This is a follow up to my piece in 011103 MMDigest, titled "Replacement
Motor for Welte Vorsetzer".  Before those of you without Red Welte
equipment tune out, let me say that for anyone who has a reproducing
piano without the original motor, using a DC motor and the Minarik
Adjustable Speed Drive might make sense.

I now have the unit connected to a motor, and it seems unreal to be
able to control the speed of a 1/4 hp motor, from stop to maximum,
with a tiny potentiometer such as that used in radio volume controls.
(I erred in my last MMD piece in stating that there was a minimum
speed; I had misread the user's manual.)

The advantage would be that you would be able to set the speed to the
minimum that does the job, rather than settle for the speed given by
available AC motors and pulley sizes.  This would reduce noise and
prolong pump life.  Another advantage would be that you could use its
"soft start" feature (gradual acceleration to the preset speed).

The only modification needed to the motor is to disconnect the wires
leading to the brushes.  Then the motor's terminals feed the field coil
only, and they should be connected to the field supply.  Then the
brushes are connected to the armature output of the drive.

I did not mention that this drive provides some speed regulation.
Presumably it does this by increasing the armature voltage when the
current increases.  This should compensate for the loss of the series
coils in a compound motor, as these coils now carry no current.

One discrepancy: both the user's manual and the Brigar catalog list
3 amperes as the maximum armature current, but a nameplate on the unit
lists 2.5 A as the maximum.  This should be more than enough for a
1/4-hp motor.

My Vorsetzer is not restored, so I have not driven a pump, but I have
controlled my Emerson 110-volt 1200-rpm 1/4-hp motor running without
load.  I used the 100-volt field supply directly on the field, but
I have ordered a 10.5 volt "wall wart" (plug-in power supply) to
connect in series to obtain the correct voltage.  These units in
various voltages are obtainable cheaply from several surplus houses.

Cecil Grace