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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


4 posters

    Faint blue glow in one KT88

    jhoak
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    jhoak


    Posts : 46
    Join date : 2009-10-16
    Age : 66
    Location : Central Florida
    • Post n°1

    Faint blue glow in one KT88 Empty Faint blue glow in one KT88

    Post by jhoak 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?
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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3276
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    Faint blue glow in one KT88 Empty Re: Faint blue glow in one KT88

    Post by Bob Latino 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
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    Sal
    Sal
    Sal


    Posts : 221
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com
    • Post n°3

    Faint blue glow in one KT88 Empty Re: Faint blue glow in one KT88

    Post by Sal 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
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    Westy56
    Westy56
    Westy56


    Posts : 58
    Join date : 2011-05-09
    Location : Albuquerque
    • Post n°4

    Faint blue glow in one KT88 Empty Re: Faint blue glow in one KT88

    Post by Westy56 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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    • Post n°5

    Faint blue glow in one KT88 Empty Re: Faint blue glow in one KT88

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