Re: {Collins} 75A-4 Curious Issue



I also tried comparing both of my 75A-4's for hum.
One had it and the other is as quiet as a mouse. Only difference between them
is C-94 was replaced in the no hum 'A-4. Looks like section C-94A is the
culprit as it is the plate supply filter for V-22 (6AQ5), the audio output tube.
Time to replace C-94 in 75A-4 #2!

73,

Deric VY2DA

"Turn the RF gain full CCW, AF gain to where you can hear. Note that there is almost no hum/noise in the AM position (even with AF gain full CW). Now switch to CW-SSB. Note the rise in hum!"






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