The Dynaco Tube Audio Forum

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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


5 posters

    Blue glow..

    Ernstmach
    Ernstmach
    Ernstmach


    Posts : 98
    Join date : 2015-08-30
    Location : The Great Mitten.
    • Post n°1

    Blue glow.. Empty Blue glow..

    Post by Ernstmach Fri Oct 13, 2017 8:38 pm

    I'm listening to some Johnny Winter vinyl. I notice one of my MKIII's KT88's has a blue glow  in the tube. I have it cranked up so I'm working the amp.
    So what does this indicate? The other Amp is not showing this.  Bad tube, Quad Cap? The glow looks like a reflection below the top plate of the tube onto the glass.
    Tried to take a photo but my Cannon 6D won't capture this phenomenom... Any thoughts?
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    Tubes4ever
    Tubes4ever
    Tubes4ever


    Posts : 167
    Join date : 2015-07-14
    Location : Star, Idaho
    • Post n°2

    Blue glow.. Empty Re: Blue glow..

    Post by Tubes4ever Fri Oct 13, 2017 9:00 pm

    If the glow looks like it is on the inside of the glass, then it isn't a problem. The only blue glow you should worry about is if you see a glow in the open space between the cathode and plate. A glow on the inside surface of the plate where the electrons hit it is also normal.
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    sKiZo
    sKiZo
    sKiZo


    Posts : 1530
    Join date : 2013-04-01
    Location : Michigan USA
    • Post n°3

    Blue glow.. Empty Re: Blue glow..

    Post by sKiZo Sun Oct 15, 2017 6:30 pm

    Wouldn't lose any sleep over it. They've probably been doing it since day one and you're just now noticing it ...

    Blue glow.. Big-bottles-lit-003
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    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3277
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°4

    Blue glow.. Empty Re: Blue glow..

    Post by Bob Latino Mon Oct 16, 2017 7:27 am

    A blue glow inside some tubes (usually output tubes) is harmless and fairly common. Read at the link below about the causes of "blue glow" in vacuum tubes.

    The Tubestore - blue glow explanation

    Bob
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    deepee99
    deepee99
    deepee99


    Posts : 2244
    Join date : 2012-05-23
    Location : Wallace, Idaho
    • Post n°5

    Blue glow.. Empty Re: Blue glow..

    Post by deepee99 Mon Oct 16, 2017 5:42 pm

    Uff Da. I just round-filed a perfectly KT-88 for blue-flaming a couple of months ago. Thought it was a prelude to red-plating. Turns out it was the lighting and angle of view, I guess. Damn!
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    Ernstmach
    Ernstmach
    Ernstmach


    Posts : 98
    Join date : 2015-08-30
    Location : The Great Mitten.
    • Post n°6

    Blue glow.. Empty Re: Blue glow..

    Post by Ernstmach Mon Oct 16, 2017 7:19 pm

    Thanks for the replies everyone!
    Thanks for the link Bob.
    I learn lot's of new things with each visit here.
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    • Post n°7

    Blue glow.. Empty Re: Blue glow..

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