[RFI] Fixing Pin 1 Problems

[Jim Brown]

On 1/13/2011 2:16 PM, Roger (K8RI) wrote:
> why did it work for several years and then suddenly
> start picking up AC?

One possibility that some weak connection broke.  Another is that some 
new noise source was introduced into your shack.  HUM (that is, pure 60 
Hz) is usually the result of a magnetic field being picked up in system 
wiring, as opposed to BUZZ (harmonics of 60 Hz), which is usually caused 
by leakage currents from the AC power line setting up voltage 
differences between the chassis of equipment that are interconnected.  
See http://audiosystemsgroup.com/HamInterfacing.pdf

73, Jim K9YC