Hammond Organ Service Manual - Early Models (A,B ... - Audiofanzine

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CONSOLE POWER WIRING
{Main and Chorus Generators)
0.
Starting and Synchronous Motors
A shaded pole induction motor is used for starting the generator and
is located at the right end of the generator as viewed from the back.
The rotor of this motor will slide endwise when current is supplied
and engage a pinion on its shaft with a gear on the generator driving
shaft, bringing the tone generator up to slightly greater than synchronous
speed.
When the organ is started, the starting switch is turned on and held
for about 8 seconds while the starting motor brings the system up to
speed. The "run" switch is then turned on. This switch simultaneously
connects the synchronous motor and introduces a resistor in series
with the starting motor (Figure l), thus reducing its driving power.
With a braking action of the synchronous motor and a loss of power
of the starting motor, the system slows to synchronous speed and
the synchronous motor begins to carry the load. A period of about
B seconds should be allowed for this to take place, after which the
starting switch may be released. The starting switch springs back
to the "off" position, and turns off the starting motor, which is
disengaged from the rotating shaft by a spring-
should be noted that the synchronous motor can supply power only
at synchronous speed, Thereforei if for any reason the system fails
to reach synchronous speed it will not continue to run after the starting
switch is released. Failure to start properly is usually due to
increased oil viscosity and may be overconne by an increase in starting
time.
As the schen-iatic diagram (Figure 1) indicates, the "run" switch in its
"off" position shorts out the wirewound resistor attached -o the line
panel. If the "run" switch is defective in its '"off*" position, the generator
will not start because this resistor will be permanently in series with
the starting motor. Before assuming that there is anything amiss with
the motors, short out this resistor and start the generator in the norrnal
manner. If the generator operates satisfactorily, replace the "run" switch
The "run" switch on all consoles is a two-circuit switch, but types of
switches having two different terminal arrangements have been used, as
shown in Figure 2. When replacing a switch, observe the wiring of the
old switch and check the connections of the new switch with an ohmmeter.
Note that black and blue are connected in the "on" position, and yellow
and brown are connected in the "off" position, no rnatter which type of
switch is used.
STARTING MOTORS
CHORUS
MAIN
<
I
W
m
o
Q
Z
< -J a
<
MAIN
SYNCHRONOUS MOTORS
CHORUS
ON
ON
u
<
A A
OFF
OFF
-START" rvVXAA*-
SWITCH
"RUN"
SWITCH
WIRE WOUND RESISTOR
U5V, LINE, 1 GEN. - ISO OHMS
115V. LINE, 2 GEN. - 125 OHMS
230V. LINE, 1 GEN. - 1000 OHMS
230V. LINE. 2 GEN. 500 OHMS
FIGURE I
SWITCH AND MOTOR CIRCUITS
2-15