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Repairing the Keyboard on the Apple Lisa

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I have no idea WHY the hell Apple decided for the Lisa they should use a capacitive keyboard. Everything before it did not use it and nothing after used it either.

Anyways, like the TRS-80 model II and the SOL, by this point the foam pads that sit under every key has degraded until the entire keyboard no longer works. They need to be replaced. However sourcing new pads may be otherwise a fun task. From time to time someone sells a few dozen on ebay but you can get away with building them yourself.

For this you will need the following:

- 4-5mm sticky-backed closed cell foam (1 to 2" wide)
- A metallic mylar party balloon
- Xacto knife
- Spray-on adhesive
- Wax paper
- block of wood (4x4 or better)
- Hammer or mallet
- 7/16" hollow punch

1) Dismantle your Lisa keyboard. The goal is to remove the PCB. There's over a dozen small screws that attach it to the metal frame and four or five more larger screws that do the same.
You'll end up removing all the screws in the keyboard.
For testing later I recommend you then put the PCB back in the lower half of the keyboard enclosure and reconnect the cable. You will need it test something later.

2) Take the balloon and deflate it if it came pre-filled. Hopefully one side of the Balloon is silver or otherwise unpainted. Cut that side into the largest square possible. You will probably need to tape it down because it will want to curl.
Because this is is a Capacitive keyboard we do NOT want the metallic side. Cut a scrap off and try it on the keyboard. One side will keybounce like mad and the other will act like you normally pressed a key. When taping the mylar down, have this side facing down (that is, don't make it the side you are attaching the foam to)

3) Take strips of the foam and cut to the length of the square. Cover the sticky side with wax paper, then spray the other side with adhesive. Lay this sprayed side down on the mylar and use a roller or the can to make sure it's stuck to the mylar. Rinse and repeat for another 4-5 strips. When done use a piece of plywood or something to press the strips and let the adhesive sit for an hour.



(in my case the foam had plastic on the side which did NOT have adhesive from the factory. I attached the mylar to this side.)

4) Use the xacto knife to cut up the mylar so you have multiple loose strips.
Using the wooden block, hammer and punch, begin punching out new pads and put them all in a bowl or something for later. I'm using 1.5" wide foam so I can have two rows of 18 pads punched. I'm punching more than I need because you will get a decent number of bad punches and otherwise unusable pads.



5) Take the metal frame from the keyboard that has your old foam pads. Use a small flat blade screwdriver to pop them out. You do not need to remove the keys from the keyboard. There's a plastic disc on the backside of each pad so make sure the capacitive pad, the foam and that disc all come out.

Here's an old pad compared to one of the new pads.


Most of your old pads will come out in a mess.


6) With the old pads gone you can install the new ones. Take a new pad, peel off the wax paper, press on the key you want to fit a pad to (so the yellow plastic part pokes out of the assembly) and push the new pad into place.



7) Reassemble the keyboard. There's three different size screws but their lengths do not vary. If it fits in the hole, you're OK to screw it in. Your keyboard is now refurbished and ready to go back into use.

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Comments

  1. Ozzuneoj's Avatar
    Just wanted to thank you for this post! I recently came into possession of a Dimension 68000 keyboard (looks like an XT-style Model F clone) and it was made by Keytronic using an almost identical setup to the Lisa keyboard in this post. It has exactly the same problem with the foam as well.

    As an experiment, I bought some 3/16" adhesive Neoprene on ebay, since it likely lasts significantly longer than basic open cell foam. I made a bunch of replacement pads and installed them and while it does work, the neoprene is much too hard and doesn't compress enough to allow full key travel. I'm not sure if using a 1/8 inch thickness would work, but I don't think so... it feels like it just needs something softer. I've seen some other posts online where people had speculated as to whether neoprene would work or not for this kind of repair, and I would personally say no. If someone wants to experiment with 1/8" or thinner neoprene, it may be worth looking into but would probably still give the keyboard a much different feel (probably not in a good way).

    The process does work perfectly though! I bought a 7/16" punch on eBay to punch holes and used an old mylar party balloon and some spray adhesive to attach it to the neoprene. It was super easy. I'm hoping that whatever foam I can find (maybe some weather stripping?) will also be double-sided adhesive, so I can skip the spray-adhesive step entirely... its 30F outside here, and I don't recommend using spray glue inside.
  2. KLund1's Avatar
    Hi,
    Very helpful directions!!
    Where could I purchase the correct foam? It seems hard to find. Links, sites please
    Thanks!!
    kl