SERVICE MANUAL

HMM20-1STD MIXER
HMM20-1STD ML - 141157

- NOTICE -
This Manual is prepared for the use of trained Hobart Service
Technicians and should not be used by those not properly
qualified.
This manual is not intended to be all encompassing. If you have
not attended a Hobart Service School for this product, you should
read, in its entirety, the repair procedure you wish to perform to
determine if you have the necessary tools, instruments and skills
required to perform the procedure. Procedures for which you do
not have the necessary tools, instruments and skills should be
performed by a trained Hobart Service Technician.
The reproduction, transfer, sale or other use of this manual,
without the express written consent of Hobart, is prohibited.
This manual has been provided to you by ITW Food Equipment
Group LLC ("ITW FEG") without charge and remains the property
of ITW FEG, and by accepting this manual you agree that you will
return it to ITW FEG promptly upon its request for such return at
any time in the future.

A product of Hobart Service 701 S. Ridge Ave Troy, OH 45374

F45701 Rev. B (0419)
 HMM20-1STD MIXER

TABLE OF CONTENTS
SERVICE UPDATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SERVICE UPDATES PAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
TIS DOCUMENT LIST - HMM20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
ADDITIONAL RESOURCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

REMOVAL AND REPLACEMENT OF PARTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

UPPER LID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
PLANETARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
AGITATOR SHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
INTERNAL GEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
CONTROL PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
SHIFTER ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
ATTACHMENT HUB REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
ATTACHMENT HUB DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
TRANSMISSION DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
TRANSMISSION ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
SHIFT FORK ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
MOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
POWER BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
BOWL IN SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
BOWL GUARD SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
SPEED SHIFT SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

SERVICE PROCEDURES AND ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

BOWL GUARD TAB ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
BOWL GUARD SWITCH ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
BOWL TO BEATER CLEARANCE ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
BOWL LOCK ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
BOWL IN SWITCH ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SPEED SHIFT SWITCH ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
MOTOR CENTRIFUGAL SWITCH ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
SHIFT FORK PLUNGERS ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

ELECTRICAL OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
COMPONENT FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
ELECTRICAL TESTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
ELECTRICAL DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
POWER FLOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
TABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

© HOBART SERVICE 2019

F45701 Rev. B (0419) Page 2 of 35
 HMM20-1STD MIXER - SERVICE UPDATES

SERVICE UPDATES
SERVICE UPDATES PAGE

April 2019
• Updated TROUBLESHOOTING TABLE.
November 2018
• Released Service Manual

TIS DOCUMENT LIST - HMM20

SERVICE TAB
Document Title Document Type
HMM20-1STD MIXER Service Manual
TOUCH UP PAINTING Service Manual

SERVICE TAB (Multimedia)

Document Title Document Type
PLUGS AND RECEPTACLES SPECIFICATION SHEET Specification Sheet

Page 3 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - GENERAL

GENERAL
• VOM with measuring micro amp current tester.
INTRODUCTION Any VOM with minimum of CAT III 600V, CE
certified. Sensitivity of at least 20,000 ohms per
The HMM20 is a 20 quart mixer with a heavy duty, 1/2 volt can be used. In addition, meter leads must
HP motor and GearSafe™ transmission. It has three also be a minimum of CAT III 600V.
fixed speeds plus a stir speed and is equipped with a
digital timer. It has a removable, stainless steel bowl • Clamp on type amp meter with minimum of
guard and large, easy to reach controls. Standard NFPA-70E CAT III 600V, UL/CSA/TUV listed.
accessories include a 20 quart stainless steel bowl, 20 • Field service grounding kit.
quart beater, 20 quart whip, and 20 quart dough hook.
Special
SPECIFICATIONS • (2x) 1/4"-20 x 2" bolts, fully threaded, preferably
hardened, used as transmission cover jack bolts.
Motor • Puller set, part # 528347 or equivalent.
• 1/2 HP High Torque Motor.
• Torque wrench capable of measuring 470 inch-
Electrical lbs.
• 100-120/50/60/1 8.0 Amps.
• 200-240/50/60/1 5.0 Amps. ADDITIONAL RESOURCES
• UL Listed LUBRICATION MANUAL
Controls
• Magnetic contactor with thermal overload
protection.
• 20-minute digital timer is standard.
Transmission
• Gear-driven.
• Gears are constant mesh heat-treated hardened
alloy steel along with anti-friction ball bearings.

