Re: Lisa Keyboard Repair - Here comes how to...

2005-11-06 Thread macmoni

Hi,

open the keyboard and check the board, whether you can see any corroded 
parts.
Then check with a Ohm-Meter, whether there is contact if you push the 
space bar.


If not, try to clean the button (often full of dust) with air pressure.
If yes, try to check the multiplex connection from the two pins of the 
button to other buttons and to the arry with a lot of pins in one row 
on top of the reverse side of the board. You can easily trace the 
connections visually, this is a one layer board.
If there are interrupted connections, just resolder them (the button 
itself, the perhaps interrupted connections) or just solder a new wire, 
where corrosion took place and destroyed the connections


No need to throw away and replace the original part of your Lisa !

greetings TOM from Bavaria, the center of europe, the marvellous 
castles of Koenig Ludwig e.g. Neuschwanstein and last but not least the 
original Oktoberfest !



Am 06.11.2005 um 03:59 schrieb [EMAIL PROTECTED]:

I have a keyboard with one key (space bar) not working. Any 
suggestions?

Anyone have a working keyboard for sale?
Ron
San Diego
619-225-8281

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Re: Lisa Keyboard Repair - Here comes how to...

2005-11-06 Thread Dr. Helmut Post
on 06.11.2005 13:56 Uhr, Philip Lord at [EMAIL PROTECTED] 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!


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