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Thread: Cold scanners

  1. #1
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    Default Cold scanners

    Can cold weather make scanners do funny things?

    I was running an outdoor show the other day for Holiday Inn and one of the projectors scanners started having a fit.
    The outdoor temp was 50F. Both projectors shared the same mains supply. I swapped out ILDA cable and swapped FB3s.
    The projector started off just fine and then all of a sudden went crazy.

    I thought it was a grounding problem but with both projectors sharing the same supply surely it would have happened to both. I'm going to pop the lid and check the internal connections later today.

    Thoughts and things to check?

    Cheers
    Rich

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    This should be the Holiday Inn "H" logo

  2. #2
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    Nope it Shouldn't be able to..
    In fact it could only increase gain performance from what I've noticed.
    I've tried multiple times to cool down a scanner amps and blocks as much as I could using upside down air duster cans to try and chill down scanners and amps for a short period of time to little effect minus a slightly improved gain performance due to (I believe) reduced resistance.

    It's looking like a grounding or signal wire problem here...

    possibly it's humidity though?

  3. #3
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    Good to know.

    Yea, I am leaning towards the grounding too.

    Don't think it is humidity as the projectors are sealed. Humidity is currently 29%

  4. #4
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    Default

    Really high end planetarium projectors used to have water cooled blocks for the scanner mounts.
    +
    I have a few scanner mounts with forced air cooling.
    +
    As long as you do not chill them so cold that you are not: 1. Below the dew point, causing condensation in the bearings or sensor, 2. Stiffening the bearing oil, 3. Causing excess drift in the position sensors. 4. Shrinking the moving coil to magnet distance too much, You should be fine.
    +
    The data sheet for the US or European made scanners will have a lower limit temperature and a spec for sensor drift vs. temperature.
    +
    50F should not have been a problem.

    Steve
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  5. #5
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    Thanks Steve. I'll keep looking into this

  6. #6
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    If this problem is not present when you first star scanning but then appears after a short period of time then I would be inclined to think it's the Poly switch (Resettable fuse) on one of the scanner amps.
    When a Poly switch trips out it dose not completely stop the galvo from scanning. And the only way to reset a Poly switch is to power down the projector.
    Looking at the photo I'm thinking the Y axis is the issue but best to check both.
    Hope this helps.

    Carl
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  7. #7
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    Is this a home built projector?
    If so, make sure you have the correct grounding scheme.
    Pangolin has diagrams on their website for reference.
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  8. #8
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    A similar thing happened to me recently.. and a power cycle fixed it. The consensus was the poly switch.

    http://www.photonlexicon.com/forums/...anner-behavior

    Haven't had the same problem since.

  9. #9
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    Perhaps we should just run these projectors in Utila on a regular basis.
    PM Sent...

  10. #10
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    Yes, that looks like the poly switch, if it keeps happening, it means you are trying to drive the scanners harder than they can handle. Try slowing down the scan rate or reducing the size of the image and that should fix the problem.

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