[R-390] hum

[Les Locklear]

The power in EAC's have a tendency to hum. Maybe you will just need new filter electrolytics.

Les Locklear
Gulfport, Ms.
Dx'ing since '57
http://www.hammarlund.info/

  ----- Original Message ----- 
  From: Natan Huffman 
  To: r-390 at mailman.qth.net 
  Sent: Friday, July 24, 2009 10:40 PM
  Subject: [R-390] hum


  I'm a very new subscriber and just received my first R390A today although I
  became very familiar with this receiver during the 60's courtesy of Uncle
  Sam.  After checking tube seats I applied 120 VAC to the radio for the first
  time today and was greeted by a nasty audible hum as soon as it was turned
  on and before the tubes had emission.  The hum is heard even with no speaker
  attached and turning controls do not change the amplitude or frequency of
  the hum.  Tomorrow, I'll look at the output of the power supply board with
  my scope to verify any presence of ripple.  

   

  Have I made an old beginner's mistake?  I do not remember this design having
  a pronounced electro mechanical hum that is persistent after being turned
  on.  My R390A is a late model 1967/68 contract EAC model. 

   

  Thank you,

   

   

   

  Natan W6XR    

   

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