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    Tube glow question

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    jsl1234

    Posts : 32
    Join date : 2017-08-28

    Tube glow question

    Post by jsl1234 on Fri Sep 07, 2018 12:58 pm

    Hi,

    I have four (fairly) new matched Kt88s courtesy of Jim McShane. They have about 40 hours of use on them and sound great and bias fine.

    However from the first day one of the tubes has glowed noticeably brighter compared to the others. Specifically on the bottom of the tube (not the top where all seem to glow about the same).

    I've moved the tubes around and re-biased--it is definitely the tube that glows brighter.

    Does this kind of small anomaly matter if everything else seems in order?

    Thanks

    Jay
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    j beede

    Posts : 469
    Join date : 2011-02-07
    Location : California

    Re: Tube glow question

    Post by j beede on Fri Sep 07, 2018 1:12 pm

    I've not heard of anyone that included filament alignment or brightness as part of the matching process. The effect you are describing is usually due to the physical alignment and visibility of the filament--not that it is actually glowing brighter. If you see a difference in plate color or the blue/indigo/violet plasma while the tube is operating, that might be a different situation.

    Jim McShane

    Posts : 207
    Join date : 2011-10-19
    Location : South Suburban Chicago

    Re: Tube glow question

    Post by Jim McShane on Fri Sep 07, 2018 1:51 pm

    jsl1234 wrote:Hi,

    I have four (fairly) new matched Kt88s courtesy of Jim McShane. They have about 40 hours of use on them and sound great and bias fine.

    However from the first day one of the tubes has glowed noticeably brighter compared to the others. Specifically on the bottom of the tube (not the top where all seem to glow about the same).

    I've moved the tubes around and re-biased--it is definitely the tube that glows brighter.

    Does this kind of small anomaly matter if everything else seems in order?

    Thanks

    Jay

    It is no problem whatsoever!

    Look here at my FAQ post:

    https://www.audioasylum.com/messages/tubes/253369/quot-tube-problems-quot-that-aren-t-tube-problems

    Item #7 deals with this issue and should completely clear up your concern. You can refer to that FAQ post for a lot of answers to common questions. Since you got the tubes from me you could have just dropped me a note and I'd have been happy to help as well!

    jsl1234

    Posts : 32
    Join date : 2017-08-28

    Re: Tube glow question

    Post by jsl1234 on Fri Sep 07, 2018 6:23 pm

    Jim McShane wrote:

    It is no problem whatsoever!

    ......Item #7 deals with this issue and should completely clear up your concern. You can refer to that FAQ post for a lot of answers to common questions. Since you got the tubes from me you could have just dropped me a note and I'd have been happy to help as well!

    Hi Jim!

    You are right on the money--both the description and pictures in your FAQ describe what I'm seeing.

    As I mentioned, they sound great and bias fine--I was just wondering if what I was seeing was perhaps an early indication of an emerging problem.

    Obviously I can rest easy.

    Now back to the music Smile Very Happy Very Happy

    Jay

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