Apple Lisa Keyboard fix

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Apple Lisa Keyboard fix

Postby mrad01 on Sun Dec 22, 2013 5:49 pm

I've just completed a full fix of the keyboard of my Apple Lisa. Turns out that a few of the older keyboards used a similar method to activate keypresses. Rather than a switch, the Lisa keyboard has 2 pads which sit apart from each other under each key. The key itself has a piece of foam with a foil disk (covered with plastic) inside it. When you press a key, the foam pushes the plastic covered foil disk across the 2 pads creating a capacitor.
The issue is that the foil and foam degrades over time and the capacitor "switch" stops working.

So, this is a long process. It isn't difficult - just takes time. Only start if you have 3-6 hours to focus on it.

You will need:
- Lisa Keyboard
- 1.5m foam strip (12mm wide, 3mm thick, one sticky side)
- 60 Sticky foil labels
- Sellotape
- 10mm hole punch / small hammer
- Brush
- Scalpel
- Cutting mat or wood

I won't detail how to take apart the Lisa keyboard itself - it is very simple. Once you have it apart you will very quickly see how it works.

Quick guide:
- Use the scalpel & brush to clean out the underside of the each key.
- Use the punch to cut out foam disks (10mm x 3mm)
- Stick the disks into the keys
- Cover the foil stickers with sellotape
- Use the punch to cut out foil disks
- Stick the foil disks onto the foam disks
- Test. Done.

Long version:
Go to your local hardware store and get some foam seal. Make sure you choose the softest foam you can. The foam should be around 3mm thick and 12mm wide. You will be cutting a 10mm wide disk. Here is the display at my nearest store:

Image

I bought some foil heart stickers from a craft store. Ignore the hearts - you can get any foil stickers you like.

Image

Here is a 10mm hole punch and my rusty little hammer

Image

Here is the keypad before we start. You'll see some old disks have foil - some don't.

Image

Using the scalpel and brush, take out the old disks

Image

Image

Next, get the foam tape and cut out some 10mm disks, stick them into the keys

Image

Once those are all done, put sellotape over the top of the foil stickers

Image

Use the punch to cut out some 10mm foil disks and stick those on the foam pads

Image

By the end of the job, you should have something like this

Image

Put it all back together and test!

Image

Success!

Make sure you put the sellotape over the foil - do not short out the connectors with a direct connection - you may damage some chips.
Use 3mm foam - any thicker will affect the keyboard feel. Once you have it apart you'll see what I mean.

It's not hard - so if you have a keyboard like this - give it a go!
Last edited by mrad01 on Sun Dec 22, 2013 11:16 pm, edited 2 times in total.
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Re: Apple Lisa Keyboard fix

Postby tezza on Sun Dec 22, 2013 10:53 pm

Great post! This detailed description will come in handy for anyone who wants to not only repair a LISA keyboard, but any keyboard using the same sort of switching mechanism. Thanks for writing it up.
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