22 Dec
2010
22 Dec
'10
1:31 p.m.
On 12/22/2010 12:56 PM, terry stewart wrote:
I once saw a Tektronix-badged Keytronics keyboard where all the
metalisation ahd vanished. The foam was fine, the keys felt fine, but
none of them worked.
Alex, so you really think this might be the
cause? The web-info I've
read on the Lisa suggests it's usually the pads that wear out causing
non-responsive keys and that these should be replaced. However what's
odd is...
1. All the keys feel very firm, with no sign of the "mushiness"
mentioned in some of the info.
The mylar disks can still go bad. There maybe be dirty areas where the
mylar disks go down, there might be a short. 2. ALL the keys expect for one (in two keyboards)
are not working AT
ALL no matter how hard you press. Yet the '4' in one and the '/' in
another are working fine and with no pressure needed at all? In the
third keyboard NONE are working.
It would be great if the problem wasn't the pads, but something more
easy to fix.
Laziness is only a virtue for programmers. :-) Whatever's broken is
whatever must be fixed. Could be pads, could be something else.
Another thing to do: Get a can of contact cleaner, the spray kind.
Unplug the Lisa. Get some paper towels and lay them down under the
Lisa. Spray the stuff nice and thick into the keyboard jack, wait a
minute, flip the Lisa forwards so the stuff can run out, hold it like
that for 15-20 minutes until dry. Might be the jack.
Also wipe down the contacts on keyboard jack too.
I don't get this. As I understand the schematics, the keybaord intereface
is 3 wires (on a 1/4" e-pole jack plug as we call them over here).Power,
ground and a signal line. I don't see how bad contacts there (or indeed
broken wires in the keyboard cable) could leave one key still working.
-tony