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  • AO-29 noise

    Hi,

    I still have some problems with noise from my AO-29. It's not always present. Sometimes I can play the organ for an hour without hearing that noise. Sometimes it's very strong. The volume pedal does not affect the volume of the noise. I already replaced the electrolytic caps (and all tubes). Now I think of replacing resistors. Does anyone have an advice which resistors could most likely be a source of noise, considering that the volume pedal has no effect on the volume of the noise?

    greetings Christian
    1958 B3, 1960 M3, 1953 M2 converted into M3, 2x Leslie 122, Ventilator II, Viscount Legend Solo

  • #2
    Have you cleaned the tube sockets when you replaced the tubes? The two studios whose Hammonds I care for have both been victims of this issue.
    Hammond C3, M102, XB3, XB5
    Lowrey Heritage DSO-1, H25-3, Yamaha E70
    Farfisa Compact Duo Mk2, Vox Continental 300, Korg BX3 Mk1, Leslie 122, 145
    www.drawbardave.co.uk

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    • #3
      Yes I did. I don't think that it has to do with the tube sockets. When I slightly move the tubes in their sockets while i hear the noise, nothing happens.
      1958 B3, 1960 M3, 1953 M2 converted into M3, 2x Leslie 122, Ventilator II, Viscount Legend Solo

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      • #4
        Hello christian.

        If the pedal have no effect on the noise, the noise source is between the pedal itself and the Loudspeaker.
        Because at this end of the schematic, the amplifier have no sufficient gain, I don't beleive this noise come from a resistor.
        Look for a bad contact in the wiring or in the pedal's cabinet.
        Hit gently the parts with the handle of a scewdriver and try to identify sensitive areas.

        JP

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        • #5
          Are you experiencing this through the organs built in speakers or through an attached cabinet?
          Hammond C3, M102, XB3, XB5
          Lowrey Heritage DSO-1, H25-3, Yamaha E70
          Farfisa Compact Duo Mk2, Vox Continental 300, Korg BX3 Mk1, Leslie 122, 145
          www.drawbardave.co.uk

          Comment


          • #6
            Resistors generally need to have a voltage across them to produce noise, so the most likely suspects would be the 330k plate resistor on the second 12AX7 stage or the 100k (or even the 5.6k) resistors that make up the split-load phase inverter 12AU7 stage driving the output tubes.

            That said, tubes themselves can develop intermittent internal noise due to bad welds, but I guess you have tried swapping tubes.

            And, of course, a poorly soldered solder joint can produce intermittent noise.

            Intermittent noises are some of the hardest things to track down precisely because they are intermittent.
            I'm David. 'Dave' is someone else's name.

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            • #7
              Originally posted by Drawbar Dave View Post
              Are you experiencing this through the organs built in speakers or through an attached cabinet?
              Through both. Not very loud through the internal speakers. But really disturbing through the leslie.

              I think I will check with the screwdriver method first, and check for poorly soldered solder joints.

              Don't know if it helps finding the problem, but if i had to describe the noise, i'd say it is always beginning with lower volume, getting louder, then some very loud cracks and pops, and then lower volume again. Like a thunderstorm.

              1958 B3, 1960 M3, 1953 M2 converted into M3, 2x Leslie 122, Ventilator II, Viscount Legend Solo

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              • #8
                Originally posted by geldo79 View Post
                Don't know if it helps finding the problem, but if i had to describe the noise, i'd say it is always beginning with lower volume, getting louder, then some very loud cracks and pops, and then lower volume again. Like a thunderstorm.
                That sound like a faulty electron tube (Gaz test =KO).
                Ions moves between the electrodes and produces this thunderstorm sound.
                JP

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                • #9
                  Hmm.....thought i checked all tubes. And i installed new 6v6 (v5 and v6). I could check again. Are there any tubes which can't be responsible for the noise, concerning that the noise is not related to the volume level of the organ (volume pedal)?
                  1958 B3, 1960 M3, 1953 M2 converted into M3, 2x Leslie 122, Ventilator II, Viscount Legend Solo

                  Comment


                  • #10
                    Hello,

                    Have you checked the tubes for gas ?
                    Some tube testers don't do it.
                    Swap the 12AX7 with another one.

                    JP

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                    • #11
                      I don't have a tube tester. My "testing" is only was to switch all tubes between this and my other (working...no noise) m3. The noise did not disappear. Thus, I thought it should be the resistors or other components.
                      1958 B3, 1960 M3, 1953 M2 converted into M3, 2x Leslie 122, Ventilator II, Viscount Legend Solo

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