Gear Agitator RPM

First (Low) 40
Second (Intermediate) 75
Third (High) 137

Attachment Hub
• Front-mounted Hobart standard #12 taper
attachment hub.
• Use with Hobart #12 size attachments.
Dimensions
• 189 lbs. net; 204 lbs. domestic shipping.

TOOLS
Standard
• Standard set of hand tools.
• Metric set of hand tools.

F45701 Rev. B (0419) Page 4 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

REMOVAL AND REPLACEMENT OF PARTS

UPPER LID

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove screws from upper lid.

Fig. 2
3. Remove acorn nut and lock washer from
planetary shaft.
NOTE: Support planetary while removing acorn nut
and lock washer.

Fig. 1
2. Lift upper lid off of mixer.
3. Reverse procedure to replace.

PLANETARY

Fig. 3
Disconnect the electrical power to
the machine and follow lockout / 4. Remove planetary shaft lower key (1, Fig. 4).
tagout procedures. NOTE: Planetary shaft lower spacer (2, Fig. 4) may
1. Remove agitator, bowl, and bowl guard. fall out with key (1, Fig. 4). If so, retain spacer.

2. Remove rear splash guard by removing two

screws.
NOTE: One screw on either side.

Page 5 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

3. Drive agitator shaft out of planetary from top side

down.
NOTE: Replace agitator shaft nut so that nut and end
of agitator shaft are flush. This will protect agitator
shaft threads.

Fig. 4
5. Reverse procedure to replace.
NOTE: Torque acorn nut to 372-415 in-lbs. (Approx.
31-34 ft-lbs.)

AGITATOR SHAFT

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures. Fig. 6
1. Remove PLANETARY. 4. Remove pinion and key.
2. Remove agitator shaft nut and washer. NOTE: Pinion shoulder (4, Fig. 7) is oriented toward
bearing.
NOTE: Rounded side of key is oriented toward
bearing.
5. Drive upper planetary bearing (1, Fig. 7) from
planetary.
NOTE: Open / unsealed side of bearing faces up.
6. Pull off lower planetary bearing (2, Fig. 7)
NOTE: Open / unsealed side of bearing faces up.
7. Remove oil seal (3, Fig. 7)

Fig. 5

F45701 Rev. B (0419) Page 6 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

5. Pull internal gear downward.

6. Reverse procedure to replace.

CONTROL PANEL

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Peel back control panel overlay at corners.

Fig. 7
8. Reverse procedure to assemble.

Pack open bearings with FGL-2 lubricant upon

reassembly.

INTERNAL GEAR

Disconnect the electrical power to

Fig. 9
the machine and follow lockout /
tagout procedures. 2. Remove screws from control panel.
1. Remove agitator, bowl, and bowl guard. 3. Pull control panel and gasket away from mixer.
2. Remove splash guard by removing two screws 4. Disconnect speed shift switch cable (1, Fig. 10)
and gently pull down. and power board cable (2, Fig. 10) from control
panel.
3. Remove PLANETARY.
4. Remove bolts from internal gear.
NOTE: Support internal gear while removing last bolt.

Fig. 10
5. Reverse procedure to replace.
Fig. 8

Page 7 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

SHIFTER ASSEMBLY

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove CONTROL PANEL.
2. Remove shifter lever switch by removing screws
(1, Fig. 11).
NOTE: Disregard gear numbers printed in shifter
plate.
Fig. 12
2. Remove screws from attachment hub.

