1. skeeterbuck

    skeeterbuck Member

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    I was given a pair of 12ax7 tubes with "Bogen Gt. Britain" on them. I was told they are Mullard's from the early 70's.

    When I first installed them they heaters glowed brightly for a second and then settled down to normal. That leads me to believe that they were new and had never been used before.

    Any ideas?

    Thanks for the help.
     
  2. Trout

    Trout Member

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  3. DEMENTED

    DEMENTED Supporting Member

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    That's typical of Mullards and other Euro tubes when you power up. :dude
     
  4. rockon1

    rockon1 Member

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    Yep typical of Philips(Mullard) and other european tubes. Its not because they are new. They will do it virtually everytime you power them up.
     
  5. Blue Strat

    Blue Strat Member

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    They probably are Mullards based on the information given.

    The ultimate identifier is the codes etched near the base of the tube. There are two lines of 3/4 characters. Google "Philips tube production codes" for the secret decoder ring.
     
  6. skeeterbuck

    skeeterbuck Member

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    They only did it the first time, after that the heater came on like any other tube I've seen.

    Mike, thanks for the search info about the tube codes.

    The ones I have are marked B1A2. I read that to be Blackburn, England in 1971 in January, the second week. If you really need pics, I'll see what I can do.
     
  7. rockon1

    rockon1 Member

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    Or just click here. ;)

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



    .
     
  8. Blue Strat

    Blue Strat Member

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    Were they still warm the other times you fired them up?
     
  9. rockon1

    rockon1 Member

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    They will do it again. ; > ) Bob
     
  10. Blue Strat

    Blue Strat Member

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    Yep, unless they were still warm from the previous turn on or they're dead.
     
  11. skeeterbuck

    skeeterbuck Member

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    I checked them this moring when they were sure to be cold and they did glow brightly for a second before settling down like before. They must have been too warm like you suggested. I have never had any Euro tubes and this was a new experience for me. I've learned a couple of things new these last days. Thanks all for the help. :AOK
     

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