Although I do not have either a schematic nor an operations manual, most
generators are not designed to directly operate into the low impedance of a
speaker. The speaker might act like a dead short.

They are usually designed to drive 600 ohms or higher. Some of the very
small speakers may have an impedance of close to 100 ohms and may put out
some audio.

But, as Edward said, the electrolytic capacitors are probably bad. Most of
the old capacitors are aluminum cylinders above the chassis. They can most
easily and inexpensively be replaced by cutting the leads and installing a
similar value capacitor under the chassis. It does not have to be the exact
capacitance and can be a bit more capacitance. New capacitors are much
smaller than older ones.

Good luck, Colin Lamb