On Fri, 8 Mar 2002 at 06:20:22, Al Feng wrote:
(ref: <[EMAIL PROTECTED]>)
>EVERYONE!
>
>Speculation about the material used in the QL's membranes by Sinclair
>or otherwise seems futile.
>
>It is worth noting, IMO, that the reason that the membranes have failed
>in the past, and will probably fail in the future in a standard QL
>configuration IS singularly BECAUSE of the proximity to the heatsink.
>
>Think about it.
>
>As long as the standard PS configuration is used, you are baking the
>tails. The rest of the keyboard membrane does not appear to suffer
>from the problem of becoming brittle.
>
>If you want to make a BETTER *membrane*, then get hold of a TS-2068 and
>see how Timex made their keyboard -- printed circuit, carbon pads to
>close the circuit, ribbon wire tails attached to a connector.
>
>Worrying about the pressure needed to actuate a "key" is a silly
>exercise if you are simply trying to create a replica of the original
>membrane because your keyboard membrane's tails will inevitably suffer
>the same fate which the original membranes experienced ...
Nope. As I said earlier in this thread, Sinclair used a good clear
plastic for earlier machines, and this is 100% OK. I know this 'cos I
have a few and seem to last for ever and are showing no sign at all of
failing. The conducting strips also show little sign of oxidisation -
and these all date from 1984. My experience of the std membranes is
that they become brittle on exposure to air. Heat simply accelerates
this. I have had a lot of people who report their QLs have not been used
for many many years. They worked fine when hibernated, but membranes
failed while not used. This happens because the tails are bent round
in a tight 180% degrees, and the bend is under tension.
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