Sunbeam Mixmasters Troubleshooting guide

Instructions for Servicing Vintage
Sunbeam Mixmasters
Original Sunbeam Factory Service Information for Models:
1, 3A, 3B, 3 ‘Automatic’
Compiled by
Dave’s Repair Service
New Albany, PA
2004 All Rights Reserved
www.DavesRepair.com

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

or “dummy” set is made of cold rolled steel. The purpose of the steel point and
lever arm is to balance the movement of the tungsten point and its lever arm
and to give smooth, quiet operation, which is important. Since the breaker
points are mounted on a rotating disc to enable centrifugal force to act upon
them, the current is fed to the rotating governor through a pair of stationary
brushes, hence there are two governor brushes.
The wiring diagram below will help clarify the servicing and repair of this
model.
Governor
Condenser
Circuit
Shielded
Leads
Governor Breaker Points
Line Switch
Resistor
Filter Condenser
Circuit
Mixer Case
Top Field Coil
Wiring Diagram for MIXMASTER
Model 1 AUTOMATIC

HOW TO SERVICE MODEL 1 AUTOMATIC MIXMASTER
1. If Mixmaster does not run when electric cord is plugged into an outlet of
the same voltage shown on the motor name plate, detach the cord from the
socket and remove switch cover (see Key #71 on the general diagram at the
end of this bulletin) by taking out the two screws (90 and 65); then plug
the cord into the socket again and with a piece of wood press down on
phosphor bronze switch (105), taking care to keep the wood clear from
rotating governor disc (100). If mixer should start that is an indication
that switch rod and bakelite insulator (115) is short and should be removed
from switch cover and a new one installed.
If, on the other hand, the motor should not start when pressing down switch
part (105) remove the governor disc assembly (100) and install a new
governor disc as outlined in sections 5—A and 13—B. Then close the switch
again as mentioned above. If motor still does not start proceed as follows:
1—A. Reassemble original parts (see sections 14.A and 15) and check for
continuity of circuit with a test lamp. Place tips of tester wires on each
prong of the appliance plug at the end of the cord. If the lamp (50W) lights
to nearly normal brightness with the mixer control knob in any position
other than “OFF” it indicates that the electric circuit is complete and the
motor should run, otherwise the bearings may be tight--see section 3. If the
lamp does not light the circuit is open, and a complete test should be made
of the electric cord as in section 2. If light is illuminated to
approximately half normal brightness, that indicates that the motor circuit
proper is open and current is flowing through resistor (43) only--proceed to
take motor down as in sections 5, 5—A, 5—B and 6 and test armature (27) and
field coils (44), for open circuit, also inspect brushes (19) and brush
springs (18).
2. Testing and Replacing the E1ectric Cord (33)
Take out screw (87), remove cover (84) arid rubber insulation (95) and pull
out connections from terminal insulation box. Place test tip on one of these
connections and the other tip on first one prong of the appliance plug and
then the other. One of these wires should light; if it does then move test
tips over to the other connection in terminal box and to the other prong of
the plug. A light should be obtained there also if the cord is in good
order. If either one of these wires do not light thru, cord should be
replaced.
2—A. Next, use a hot soldering iron and pliers, untwist the terminal leads and
detach cord. Attach a new cord and plug and twist and solder leads. No
taping of the leads need be done but fold leads carefully into terminal
insulation box (96) so they do not touch the case. Replace rubber insulation
(95) cover (84) and screw (87) and test mixer for ground by touching first
one terminal prong of plug on cord with one tip of test lamp, and the other
test tip on the motor case. Then move over to the other prong of the plug.
The lamp should not light. If it does go back and check wiring.

