Text 2515, 83 rader
Skriven 2006-04-14 05:51:02 av James Bradley (1:134/77.0)
     Kommentar till en text av Wayne Chirnside
Ärende: Carbon-Latex Contacts
=============================
WAYNE CHIRNSIDE wrote JAMES BRADLEY on 04-13-06 10:54

 ->  -> I have to rejuvenate some of those carbon impregnated
 ->  -> latex-rubber type push
 ->  -> buttons, found on almost every remote control on the
 ->  -> planet these days. One was
 ->  -> acquired that had vodka, and orange juice spilled in
 ->  -> it, where I figured I
 ->  -> could at least pour some H2O over it, to dislodge most
 ->  -> of it, but the remote is
 ->  -> unusable now.

 ->  -> Is there a contact-improving electrolyte that is used on
 ->  -> the contact pads? I
 ->  -> understand the acid, and alcohol may have bitched the
 ->  -> one remote, but I've a
 ->  -> few devices that could use some encouragement.

 ->  WC> Two bits of advice, one I've done several times
 ->  WC> and one I've merely heard of.

 ->  WC> First if you act FAST get a gallon of distilled
 ->  WC> water, place in bag with remote, batteries
 ->  WC> removed first, shake vigorously and repeat.
 ->  WC> Saved two remotes this way.

 ->  WC> Second and I've only heard accounts of this is
 ->  WC> it appears Radio Shack sells ( or sold) a pen
 ->  WC> that allowed you to paint on short traces to
 ->  WC> repair circuit traces that'd been cut. That's my
 ->  WC> two cents. --- Platinum Xpress/Win/WINServer

 -> The traces are not the problem, AFAICT. I think there's electrolyte that
 -> comes smeared on the contact buttons. Now that that got
 -> washed off... It's not
 -> the first time I've seen it either. I had one lazy unit,
 -> that I squirted a bit
 -> of contact cleaner on, but just the faulty spots, which
 -> made it go from bad to
 -> worse.

 -> Again, I suspect that there is a chemical problem between the rubber push
 -> buttons, and the wire traces that those buttons are supposed to contact.
 -> Either, it gummed up by the tap water salts, or a layer of conduction was
 -> removed, but from the composition of the rubber. As if there was a membrane
 -> there, but the rubber must touch the wire traces to provide the conduction.

 WC> Well there's still some hope.
L... Speak for yourself! I found Slackware yesterday, and have one install in,
waiting for my input.

 WC> If it's the rubber membrane that must make the
 WC> contact with today's extremely high impedence
 WC> MOSFET inputs it need not be a great conductor
 WC> to manage the task.
I didn't look at what is driving the switch matrix.

 WC> Heck I'd try a pencil and see if that took.
 WC> Carbon black and some kind of conductive
 WC> adhesive is another option but that's mere
 WC> speculation. --- Platinum Xpress/Win/WINServer

We almost see the same device. It has no membrane, other than the solid latex
sheet that the user depresses directly. The other side of the 'button' presses
on the traces of the PC board, and on this pad, I suspect is the doped
electrolyte and/or the impregnation of an impurity. You are 100% correct, AFAIK
that the latex is impregnated with carbon, in order to pass the command + close
the two traces.

The first time I saw this structure, was in a contact to an LCD display, with
an old cell phone. If you placed the latex block 90^ askew - nada. 180^ - no
problem. Turn it another quarter - buttcus. So in a process where they stripe
the latex in one direction, and not the other in the latex carrier, depends on
if the block would pass the output along as designed, or find two open
circuits.

Only because I was able to totally bitch one device, and one column of keys on
another, led me to believe a substance was being washed off.
... James
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