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  • #16
    Something is seriously wrong with the Pro Jr. Pin 3 of the EL84s is supposed to be grounded. Until this is resolved, consider it Extremely Dangerous to touch this thing with the power cord plugged in!!!

    Are there cables between circuit boards that could be plugged on backwards or off to one side by one or more pins? Where are you connecting the black lead of your meter?
    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
    REMEMBER: Everybody knows that smokin' ain't allowed in school !

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    • #17
      Originally posted by loudthud View Post
      Something is seriously wrong with the Pro Jr. Pin 3 of the EL84s is supposed to be grounded. Until this is resolved, consider it Extremely Dangerous to touch this thing with the power cord plugged in!!!

      Are there cables between circuit boards that could be plugged on backwards or off to one side by one or more pins? Where are you connecting the black lead of your meter?
      I didn't mod anything with the tubes, so I pulled up a diagram of the EL84 & realized I numbered my drawing of the pins backwards. Pin 1 should be 9 & so on. Don't I feel stoopid. Anyway, fixing that, the correct readings are:

      EL84 -A
      Pin 2 (Grid) = 12v
      Pin 3 (Cathode) = .7mv
      Pin 7 (Plate) = 330v
      Pin 9 (Screen) = 308v

      EL84 -B
      Pin 2 (Grid) = -12v
      Pin 3 (Cathode) = .4mv
      Pin 7 (Plate) = 330v
      Pin 9 (Screen) = 308v

      I am going to go read more about tubes now.

      My husband just told me he received the virgin Pro Jr this morning. I finally get two side by side. Now I can really learn something.
      Gina Veesaert

      "Opportunity is missed by most people because it is dressed in overalls and looks like work." ~Thomas Edison

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