On 23 Apr 2002, at 21:19, Ian wrote:

> Anyone know why mice go bad?

> I don't mean dirt in the mechanism, I mean the jerky, patchy
> behaviours that some mice begin to exhibit after varying periods of
> time.

> Sure, I know that a busy CPU can affect them too, but I've seen
> this flakiness occur when nothing has been running, background or
> otherwise. Like yesterday.  Went to fix an email problem for a
> customer and she had a crazy mouse. Looked inside - no dirt.
> Checked the connection - no probs. But the mouse still wouldn't
> behave.

> Sold her a new mouse - voila!  No problems - customer over the
> moon.  Thinks I'm brilliant.

> Well....I can't be.  Cos I can't tell her why the first one
> crapped out.
>
> Ian Porter
> Computer Guys
> Arrowtown
> New Zealand
> [log in to unmask]


  Well, there ARE two places where dirt in the works could induce
"patchy behaviour" in a typical mouse:

1.  The most common scenario I've seen is a build-up of "gunk" on the
rollers, around the point where the ball touches them.  This can lead
to a loss of friction between the mouse and the rollers -- the mouse
moves, the ball rolls, and the rollers don't.

2.  Each roller is attached to a wheel with slits in it, which passes
between a tiny light source and a photoreceptor.  If dirt blocks the
slits, the ball rolls, the roller turns, and the photoreceptor
doesn't notice.


  The ball is pressed slightly against the two sensor rollers by a
sprung third roller, set at a 45-degree angle.  I HAVE seen one mouse
where the spring for this third roller was not up to snuff, with the
result that when the mouse was moved suddenly in certain directions,
it could lose contact with one or both of the sensor rollers.  That
would be a non-dirt loss of friction, and might be another cause for
the problem you've described.

  (I've also had one cheap mouse where the microswitch under the
primary mouse button eventually wore out, but that didn't affect
movement of the cursor, so I'm pretty sure that's a different
problem.)

David Gillett

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