Proper switches for the spacewar controllers

[Bill E]

Here is a source of what looks reasonably correct. A little pricey, but if you want more authenticity, give this a try.

https://www.surplussales.com/items/100636/switchcraft-leaf-switch/

Same place has a big assortment of similar, just be sure you get a center-return one, not toggle on, off one. I haven't ordered any yet, but I will eventually. Jealous that some have already received their kits!

Bill

[Bill E]

Ok, just ordered some. I'll update when I get them.

Bill

[Oscar Vermeulen]

I have not seen them cheaper anywhere, either. They are probably the most authentic option!

(Whether they add to player's performance over the included tact switches is up for debate...)

[Marc Howard]

How many switches are required?

Marc

On Sun, Aug 31, 2025 at 4:26 PM Oscar Vermeulen <vermeul...@gmail.com> wrote:

I have not seen them cheaper anywhere, either. They are probably the most authentic option!

(Whether they add to player's performance over the included tact switches is up for debate...)

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[Bill E]

If you get the center-off double-pole switch above, you need 2, one for left-right, one for thrust-hyperspace plus one pushbutton for 'fire', per controller. Note that what is considered authentic is all over the map. Some had just pushbuttons, some had switches. I just can't remember what the -1 at MIT had when I played, but I think switches like these. (Hey, it's been quite a while.)

Bill

[Paul Birkel]

Does one really need 4 poles?

[Bill E]

You only need a SPDT switch, but the 4 pole one is the one I found that looked the closest to the original. The mentioned site has a LOT of lever switches, could be an SPDT in there somewhere. But, the extra poles can just be ignored. The critical thing is that it has to be center-off and return-to-center.

Bill

[Glenn Babecki]

Like Bill, it's been a while since I laid eyes and hands on the MIT PDP-1 (like 50+ years ago).  A fraternity brother took a few of us newly minted freshman in 1971 on an ad hoc tour of various computers on campus.  Of course we stopped at the PDP-1 and played Spacewar; the rest is history as they say.

While my memory of that period is sketchy, I do believe the Spacewar control boxes were as pictured in the photos on this website.

https://www.masswerk.at/nowgobang/2021/train-spotting-1

Steve Russell, Peter Sampson, et. al. we're also associated with the Tech Model Railroad Club (TMRC, which is still a thing at the Institute).  The early equipment at TMRC used a lot of Telco parts, most notably relays, so I suspect that might have been the origin of the use of spring-leaf switches.  These switches were prevalent in early Telco gear.

On Mon, Sep 1, 2025, 9:15 AM Bill E <wjegr...@gmail.com> wrote:

You only need a SPDT switch, but the 4 pole one is the one I found that looked the closest to the original. The mentioned site has a LOT of lever switches, could be an SPDT in there somewhere. But, the extra poles can just be ignored. The critical thing is that it has to be center-off and return-to-center.

Bill

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[Paul Birkel]

Bingo!  I was thinking about telco gear and the possibility that I have some center-off return-to-center lever switches in an old box of bits.  Possibly double-pole.  May be missing handles :-<.  Sounds like I need to go digging to see what's what there.

Looking at https://www.masswerk.at/nowgobang/2021/train-spotting-1I see that the second and third photos have a "short stack" PDP-1 housing with just the tape reader above the console, plus a separate smaller box on top.  What was the purpose of that box?

In both photos, but clearer in the third photo there are three (19"?) racks in the background.  Are those housing the PDP-1 electronics?

On Monday, September 1, 2025 at 10:13:54 AM UTC-4 Glenn Babecki wrote:

... The early equipment at TMRC used a lot of Telco parts, most notably relays, so I suspect that might have been the origin of the use of spring-leaf switches.  These switches were prevalent in early Telco gear.

[Randy Eubanks]

I assume then that you would need 4 of these switches in total to build 2 controllers to allow for two-players.

Randy

[Paul Birkel]

And two pushbutton switches.  I wonder what diameter head/disk would be appropriate?  These days I suppose one of those wide-flat arcade pushbutton switches would be appropriate, but not BITD.  Maybe 3/8" diameter?  The ones in the trainspotting photos are hidden by player hands :-{.

[Glenn Babecki]

I agree you want an arcade style button approximately 3/4 - 1 inch in diameter with a domed surface.  Such a button makes it easier to hit the button with your thumb without fishing around for it.  Here are a couple of button examples and I'm sure there are more sources.

https://www.adafruit.com/product/3489

https://paradisearcadeshop.com/products/sanwa-obsf-30-snap-in-button-black-red?variant=34672572858530

I recently experienced replica controllers with the spring-leaf switches and arcade button at the Rhode Island Computer Museum (RICM).  They had the control boxes set up on their PDP -12, which was fun.

