The logical reason for the fuse blowing is that a 5-amp time-delay fuse
was probably replaced with an ordinary (fast-acting) one.  Normal
current draw for a motor in a reproducing piano or a smaller
nickelodeon would be around 3.5 amps, depending on the brand and
horsepower rating.  However, the starting winding draws considerably
more current, possibly as much as 12 amps.  As the motor comes up to
speed, a centrifugal switch cuts out the starting winding.

However, if the motor fails to start or freezes up while running, the
starting winding, being not rated for continuous duty, will quickly
overheat and burn up.  Also, the running winding requires a "back EMF,"
created by the spinning armature acting as a generator, to limit the
current passing through it.  So if the starting winding doesn't
automatically engage when the motor is shut off and stops, it won't
know in which direction to run when turned back on, so it runs in
neither direction, and without the back EMF, will still draw enough
excess current to burn out in short order.

This is why a time delay fuse or circuit breaker is a good idea, even
though these instruments rarely had any built-in fusing at all.  For an
instrument controlled by a clock, such as the Ampichron Ampico, this
kind of protection is absolutely essential.  Has anyone ever come
across a reproducing grand with a hole burned in the soundboard?

Jeffrey Wood