Fig. 11
3. Remove shifter lever by removing screws (2, Fig.
11).
4. Remove shifter lever from transmission case.
Fig. 13
NOTE: Ensure shifter lever is in first gear.
3. Remove attachment hub.
5. Reverse procedure to install.
NOTE: Do not over tighten shifter switch screws.
Paint is easily chipped during this procedure.
ATTACHMENT HUB REMOVAL NOTE: Use a rubber mallet to loosen attachment hub.

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove attachment hub ring.
NOTE: Attachment hub ring has two tabs on either
side that pass through notches in attachment hub. It
may be necessary to spin attachment hub ring and
align tabs with notches in order to remove.

F45701 Rev. B (0419) Page 8 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

TRANSMISSION DISASSEMBLY

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove UPPER LID.
2. Remove transmission bearings cap by removing
screws.
NOTE: Place a rag between motor and transmission
cover to prevent screws from falling into motor.

Fig. 14
4. Reverse procedure to install.

Ensure weep hole (1, Fig. 14) in attachment hub face

is oriented up.

ATTACHMENT HUB DISASSEMBLY

Fig. 16
3. Remove planetary shaft upper bearing cap by
Disconnect the electrical power to removing screws.
the machine and follow lockout /
tagout procedures.
1. Remove ATTACHMENT HUB.
2. Pull bevel gear assembly from attachment hub.

Fig. 17
Fig. 15 4. Remove transmission nuts and lock washers (1,
Fig. 18).
3. Reverse procedure to assemble.
NOTE: Ensure o-ring stays seated in attachment hub
when assembling.

Page 9 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

Fig. 20
Fig. 18
NOTE: All transmission cover bearings are slip fit in
5. Remove planetary shaft top nut and lock washer transmission cover.
(2, Fig. 18).
8. Remove upper shouldered spacer (1, Fig. 21).
6. Remove transmission cover screws.

Fig. 21
Fig. 19
9. Remove roller clutch spacer (2, Fig. 21).
7. Remove transmission cover using 1/4" x 20 bolts
10. Remove roller clutch assembly and bevel gear
(preferably hardened) as jack screws.
simultaneously.
NOTE: Alternate turning each jack screw 1-2
rotations each until transmission cover frees from
transmission shafts.
NOTE: Ensure front and back sides of transmission
cover raise evenly from transmission case.

F45701 Rev. B (0419) Page 10 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

Fig. 24
12. Remove third gear and bushing (2,3, Fig. 24).
13. Remove transmission shaft assembly (4, Fig.
24).
14. Remove worm gear shaft assembly.
NOTE: Gently turn motor fan to aid in worm wheel
Fig. 22 shaft assembly removal.
NOTE: Roller clutch assembly and bevel gear are
press fit on planetary shaft.
NOTE: Remove together so roller clutch assembly
does not fall apart.

Orientation of springs and rollers in roller clutch

assembly is critical.

Fig. 25
15. Remove PLANETARY.
16. Remove SHIFTER ASSEMBLY.
Fig. 23 17. Remove shifter rod nut.
11. Remove planetary shaft upper key (1, Fig. 24).

Page 11 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

Fig. 26 Fig. 28
18. Remove shifter rod (1, Fig. 27). 23. Press oil seal out of transmission case from
above.

TRANSMISSION ASSEMBLY

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Press oil seal into transmission case from
underneath.

Ensure cupped side of oil seal faces up.

Fig. 27
2. Replace snap ring.
19. Remove yoke assembly and clutch sleeve (2,
Fig. 27).
20. Remove ATTACHMENT HUB.
21. Remove planetary shaft upwards from beneath
transmission case.
NOTE: Planetary shaft lower spacer may fall out if not
previously removed. Retain spacer.
22. Remove snap ring.

Fig. 29
3. Press planetary shaft assembly into transmission
case from above.
4. Replace ATTACHMENT HUB.

F45701 Rev. B (0419) Page 12 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

5. Lower yoke assembly and clutch sleeve (2, Fig. 9. Replace transmission shaft assembly (4, Fig.
30) onto planetary shaft. 33).

