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Conventional Fixtures Alt 360 lamp image

Discussion in 'Lighting and Electrics' started by sejordan, Dec 12, 2008.

  1. sejordan

    sejordan Member

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    Location:
    Birmingham, AL
    We have a few Alt 360 radials we're trying to clean up and keep in stock. When you turn them on, however, you see an image of the lamp projected on the wall. I thought this was caused by the wrong type of lamp what with the precise position needed inside the reflector. When we installed a suitable lamp (EGE based on an old Alt data sheet) the problem didn't go away.
    Any ideas on the cause of this and any solutions to fixing it? Is it a reflector problem instead?
     
  2. icewolf08

    icewolf08 CBMod CB Mods

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    You probably need to bench focus the units. there should be 4 screws on the back of the lamp base. Using them all in delicate concert you should be able to center the lamp and optimize the fixture.
     
  3. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    check and make sure the lens train has TWO lenses in it. I recall this happening when one lens is missing.

    Other than that, I agree with Icewolf, bench focus!
     
  4. Footer

    Footer Senior Team Senior Team Premium Member

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    It it a spider web looking thing? If so, check for both lenses and check to see if the lenses in the fixture are the proper one for that fixture. To check, swap out the from lens train with a known working fixture of the same size.

    BTW, this is my cheap way of getting a template system onstage...
     
  5. ship

    ship Senior Team Emeritus Premium Member

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    also ensure while harder, that the proper lenses are in the lens train and that the proper lens train is in the barrel/snout of the fixture.

    Start with the bench focus - constantly after ever few turns of the screw driver open up the can and ensure the lamp is near it's center and especially won't be touching the reflector, than go back to focusing once corrected or ok. Mostly a question in bench focus of where that "filament" image is in the center of the beam for relative terms of how on center the filament is to the center of the reflector/lens plane. Than if the bench focus after that how far up or down in proximity to the reflector is the lamp out of adjustment in being able to focus to it's natural distance to the reflector.

    After this, and only so much play you should be able to do in it getting better or not, I would suspect wrong, not enough lenses or wrong lens train for barrel in yes the lights coming out correctly from the reflector but the lens train assembly is not optimized for that beam of light. First guess would be too small of lenses say a 6x16 lens train in a 6x9 barrel would show the filament.

    Also a question of bench focus distance. Run the lens train of course to get a hard edge around the outside of the beam to start and you should be between say 14 and 20 feet from the screen projected on. If other than this - especially less and a not hard edge, you might also get a filament image.
     
  6. waynehoskins

    waynehoskins Active Member

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    I've seen that before on a 360 or 360Q .. probably 360 .. with only one lens, back in college. We ended up using it for a theatre open-house hang once .. but then we either retired, cannibalized, or fixed the unit.
     

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