SERVICE BULLETIN NO. 14 - Revised April 27, 1949
Sunbeam Corporation
5600 Roosevelt Rd., Chicago
INSTRUCTIONS FOR SERVICING SUNBEAM MIXMASTERS
MODEL 1 (ONE) AUTOMATIC
MODELS 3A and 3B AUTOMATIC
(See Model Number Stamped on Motor Name Plate or on Mixmaster Base)
GENERAL
Before giving detailed instructions for servicing Models 1, 3A and
3B, a few general remarks should be helpful. Models 3A and 3B are
alike except for color and are very similar to Model 1 except for
external design and alight changes in electric circuit (compare
wiring diagram on Page 2 with blue print over Page 3). The servicing
instructions starting on Page 3, although referring directly to Model
1, actually apply to all three models.
The AUTOMATIC Mixmasters have greater power, and the speed control
differs from that in earlier models, and in other mixers. Older
Mixmaster models had a rheostat connected in series with the motor,
to limit the voltage applied to the motor; which, in turn, limited
the speed when a slower whipper speed was required. With this method
there was a loss of power on the lower speeds.
The automatic Mixmasters have a governor control. The governor
consists of contact breaking points placed in series with the motor,
which open at a predetermined speed, and close again at a speed only
slightly lower. Thus a constant speed is maintained, even with
variations in the load or line voltage, and full power is available
at all speeds. The breaker points are mounted on a lever arm and so
arranged on a disc, which revolves with the armature, that
centrifugal force opens the breaker points as the speed goes above a
certain value. This value is varied when the switch knob is turned,
changing the distance between the governor slide and the governor
breaker point arm, and determining the speed at which the contact
points will open.
To give the breaker points a long life, a condenser and a resistor
are shunted across them. The resistor not only lengthens the life of
the points but also smoothes out the motor speed by allowing a small
fraction of the current to flow through the motor when the breaker
points- are open.
A second condenser is included in Automatic Mixmasters to eliminate
radio interference radiated by the brushes and breaker points. Both
condensers on Model 1 are housed in the same metal container. To
distinguish between the lead wires running from each of the two
condensers note that the breaker point condenser has metallic
shielding on the lead wires, but the other condenser has no such
shielding on the leads. On Models 3.A and 3B these two condensers are
separate. See Key numbers 69 and 140 on parts list diagram.
There are two sets of breaker points on the governor disc but only
one set is connected in the electric circuit and these are Tungsten
points. The other
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