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    Faint blue glow in one KT88

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    jhoak

    Posts : 46
    Join date : 2009-10-16
    Age : 58
    Location : Central Florida

    Faint blue glow in one KT88

    Post by jhoak on Sat Sep 03, 2011 7:13 am

    I happened to crank up my ST-120 this morning in a dark room. I had never noticed prior but I don't recall ever having it on in the dark. Anyway the KT88 closest to the rectifier is showing a very faint blue glow in addition to the normal filament glow.

    Do I have a tube on the way out?

    Bob Latino
    Admin

    Posts : 2415
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Faint blue glow in one KT88

    Post by Bob Latino on Sat Sep 03, 2011 7:32 am

    Hi Jeff,

    This blue glow is normal. Some tubes show it more than others. Also - sometimes you may have four of the same output tubes and one or two may have more "blue" than the others.. The tubestore has an explanation at the link below ..

    Blue Glow in tubes

    Bob

    Sal

    Posts : 221
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: Faint blue glow in one KT88

    Post by Sal on Mon Sep 05, 2011 12:33 am

    I have seen a blue glow on new issue tubes so I wouldn't worry about it.

    Sal

    Westy56

    Posts : 58
    Join date : 2011-05-09
    Location : Albuquerque

    Re: Faint blue glow in one KT88

    Post by Westy56 on Mon Sep 05, 2011 12:58 pm

    The blue glow faded as my SED's aged, so in my case blue was a good sign.


    Steve

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