Info on this Mullard?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by krall, Feb 27, 2009.

  1. krall

    krall Supporting Member

    Messages:
    927
    Joined:
    Sep 6, 2007
    Location:
    Canada
    I just bought a 6 watt amp (Savage Macht 6) and it has these two identical preamp tubes..I photographed one of the tubes (they are both identical)..Could you guys tell me what's the story on this tube (quality, date, why "A" designation after 7025/12AX7, why Philips stamped over the Mullard print, value)? Thanks!
    Info printed on tube:
    -branded Mullard with a Philips logo printed over
    -7025A/12AX7A
    -Made in Great Britain
    -KE6
    -163

    Pics:
    [​IMG]
    [​IMG]
    [​IMG]
     
  2. rockon1

    rockon1 Member

    Messages:
    11,294
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    That code looks weird spaced apart like that and isnt the correct one for a Mullard which should start with B for the Blackburn England plant. Maybe TW knows something about this one. Im not as much concerned about the paint.
    IIRC the12AX7A was a 12AX7 with an improved heater design to lower hum and noise. Must have been done in the 50's since I have 59 Raytheon 's that are 12AX7A's. I think all 12AX7's made after a certain time were 12AX7A's even if they didnt label them as such but Im not sure. Everything else is the same and they are interchangable. Bob
     
  3. krall

    krall Supporting Member

    Messages:
    927
    Joined:
    Sep 6, 2007
    Location:
    Canada
    See, I don't know anything about tube codes, but my quick search online keeps mentioning the "B" code for Blackburn, and mine doesn't have that..Also there are two different Mullard shield logos, mine seems to be the second later version..I have not found anything like mine in either Mullard or Philips brand searches online..
     
  4. rockon1

    rockon1 Member

    Messages:
    11,294
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    The etch code and inards of the tube are far more telling than any paint on the outside. So far the etch code doesnt look right. I cant see the inards very well in these pics. A detailed pic of the plates straight on and a side shot would be helpful. Ive seen this type Mullard paint/logo before though. Bob
     
  5. krall

    krall Supporting Member

    Messages:
    927
    Joined:
    Sep 6, 2007
    Location:
    Canada
    I'm not sure what you mean by "etch code"..If you meant an etching inside, I looked closely and there were none..I just took/uploaded two more pics..Let me know if these help:

    [​IMG]

    [​IMG]
     
  6. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

    Messages:
    9,005
    Joined:
    Oct 14, 2005
    Location:
    Berkeley, CA
    Funny - I just picked up a '70s short-plate Mullard 12AX7A/7025 today, with the later-production logo (for free! lucky me, I guess!). It didn't have the bad over-paint, though. Seems he wanted a new tube, no matter how much I tried to convince him that he may like that old tube better.

    Anyway, it looks as if this is etched upside-down, as they sometimes were. Krall - you need to take it out in bright sunlight, turn it upside down, and look under the "I63" for a 4-character line that starts with "B" The number, following the "B" will tell you which of the '70s year it is from (for instance, "B4" will be from 1974).

    - Thom
     
  7. krall

    krall Supporting Member

    Messages:
    927
    Joined:
    Sep 6, 2007
    Location:
    Canada
    Hey Thom..I have an extremely bright light source here and scrutinized both of them..There are no such numbers on these tubes..:confused:
     
  8. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

    Messages:
    9,005
    Joined:
    Oct 14, 2005
    Location:
    Berkeley, CA
    Sometimes you can rub your finger over the coded area, gently, and get a bit of finger oil on to help distinguish. Or try to "steam" it up with the humidity of your breath.

    Here's a site that'll help you see what you're looking for: http://www.tube-classics.de/TC/Tubes/Valvo/Phlipscode.htm

    Other than that, you'll just have to live with the mystery, and enjoy the tube as-is.

    - Thom
     
  9. rockon1

    rockon1 Member

    Messages:
    11,294
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    The guts loook genuine Mullard. Perhaps as TW suggested the etch code is very faint. It may not be there but sometimes I need bright light,a magnifying glass and the right angle to see it. Bob
     
  10. krall

    krall Supporting Member

    Messages:
    927
    Joined:
    Sep 6, 2007
    Location:
    Canada
    Ok, tried again..And this time I can confirm..Will even bet my life on it..No 4 character etched lines, nor is there any evidence there ever was..In fact those tubes look like new and the glass is crystal clear..I looked at every angled under very bright light, tried the steaming with my breath..No dice..

    So ok, we have oddballs with codes missing..Any clues around what time/era they were made? Value?

    They both were tested at my friend's earlier this evening, they both test better than 100%.
     
  11. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

    Messages:
    9,005
    Joined:
    Oct 14, 2005
    Location:
    Berkeley, CA
    Okay - no code, which sometimes happened (or too faint). It is from the early '70s. The "value" can cover lots of range, depending on many psychological factors. Value could be from, say, $30 to $50, depending on actual test values, and who happens to be buying.

    - T
     
  12. rockon1

    rockon1 Member

    Messages:
    11,294
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    +1 but I think the value would be lower. With a flaky partial code anybody knowing what they are looking for might not want it for this reason. Double inked somebody with less knowledge still might not want it because of the appearance. Bob
     
  13. krall

    krall Supporting Member

    Messages:
    927
    Joined:
    Sep 6, 2007
    Location:
    Canada
    Thanks for your responses guys...I assume Philips owned Mullard?
     
  14. rockon1

    rockon1 Member

    Messages:
    11,294
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
  15. jcs

    jcs Member

    Messages:
    7,644
    Joined:
    Sep 15, 2002
    Location:
    on a hill
    what matters is how it sounds and responds!

    i also have some similar europe 12ax7 with no visible etched codes as well, i can say these tubes are excellent and i guess i will hang on to them for my own use (lucky me!)
     
  16. krall

    krall Supporting Member

    Messages:
    927
    Joined:
    Sep 6, 2007
    Location:
    Canada
    Of course!
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice