OT laptop keyboard circuit trace repair

[Duane Attaway]

On Mon, 17 Nov 2003, rod holcomb wrote:

> Q #1 )Does anyone have a conductive paint or marker that is used to
> repair the traces on a circuit board or in this case the traces on the
> film under a laptop keyboard?

You can get this at Electronic Supply Company on Main next to the
Community Blood Center.  Its called silver print or nickle print and its a
small glass bottle of metal paint with a brush inside the lid.  I believe
they sell pens with this conductive ink.  It works well and can also
repair rear window defrosters in cars.  The conductive traces can take
good amounts of current with low reisistance, but can fail under short
circuit conditions.

It is just metal flakes in an acrylic-solvent base.

> Q #2) Have you had good luck with it?

:)

> Over the weekend was able to make the keyboard operational by cleaning
> it and using aluminum foil held down by Scotts tape over the damaged
> traces.  Juice was spill on it. What I’ve done by-and-large does work
> however; some of the Cntl and Alt combinations do not work.

Electricity and water are the number one killer of weathered devices.

> Q #3 ) would a _poor_ trace work for a single key press but not work for
> some key combinations?

Its all about poor and intermittent connections.  Pressing multiple 
keys may allow the scanning row current a new path to the severed key. 
Your keyboard will scan the keys at a frequency not high enough to cause
interference, but sample enough times to allow a small software program in
the keyboard microprocessor to catch key bounces.  A poor connection may 
work sometimes and not others due to resistance and possible capacitance 
in the damaged area.

> I will be at meeting tomorrow if anyone has a product they are confident
> will work.

The conductive pens are cool.  If you can sign your name, you can fix a 
keyboard.

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