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Thread: Kaypro II keyboard rebuild - update

  1. #1
    Join Date
    Feb 2015
    Location
    Cleveland, OH, USA
    Posts
    718

    Default Kaypro II keyboard rebuild - update

    About a year ago I posted (http://www.vcfed.org/forum/showthrea...ghlight=kaypro) my troubles with missing keys on a Kaypro II keyboard. People were kind enough to respond; some suggesting I purchase replacement key "foams" from eBay. A reseller there was selling kits of replacement foam disks; as I recall it was something like $30 for 20-30 and they were not drop-in replacements as you needed to re-use the mylar disk at the bottom of the key. And he was shipping from Germany.

    Cheapskate that I am I tried to make my own. The first attempt didn't work very well but I learned something from the effort. I tried again recently and succeeded, so I am posting the results.

    In the first attempt I made several errors: The foam I used was too thick and too stiff; the glue I used (super glue) was too thin and runny, and seeped onto the face of the mylar foil, ultimately preventing good contact. I tried several manufacturers of foam without success, then one day in Home Depot I found what I was looking for, on the cover of a paint roller. Thin, soft and flexible, and cheap.

    I made a cutter of sorts by sharpening one end of a 1/2 inch copper tube and cut dots out of the cover. The 1/2 inch tube was a little large so I had to trim them with a razor blade. A diameter of about 0.370 works well.

    The keyboard key moves a spring-loaded plunger; the plunger pushes a sandwich of plastic disk, foam and mylar down to meet the keyboard circuitry. The plunger travel is about 0.300 inch and of course the mylar has to sit above the circuit. I found a thickness of about 0.250 inch for the foam works well. I cut a piece of a DigiKey foil bag as a replacement mylar. I used white glue to join the pieces and tucked the plastic disk back under the tabs of the plunger when dry.

    Disassembly and reassembly of the keyboard probably was the most time-consuming part of the job. When reassembled I tested my work and was pleased to find it was effective. Note too that you can swap key switch positions (from the underside of the board; there are little tabs holding the bodies in place) so even if you don't have time to fix a key you can swap it out with something you never use - like the line-feed key, for example.

    Hope this helps... happy hunting (and pecking...)

    -CH-

    KeyPad.jpg
    Last edited by clh333; April 23rd, 2018 at 01:35 PM.

  2. #2

    Default

    Hats off to you for posting this. Luckily I have not needed to do this yet, but when I do this will save me some research time. Most of the keyboard restoration work I've done has always been tedious regardless of what system it's for, but the thought of foam/foil replacement work has always made me cringe a little.

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