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projector image "surge"

Discussion in 'Displays' started by Robb Cadigan, Apr 20, 2004.

  1. Robb Cadigan

    Robb Cadigan Auditioning

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    I'm having a strange problem with my Marantz DLP S2 projector.

    At random points in a DVD, the image will suddenly get brighter. It is as though the image "pops" -- like the blink of an eye -- and then looks brighter. It happens quickly and is almost imperceptible to some, but it drives me crazy.

    The best I can explain is it looks like a power surge of some sort -- like the image suddenly has more juice, if that makes sense.

    The room is on a separate circuit, so an electrical surge doesn't seem likely, but I could be wrong.

    Can anyone give me any ideas on what to look for?

    I did try another DVD player and got the same problem, so that seems to rule out the player. The surge happens at random intervals and rarely happens in the same place on a disc.

    Thanks for any help!

    Robb
     
  2. ChrisWiggles

    ChrisWiggles Producer

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    Does it happen for all sources? It could be the bulb.
     
  3. Robb Cadigan

    Robb Cadigan Auditioning

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    Thanks for the response.

    It seems to happen only with the DVD player or laserdisc player.

    I don't believe it is the bulb, because I am on my second bulb and it happened with both.
     
  4. Leo Kerr

    Leo Kerr Screenwriter

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    Consider also the possibility that it's the lamp's ballast. (Flourescent, mercury, high and low pressure sodium, HMI, HID, CSI, Xenon lamps, carbon arc lamps.. all require ballasts. They all serve the same function.)

    From what you're describing, it almost sounds like the ballast is getting confused and is attempting to restrike the lamp that's already on - hence the sudden, momentary brightness pulse.

    (Aside: Traditionally, the ballast strikes the arc by a really high voltage spike - sometimes >7000 volts, depending on the type and size of the lamp - before cutting the voltage back (often to, say, 12v) The initial current is quite high, and as the lamp warms up, the current is limited by the ballast into it's happy, operating mode. Xenon arcs for film projectors often have a dial where the projectionist can up the current as the lamp ages over its 1000-2000 hour lamp.)

    The question then becomes a sequence of...

    1. is the restrike attempt bad for the lamp?
    2. is the restrike attempt bad for the ballast?
    3. is the ballast replaceable?
    4. is it worth replacing the ballast?
    5. are there any provisions by the manufacturer to have the ballast replaced, either by the user or the factory?

    My guess is (and remember it IS a guess,)
    1. - I don't know; probably not very.
    2. - possibly.
    3. - yes.
    4. - I don't know
    5. - probably not. Probably not until the projector goes over the, say, $10,000 limit.

    If it turns out to be the ballast, and the ballast IS replacable, it shouldn't be a very difficult operation: there are wires that come from the power supply (it might be built into the power supply,) and wires that go to the lamp. Probably two screws to hold it to the chassie. Opening the shell to get to the ballast is probably the hardest part of the operation.


    Of course, it might be something completely different. Like a herring...

    Leo Kerr
     

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