carry-1 covox sound card / cast epoxy key

Frank and I picked up a nice PC compatible computer at an estate sale, the Carry-1. It’s (at the time at least) the world’s smallest PC compatible computer. It takes an XT protocol keyboard, has the whole chipset boiled down into one chip, has ram upgradeable to 640k, up to 2 floppy drives, and the chipset also has a CGA compatible output (but it doesn’t run the 8088mph demo) with composite and a parallel port. It runs a NEC V20 processor with firmware that can clock it up to 10Mhz. So now my problem is getting an XT compatible keyboard. Luckily at VCFmw there was one for sale for only a couple bucks. It was missing one key however. That was a problem because the spring that sat between the keyswitch and the key held up the foam and foil keyswitches, so without the spring it had a stuck escape key. I swear I almost cried when I saw those foam pads again, but miraculously these had not perished, not one.

Here you can see my setup, a vacuum pump, vacuum chamber, mold release spray, 2 part silicone for making molds, and foam core board and a hot glue gun for making the mold. I decided to vacuum degas the silicone before pouring into the mold (the other half of the first mold was filled with that crayola brand modeling clay stuff). You can tell I watched Adam Savage’s video on this. Some tips:

  • take some care in making a foam core mold base, it doesn’t seem like it being rectangular matters, but it helps to make the second half of the mold.
  • spray vegetable oil as mold release works well, but flashes off under vacuum, you should really degas your resin or silicone, but pressure cast your items once you pour into the mold.
  • resins take a lot longer to cure than the manufacturer says, especially when it’s amazon cheapie-special
  • silicone mats are great for peeling epoxy messes off of
  • clean up your parts when they’re slightly gummy, they are easier to work
first key, with void, second time the mold didn’t seal perfectly

It works though!

So, now, what do we do with the carry-1? Well, it’s going to be a testbed platform for developing a usb-to-xt keyboard converter. It also needs sound, clearly…

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