It's probably worth noting that the long spring-leaf switches obviously require a deeper enclosure.  This makes the box a bit chunkier to hold.  I suppose this automatically limits your screen time. 😉

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[Randy Eubanks]

I will probably build a couple of these style Space War controllers, but also intend to make up a set similar to what is in use at the Computer History Museum in Mountain View, California on their PDP-1. I took pictures of their system when I was there for VCF West a month ago, but neglected getting a good shot of the controllers. 

I'll have to take better shots and get measurements the next time I head to the CHM unless someone already has the info available or happens to be in the neighborhood.

Randy  

[Kristen R.]

Maybe this will help?

[Kristen R.]

[Kristen R.]

And I'll post a few more here...

[Kristen R.]

[Kristen R.]

On Wednesday, September 3, 2025 at 8:29:29 PM UTC-7 Kristen R. wrote:

[Kristen R.]

[Kristen R.]

On Wednesday, September 3, 2025 at 8:32:41 PM UTC-7 Kristen R. wrote:

[Kristen R.]

[Randy Eubanks]

Yes, those are much better than what I had! Now all I need to do is photoshop a proper scale across the X and Y axes. (or draw up my own layout to best fit my hands...) 

Thanks!

[Bill E]

I prefer the leaf switch version, because that's what I think I remember from the MIT -1, but that could just be a delusion. :)

Also note the nifty Tek 547 oscilloscope.

[Kristen R.]

Hi Randy, maybe these pictures will help?

--Kristen

[Lars Brinkhoff]

Glenn Babecki:

Steve Russell, Peter Sampson, et. al. we're also associated with the Tech Model Railroad Club (TMRC, which is still a thing at the Institute).

I swung by TMRC when I visited MIT last year.  No one was there.  It seemed rather desolate and semi abandoned.  But the Tetris game worked.

[Glenn Babecki]

I was just there this past May/June for my 50th reunion and I found the facility in the same state (see attached pictures).  There was supposed to be an open house for alumni but clearly they didn't get the memo.

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[ChrisK]

Kristen, thank you for these wonderful pictures!  

Chris

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[Paul Birkel]

Check out https://tomtilley.net/projects/spacewar/ for what may be the best available documentation for the original controller design and dimensions.  Information provided by Dan Edwards.

[Randy Eubanks]

I placed an order for these a couple of days ago. I just received an email that the order has been cancelled as they are out of stock.

Sigh...

On Saturday, August 30, 2025 at 9:34:15 AM UTC-7 wjegr...@gmail.com wrote:

Here is a source of what looks reasonably correct. A little pricey, but if you want more authenticity, give this a try.

https://www.surplussales.com/items/100636/switchcraft-leaf-switch/

Same place has a big assortment of similar, just be sure you get a center-return one, not toggle on, off one. I haven't ordered any yet, but I will eventually. Jealous that some have already received their kits!

Bill

[Bill E]

Bummer. My order is still showing as 'processing' after almost a week. I'm anticipating bad news.

Bill

[Paul Birkel]

:-{.  I'm curious as to what they quoted as the shipping cost to your location.  I'm leery of vendors who won't provide (or even estimate) a shipping cost prior to you committing to purchase :-{.

[Paul Birkel]

I've dug up several sets of suitable switches, including handles.  Pleasantly surprised am I!  Manufactured by C.P.CLARE & CO.  They are NOS (literally; never soldered), although the four small screws that attach the non-conductive front plate have varying degrees of superficial rust that does not interfere with their operation.  The rest of the assembly is exceedingly clean.  The return action has a good feel and is the same strength in both directions.  One direction is SP N.O.; the other is DP N.O.  The length from a flush surface (the four screw-heads would touch that surface) to the ends of the solder-lugs is 3.25"; to the ends of the phenolic plates is 2.75" (so with some lug bending and applied shrink tubing they'd certainly fit into a 3" deep cavity).  The front non-conductive plate is 2" x 7/8".  The handle extends forward from that plate 1.25".  The black handle itself is 7/8" by 3/8" diameter.  These dimensions appear to be consistent with the design by Thomas Tilley mentioned earlier in this thread as well as in the assembly instructions.  IMO these are nicer than the ones that Surplus Sales no longer stocks :-{.  Asking $25 per pair (enough for one controller), plus shipping to your location from 20902.  A USPS Small Flat-Rate Box is $11.70 and would certainly be roomy enough to accommodate 2 pairs with plenty of space left for padding.  Contact me directly if interested in "upping your game", so to speak :-}!