Re: Strage behavior (MFS-1200SP & sane 0.73)

Anthony Mallet (mallet@laas.fr)
Thu, 8 Oct 1998 20:54:13 +0200 (CEST)

Dr. Andreas Bolsch wrote :
| The head is moved by a wire wound around a cylinder
| which is driven (indirectly) by a motor. Maybe one of
| the windings has slipped off. Should be easy to fix.
| Poor construction not to use a simple mechanical
| switch for the end position, I would say.

Oh sorry, I think I did not insist on what I did exactly...

The problem I'm experiencing is very very strange :
Everything works fine : that is, while scanning, the head moves gracefuly
from top to bottom and I get the image. Quite normal.

BUT, after the scan is complete, the head does not RETURN to the top. It
stays where it stoppped, and the problem appears when I want another scan :
the head does not start from the top and there's no way to get it start
from the top but switching the scanner off and then on (it resets its
position).

I opened the box, moved the head by hand, tried to remove the (sort of)
band that drives the head in order to check if the wheels and the
step-by-step motor did not have an hardcoded zero that would have been
modified when the head first reached the limit of the scan area, and
everything I could imagine. Nothing to do : the head does not want to
return home after a scan...
The only sensor I could find is an optical cell that tells the head when
it is at the top (and it works). But nothing at the bottom. And nothing in
the middle that could block the head.

That why I say it does not really looks like a hardware problem, because I
can't see what kind of hardware could be able to scan correcly and not to
put the head back where it was (and the scanner reset actually moves the
head correctly).

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