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5F6A low volume

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  • V3
    pin1 271
    pin3 18
    pin6 375
    pin8 18
    Seems we still have the same problem as discussed before the socket change. As already mentioned, the high plate voltage at pin 6 (as well as the low common cathode voltage) mean that one of the triodes is not conducting current. (Its a double-triode having 2 separate heaters. One is internally connected to pins 9 and 4 , the other to pins 9 and 5. By jumpering socket contacts 4 and 5 the heaters are wired in parallel.)
    If only one of the triodes is operative, this results in low output and hum.

    Can you check that both filament wires are glowing?

    I suspect a socket wiring error/problem, especially regarding heaters. Can you check heater voltages between pin 9 and pins 4/5.
    Please check socket jumper connections between pins 4 and 5 as well as between pin 3 and 8. Also any wires shorting?
    Last edited by Helmholtz; 01-13-2019, 02:53 PM.
    - Own Opinions Only -

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    • Originally posted by Helmholtz View Post
      Seems we still have the same problem as discussed before the socket change. As already mentioned, the high plate voltage at pin 6 (as well as the low common cathode voltage) mean that one of the triodes is not conducting current.
      Can you check that both filament wires are glowing?

      I suspect a socket wiring error/problem, especially regarding heaters. Can you check heater voltage between pin 9 and pins 4/5.
      Please check socket connections between pins 4 and 5 as well as between pin 3 and 8. Also any wires shorting?
      vinceg's reports indicate that this voltage condition only happens with one of his preamp tubes and not others and that it was that tube that was in the amp when these last voltage readings were taken.
      "Take two placebos, works twice as well." Enzo

      "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

      "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

      Comment


      • Originally posted by Chuck H View Post
        vinceg's reports indicate that this voltage condition only happens with one of his preamp tubes and not others and that it was that tube that was in the amp when these last voltage readings were taken.
        Dumb question. Is it always the same tube in that socket or does a differsnt tube give roughly same data?

        nosaj
        Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

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        • Update

          Heater problem is resolved, the cause was fuse holders. I noticed that moving heater wires pilot lamp went out. Now I've wall voltage of 230V and heater voltage of 6.1V

          Also I change the tube and now amp has right volume. I'm surprise to note how tubes are bad

          Hum remain to be fixed.

          Comment


          • Originally posted by nosaj View Post
            Dumb question. Is it always the same tube in that socket or does a differsnt tube give roughly same data?

            nosaj
            Believe me, I got confused. I think that tubes fall down because low heater voltage

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            • Originally posted by vinceg View Post
              Update

              Heater problem is resolved, the cause was fuse holders. I noticed that moving heater wires pilot lamp went out. Now I've wall voltage of 230V and heater voltage of 6.1V

              Also I change the tube and now amp has right volume. I'm surprise to note how tubes are bad

              Hum remain to be fixed.
              Please update V3 voltages.
              - Own Opinions Only -

              Comment


              • Originally posted by Helmholtz View Post
                Please update V3 voltages.
                Now it is correct

                V3
                pin1 255
                pin3 41
                pin6 252
                pin8 41

                Comment


                • Update

                  It seems that the cause of the hum is heater wires. I got up heater wire from V2 with a chopstick and hum has significantly reduced but not completely gone.

                  What can I do to get better? Are they too close to signal wires? Can Heater elevation resolve?
                  Attached Files

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