do we have any mullard date code experts among us?

Discussion in 'Amps and Cabs' started by JimAnsell, Jan 17, 2008.

  1. JimAnsell

    JimAnsell Member

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    i have a pair of 12ax7's that the silk screaning is all gone on except
    "GT BRITAIN" "12AX7A" and this 2 line code: "I63" and under that " BOK 2" that 2 might be a backwards S or something...

    any idea of the year of these?
     
  2. rockon1

    rockon1 Member

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    Yes Blackburn England. I63 is fairly early constuction so I'd say they are 1960 . Heres a link for Philips family codes. Bob

    http://www.tube-classics.de/TC/Tubes/Valvo/Phlipscode.htm
     
  3. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Bob, I've got to differ with you on this one. In 1960, Mullard had just gone from their long-plate to the first short-plate 12AX7, which was the I61 version. A few years later, they went to I63 (what happened to I62?), and continued making I63 at the Blackburn facility for many more years.

    I'd say, most certainly, that the tube in question is from 1970.

    - Thom
     
  4. teleman1

    teleman1 Supporting Member

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    IF all the markings are gone, is there anyway to ID a tube by looks?
     
  5. hamfist

    hamfist Member

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    The markings are etched into the glass on Mullards, so it would be extremely unusual to find one which had lost it's code. Sometimes the etching is rather shallow, but you can almost always make it out (under good light !).
     
  6. crosse79

    crosse79 Member

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    Man I am amazed by the knowledge on this board!
     
  7. rockon1

    rockon1 Member

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    Actually it as 1959 they went to thier first short plate the I61. Ive got a couple. You very well may be right about it being a 1970 but the Philips tubes I have like orange globe Amperexs I dated from 1970 were I65 hence the thought these were earlier. I'll have to look thru my stash and see if I can infer any more info.
    :BEERBob
     
  8. Blue Strat

    Blue Strat Member

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    I agree.:AOK
     
  9. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Yes, you're right, the first I61 were made in '59. The Dutch Philips short-plate I65 were contemporary with Mullard's Blackburn I63 types. Mullard didn't make a higher number I6* type than the I63, as far as I know.

    - Thom
     

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