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Hum

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  • k4elo
    I m stumped and out of ideas. Need some advice here. A few days ago a small hum suddenly appeared when using my Heil mic through the SPII. First the history.
    Message 1 of 5 , Mar 28, 2014
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      I'm stumped and out of ideas.  Need some advice here.
      A few days ago a small hum suddenly appeared when using my Heil mic through the SPII.
      First the history.  I was using a Yaesu and a Flex with the SPII.  No hum.
      Both SPII mic connectors were wired for Yaesu.
      Sold the Yaesu and got a Kenwood.  Built a pod for the Kenwood and all worked fine for several months.  Until the hum showed up.  I thought maybe the old mic extension cord I had on the Heil had developed a problem.  So I built a new cord for the Heil, wired for Kenwood.  Changed one of the SPII mic connectors to Kenwood wiring.  Hum is even worse.
      If I change the Heil cable back to the one wired for Yaesu and use the other SPII connector, the hum is still there but smaller.
      If I plug a hand mic into the SPII Yaesu connector, no hum.
      If I plug the Heil Kenwood cable directly into the Kenwood, no hum.
      The hum situation is the same whether the Kenwood or the Flex is selected on the SPII.  Tried disconnecting everything but the mic from the Kenwood - same hum.
      So I'm open to ideas - anyone?
      73
      Wayne
      K4ELO
    • Torrey Mitchell
      Wayne, have you revisited your Kenwood SP II pod? I would be sure that both the mic (-) and the mic (gnd/braid) pads are well soldered and that there is no
      Message 2 of 5 , Mar 28, 2014
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        Wayne, have you revisited your Kenwood SP II pod?  I would be sure that both the mic (-) and the mic (gnd/braid) pads are well soldered and that there is no shorting between them.   Same applies to the other end…the mic connector attaching the SP II to the Kenwood front mic jack.

         

        Good luck and 73,

        Torrey N9PY

         

        From: stationpro@yahoogroups.com [mailto:stationpro@yahoogroups.com] On Behalf Of k4elo@...
        Sent: Friday, March 28, 2014 09:53
        To: stationpro@yahoogroups.com
        Subject: [stationpro] Hum

         

         

        I'm stumped and out of ideas.  Need some advice here.
        A few days ago a small hum suddenly appeared when using my Heil mic through the SPII.
        First the history.  I was using a Yaesu and a Flex with the SPII.  No hum.
        Both SPII mic connectors were wired for Yaesu.
        Sold the Yaesu and got a Kenwood.  Built a pod for the Kenwood and all worked fine for several months.  Until the hum showed up.  I thought maybe the old mic extension cord I had on the Heil had developed a problem.  So I built a new cord for the Heil, wired for Kenwood.  Changed one of the SPII mic connectors to Kenwood wiring.  Hum is even worse.
        If I change the Heil cable back to the one wired for Yaesu and use the other SPII connector, the hum is still there but smaller.
        If I plug a hand mic into the SPII Yaesu connector, no hum.
        If I plug the Heil Kenwood cable directly into the Kenwood, no hum.
        The hum situation is the same whether the Kenwood or the Flex is selected on the SPII.  Tried disconnecting everything but the mic from the Kenwood - same hum.
        So I'm open to ideas - anyone?
        73
        Wayne
        K4ELO

      • k4elo
        Thanks Torrey. I ve looked carefully at those. One interesting thing is that if you turn the Kenwood off, disconnect the mic and measure pin 7 (mic -) it has
        Message 3 of 5 , Mar 28, 2014
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          Thanks Torrey.  I've looked carefully at those.  One interesting thing is that if you turn the Kenwood off, disconnect the mic and measure pin 7 (mic -) it has continuity to the chassis ground.  Just the way Kenwood does it I guess.  What I don't understand is why it all worked for months with no hum and then it just showed up.

