Hi @Greazygeo 
and welcome to the community,
Thanks for describing the setup so well, it really helps.
Firstly, the signal that you hear when the volume is on zero is not coming from the speaker, it the coming from the transformers.
If the volume knob has not been turned for a long time it should be build up of oxidation. One way to fix this is to turn the post all the way to the left and right many times.
Otherwise, your power station might need a service. Hopefully someone from Fryette or the community can also give their opinion.