:I changed the filter caps on my Sears 4486 but still have a loud hum when the volume control is all the way down. What could cause that? Schematic shows a 6C5 as a phase changer. What is a phase changer?
:
A phase changer is an audio stage with a gain of 1, but a phase shift of 180 degrees. It is necessary in radios with a push pull output stage. The signals to each tube needs to be fed 180 degrees out of phase so that one tube will pull while the other is pushing.
As for the humm, you may want to look for a short.
Best Regards,
Bill Grimm