Anyone got a bad 12ax7??

Discussion in 'Member Classifieds' started by Sg-ocaster, Aug 5, 2020.

  1. Sg-ocaster

    Sg-ocaster Well-Known Member

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    I know you guys are opening this thread thinking...." Damn quarantine poor guy done lost his mind"(happened well be for that lol)
    Anyways got my tube tester and have a reading for most of my nos 12ax7s.....but even the few old black 12ax7s I have are testing well into the green.
    Does anyone have a 12ax7 that tests well into the red/bad zone on an cathode emission tester??(that you haven't canned yet) I need one to verify this old thing isn't just reading everything as "good"......yea I plan to rebuild and calibrate( or try to)....but for now just to check it.
     
  2. IOSEPHVS

    IOSEPHVS Well-Known Member

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    I have a Westinghouse 12AU7 that failed the shorts test. For some reason, I have it as testing 1500/2050 micromhos out of 3300 which is odd because I normally stop the testing process if there is a short.
     
  3. Seanxk

    Seanxk Well-Known Member

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    I'm not entirely sure on your machine and I'm not near my AVO, but if your machine is not sending the right amount of Neg grid volts, it can easily make a good valve look very good, or bad.

    On an EL34 I will not trust machine to set Ngv, but set machine to Test without valve and adjust with help of a DMM on DCV to pin 5 and 7 to give half the amount specified for that valve, in my case 13.5, so dial moved to read 6.75 on DMM.
    Which pins on an ECC83 I'm not sure right now.
     
  4. MarshallDog

    MarshallDog Well-Known Member Gold Supporting Member

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    Sorry man, I have tossed into the circular file any bad 12AX&'s I have had. If one pops up bad, I'll let you know.

    FYI, however, any that I have had go bad only seem to go micrphonic in the V1 position, any other position they are fine.
     
  5. T-Boy

    T-Boy New Member

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    Hi guys, sorry to hi-jack this thread, but I'm new to the forum and not too sure if the one I created for this question will be noticed.

    I have question regarding period correctness of tolex on a 1974 MKii Super Lead. can anyone point me in the right direction or even help out or suggest how to make my thread "known"

    Appreciate any help,
    Regards
     
  6. Micky

    Micky Well-Known Member VIP Member

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    I have a few. Microphonic, half bad, cracked, broken pins, you name it.

    Want 'em?
     
  7. Sg-ocaster

    Sg-ocaster Well-Known Member

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    Yea just to check this thing out with.
     

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