What's wrong with your current one? Have the foam contacts degraded? You can make new ones... Helmut had some excellent suggestions.
"
on 06.11.2005 13:56 Uhr, Philip Lord at
philip@rodoracing.com wrote:
>
I have a spare keyboard I'd like to get going. There are maybe 10
> dead
keys, and a few really sticky ones. what causes them to stick?
>
>
P
>
>
> On Nov 6, 2005, at 7:36 PM, macmoni wrote:
>
Hi Phil,
the Lisa keyboard is totally different from other Mac
keyboards- the Mac
uses switches (Alps inc.) which can produce corrosion over
the years, but
not the Lisa keyboard:
The Lisa uses a 3mm-4 mm thick foam
material ( as found in many candy
packages/boxes or tool boxes
etc...)
This foam material is glued to a small round plastic disc on one side
to
"snap" inside the key itself. On the other side there is a special
metallic
looking foil (like christmas paper)- this foil is not electrical
conductive!
Don't use any aluminium foil- this could ruin your Lisa
keyboard.
Recycle your foil pieces and reuse them again.
As a replacement
for the glue don't use fluid glue- this may ruin your
keyboard- just use a
sticky glue ( Pattex etc...)
The foam material deteriorates over the years
and forms a kind of sticky
mess... this produces the sticky effects on
several of your keys.
The keyboard uses a "capacitive" concept- a switch is
built from an
aluminium pad on the PCB and the non-conductive metallic
looking foil.
If you press the key, the foil presses against the pad (under
the pressure
of the foam material) and forms a capacitor- this capacity
change is
translated into an electrical impuls. if you use fluids or
pressured air,
you can easily ruin your keyboard. You have to open it very
carefully and
reconstruct all key switches with new foam material. Don't
forget to clean
the pads on the PCB from sticky glue and foam smudge.
The
whole work took me a full afternoon- but if you completed your task you
have
a brand new fully operational keyboard.
Measurements with an Ohm meter is
not possible- you can only measure a
capacity change with a capacity
measurement tool- but that is not
necessary.
I have successfully
refurbished 3 keyboards- they are fully operational now,
and will be for the
next decade...
there was no need to solder anything... only cutting foam
disks- you can use
Guido Deiana- he has successfully completed the same task
as I did.
Helmut
P.S.: Don't use any cleaning fluid!
This
ruins all!
"
-Jason
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