Electrolytic filter caps dry out and allow hum. It's best to replace these caps as old ones can short and damage other components in your radio. You may hear a slight hum with an ear near the speaker. Much more is excessive. New filters should reduce or eliminate hum.
Norm
: Before I start replacing electrolytic caps on this set, I have noticed that the hum on this model is coming from the speaker, even with the volume at its lowest setting (basically off). The cone starts vibrating at initial power up, even with no sound volume. (I can't tell exactly if it is 60 or 120 Hz.) Stations come in fine and they tend to override the residual hum, but it is a bit annoying. Could it just be the nature of this design, with the electrodynamic speaker? I would like to know if this is normal before I begin a capacitor swap-out.