OK so a little update on this Radio, I think I may have figured out where the hum is coming from in this radio... The original speaker is where the hum is coming from, because the guy I bought this radio originally had a second radio just like this that he gave me to use for parts to get the one I bought from him up and running, and when I used the speaker from the parts unit on the radio, there was no hum to be heard, but as soon as I hooked it back up to the speaker, the hum came back!
So I'm wondering if the filter choke (L15) which is the coil that is in the back of the speaker assembly (see picture below) is bad?
Would a bad filter choke cause the kind of hum that I've been describing that I've been having issues with on this radio?