The note sheet drive motor in the Ampico B has a flyball governor
interrupting the current to a series wound universal motor; the
motor rotates about 300 rpm while playing the music roll.  The points
interrupt the full motor current, at 30 to 70 vrms typical across the
points, varying with the load.

The principal cause of points failure is the failure of the shunt
resistor, which otherwise absorbs the stored inductive energy when the
points open.  Warped brush holders also have been blamed for causing
the points to fail (because the total power consumption increases due
to increased commutator contact resistance).

The points are easily removed and can be rebuilt by a shop which
rebuilds old engine magnetos and distributors.  A compact triac
switch circuit could be installed in order to reduce the power
through the points.  See the discussion, "Ampico B Spool Motor",
and illustrations at  http://mmd.foxtail.com/Tech/Ampico/

Robbie Rhodes