki that there were 4 holes, "implying" a DPST variant, so I registered for an account and here I am.

In addition, there are several different weighted switches identifiable by color. The Blacks are very heavy for caps lock and such, the yellows are very light because they used 2 lightweight switches instead of one normal switch and a stabilizer, and the whites are normal from what I can tell. Typing is very smooth, I'm guessing typical for a Mitsumi Type 1 board.

On to the good stuff:

http://imgur.com/Se4odRx - Here's the full keyboard without keycaps

http://imgur.com/76nCKoh - Here's the rear of the keyboard which highlights the Nakajima All and Mitsumi branding. Date code hints that the keyboard is from 1984

http://imgur.com/vD3PD1G - This highlights the FLIPPING EPIC THICK doubleshot keycaps that came shipped with this thing

http://imgur.com/okJa8rn - Switch with top popped off to show internal structure

http://imgur.com/lffZ5Pu - Internal structure spread out on the table, with XXX key for good measure. This is switch porn after all

Here's the Album link for all photos: http://imgur.com/a/AagD5

As you can see the switch uses two springs. A light spring for what feels like a normal press and an incredibly heavy spring which requires a considerable amount of force to depress (something impractical for a Rip-o-meter test methinks).

A light press will depress the first spring and trigger the first actuation, then you press harder and the second spring depresses which causes 2 lips near the spring on the slider to depress the little metal tabs on the second part, which triggers the second actuation. It's a really clever switch design. I don't have the nickels required for a Rip-O-Meter test right now, but I'll be sure to attempt to measure the different weights when I have the chance.

EDIT: There appears to be ANOTHER Mitsumi Dual-Stage switch in the BACKSPACE/DELETE key. This makes sense for rapid delete. Press it harder to rapidly delete.

EDIT2: Found 2 more dual-stage switches in the keys to the right of the keyboard to the left of the red LEDS. that makes 4 dual-stage mitsumi switches in this device altogether.

Uhhh, shouldn't this be SPDT/SPCO rather than DPST?

That's a very nice find though, very interesting! A rapid delete key, that would be pretty cool xD . I've not tried Mitsumi standard before, what do the switches feel like?

Welcome to DT! Quite a first post. Thanks for sharing. More data for our wiki.

wiki/Mitsumi_standard_mechanical#Type_1

DPST = double pole single throw? one press actuates two switches/poles? I think that's how it works. There are two separate switch mechanisms in the unit for 2 poles, they just have 2 different actuation points.

EDIT: did some research, these are definitely DPST switches according to wikipedia.

Now that I think about it, these are keyboard keyswitches with 2 separate actuation points. Concept keyboard with capital letters without having to press SHIFT anyone? I'm tempted to whack 4 of these into a WASD configuration...

The linear ones are mostly linear with a slight change in feel at the end, a sort of roundness, like a tactile switch has but without the tactile. It's barely noticeable. The dual stage switch is perfectly linear until it hits the second spring, where the force required jumps sharply. It's like bottoming out, but if you press really hard the key will give at the end. The amount of force required for the second actuation is enough to cause my g410 to flex. It really is a lot. I wonder if there's anyone around me with the tools required for force curve measurement...

If anyone knows how to get a force curve for these, I would be happy to donate them for keyboard science.

I...have a force gauge. Would be happy to measure.

Great, throw me a PM, I'll suck one of each off the board for you