opinions please

Discussion in 'Displays' started by Wayde_R, Jun 8, 2005.

  1. Wayde_R

    Wayde_R Stunt Coordinator

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    Someone has a DLP projector in a theater room with all the AV components in a remote room and a 35' component cable between. Owner reports a black horizontal line scrolling vertically every five seconds or so. It is very noticeable on dark screens and less noticeable on lighter scenes.

    Does a problem with lack of magnetic shielding on the composite cable and interference from electrical cables running thru the walls too close to the composite cables sound like a reasonable cause for such a long run of composite? Any other possibilities for this problem? Any advice I can pass along to the owner would be great. I have no idea.

    Thanks
     
  2. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Greetings

    Is this a ground loop problem? Unhook the cable TV wire coming into the house ... see what happens.

    Regards
     
  3. Victor Ferguson

    Victor Ferguson Stunt Coordinator

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    yep, sounds like a ground loop to me too. start unplugging stuff until you find the culprit and the use a cheater plug if you have too.
     
  4. Wayde_R

    Wayde_R Stunt Coordinator

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    Hi.

    What's a "cheater cable"?

    So, the theory is that ground is polluting one of the components and somehow the video on the projector?

    Possibly caused by the cable box, cable line? Or one of the other components? When you suggest unplugging things you mean from the projector itself, right?

    The black line could be a ground loop to the video signal polluting it with a black line, like a hum in your audio?

    Thanks for the help guys.
     
  5. John S

    John S Producer

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    It can be interference related as well...

    Start with the grounds, if it does not solve it, make the component cables out of RG6 and see if it helps any.

    EMF problems are not near as common as these ground issues are on this one for sure.


    Be patient somewhat, these sorts of issues can really drive a body totally mad figure'n them out.
     
  6. Victor Ferguson

    Victor Ferguson Stunt Coordinator

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    When i say cheater plug I mean an adapter that allows you to go from a grounded connector (3 prongs) to an ungrounded one (2 prongs). This will get rid of a ground loop if its in one of your components. More than likely this would be a cable or satelite box as they are often grounded in a different location that your equipment. When I say start unplugging things what I mean is to unplug your equipment and your video connnections (sat or cable rg6 for sure)one at a time until you figure out which one is causing it.
     
  7. Wayde_R

    Wayde_R Stunt Coordinator

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    Thanks everyone. I've been doing some reading on ground loop problems, by all accounts cable line in is a huge cause of it.

    I've learned! Thanks a log guys. And thanks for the explaination Victor, I know what you're talking about now, those three to two prong adapters.
     

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