On 24 Apr 2002, at 22:43, Ian wrote:

> David, thanks for that.  To recap then, you're saying that even
> though there may be no visible dirt or gunk anywhere in the 'ball
> pit', it's possible that the light-admitting slits may be partly
> obscured?  I take it these slits are not immediately visible when
> the ball is removed?

  That's correct.  They're almost always part of a single piece of
plastic with each roller, but they're further along the shaft,
outside the "ball pit", and a good percent of the wheel is hidden
between the light source and sensor at any given moment.  You can see
them a bit more easily if you dismantle the mouse shell.
  (I've done this with mice of my own, but I think most customers
would prefer a new mouse.)

David Gillett

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