{Collins} 75S-3 Receiver Audio Hum Solved



 Thank you to everyone that replied to my question about the 75S-3 audio
hum. It turns out the schematic that came with manual wasn't exactly the
right one I think. My radio says 75S-3 on the front and on the sticker on
the inside. (serial number 10493) My manual which is a reprint says 75S-3
and 75S-3A but when I went to the Collins web site I downloaded the 75S-1
manual on a hunch. This had the right tube V8 listed as 6U8 as opposed to V8
6EA8 for the product detector. Well after trying about 2 more spare 6U8's
that I had I found one that didn't produce any hum when the audio gain was
set for max in the standby position. I wonder if my radio is an older 75S-3
and this is why the manual that came with it when I bought it was really for
a newer model.


Thank You
Thomas Elmore KA1NVZ
Anchorage, Alaska

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