A very common trouble area on a well-used Ampico "A" is the bearing on the
left side of the take up spool.  This was a cone-and-nozzle contraption
in a ball bearing race.  Also included in the installation was grease, as
a sealer, and some highly technical paper washers used for additional packing.

Lack of grease, and or general wear will have the effect of sending a
signal to turn the switch off.  This is more pronounced when more suction
is available, i.e. before the music starts to play.  Once the music starts
to play the suction level drops just enough to cancel the effect of this
small leak.

You can mess with this air tight bearing and may correct the problem,
however, my advice would be to buy the new replacement part from the
Player Piano Company. It is a one-piece nylon bit that takes the place
of the ball bearings and the grease and paper seals.

On the Ampico systems I restore I replace that part automatically, if only
to offset future problems.

Ken Vinen