interference on projector screen from all sources

Discussion in 'Projectors, Screens & Video Processors' started by paulcharlier, Mar 11, 2006.

  1. paulcharlier

    paulcharlier
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    Hi there,

    before I start I hoping this is the place to be with questions about AV.

    I have also posted in the All-in-one section, but am not sure of the correct place to post this, so if there are any admins present, please can it be moved to a more relevant section.

    Okay right, first off I'll describe the setup we have:

    Toshiba 3377DB Television
    Panasonic NV-SV121EB S-VHS Video recorder
    Sony VTX-S760U Digital TV Box (Sky)
    Toshiba DVD SD-500E
    Goodmans GHC56 Pro Audio Amplifier
    Acer PD-116 DLP Projector

    Okay the setup is as follows:

    Toshiba TV + Sony Digital Box are plugged into Panasonic VCR for output to projector.
    DVD player is setup for connection to projector.

    To enable switching between the two sources we have a AV switcher box, I am not sure of

    the make, but we purchase it from Maplins with a model number L63AB Audio/Video Source

    Selector. From the AV switcher it connects directly up to the projector.

    In terms of cabling, we have an S-video output from the VCR to provide picture on the

    projector for Analogue TV, Digital TV and normal VHS tapes. The DVD player also has an

    S-video output to the AV switcher, from there it connects up to the projector.

    Okay now the problem, when viewing ALL the sources on the projector we get a strange

    kind of interferance on the picture, the best way I can describe it is that it has

    diagonal converging lines, which seem to dissapear when there is pure white, but with

    any other colour the lines are apparent.

    When trying to remedy the situation we connected the VCR directly up to the projector

    with a Composite video cable, this still did not remedy the problem. So from what I can

    tell is that the problem lies where all the equipment is installed.

    But to help desribe the symptoms and problem better I have recorded a small video

    showing the lines, you can download it from here:

    www.paulcharlier.com/interferance.mpg

    The file is approximately 10mb.

    Also I have taken a few photos of the setup, the locations and hopefully give an

    impression of the lengths of cable used.

    www.paulcharlier.com/projector/1.jpg
    www.paulcharlier.com/projector/2.jpg
    www.paulcharlier.com/projector/3.jpg

    I hope this is enough information about the setup we have,

    thanks in advance for any help given, I really hope we can find an answer to our problems,

    thanks,

    Paul :)
     
  2. paulcharlier

    paulcharlier
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    Anybody able to offer any advice? :rolleyes:
     
  3. inzaman

    inzaman
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    I have moved this to projectors to see if any fellow pj owners might be able to help :)
     
  4. throwit

    throwit
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    sounds most like a ground loop issue...usually caused by using power sockets that are not on the same circuit - if possible, ensure that all interconnected equipment is running off the same supply or plug strip, or best of all running from an uninterrruptable power supply
     
  5. paulcharlier

    paulcharlier
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    Hi mate,

    thanks for the reply :)

    All of the devices we have are plugged into a power 'strip', well an extension block consisting of 8 sockets, this extension block is plugged into one main socket behind the television.

    I have done alot of searching on the group loop issue, but have not really been able to find anything conclusive. I have also heard of the 'Chicken wire effect', but on further research found it was something different to the problem we have.

    But thanks again,

    Paul :)
     
  6. throwit

    throwit
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    sorry i didn't have the solution :)

    could still be worth looking at whether any cables are interfering with each other, or also, the power cable for the projector may be passing close to a power supply which may be causing interference, or possibly any source of electromagnetic inteference could be the cause

    hopefully someone'll know the answer...good luck
     
  7. paulcharlier

    paulcharlier
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    Okay thanks, will try to see if there are any cables interfering. Do you think it could be the close proximity of the short s-video cables around the back of the devices and the power cables causing this problem?

    Paul
     
  8. throwit

    throwit
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    that, i'm not sure about
     
  9. Thor

    Thor
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    Not sure if it's any help but the pattern your describing is almost like rf interference from the tv or vcr. Try removing any aerial leads you have connected and see if that affects it.
    Try one piece of equipment at a time with shorter connecting cables near the pj and try to isolate where the problem is.
     
  10. paulcharlier

    paulcharlier
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    Okay thanks Thor, I appreciate the advice :)
     

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