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Ampeg V2 bias question

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  • #31
    As lifting the coupling caps changes DC voltages they should be replaced.

    Apart from that, some of your measurements don't seem to make sense, e.g. 12AU7 pin 2: -35V?
    - Own Opinions Only -

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    • #32
      Agree with Helmholtz , replace those coupling caps. If that doesn't cure things we can consider HF oscillation (and strange meter response to it).
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


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      • #33
        I removed the 12au7 and the socket measures zero. All components around tube have been checked and are fine. I can’t see a path for the negative bias to be bleeding to PI tube but that’s what it seems.

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        • #34
          Originally posted by Eggman View Post
          I removed the 12au7 and the socket measures zero.
          Not clear.
          Which socket pin?
          Zero voltage or zero resistance or what?


          - Own Opinions Only -

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          • #35
            Pin 2 +7 on 12au7 which is the pins that have negative voltage as noted previously. C11 and C 13; .3 were replaced so voltages are not coming through those. All measurements are to ground.

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            • #36
              Also C10 was replaced.

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              • #37
                Can you re-check DC volts on power tubes, pins 3 and 5. First with PI tube installed, then with PI tube removed.
                Originally posted by Enzo
                I have a sign in my shop that says, "Never think up reasons not to check something."


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