Fig. 30 Fig. 33
6. Place shifter rod (1, Fig. 30) into yoke. 10. Replace third gear and bushing (2,3, Fig. 33).
7. Replace shifter rod nut and washer. NOTE: Third gear notches face down.
11. Replace planetary shaft upper key (1, Fig. 33).
12. Replace bevel gear and roller clutch assembly.

Orientation of springs and rollers in roller clutch

assembly is critical.

Fig. 31
8. Replace worm gear shaft assembly.
Fig. 34
NOTE: Shoulder of bevel gear faces down.
NOTE: Replace together so roller clutch assembly
does not fall apart.
NOTE: Bevel gear and roller clutch assembly are
press fit on planetary shaft. Attachment hub can be
used as a pressing sleeve.
NOTE: Place a rag between attachment hub and
roller clutch to prevent chipping paint. Shown without
a rag for clarity.

Fig. 32

Page 13 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

Fig. 37
18. Replace planetary shaft washer and top nut (2,
Fig. 38).

Fig. 35
13. Replace roller clutch spacer (2, Fig. 36) and
upper shouldered spacer (1, ).
NOTE: Shoulder of spacer faces up.

Fig. 38
19. Replace transmission shaft lock washers and
nuts (1, Fig. 38).
20. Replace planetary upper bearing retainer and
cap
Fig. 36
14. Replace transmission cover.
15. Replace PLANETARY.
16. Replace transmission cover.
17. Replace transmission cover screws.

F45701 Rev. B (0419) Page 14 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

MOTOR

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove UPPER LID.
2. Remove screws from rear head cover.

Fig. 39
21. Replace transmission shaft cap.

Fig. 41
3. Remove rear column cover.

Fig. 40
22. Replace UPPER LID.
23. Check for proper operation.

SHIFT FORK ASSEMBLY

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Disassemble TRANSMISSION.
NOTE: Remove only enough parts from transmission
to remove yoke assembly.

Fig. 42
4. Remove cable ties.
Page 15 of 35 F45701 Rev. B (0419)
 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

5. Disconnect motor lead wires. 8. Remove capacitor mounting plate.

9. Remove 40 MFD capacitor by loosening loop
clamp screw.

Fig. 43
6. Disconnect ground wire.
7. Remove screws securing capacitor mounting
plate.

Fig. 45
10. Discharge 500 MFD capacitor.
11. Disconnect 500 MFD capacitor leads.

Fig. 44
Fig. 46

F45701 Rev. B (0419) Page 16 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

12. Dismount power board from column by removing

screws. POWER BOARD

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove rear column cover.

Fig. 47
13. Position power board away from capacitor
mounting plate.
14. Remove motor mounting screws (1, Fig. 48).

Fig. 49
2. Remove power leads (1, Fig. 50) and motor leads
(2, Fig. 50) from bottom of power board.

Fig. 48
15. Pull motor away from transmission case.
16. Carefully draw motor leads and 40 MicroFD
capacitor out of column with motor.
17. Reverse procedure to install.
NOTE: Run 40 MicroFD capacitor down column
before replacing motor.
Fig. 50
3. Remove power board by loosening mounting
screws (3, Fig. 50).
4. Remove harnesses (1,2,3, Fig. 51) from top of
power board.
Page 17 of 35 F45701 Rev. B (0419)
 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

NOTE: Observe location of harnesses.

NOTE: It may be necessary to push power board up
toward top of column to disconnect.

Fig. 51
5. Reverse procedure to install.

BOWL IN SWITCH
Fig. 53
4. Disconnect bowl in micro switch (2, Fig. 54) from
power board.
Disconnect the electrical power to
the machine and follow lockout / NOTE: It may be necessary to loosen power board
tagout procedures. mounting screws and push power board up toward top
of column to disconnect.
1. Remove UPPER LID.
2. Remove rear head cover.

Fig. 54
5. Remove bowl in micro switch by removing
Fig. 52 screws.
3. Remove rear column cover.

F45701 Rev. B (0419) Page 18 of 35

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

NOTE: It may be necessary to loosen power board

mounting screws and push power board up toward top
of column to disconnect.

