[Coco] Coco3 Keyboard

[jdaggett at gate.net]

Bob

After rethinking, I remember that carbon  was used a lot for contact switches 
used on PCBs and even mylar.  I doubt that the mylar membrane was routed 
with pure silver anyway. A conductive silver bearing compound would be 
more probable. The actual contacts would more likely be carbon. 

Judging by how cost conscience that Tandy was, I would definitely agree that 
Tandy could have weighed cost over quality on many aspects of the design 
of the Coco. 

james


On 15 Aug 2006 at 20:02, Robert Emery wrote:

> Well, I kind of doubt Tandy used silver traces on the keyboards...
> at any rate, the intermittent nature of it was annoying as hell.
>  
> cheers,
> Bob
> 
> ----- Original Message ----
> From: jdaggett at gate.net
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Tuesday, August 15, 2006 9:24:59 PM
> Subject: Re: [Coco] Coco3 Keyboard
> 
> 
> Bob
> 
> Silver oxide is conductable. While not as conductive as pure silver, it is the 
> only oxide of the transisition metals that is conductive. In RF applications, the 
> silver oxide coating is generally left alone unless one is dealing with 
> microwave frequencies. Then the prefered metal is gold.
> 
> Not so sure Tarnix is a wise choice to clean the contacts. 
> 
> james
> 
> On 15 Aug 2006 at 15:16, Robert Emery wrote:
> 
> > That said, I've noticed on more than one CoCo3 keyboard sections
> > of the traces turning from silver to black, apparently due to oxidation.
> > This seems to lead to intermittent operation of either a row or column of
> > the keyboard grid, getting progressively worse until it quits working
> > altogether.
> > 
> > I've not tried repairing a keyboard in this codition. Perhaps our resident
> > chemist, Robert Gault, could shed some light on whether this might be
> > reversible... Tarn-X ?
> 
> 
> 
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