[Collins] 75S-1

[kiyoinc at attglobal.net]

I put a scope on the speaker. 

It's two sawtooth waves.

60 Hz, 48 mv peak to peak.  The bias supply cap.

120 Hz, 32 mv peak to peak.  HV 3 stage cap.

>From what you say, the easy fix is to replace the bias cap. 
Then I'll figure out how to refill the aluminum can. 

AF gain has no effect on the hum.  

I'd like to keep the radio as "correct" as possible.

This weekend I'll pick up some covers for the radios.  This'll
just be plastic sheets 

de ah6gi/4