Fig. 57
Fig. 55 4. Remove control panel.
6. Reverse procedure to install.
7. Check for proper operation.

BOWL GUARD SWITCH

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove UPPER LID
2. Remove rear head cover.
Fig. 58
5. Remove jam nut from bowl guard switch.

Fig. 56
3. Disconnect bowl guard switch (1, Fig. 57) from
power board. Fig. 59

Page 19 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - REMOVAL AND REPLACEMENT OF PARTS

6. Unscrew bowl guard switch from outside and pull

switch through.
NOTE: It may be necessary to remove bowl safety
cover.
7. Reverse procedure to install.
8. Verify bowl guard switch function:
A. Machine operates when bowl guard is
closed.
B. Machine stops when bowl guard is opened.

SPEED SHIFT SWITCH

Fig. 61
Disconnect the electrical power to 3. Remove speed shift micro switch by removing
the machine and follow lockout / screws (2, Fig. 61).
tagout procedures.
4. Reverse procedure to install.
1. Remove control panel by removing screws.

Do not overtighten speed shift switch screws.

5. Check for proper operation.

Fig. 60
2. Disconnect speed shift micro switch from control
panel (1, Fig. 61).

F45701 Rev. B (0419) Page 20 of 35

 HMM20-1STD MIXER - SERVICE PROCEDURES AND ADJUSTMENTS

SERVICE PROCEDURES AND ADJUSTMENTS

BOWL GUARD TAB ADJUSTMENT BOWL GUARD SWITCH
ADJUSTMENT

Disconnect the electrical power to

the machine and follow lockout / Disconnect the electrical power to
tagout procedures. the machine and follow lockout /
Bowl guard shoes are properly adjusted when: tagout procedures.
• Up and down movement of bowl guard is no more 1. Remove control panel by removing screws.
than 2mm when guard is closed.
• Up and down movement of bowl guard is no more
than 3mm when guard is open.
• Left and right movement of bowl guard is no more
than 1mm when guard is closed.
1. Remove bowl guard.
2. Loosen Tab B screws.
NOTE: Tab B is attaches to the safety guard ring
holder.

Fig. 63
2. Loosen jam nut from bowl guard switch.

Fig. 62
3. Press Tab B completely inboard (towards Tabs
A and C).
4. Tighten Tab B screws.
5. Replace bowl guard.
Fig. 64
6. Open bowl guard enough to access Tabs A and
C. 3. Adjust height of switch to allow a 2-4mm gap
between switch and magnet.
7. Repeat above procedure for Tabs A and C until
bowl guard does not rattle and above
specifications are met.

Page 21 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - SERVICE PROCEDURES AND ADJUSTMENTS

Fig. 65 Fig. 67
4. Tighten jam nut. 4. Remove safety guard.
5. Reassemble in reverse order. 5. Replace bowl and agitator.
6. Check mixer for proper operation. 6. Loosen jam nut (1, Fig. 68).

BOWL TO BEATER CLEARANCE

ADJUSTMENT

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove agitator, bowl, and bowl guard.
2. Remove bowl safety cover by removing two
screws and gently pull down.

Fig. 68
7. Adjust bowl lift stop screw (2, Fig. 68) until bowl
to beater clearance of 0.054" - 0.115" is
achieved.
NOTE: Bowl to beater clearance should be conducted
with 20 quart beater.
8. Tighten jam nut.
9. Reassemble mixer.
10. Check for proper operation.
NOTE: If bowl lift no longer locks, perform BOWL
Fig. 66 LOCK ADJUSTMENT.
3. Remove front column cover.

F45701 Rev. B (0419) Page 22 of 35

 HMM20-1STD MIXER - SERVICE PROCEDURES AND ADJUSTMENTS

3. Adjust compression spring tension.

BOWL LOCK ADJUSTMENT
A. If bowl lock is too loose, turn bowl lock nut
(2, Fig. 70) CCW (as seen from above) until
proper locking action is achieved.
B. If bowl lock is too tight, turn bowl lock nut
Disconnect the electrical power to CW (as seen from above) until proper
the machine and follow lockout / locking action is achieved.
tagout procedures.
4. Tighten jam nut.
1. Remove rear column cover.
5. Replace rear column cover.

