[TenTec] Argonaut 505 - The Answer

[JAMES T HANLON]

I want to thank everyone who replied to my message for help with hum on my Argonaut 505.  In retrospect I feel a good bit like Click and Clack, those well known NPR Auto Mechanics, with their Weekly Puzzler.  As you can see from my original plea below, the real clue was the speculation that it might be FM on the local oscillator.  

Dave, K8BBM, had the right answer when he wrote, "move power supply away from rig some, some TT rigs subject to hum is PS too close to one end of rig."  Indeed, if I position the 210 power supply so that the power transformer is over the front, center of the rig and thus on top of the vfo box, the hum as judged by the audio output of my R4B monitor receiver becomes extreme.  At the same time there is absolutely no ripple present on the RF wave envelope.  So I presume that the AC field from the transformer is interacting with the permiability of the tuning slugs in the oscillator coils and creating FM.  I also see the same effect when I run the rig from a battery supply and I either position the turned-on but disconnected 210 AC supply above the vfo or even when I position a turned-on Autek audio filter with an internal AC power supply above the vfo.  

Further, when I move the 210 away from the transceiver and use it as the power source, the hum disappears.  

So I have my answer.  Thanks again to all and especially to Dave.

73 and Merry Christmas,

Jim, W8KGI
  ----- Original Message ----- 
  From: JAMES T HANLON 
  To: tentec at contesting.com 
  Sent: Wednesday, December 17, 2003 9:49 AM
  Subject: [TenTec] Argonaut 505


  Y'all,

  I just became a new owner of an Argonaut 505, the very first Argonaut and my first Ten Tec rig.  It came with the model 210 power supply.  I am noticing a 120 Hz hum on the transmitter note on CW and a corresponding hum on the SSB signal when I run the rig from the 210.  When I power it from a battery there is no hum.  It is most noticable on 40 meters which is where the local oscillator is tripling, and I don't see a hum on the wave-envelope with my HP1740A 100 mHz oscilloscope.  So it may be FM on the local oscillator.  

  I would appreciate first of all a circuit diagram for the 210 power supply, and then of course any suggestions about what to do.  It is a really fun little rig when I run it from the battery.

  Thanks,

  Jim Hanlon, W8KGI
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