3. Frozen Bearings
To check the bearings to find if any have seized because of lack of oil or
other causes, grasp the lower part of the whippers (21), and turn inward. If
the bearings for whipper spindle sleeves (13 and 20), motor bearings (45), or
governor slide bearing (113) have seized it will be impossible to turn the
whippers. To locate seized bearing and repair see sections 4, 5, 5-A, 5-B, 6,
7 and 9. If all bearings are free the whippers will turn freely. The whippers
should not turn at all in an outward direction; if they do, that indicates a
worm gear (9) is stripped and the gear should be taken out and replaced as in
sections 4 and 16.
4. Removal of Whipper Spindle Sleeve and Oil Retainer Assemblies (13 and 20)
To remove whipper spindle sleeves unscrew the two gear case cover screws (8)
and take off gear case cover (7). Put both whippers (21) in place and rotate
inward until worm gear set screws (10) can be seen, then loosen set screws
with “T” handled worm gear set screw wrench. Next, grasp the sleeves and pull
them down and out of the gear case (5). If juicer sleeve (20) is frozen in the
bearing it may be necessary to drive it out, using a brass rod which will pass
thru the bearing and which can be driven downward from the hole in top of gear
case. Another helpful method of removing frozen spindle sleeves is to turn the
motor up-side-down and squirt kerosene from a can between the outside of the
sleeve, and the bearing part of the gear case; then remove switch cover
assembly (71) as in section 5. Grasp the governor disc (100) in one hand and
insert a whipper in the frozen spindle sleeve and try to turn both in the same
motor direction with a back—and—forth movement. The frozen spindle should
gradually loosen until it can be rotated and set screw (10) is brought to the
front of the gear case. If whipper spindle sleeves are frozen it is necessary
to replace the sleeves only, see sections 16 and 17. But if the whipper
spindle sleeves come out easily and the armature cannot be turned by grasping
the worm shaft, the motor bearings (45) are probably seized or are badly
gummed up. To continue it will be necessary to disassemble motor as in
following sections.
5. How to Remove Governor (100) and
Switch Mounting Bracket (105).
Remove screw 90 and 65 and gently tap switch cover 71 until the lacquer is
broken and cover can be pulled straight back and off. A final test for frozen
or gummy motor bearings (45) may be made at this point by grasping the
governor disc (100) and turning it, which normally should turn freely (with
the armature shaft) if bearings are in good order. If governor and armature do
turn, it is probable that the governor slide bearing in the switch cover is
frozen or gummy and should be examined, washed out with kerosene and re-oiled,
or replaced with a new governor slide, bearing and lever assembly (113).
5-A. To continue the removal of governor (100) insert the Allen Head governor
wrench into governor set screw (101) and loosen set screw, two or three turns,
to the left. Governor may then be pulled off the armature shaft.

5-B. Next disconnect the three leads fastened under screws and nuts 106, 92, and
94 and take out two screws (91) which hold switch mounting bracket assembly
(105) in motor. Remove this assembly, including the two governor brushes (97)
and resistor (43).
6. Removing the Armature (27)
Following the work outlined in the preceding sections take out the two
retaining screws (23) and gently tap front housing to help break the lacquer
finish at the point where the front part of the motor case joins the rear part
(28). When the two pieces have been separated the armature may be removed and
a tight bearing located.
7. To Free Tight Motor Bearings (45)
First, thoroughly clean bearing holes by wiping with a clean rag, F1ush out
oil holes and bearings (45) with kerosene fed from the spout of an oil can.
Wipe thoroughly until dry. Rub armature shaft with an oilstone to remove
scoring or roughness, apply oil to the shaft and see that it is free to turn
in either bearing. (NOTE: If bearings are worn, or require replacement for
any reason, return motor to factory for service. Bearings in Model 1 are oil
less-type and must not be reamed.) It is well at this point, since the
armature is out, to test it, and the field coils, for grounds, etc. as
follows.
8. Testing Armature (27) and Field Coils (44)
To check the armature for grounds touch one wire tip of test lamp on the
armature shaft, then touch the other on any commutator bar or bars. If test
lamp lights a ground or conducting path is present between live parts and
laminations, a condition that should not exist, and the armature should be
replaced with a new one. Examine commutator bars to see if there are burned
marks along the edges of any of the bars. Such marks indicate short circuited
winding and armature should be replaced. Also observe if any wires leading
from winding to the commutator are broken or damaged from rubbing on the brush
leads. Replace armature if this condition is found.
Commutator should be smooth without excessive ridges or rings cut in it.
Commutators with excessive rings cut in them by the motor brushes (19)
should be replaced, or if a lathe is available they may be turned down with
a smooth cut.
Check field coils through leads and motor case, for grounds, and through both
leads for open circuit.
9. Assembling Motor
The armature shaft should be inserted into the back bearing, and the front
housing then slipped part way onto the front of the armature shaft. The brush
lead wires with the clips should be clipped onto the brush holders (18). The
lead and clip coming direct from the field coil (44) should put on the brush
holder on the right, and the lead and clip from the condenser on brush holder
on the left, as the workman looks at the back of the motor, After the brush
clips are put on the brush holders and the lead wires are carefully arranged
not to rub against the armature, and when the condenser (69) has been started
into the space provided for it in the