BOWL IN SWITCH ADJUSTMENT

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
Bowl in switch is properly adjusted when:
• Switch actuator is always in contact with bowl
switch bushing.
NOTE: Bowl switch bushing pin should be inset
approximately 2-4mm from surface of housing (where
bowl contacts bushing pin).
• Switch is un-actuated when bowl is removed.
• Switch is actuated when bowl is in place.
• Switch actuator does not deform or overtravel
when bowl is in place.
1. Remove rear column cover.
Fig. 69
2. Loosen jam nut (1, Fig. 70).

Fig. 70
Page 23 of 35 F45701 Rev. B (0419)
 HMM20-1STD MIXER - SERVICE PROCEDURES AND ADJUSTMENTS

Fig. 73
5. Adjust bowl in switch so that actuator arm
actuates switch when bowl is installed and bowl
lift is raised.
Fig. 71
NOTE: Verify actuator arm does not bend or deform
2. Verify bowl switch bushing depth is between during actuation.
2-4mm.
6. Replace in reverse order.
A. If bushing is too shallow, turn bushing
counterclockwise. 7. Check mixer for proper operation.
B. If bushing is too deep, turn bushing
clockwise.
SPEED SHIFT SWITCH
ADJUSTMENT

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove control panel.

Fig. 72
3. Install bowl.
4. Loosen bowl in switch screws.

F45701 Rev. B (0419) Page 24 of 35

 HMM20-1STD MIXER - SERVICE PROCEDURES AND ADJUSTMENTS

MOTOR CENTRIFUGAL SWITCH

ADJUSTMENT

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Remove UPPER LID.
2. Remove rear head cover.

Fig. 74
2. Place speed selector in first speed.
3. Loosen speed shift switch screws.

Fig. 76
3. Remove screw and washer from motor fan.

Fig. 75
4. Adjust switch so that actuation occurs between
grooves in shifter, but actuator arm does not
bend or deform.
NOTE: Verify switch fully un-actuates when actuator
arm settles into grooves in shifter.
5. Tighten speed shift switch screws.
6. Replace in reverse order.
7. Check mixer for proper operation.
Fig. 77
4. Remove motor fan by loosening set screws.
5. Set governor switch as close to governor switch
plate as possible.

Page 25 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - SERVICE PROCEDURES AND ADJUSTMENTS

Fig. 78
6. Press fan onto shaft until fully seated against
governor switch.
Fig. 79
7. Tighten set screws.
3. Replace shift fork.
NOTE: Ensure one set screw is tightened against the
flat of motor shaft. 4. Assemble transmission. Refer to
TRANSMISSION ASSEMBLY.
8. Replace remaining parts in reverse order.
5. Check mixer for proper operation.
9. Check mixer for proper operation.

SHIFT FORK PLUNGERS

ADJUSTMENT

Disconnect the electrical power to

the machine and follow lockout /
tagout procedures.
1. Disassemble TRANSMISSION.
NOTE: Remove only enough parts from transmission
to remove shift fork.
2. Set lock screws flush with shift fork.

F45701 Rev. B (0419) Page 26 of 35

 HMM20-1STD MIXER - ELECTRICAL OPERATION

ELECTRICAL OPERATION
COMPONENT FUNCTION
Centrifugal Start Removes power from start windings when motor reaches operating speed.
Switch . . . . . . . . . . . . . . . .
Bowl In Switch . . . . . . . . Ensures the bowl is fully inserted into bowl support and bowl support is fully raised before
mixer will run.
Bowl Guard Switch . . . Prevents operation of agitator and attachment hub when bowl guard is open.
Speed Shift Switch . . . When operated, turns motor off to allow smooth shifting between gears.
Start Capacitor . . . . . . . The capacitor shifts electrical phase between the motor start winding and run winding so
the motor will start in the proper direction.
Run Capacitor . . . . . . . . Creates a rotating magnetic field to improve performance of motor operation while
running.
Motor . . . . . . . . . . . . . . . . . Drives transmission.
Timer Control Allows time input and start and stop function. Also controls power board operation.
Panel . . . . . . . . . . . . . . . . .
Power Board . . . . . . . . . . Receives input from Timer and directly controls power to motor.

