deskthority

Weird question I know, but I have recently come across a reproduction of the space cadet pcb board for sale on etsy:
https://www.etsy.com/uk/listing/1254501 ... 1254501724

According to the seller it is intended as a "drop in" replacement for the keyboard and is compatible with the original components. This got my layman mind working and curious weather it would be possible to use the pcb to not just replace a pre-existing space cadet pcb but instead use it to make one from scratch.



Would this be even feasible? One of the first things that comes to mind is finding a stand in for the honeywell hall effect microswitch which, aside from switch harvesting, appears to be remote. Another is the micro controller, I doubt anyone has any clones of that lying around, so would it be plausible to drop in a modern micro controller?

Again I apologize for the lack of extensive knowledge surrounding this topic, but I don't see myself buying a space cadet anytime soon so I guess second best would be to attempt at making a replica, and a pcb like this would help act as a base for such a project.

Thanks in advance

While it doesn't use the honeywell switches, you may enjoy this project which is a spiritual successor of sorts

viewtopic.php?t=25131

Subject: Feasibility of building a Space Cadet using replica PCB?

ArtyomTheMetroHopper wrote: 01 Dec 2022, 09:56 According to the seller it is intended as a "drop in" replacement for the keyboard and is compatible with the original components. This got my layman mind working and curious weather it would be possible to use the pcb to not just replace a pre-existing space cadet pcb but instead use it to make one from scratch.

Hi! I am the creator and seller of the Space Cadet PCB. I am doing exactly what you are asking about, making a Space Cadet keyboard from scratch.

"Feasible" is a subjective word. The most difficult part of the build is sourcing the switches. The board has 122 D Series switches of various models. These switches haven't been manufactured for decades. You can sometimes find them in small numbers on eBay, but they usually sell for $8-$12 per switch. I personally consider $1,572 just for the switches to be infeasible. The best strategy is to try to find a couple of vintage keyboards that use the same switch.

I'm going a different route. I am trying to create a 3D printable replica of the switches. I have only just started on this part of the project. A few reference switches are on their way to me from eBay. In the end, I might make resin casts of the plastic parts and fabricate the switches that way.

Depending on how you solve the switch problem, you might also need to source Hall sensors. In my case, even the genuine switches I ordered are missing their original Hall sensor. Again, it is possible to occasionally find these sensors in very small numbers on eBay and other places on the internet, but sourcing ~118 of then is probably not feasible by most definitions. The better strategy is to find a modern replacement, of which there are several reasonable options available. I don't know what difficulties, if any, trying to use a modern replacement will present. It might "just work," or it might be a huge hassle.

There are a few possibilities for the keycaps. Signature Plastics sells their own version of the Space Cadet keycaps with MX mounts. This might be the easiest route. You will need an adapter to use MX keycaps on the Micro Switch Series D stems, which use a different mount, but these are easily 3D printed.

If you insist on more accurate caps, you will need to make them yourself. The profile of the keycaps actually isn't anything special. It's the same profile you can find on most Micro Switch keyboards of the era. The hard parts are the legends and the color. My plan is to resin cast the keycaps from keycaps I already have and then laser etch the legends onto the keys. I've done a few experiments that suggests this will work. It probably is not very much cheaper than the Signature Plastics set—especially if you factor in labor—but it will be a bit more true to the original, and I'm just doing it for fun anyway.

The rest of the components are pretty much off-the-shelf electronics components. Personally, I am going to use a modern microcontroller to emulate the original Intel 8048 processor, because I am going to use the keyboard with a modern computer. However, the original source code and binary are available online if you do wish to use the 8048. (You will need a programmer.)

Finally, you need to decide what to do about the enclosure. The Space Cadet keyboard was sold with a variety of different enclosures. I personally don't think any of the original enclosures are particularly beautiful, so I plan on fabricating a simple enclosure of my own design.

If you are a stickler for accurate details, the original keyboard has a daughter board that interfaces with the speaker and holds the external connector. I did not see much point in replicating it, as most people won't be connecting the board to vintage machines, and the people that will want to connect it to a vintage machine will know how to wire their own connector without the daughter board.

Sorry to be a contrarian but I feel that this project is a bit misguided. Procuring these switches is nearly impossible and chopping up a vintage board is heresy. Additionally the sensors in these switches can be particularly prone to heat damage from the desoldering process. There were some vintage Micro Switch boards which actually shared the same basic PCB or PCB layout with varying numbers of switches which would ultimately be a better starting point if you are lucky enough to come across a similar type of board. I do like the idea of a replica or tribute board but modern MX mount is the way to go.

JP! wrote: 01 Feb 2023, 16:59 Sorry to be a contrarian but I feel that this project is a bit misguided. Procuring these switches is nearly impossible and chopping up a vintage board is heresy.

I don't think this is contrarian. It's just a reasonable concern over the preservation of vintage equipment and helpful information about the risks of desoldering.

I do not advocate destroying vintage boards. There is some risk involved, but removing switches is a reversible process that need not destroy a board. However, this is the first time I have heard about the sensors being sensitive to heat damage. I'll be sure to mention this to anyone planning on going this route.

For my own build, my plan is not to use switches from vintage boards but rather to find some way of fabricating a functional replacement. My replica board will not work with standard MX contact switches, and I have no desire to design a board that will. I think making a Space Cadet keyboard with a modern PCB and components is actually a lot easier than what I am doing but at the cost of historical accuracy. Anyone who makes a replica of a historical object (or movie prop, etc.) has to decide for themselves how far they want to go to be true to the original object.

Nice to see you here, describing the true, rather epic scope of your work. A noble endeavour! Without all your context, I’d have guessed the purpose for these PCBs was as wall decorations for wannabe scape cadets, grounded here on earth. But no, you’re really up to something. I like it.

There's no shortage of hall sensors today, in various shapes and forms. Also, hall sensor doesn't contribute to the key feel in the slightest, so it's not a problem replacing them to some contemporary variant in your newly 3d-printed keys.

For connection to modern computer, no sense in preserving the original controller either.

Replacing the PCB.. doesn't make any practical sense: even if tracks are completely rotten (which doesn't make much difference for hall effect switches, but can completely ruin the MagValve keyboard) - just greenwire them. Sure it won't look pretty - but who cares, its well-hidden by the case.

PS: don't ever leave any bare copper on the PCB. If ENIG feels too expensive - well, at least HASL them. Bare copper oxidizes like crazy, and it takes couple years tops for 1oz copper to rust thru, ruining the PCB.

Good points. I quite agree on the native modern controller, but that’s my disinterest in retro computing shining through. I always look at keyboards with everyday use in mind, not their original systems. Retro computing folks rightly begrudge my type for snatching their best keyboards!

As for harvesting components: grab them while they’re hot!