projector has a "scrolling" line in display????

Discussion in 'Archived Threads 2001-2004' started by Jeff Holton, Nov 11, 2002.

  1. Jeff Holton

    Jeff Holton Stunt Coordinator

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    At times, my projector creates a "scrolling" line on the screen... a faint line that starts at the bottom of the screen, and slowly moves to the top... then starts over again at the bottom.

    It doesn't do it all the time, just sometimes ( at least it is not noticable at certain times).

    Does anyone have any ideas... is this a problem with the signal (I'm using S-video), is it a problem with the projector (Sanyo PLC-SW15)...

    Any help would be appreciated.
     
  2. Allan Jayne

    Allan Jayne Cinematographer

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    This slowly moving line generally means there is some kind of interference.
    Often unplugging and replugging cables improves the contact and eliminates the problem. Insufficient grounding sometimes result in the problem and can be improved by the cleaning action on the contacts done by unplugging and replugging.
    If they fit the other way, try reversing power cord plugs in the outlets in different combinations.
    Try moving cables behind the TV, including running power and speaker cables so they don[t come so close to video cables.
    Turn off fluorescent lights and computers. You might find that a particular computer or appliance is causing this interference. Interference can travel either through the air or through power lines.
    Try (for a few minutes at least) a shorter or a different video cable. Video cables can pick up interference right through their plastic cover from the air, lower grade cables can pick up more.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     
  3. Chris Moe

    Chris Moe Screenwriter

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    I had this same problem with my CRT projector. Turned out it was a ground loop. Pain to track down, but easy to fix.
     
  4. Jeff Holton

    Jeff Holton Stunt Coordinator

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  5. dave_brogli

    dave_brogli Screenwriter

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  6. PaulG

    PaulG Stunt Coordinator

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    Ground loops will cause interference on every device you watch, not just the device causing the problem. Basically it is a potential difference between 2 grounds. This causes a small amount of 60Hz AC current traveling on the shield side of your interconnects and RF coax cables. It gets induced into the signal. You may be able to hear it in your speakers, I could on mine.
    Cable TV is a common cause for ground loops. Disconnect the cable at a point where the cable is no longer connected to ANY device in the house, then check again for interference. TiVo will amplify the ground loop interference because of the way it encodes the video. The interference gets recorded onto it's HD. Don't use a prerecorded show to test.
    I ended up replacing the ground clamps where the cable TV entered the house, and still had to put an isolation transformer on it at the entry point. I hope my experience with those pesky ground loops is of some help.
     

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