Welcome, A.B. Bonds, and thanks to "BamBam" Bill Jelen for telling
the world about the Automatic-Music Digest.

Have you compared the Ampico A versus B control systems?  Quite
a difference.  In my humble (?) opinion, the Ampico B and the
earlier Welte system are the only reproducing piano systems that
were really _engineered_, instead of just cobbled together by
tinkerers.  [Yas, yas, those are strong words. What do _you_
say, Robin Pratt?!!!]

Anyhow, I can tell you of my experiences with the spool drive motor.
When I brought home my Weber Ampico B in 1957 my mother yelped, 
"You're wiping out the television at the neighbor's homes."  
Well, I wiped 'em out with my ham radio, too...

So I cured the interference in two steps:

1.  I installed ceramic disk capacitors (0.01 microfarad, 600 volts)
on the outside of the motor end-bell, connected from each brush
holder to the frame. 

2.  I installed a "buffer capacitor" network across the tungsten 
governor points, in the fashion of the old vibrator chopper used in
vacuum-tube auto radios.  I think the capacitor was 0.05 ufd at
600 volts, with a 22-ohm series resistor.

After these modifications I could run the piano on the same branch
electric circuit with our TV receiver, with only minor interference.
Mom and the neighbors were much happier!

Regarding the Ampico B unit valve with the ball-check:  

In the late 1950's Wayne Stahnke interviewed Dr. Clarence Hickman, 
the engineer who developed the system.  When asked if he had ever 
tried the valve with 5 feet of tubing (as in the grand piano), 
Dr. Hickman replied that he hadn't thought of that, and changed 
the subject of conversion. ...!

The professional player techs in this group can advise you better than
I about repair of the Ampico B valves.  Do verify that the ball
check is working.  If not, you can remove the little check valve
and clean it in an ultrasonic tank.  (See your friendly local
jeweler.)

My Ampico B piano is now under restoration with technician 
Randy Cox, and we have made a new _Ampico A_ valve set and primary 
valves for the piano.  I decided, with reassurance from Randy and
Wayne, that the slightly lower noise of the ball valve did not 
offset the poor performance at low intensities.

-- Robbie Rhodes