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Thread: Scanner help

  1. #1
    Join Date
    Apr 2010
    Location
    Grand Rapids, Mi
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    2,465

    Default Scanner help

    In going through some of my spare scanners, I have a set that does a decent test pattern at 30K, looks good with graphics and most abstracts, but with heavy abstracts with many circles tight or triangles very close and spinning the signal seems to get noisy and ripple. Looks like hash on a supply voltage when caps fail.

    Ideas, I seemed to remember reading something about grounds and there level changing during heavy swings of scanners. What might I look for or do scanners just fail like this as they die.

    Thanks

    John
    leading in trailing technology

  2. #2
    Join Date
    Jun 2010
    Location
    Australia
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    3,730

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    Hypothetically speaking, "ripple" or ground currents could case such symptoms. How is your grounding setup? Star topology?
    This space for rent.

  3. #3
    Join Date
    Jan 2006
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    Charleston, SC
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    2,147,489,091

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    Quote Originally Posted by polishedball View Post
    with heavy abstracts with many circles tight or triangles very close and spinning the signal seems to get noisy and ripple.
    Sounds to me like you're scanning those abstracts too wide.

    Remember that abstracts can be *very* taxing on your scanners. Try reducing the scan angle and see if the image improves. If so, then you were probably pushing them too hard.
    do scanners just fail like this as they die.
    Not usually, no. But pushing them beyond their limits will cause them to die prematurely.

    Adam

  4. #4
    Join Date
    Dec 2010
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    DC/VA metro area, USA
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    After reading a little on scanners, it seems to me that the galvo amps would benefit from some power supply stiffening capacitors right next to the amps as is sometimes done in audio systems to improve transient response, especially if the power supplies are short on output caps. Swinging the mirror wide at high speed would take the most power at the ends of travel where the momentum has to be countered and then reversed. If you have some lying around, a handful of fat caps on the PS rails near the amps would be an interesting experiment. I'm thinking at least a few thousand uF, better a few tens of thousands. Best to add the caps with as little wire between them and the amps as possible, and with reasonable gauge wire.

    Interested to know if others have tried this before and if any visible improvement was noted.

  5. #5
    Join Date
    Sep 2010
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    Utrecht The Netherlands
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    when i got this behaviour it took little time for one of the mirrors to break, it started with wobbeling on lines, sinuslike distortion and then it broke off.
    maybe you should take a close look at the mirrors.

    Michel

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