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Thread: Sonima scanners making a high pitched noise when idle

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    Default Sonima scanners making a high pitched noise when idle

    When i turn on my new built projector with Sonima SM2803 (Scanpro 20's) scanners in them and i don't feed a signal into the projector (so they are just powered on not moving) my scanners make a very high pitched noise.

    Anyone know whats up ?

    The scanners work fine, only i see the blanking lines as dotted lines (but that has probably to do with my green module), all the stuff gets displayed just fine.

    I have to admit that one of the scanners is still a bit loose in the scanner block, need to get a new allen key (small one that fits between scanner block) to secure it, but seems to come from both scanners i think.
    I didn't fail !
    I just found out 10,000 ways that didn't work.

  2. #2
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    [QUOTE=hobbybob;168642]When i turn on my new built projector with Sonima SM2803 (Scanpro 20's) scanners in them and i don't feed a signal into the projector (so they are just powered on not moving) my scanners make a very high pitched noise.

    Anyone know whats up ?

    Some scanners do oscillate at idle, at near ultrasound frequencies. This can be either a tuning or hardware issue and depends on the brand, a bad amp can oscillate, other amps just have a very fast fine feedback loop that is too fast for their own good, and usually in that case it is not a problem.

    For example, my Eyescans whine, but work perfectly, and work just as well as when I got them years ago.

    Are the driver output stages smoking hot? On both x and y? If no and no, relax a bit.

    Does the whistle go away if the inputs are grounded, but whine when open circuited? If yes, relax a bit.

    Does the beam stay the same size and shape with the inputs grounded, when power is both off and on? Ie if the beam at some distance gets fatter with the power on, ie moving around enough to be noticed, I'd get worried.

    Does a test pattern look good?

    Do other owners of the same set report the whine?

    Add a 2000 uf or more filter cap to the PSUs with a few .1uf ceramics across it, is the whine still there? (Some switchers are just plain underfiltered)

    Steve
    Last edited by mixedgas; 10-24-2010 at 15:03.

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    Quote Originally Posted by mixedgas View Post

    Some scanners do oscillate at idle, at near ultrasound frequencies. This can be either a tuning or hardware issue and depends on the brand, a bad amp can oscillate, other amps just have a very fast fine feedback loop that is too fast for their own good, and usually in that case it is not a problem.

    For example, my Eyescans whine, but work perfectly, and work just as well as when I got them years ago.

    Are the driver output stages smoking hot? On both x and y? If no and no, relax a bit.
    No and No, cold to the touch...

    Does the whistle go away if the inputs are grounded, but whine when open circuited? If yes, relax a bit.
    Will try tomorrow, i just thought and answer what i know at this moment.
    The scanners are not grounded at this moment, as instructed in the manual.

    Does the beam stay the same size and shape with the inputs grounded, when power is both off and on? Ie if the beam at some distance gets fatter with the power on, ie moving around enough to be noticed, I'd get worried.
    will check tomorrow when i put the scanners on ground.

    Does a test pattern look good?
    Yes. Square and straight corners.

    Do other owners of the same set report the whine?
    I don't know, they're also sold as Scanpro20's i believe. Maybe Dave knows ?

    Add a 2000 uf or more filter cap to the PSUs with a few .1uf ceramics across it, is the whine still there? (Some switchers are just plain underfiltered)
    Don't have that size at home, only a few small ones.
    But first i will try to ground them.

    Thanks Steve for your quick reply. Now it's 2AM, so now i will go to bed ;-)
    Tomorrow is another day but i only have tomorrow to fix things up.... i am going crazy...
    Well grounding them is easy from there we continue.
    Never had those issues with my Raytracks 35 plus.
    I didn't fail !
    I just found out 10,000 ways that didn't work.

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