          73
          Wayne
        • ampman1961
          These are some of the top of my mind musings on the subject. This might be something worth trying. Many times, professional audio engineers in the recording
          Message 4 of 5 , Mar 28, 2014
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            These are some of the top of my mind musings on the subject.
            This might be something worth trying. Many times, professional audio engineers in the recording world will utilize single ended grounding schemes in order to prevent and correct ground loops. You may try this by using only the grounded end at the xcvr. Try lifting the braided end at the pod just to see if there is a change.
            The fact that the ground popped up out of nowhere suggests the possibility of the notorious Kenwood
            internal board level ground screw scenario. Many times in my years owning various Kenwood radios, I have corrected ground issues by tightening all board level mounting screws where the ground plane mates to the chassis. Cleanliness at those points is essential. Obviously, you have likely tried every single connection to eliminate the culprit. I'm sure you'll figure it out.
            73 de Billy N6YW
          • Torrey Mitchell
            Wayne, Try this……… Disconnect the FLEX pod cable from the back of the SP II. See if this makes a difference. You did not say if there is hum on the
            Message 5 of 5 , Mar 28, 2014
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              Wayne,

               

              Try this………

              Disconnect the FLEX pod cable from the back of the SP II.  See if this makes a difference.  You did not say if there is hum on the FLEX audio.

               

              I fretted for months about a suddenly developing hum/noise on my audio.   It was first reported to me while I was using the Tentec Orion II as net control.   At the time, I switched over the Elecraft K3 to finish the net.  Alas, the same noise was reported on my K3 audio.  I figured it was a problem in the W2IHY audio chain.  The noise came and went and the W2IHY boxes checked out OK.  After some weeks, I concluded that the noise only appeared if I had both the K3 and the Orion II turned on.  Finally, it became obvious that simply slightly wiggling whatever mic cable was screwed into the K3 caused the noise to worsen leading to high level feedback.  I worked with Elecraft who felt there was “something loose” on the PCB behind the front panel (where the solder pins of the jack are soldered) which was aggravated by any movement of the mic jack.  The K3 is on its way to Elecraft for them to figure it out and do all applicable updates.

               

              The reason for sharing the story is this…

              The noise emanating from the K3 panel jack somehow also appeared (and was first noticed) on my Orion II signal.  The assumption is that the SP II box was the only commonality between the two transceivers.  So I am wondering if removing the FLEX pod cable might be instructive.

               

              My Orion II is now in use at another operation position and has no issues.  It was replaced at my main operating position by the TS-990S as you know.

               

              I’ll keep following this thread.  I’m really curious.

               

              73 Torrey N9PY

               

              From: stationpro@yahoogroups.com [mailto:stationpro@yahoogroups.com] On Behalf Of Torrey Mitchell
              Sent: Friday, March 28, 2014 12:01
              To: stationpro@yahoogroups.com
              Subject: RE: [stationpro] Hum

               

               

              Wayne, have you revisited your Kenwood SP II pod?  I would be sure that both the mic (-) and the mic (gnd/braid) pads are well soldered and that there is no shorting between them.   Same applies to the other end…the mic connector attaching the SP II to the Kenwood front mic jack.

               

              Good luck and 73,

              Torrey N9PY

               

              From: stationpro@yahoogroups.com [mailto:stationpro@yahoogroups.com] On Behalf Of k4elo@...
              Sent: Friday, March 28, 2014 09:53
              To: stationpro@yahoogroups.com
              Subject: [stationpro] Hum

               

               

              I'm stumped and out of ideas.  Need some advice here.
              A few days ago a small hum suddenly appeared when using my Heil mic through the SPII.
              First the history.  I was using a Yaesu and a Flex with the SPII.  No hum.
              Both SPII mic connectors were wired for Yaesu.
              Sold the Yaesu and got a Kenwood.  Built a pod for the Kenwood and all worked fine for several months.  Until the hum showed up.  I thought maybe the old mic extension cord I had on the Heil had developed a problem.  So I built a new cord for the Heil, wired for Kenwood.  Changed one of the SPII mic connectors to Kenwood wiring.  Hum is even worse.
              If I change the Heil cable back to the one wired for Yaesu and use the other SPII connector, the hum is still there but smaller.
              If I plug a hand mic into the SPII Yaesu connector, no hum.
              If I plug the Heil Kenwood cable directly into the Kenwood, no hum.
              The hum situation is the same whether the Kenwood or the Flex is selected on the SPII.  Tried disconnecting everything but the mic from the Kenwood - same hum.
              So I'm open to ideas - anyone?
              73
              Wayne
              K4ELO

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