Another 12AX7 identification....

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by rockon1, Jun 8, 2006.

  1. rockon1

    rockon1 Member

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    Cant quite figure out who made this tube. Its branded Motorola and is a long grey plates with square getter wire. It has no etchings at all.I guess thats throwing me a bit...Any idea's? Thanks Bob[​IMG]
     
  2. Blue Strat

    Blue Strat Member

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    When taking photos of tubes for identification, a shot of the face of the plates is crucial.
     
  3. rockon1

    rockon1 Member

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    [​IMG]
     
  4. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Can you desribe the appearance of the metal "bar" that is welded across the top end of the getter wire: are there two bars, or is it a flattened strip of metal with two embossed dots, or...? Maybe a close-up photo of that part would help.

    With no etch codes, it is likely to be American origin.

    - T
     
  5. rockon1

    rockon1 Member

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    Cant get a good pic of the getter wire however its very similar to a tung Sol I have(and others)with a flattened bar across the front with 2 dots on it. The plates dont look like Tung Sol construction though. In fact the plate construction looks identical to the GE "black plates" I have although of all the GE's I have Ive never seen one with this type getter wire. Maybe GE?
     
  6. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Both "Ken-Rad" (really GE, but made at the formerly Ken-Rad facility with EIA code "188-5") and RCA used that double-dimpled strip design, in some of their tubes. I can't remember about Tung-Sol, but they do have square getters, too. Ken-Rad had a D-getter, not square-getter. I'm inclined to say RCA, but I'm not sure - I'll have to look at an RCA long gray-plate.

    Is there an additional partial-mica (like on Raytheon black-plate/halo-getter 12AX7A), on top of the upper mica disk? I can't quite tell from the photos. If so, that'd point to either GE or Raytheon, I believe (though Tubemonger has a photo of a Tung-Sol with one). I don't have a long gray-plate Raytheon, and I'm not sure those used that partial-mica design.

    Actually, as I think about it, I'd eliminate GE because they've got two small holes on the edge of each plate. Also, for the record, CBS/Hytron is out (horseshoe-getter) and so is Sylvania (different plate shape). My best guess is Tung-Sol.

    - T
     
  7. rockon1

    rockon1 Member

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    Yes it does have the extra mica n the top.
     
  8. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Check out the Tubemonger picture library - there's a square-getter Tung-Sol there that has the extra mica on top. I'll bet its one of those.

    - T
     
  9. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    I checked on my long, gray-plate RCAs, and they just have a simple wire, no "dimples." I'm confirming my vote for Tung-Sol on this one.

    - T
     
  10. rockon1

    rockon1 Member

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    I tried to check it out on the "Tubemonger " site but the picture library is blank. :confused: Also all the Tung Sol's I have only have one hole on each side where the plates are joined not two like these. I dont know if that means much just pointing it out.
     
  11. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Tubemonger just redid their web site. I was successful using the search function, but had the same problem as you when trying to go from the tube pictures link.

    I think it is a rare variant of a Tung Sol. Tubemonger seems to be very well-researched on tube i.d., and there's definitely a similar photo there. Its not the same as my Tung Sols, though.

    - T
     
  12. outtahear

    outtahear Supporting Member

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    Hope these help...G.E.:[​IMG] and Tung Sol:[​IMG]
     
  13. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Whoa! Good close-ups!

    That Tung-Sol (12AU7A, not 12AX7, but they're similar plate structure) has what I call a "horseshoe" getter, not the "square" getter in the photo in question. The GE picture shows a square-getter with the double-wire cross-piece I tried to describe earlier.

    - T
     

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