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Thread: Melles-Griot 643 mis firing

  1. #1
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    Default Melles-Griot 643 mis firing

    Howdy.
    Ive got a Melles-Griot 643 ar-kr that is wanting to fire down the gas return path instead of the bore.
    I ran it for about 7 hours last night and need to run it again today. This morning, it keeps starting down the returns instead of the bore. I shut it off within a half a second of it firing because I read that its very bad for it to run down the returns. Discharge going down the returns makes it more electrically conductive and wants to fire down the returns. The bore is clean because the first start pulse lases (just the pulse, not continuous).
    It stays lit on the first or second pulse every time.
    Advice? suggestions? Click image for larger version. 

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    Thanks in advance.
    -Nate.
    Last edited by Vidal Wolf; 02-21-2015 at 09:39. Reason: Homer Simpson want beer.....mmm beeeerrr...how much space are we allotted to add any info regarding why we decideed to edit?
    Will there be three phase!!!!

  2. #2
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    Default

    It sounds like a faulty high voltage connection.

    Can you provide a picture?

  3. #3
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    12 hours ago it ran for 7 hours, then this morning, it fires but fires down the gas return path instead of the center bore. Its discharging fine, just discharging down the gas return paths. All electrical connections are fine, I checked it all this morning. I removed the covers, looked over the wiring and checked the connections.
    odd failure. Pics tomorrow. =)
    Last edited by Vidal Wolf; 02-22-2015 at 01:36.
    Will there be three phase!!!!

  4. #4
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Once it goes down the paths at any level of current the arc fries the molybdenum wires that normally short the return paths.

    Salvage the optics.

    Steve
    Qui habet Christos, habet Vitam!
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  5. #5
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    Thank you Steve. I appreciate the information.

    Sooo.. I guess this leaves me with a dead tube. Any one have a suggestion on a creative way to dispose of it?
    Will there be three phase!!!!

  6. #6
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Quote Originally Posted by Vidal Wolf View Post
    Thank you Steve. I appreciate the information.

    Sooo.. I guess this leaves me with a dead tube. Any one have a suggestion on a creative way to dispose of it?
    Yeah, keep the harness, scrap the tube and save the optics. The rear mirror is HR 400-700 nM and if you dont want it, nearly everybody who has a whitelight or a krypton will. I'll take the brewster stems if you dont want them.

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
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