[sane-devel] Medion MD9850: scan range & noise probs?

[edg1 at tiscali.be]

Wolfgang Fabics wrote:
> Henning Meier-Geinitz wrote:
> > Maybe it's just backtracking? I.e. the scanner is too fast for the
> > parallel port. Does the scan head stop shortly when the noise occurs?
> > Or does it even move backe some milimeters?

That's quite impossible, unless there is a serious bug in the driver.
This type of scanner is pretty dumb and it doesn't move unless the driver
tells it to move (and the driver never tells it to track back).

Does it happen at all resolutions?

> Hmmm... hard to say, the steps are very small, ofc. It doesn't move
> back. I'd say that it... uh... hesitates in a way (maybe sometimes stops
> for a split-second) *after* 2 or 3 consecutive "clanks". I.e. the step
> rate remains the same but the steps get smaller for a while (you can hear
> that by the synchronous "uk-uk-uk-.." sound of the stepping motor). It
> definitely doesn't stop *at* a "clank", anyway.
> 
> The result is that if it "clanks" at a certain line of scanned text, the
> image is vertically stretched a bit at that line.

This sounds like a physical problem. The fact that you get similar sounds
with the Windows driver seems to confirm this.
Those vertically stretched regions may be due to the scanner head jamming
a
bit every now and then and jumping ahead when the driving belt tension
increases. Maybe the glider bars need some grease?

> I tried all combos of EPP/ECP on the parport, with both EPP 1.7 and 1.9.
> No change. May I ask a silly question here? How can a 1998 scanner that
> was designed for a 1998 parallel port be too fast for a 2003 AthlonXP
> 1400's parallel port? Any other settings I should try? Sorry, but I'm
> really clueless on those scanner things, as you might have noticed
> already ;-)

If your PC were too slow (or too fast, which would be more likely), you
would probably see other artifacts due to synchronization problems (lines
having the wrong colors or containing garbage).

Regards,

Eddy

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