[Amps] Henry 2KD-5 120 Hz Hum

[hamguy2]

I have a Henry 2KD-5 that I am using on AM running 300 watts. 
There is a low level but noticeable 120 Hz hum on the unmodulated 
carrier in CW mode.  The hum is super imposed on the AM signal 
amplitude.  Local stations can hear the hum.  I have tried two 
exciters and they are not the source.  I have recapped the filter 
capacitors to 250 mF without change in symptoms.

Is there something else to check or do I just live with the hum?

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Ron Schuster N9RC
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