Oops! Plugged in wrong tube

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Andygee, Apr 2, 2015.

  1. Andygee

    Andygee Silver Supporting Member

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    Yes I did. Ok I have an Allen Accomplice Jr...love this amp. Anyway I accidently plugged in a pair of JJEL34s where 6L6s should go and played it for a couple of hours before the 1amp fuse blew. I put in the right tubes today and biased it up and works ok.
    My question is what components do you think I may have seriously stressed by doing this? Thanks in advance.
    Andy
     
  2. AXEnGEAR4J

    AXEnGEAR4J Supporting Member

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    Maybe the OT but most likely just the fuse.
     
  3. Andygee

    Andygee Silver Supporting Member

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    Dave puts in Heyboer trannys.
     
  4. Jeff Gehring

    Jeff Gehring Silver Supporting Member

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    That's kind of weird to think of... The EL34 has pin 1 connected to the suppressor grid, and pin 1 is usually tied to pin 8 (the cathode) on most EL34 socket wiring. In the Accomplice (as near as I can tell from looking at internet gut shots) David uses pin 1 on the 6L6 sockets as Fender did: as a landing point for the other end of the 1500 grid stopper resistor (which brings the audio signal and the negative DC bias voltage to the control grid on pin 5.

    Plugging in an EL34 would put the negative bias voltage and the audio on the suppressor grid AND on the control grid, which would be weird. I don't think it would be immediately harmful, since the suppressor is usually operated at ground/cathode potential, throwing an extra 40 or so volts of negative potential on there would certainly suppress the crap out of any secondary emission from the plate!

    Hopefully you've just blown the fuse, but I'd recommend having a look at the screen resistors to see if they show signs of toastiness.
     
    Last edited: Apr 2, 2015
  5. EADGBE

    EADGBE Member

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    How did it sound?
     
  6. Blue Strat

    Blue Strat Member

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    For facts rather than guesses, the amp builder is the best guy to talk to.

    In general I agree with Jeff, above, but I think you'd know immediately that the EL34s weren't working right if Allen had wired your sockets as he described.
     
  7. Andygee

    Andygee Silver Supporting Member

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    It's been ok. Talked to Dave...he thinks the El34s must be cooked (they are). May have dodged a bullet cause the amp sounds ok with some old Ruby 6L6GCs.
    Pulling it apart not to check on parts.
     

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