ELECTRICAL TESTS

CERTAIN PROCEDURES IN THIS SECTION REQUIRE ELECTRICAL TEST OR MEASUREMENTS WHILE

POWER IS APPLIED TO THE MACHINE. EXERCISE EXTREME CAUTION AT ALL TIMES. IF TEST POINTS
ARE NOT EASILY ACCESSIBLE, DISCONNECT POWER AND FOLLOW LOCKOUT / TAGOUT
PROCEDURES, ATTACH TEST EQUIPMENT AND REAPPLY POWER TO TEST.

Page 27 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - ELECTRICAL OPERATION

TIMER CONTROL VOLTAGE TEST

Fig. 80

F45701 Rev. B (0419) Page 28 of 35

HMM20-1STD MIXER - ELECTRICAL OPERATION

POWER BOARD VOLTAGE TEST

Fig. 81

Page 29 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - ELECTRICAL OPERATION

ELECTRICAL DIAGRAMS

CONNECTION DIAGRAM

Fig. 82
F45701 Rev. B (0419) Page 30 of 35
HMM20-1STD MIXER - ELECTRICAL OPERATION

SCHEMATIC

Fig. 83

Page 31 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - TROUBLESHOOTING

TROUBLESHOOTING
POWER FLOW

First Speed
Clutch sleeve is in neutral / low speed position. Roller clutch (low speed gear) is driven.

Fig. 84

Second Speed
Clutch sleeve is in down / second speed position and engages second gear.

F45701 Rev. B (0419) Page 32 of 35

 HMM20-1STD MIXER - TROUBLESHOOTING

Fig. 85

Third Speed
Clutch sleeve is in up / third speed position and engages third gear.

Page 33 of 35 F45701 Rev. B (0419)

 HMM20-1STD MIXER - TROUBLESHOOTING

Fig. 86

TABLE

SYMPTOM POSSIBLE CAUSES

1. Worn or damaged gears.
2. Improperly meshed gears.
Noise in transmission.
3. Worn or broken keys.
4. Worn bearings.

F45701 Rev. B (0419) Page 34 of 35

 HMM20-1STD MIXER - TROUBLESHOOTING

SYMPTOM POSSIBLE CAUSES

1. Key sheared.
A. Worm Gear - 5T
B. Brass Gear - 26T
Planetary does not turn in any speed.
C. Gear - 32T
D. Planetary
2. Shaft broken.
Agitator will not turn, planetary does turn. 1. Key sheared at pinion gear on agitator shaft.
1. Key sheared.
Attachment drive does not turn.
A. Clutch Drive Sleeve.
1. Lower Seal.
Grease leaking from planetary.
2. Gear Case overfilled.
1. O-ring in attachment hub.
Grease leaking from attachment hub.
2. Gear Case overfilled.
1. O-ring on shifter handle.
Grease leaking from shifter assembly
2. Gear Case overfilled.
1. Start capacitor.
Will not run, but motor hums. 2. Centrifugal start switch.
3. Motor.
1. No voltage to machine.
2. Wiring harness connections loose or damaged.
Will not run, no Control Panel Display.
3. Power Board.
4. Control Panel.
1. Bowl Guard Switch.
2. Bowl Switch.
3. Wiring harness connections loose or damaged.
Will not run, Control Panel has Display.
4. Speed Shift Switch.
5. Power Board.
6. Control Panel.
1. Speed Shift Switch.
Display reads "OP".
2. Control Panel.
Mixer will not stay running when On/Off button
1. Control Panel.
is released.

Page 35 of 35 F45701 Rev. B (0419)