bottom of gear case (5), the two parts of the motor housing should be brought
together with care to prevent dirt, etc. from getting between the joint. The
two retaining screws (23) should be in place and then tightened up evenly so
there will be no misalignment of bearings. This is very important. Be sure
that the armature spins FREELY in the bearings at this point.
9—A. Note also how the front part of the motor housing fits into the back part.
The position of the two parts when together is held approximately by a
tongue, which is slipped into a slot, but this allows for some “play”. After
the retaining screws (23) are tightened see that the special gear Box Gauge,
or a Power Unit attachment, when inserted into whipper spindle sleeve (20)
also slips into the two holes in the base freely. If locating buttons on the
bottom of the gear box gauge (or power unit) are to one side of the holes in
the base, loosen retaining screws (23) and swing gear case (5) until
alignment is attained, then tighten screws (23) again, evenly.
10. Commutator Brushes (19)
Insert brushes into brush holders (18) so that curved end of the brush
conforms to the curved surface of the commutator (this is very important
because it, minimizes sparking at the commutator). The brushes should be
free from oil and grease and if worn short should be replaced with new. The
brush spring (17) should have as good a tension as when new. If tension is
low the spring should be replaced.
Insert brush springs and tighten brush screw (16) securely so screw will not
loosen while motor is running,
11. Fitting the Switch Mounting Bracket Assembly (105) in the Motor
Put the Switch Mounting Bracket and resistor (43) in place and screw down the
two mounting bracket screws (91). Facing the back end of the motor, the field
coil (44) lead should be connected to point 106. The longest condenser (69)
shielded lead should then be connected to point. 92 by first passing it under
the switch lever, being sure that it does not rub or make contact in any
place except under screw 92. Next fasten the other condenser shielded lead
under nut 94, also taking care that it does not make contact with the case,
which would cause a ground.
12. Governor Brush and Spring Assembly (97)
To fit the two governor brushes and springs in their holders, in the switch
mounting bracket assembly (105), first see that the holders are free from
carbon dust or any gummy substance resulting from carbon dust mixing with
oil. The governor brushes should be approximately 11/32” long and perfectly
round without worn spots forming shoulders on the sides as this interferes
with the travel of the brush The springs should be in good condition to hold
tension on the brush, and free from wear caused by rubbing on the sides of
the brush holder. The copper pigtail connection should be fastened to the
bottom coil of the spring at the brush so the spring will not have to carry
the current to feed the brush. The straight portion on the other end of the
spring locates in a hole at the bottom of the brush holder to prevent turning
of the brush and excessive side wear on the brush. The

brush should be pushed down into the brush holder a few times to be certain
that it will travel or slide freely in and out of the bolder. If governor
brushes and springs are not in first class condition as outlined above they
should be replaced.
13. Fitting the Governor (100) on the Armature Shaft
The governor assembly should be thoroughly examined before placing on the
armature shaft. First inspect the brass collector rings on the back of the
disc. If these are badly pitted or burned the governor (100) should be
replaced unless it is possible to face off the rings in a lathe. Care must
be taken, if this is done, to obtain a smooth cut and above all to see that
the governor disc runs true on the arbor before and after facing. This is
very important as a noisy motor, excessive governor brush wear, and worn
bearings will result if disc does not run true, or if it is thrown out of
balance. There is a limit to the amount of the cut or to the number of cuts
that can be taken off the rings, because if the heads of the rivets which
hold the rings to the Bakelite disc are cut away the rings will be thrown
off at high speed.
13-A. Next examine the tungsten contact breaker point (102) mounted on the end of
the lever arm. If badly pitted or burned the governor assembly (100) should
be replaced. No filing, bending or changes should be made on the tungsten
points, or on the lever arm. It will be noticed that there are two lever
arms (102 and 103) on the disc but as explained in the introduction to this
bulletin close observation will show that only one arm is fitted with
tungsten points. The other points are larger and are made of cold rolled
steel. These C.B.S. points carry no current but are for the purpose only of
balancing the governor at all speeds.
13-B. After examination has showed the governor (100) to be in good condition or
that a new one is necessary place governor on the armature shaft. First
observe the depression on the armature shaft and place the governor on the
shaft so that governor set screw (101) can be screwed into the depression,
or hole, in the armature shaft. The governor brushes (97) must be forced
back into the brush holders carefully as the governor is pushed onto the
shaft so brushes will not be damaged or broken. Be certain that the set
screw (101) is turned with the Allen Head Wrench until it is tight and that
no wires are rubbing, as the governor is revolved by hand. The governor and
armature should revolve FREELY.
The operation of the motor may now be checked by plugging the cord into a
socket and carefully closing switch (105) with a pencil or round stick in
much manner that it will not be struck by the governor (100) when it
rotates. Motor should operate on “high” speed only.
14. Fitting Switch Knob (70) and Switch cover (71) Assembly
Examine parts to see that the governor slide assembly (113) travels in and
out as the switch knob is turned, when held in the normal position. The
switch rod (115) should be thrust forward as the switch knob leaves the
“OFF” position on the outside of the cover, and should stay out for the
remainder of the travel of the governor slide.

