"John-Del" wrote in message
...
On Monday, December 1, 2014 8:23:21 PM UTC-5, Arfa Daily wrote:

He said it wasn't collapsed, although there's the possibility some
liquid
was spilled in the key matrix and is causing an unintended function
command.


Err, no he didn't. He said it wasn't jammed, which is an entirely
different
thing. I replace many many of these buttons on a variety of equipment
that
uses them, and it is not at all uncommon for the dome to collapse, whilst
the outer control button remains free to move.

If you're talking to a customer on the phone and they say it isn't jammed,
it's possible the switch collapsed and they can't tell the difference.
But Mr. S is clearly no newbie. If he says it's not jammed, it's a fairly
safe assumption that the tactile feedback of his play button is the same
as the rest of the buttons on the machine.

In servicing, it's a rule to never assume anything. It depends a lot on the
exact type of switch and how the outer 'user' button is implemented. Some of
the buttons have very little 'snap-action' feel to them, and the majority of
the return force on the user button comes from its plastic flexible hinge,
rather than from the switch itself. In those cases, it is perfectly possible
for the switch to collapse, but for the button not to feel much, if any,
different from normal or from any of the others. With some other types, the
travel of the switch plunger is so small on a correctly operating one, that
a collapsed one feels little different. Also, bear in mind that these
switches do not normally collapse spontaneously. Instead, they wear, until
one day, the last little bit of movement expires, and the switch goes short.
The switch will then feel absolutely no different today when it no longer
works, than it did yesterday when it did work ...

Yes, you are right that William is "no newbie", but by the same token, he is
not a 'current' engineer, and may not be able to feel the subtle differences
that we are talking here, without understanding the way his unit is put
together, and the failure mechanisms involved in these switches.

Arfa