Dark Groove Tube - I think somethings wrong

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by thewonders, Jan 12, 2018.


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  1. thewonders

    thewonders Member

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    Is a Groove Tube 6V6 supposed to be all dark? Looking at the photo from a GC ad the tube elements are visible:

    http://www.guitarcenter.com/Groove-Tubes/Gold-Series-GT-6V6-S-Matched-Power-Tubes.gc

    But I just pulled the 6V6 from a Vibro Champ XD and it is all dark/clouded except for the top. The reason I looked at the VC's tubes is because I'm not getting any sound from the amp. Do tubes just get clouded but are still good tubes, or is this a sign that the tube has gone bad?

    [​IMG]

    (The 12AX7s are there for comparison. The one on the left also came out of the same amp.)
     
  2. Baxtercat

    Baxtercat Member

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    Like this? [if that's what you mean].
    Common appearance for many 6V6 types.

    Maybe the speaker got unhooked?

    [​IMG]
     
  3. thewonders

    thewonders Member

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    Not sure - it doesn't look like the 1951 or 1956 tubes, I can't see any tube element at all, except from the top. It does resemble the other three, but I can't tell if those show any filaments or if they are all blacked out (mine is blacked out).

    I just received that amp - I checked the speaker cable before I powered it on, and I also checked that the speaker is good. But I don't know how it was treated before I got it. The thing that concerns me is that GT 6V6s don't seem to look blacked out when new.
     
    Last edited: Jan 12, 2018
  4. Steppin' Wolfe

    Steppin' Wolfe Member

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    there are Russian built 6V6's with darkened glass. For all I know there may be Chinese dark glass 6V6
    s. That is what you have there....a modern tube. Groove Tube does not manufacture tubes. GT rebrands and sells tubes from various manufacturers....some Russian, some Chinese, and some JJ's from Slovakia. Ruby tubes does the same thing.
    OR....maybe Fender is buying NOS RCA's to install in these magnificent modern hybird amps with digital eeeffffects????????????? Not!
     
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  5. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    That is likely to be a Russian 6V6GT - they were made with black internal coatings, just like US-made 6V6GT in the '40s-'50s. Tung-Sol also made an all-black 6V6GT that looked similar, but I don't think those are Tung-Sol.

    - T
     
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  6. thewonders

    thewonders Member

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    OK, thanks. Obviously I was hoping that the tube was the problem but I guess not, which means the board may have been damaged in shipping.
     
  7. thewonders

    thewonders Member

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    Well, I found a tube tester in town and tested the tube - no good. Bought a Ruby Tube 6V6 and plugged it in - amp working normally. :)
     
  8. Blue Strat

    Blue Strat Member

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    Congrats! Just to be sure though, the black glass is normal for that tube and was not an indication of failure.

    Enjoy!
     
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  9. thewonders

    thewonders Member

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    Yes, the former owner sent me a photo of the back of the amp when it was working - it showed the 6V6 with the darkened glass. I guess that the tube got jostled during shipping and caused it to go bad. The tube's appearance had thrown me because I hadn't seen a tube before with such darkened glass. All good now, thanks.
     
  10. Blue Strat

    Blue Strat Member

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    Just for reference
    https://www.google.com/search?q=6v6...2dXYAhXulOAKHRzjBWUQ_AUICygC&biw=1411&bih=723
     
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  11. thewonders

    thewonders Member

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