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Thread: Laser scanner problems

  1. #1
    Join Date
    Oct 2017
    Posts
    2

    Default Laser scanner problems

    Hi there since a month I own an 3 watt rgb laser.

    Since a couple of weeks the scanners are acting strange squares aren't squares (round edges)
    This is how it used to get
    https://imgur.com/YlrmHuU

    This is what it makes of it
    https://imgur.com/a/DbLuM33

    The laser is a big dipper sd3000rgb
    With(30k) scanners.
    Is it a simple galvo tuning to fix it ?
    Or is it worse. Hope someone can help me out

    With kind regards Remco

  2. #2
    Join Date
    Mar 2010
    Location
    Raleigh, NC
    Posts
    2,014

    Default

    That's pretty horrible. The jagged stairstep edges suggest you might have something funky with your software or DAC.

  3. #3
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,586

    Default

    Agreed. Also it seems that the image is being compressed at the top and bottom of the scan field. (Note how the diagonal lines start out solid at the top and bottom, but are also nearly vertical, and then transition to more of a diagonal line but also start to pick up the jagged, stair-step distortion as you get closer to the middle of the scan field.)

    The old big dipper laser projectors I've seen had pretty poor scanners in them. I don't know if they've improved much since I last saw the inside of one. If they still have the cheap 15K units, you can try lowering the scan speed and also reducing your scan size. But if that doesn't help, you may need to have the scanners re-tuned from scratch. Note that this would be a complete re-tune, which is far beyond what most laserists would be comfortable doing. (That is, not just adjusting the 3 normal pots...)

    If the non-linearity is due to bad scanner tuning, it will not be fixed by adjusting servo gain, low frequency damping, or high frequency damping. Rather, it will require adjusting all the pots on the amp. This is normally done with a frequency generator and an oscilloscope. I've never done a complete re-tune myself, and although we attempted something similar at SELEM this year, we were unsuccessful.

    I would check all connections first, and then try reducing the scan speed to 15K and also reducing the size of the scan field so you are not scanning any wider than 8 degrees. And as Gary suggested, also be sure you have the software configured correctly and are using the proper driver for your DAC. If the problems persist under these conditions, you either need to get someone to try a complete re-tune of the scanners or simply cut to the chase and replace the scanners. (For around $250 you can get a new set of PT-40 scanners that will work well in that projector.)

    Either way, good luck!

    Adam
    Last edited by buffo; 11-16-2018 at 05:05.

  4. #4
    Join Date
    Aug 2017
    Location
    Southern Netherlands
    Posts
    35

    Default

    Remco, never buy a Big Shitter ever again!

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