The felt wick (110) in the cover should feed oil to the governor slide
bearing.
14-A.If the parts referred to in the preceding section are all in good shape the
switch cover (71) may be put in place. First turn the Switch Knob
(70) to the “OFF” position, then governor slide (113) should be started on
the armature shaft in such manner that the forked shaped legs will
enter the slot provided in the governor disc (100) around the hub. The cover
should then slip into place and the two screws (90 and 65) can be inserted
and screwed in. The rear handle bracket (77) should be placed under screw
90. WARNING: Do not start mixer when back cover is on without first
adjusting armature thrust screw, if thrust screw (26) and switch knob (70)
have been disassembled (see section 15).
15. Armature Thrust Screw Assembly (26)
The armature thrust screw assembly consists of a piece of oil-less type
bearing material pressed into a hole in the end of a steel screw. The thrust
screw assembly (26) should be turned to the right with a screwdriver until
the bearing end presses against the end of the armature shaft, then the
thrust screw should be backed off (turned to the left) 1/8 of a turn. While
the thrust screw is held in this position with the screwdriver, the thrust
screw lock nut (25) should be tightened securely with the socket wrench
supplied for adjusting thrust screw lock nut. Thrust screw nut washer (88)
and switch knob (70) are also held in p1ace by thrust screw lock nut 25.
The motor bearings (45) may be checked at this point by plugging the cord
into a socket and turning the switch knob (70). All speeds should be
obtainable.
16. Fitting the Worm Gears (9) in the Gear Case (5)
Before installing worm gears, inspect the whipper spindle sleeve bearing
surfaces and if scored or rough, smooth the bearing, or if necessary replace
gear case (5). Next inspect the whipper spindle sleeves (13 and 20) and
remove scores or roughness with fine emery cloth or file. If scored too much
the sleeves should be replaced with new.
To start assembling the parts, hold gear (9) by the metal hub with the
special thin pliers and insert gear into right hand side of the gear
compartment, with the hub down. Also, hold gear so the setscrew hole in the
hub is to the front, facing the workman. This is important, because it
determines the timing of the whippers (21). Next, while holding gear (9) in
position as described above (use left hand for this purpose), take the
juicer spindle sleeve (20) in right hand, and push it up thru the gear case
(5) into the gear (9). While doing this, have the depression for worm gear
set screw (10), which is drilled on the sleeve, in line with, and visible
thru the set screw hole in the hub of the gear (9). Insert set screw (10)
using special “T” handled socket wrench and turn down set screw’ TIGHTLY.

Follow the same procedure with the other worm gear (9) and assemble it to
whipper spindle sleeve 13. Again be sure that the gears (9) are fitted to
sleeves with set screw holes held exactly in front, in order to get proper
timing of the whippers. It is well to put film of oil on the whipper spindle
sleeves (13 and 20) before inserting them into the gear case (5) bearings.
17. Greasing the Worm gears
Put about TWO TABLESPOONS ONLY of special Mixmaster lubricant (86) into the
gear compartment, placing it in the metal worm and gear (9) teeth as much as
possible. It is essential to use special Mixmaster lubricant. This grease
was chosen after many tests because it adheres properly to the surfaces to
be lubricated, and does not thin out when warm.
Fit gear case cover (7) and use new gasket (6) if necessary. Fasten cover
with two screws (8) and tighten. Place a few drops of oil in all oil holes
and run motor idle for a time to free the gears.
18. Adjusting the position of the Motor and Whippers (2l)
The adjustment screw (32) is provided in the top of the upright (46) so the
position of the whippers may be set permanently for the bowls, and to allow
a free engagement of the Power Unit Attachment and other attachments,
between the two holes in the base of the Mixmaster’ and the motor.
To properly adjust screw 32, put the motor on the standard, take the Special
Gear box gauge, or a Power Unit Attachment, and slip it into the whipper
spindle sleeve (20). Lower the motor head to its horizontal position and
note whether the two buttons on the bottom of the foot of the gear box
gauge, or Power Unit, are forward of the two holes in the base, or back of
them. If ahead of the holes, loosen lock nut (31) and turn screw (32) down
until buttons enter holes freely. Also check the space between the bottoms
of the whippers (21), and the surface of the mixing bowl (48, 49 and 62).
Whippers must come close to surface of bowl so all ingredients in the bowl
will be mixed and so bowl will turn) but the whippers should not rub on
bowl. If whippers rub set adjusting screw 32 higher. If whippers do not come
very close to surface of bowl, adjust screw 32 lower. When the screw has
been properly adjusted lock it in place by tightening nut 31.
19. Replacement of Condensers (69)
19—A. Should either the condenser for governor breaker points, or the filter
condenser (see the general remarks on page one of this bulletin) fail, the
removal of both condensers is necessary since they are housed in the same
metal container. Proceed as follows:
First, remove switch cover assembly (71) and governor (100) as in
section 5 and 5—A, an4 take out switch mounting bracket (105) as in
section 5—B.
Second, take out retaining screws (23) as in section 6 and separate
motor housing.