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MMD > Tech > Ampico > spoolmotor.htm

Ampico B Spool Motor

Schematic Diagram - Ampico B Note Sheet Motor and Governor

For 110 vac 60 Hz mains the motor nameplate will say that it's a 110-volt ac/dc (universal) motor.  Adjustable resistor R2 is set to 25 ohms and the governor resistor R1 is 360 ohms.  If the piano must be used with a different mains frequency or voltage (up to 125 vac), first adjust the tapped resistor for the highest resistance which will still provide enough motor power under the greatest load.  This is during rewind when the re-roll brake is briefly applied.  Second, starting with a low value, increase the value of R1 until the motor doesn't crawl with the points open and a music roll installed.  Resistor R1 reduces the sparking across the points and also provides a current path to the motor when the points open, which reduces motor "bumping".

If interference to television or radio recievers occur these additional components may be added:

1.  Replace the two-conductor wire which connects the motor assembly to the adjustable resistor with two-conductor shield wire rated for 120 vac.  A small twist-lock plug and socket with a center ground pin, similar to the original 2-conductor plug, is made by Hubbell.  Connect the shield to the motor case, and also to the metal enclosure of the adjustable resistor.

2.  Connect a disc ceramic capacitor, 0.001 ufd 1600 vdc, from each brush holder to the motor case.

3.  Connect a resistor-capacitor suppressor network, located in the base of the motor assembly, in parallel with the points and the governor resistor.




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14 December 1999

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