OVER THE RANGE MICROWAVE OVEN
SERVICE MANUAL
Models GLBM188HB
GLBM188HS
PLBMV188HC
This service manual is intended for use by persons having electrical and mechanical training
and a level of knowledge of these subjects generally considered acceptable in the appliance
repair trade. Electrolux Home Products cannot be responsible, nor assume any liability, for
injury or damage of any kind arising from the use of this manual.
! ATTENTION !
Part # 316439268Publication # 5995526885 October 2008
CONTENTS
SERVICING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
CHAPTER 1
WARNING TO SERVICE PERSONNEL. . . . . . . . . . . . . . . . . . . . . 4
[1] Before Servicing
[2] When Testing Is Completed
[3] After Repairing
CHAPTER 2.
MICROWAVE MEASUREMENT PROCEDURE. . . . . . . . . . . . . . 5
[1] Requirements
[2] Preparation For Testing
[3] Leakage Test
CHAPTER 3.
FOREWORD AND WARNING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
[1] Foreword
[2] Warning
[3] Danger
CHAPTER 4.
PRODUCT DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
[1]Specications
CHAPTER 5.
GENERAL INFORMATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
[1] Grounding Instructions pg. 8
[2] Oven Diagram pg. 8
[3] Control Panel pg. 9
CHAPTER 6.
OPERATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
[1] Description Of Operating Sequence
Off Condition pg. 10
Cooking Condition pg. 10
Power Level pg. 10
Power Output Reduction pg. 10
Ventilation Methods pg. 10
Sensor Cooking Condition pg. 11
Cooking Sequence pg. 11
[2] Oven Schematic pg. 12
[3] Description And Function Of Components
Door Open Mechanism pg. 13
Door Sensing Switch pg. 13
Secondary Interlock Switch pg. 13
Monitor Switch pg. 13
Cavity Thermal Cut Out pg. 13
Turntable Motor pg. 13
Cooling Fan Motor pg. 13
Hood Fan Motor pg. 13
Thermostat [60° C ON] pg. 13
Antenna [Stirrer] Motor pg. 13
Cook Top Lamp pg. 13
CHAPTER 7.
TROUBLESHOOTING GUIDE. . . . . . . . . . . . . . . . . . . . . . . . . . 14
[1] Troubleshooting Chart pg. 15
CHAPTER 8.
TEST PROCEDURES. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 16
[1] Magnetron Assembly Test pg. 16
[2] Power Transformer Test pg. 16
[3]HighVoltageRectierTest pg.16
[4] High Voltage Capacitor Test pg. 17
[5] Thermal Cutout and Temperature Fuse Test pg. 17
[6] Secondary Interlock Switch Test pg. 17
[7] Primary Interlock System Test pg. 18
[8] Monitor Switch Test pg. 18
[9] Blown Monitor Fuse Test pg. 18
[10] Hood Thermostat Test pg. 19
[11] Hood Fan Motor Test pg. 19
[12] Touch Control Panel Assembly Test pg. 19
[13] Key Unit Test pg. 21
[14] Relay Test pg. 21
[15] Open PWB Fuse Procedures pg. 22
[16] Humidity Sensor Test pg. 22
[17] Noise Filter Test pg. 24
CHAPTER 9.
TOUCH CONTROL PANEL ASSEMBLY. . . . . . . .. . . . . . . 25
[1] Outline Of Touch Control Panel Assy. pg. 25
[2] Humidity Sensor Circuit pg. 26
[3] Servicing For Touch
Control Panel pg. 27
CHAPTER 10.
PRECAUTIONS FOR USING LEADFREE SOLDER . . . . . . . . . . . 28
CHAPTER 11.
COMPONENT REPLACEMENT AND
ADJUSTMENT PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
[1] Warnings pg. 29
[2] Adjustments With Oven Installed pg. 29
[3] Removal Of Oven From Wall pg. 29
[4] Hood Louver Removal pg. 30
[5] Outer Case Removal pg. 30
[6] Power Transformer Removal pg. 30
[7] Hood Fan Motor, Hood Duct
Oven Lamp Socket, and
Humidity Sensor Removal pg. 30
[8] Magnetron Removal pg. 31
[9]HighVoltageRectierand
Capacitor Removal pg. 31
[10] Hood Fan Thermostat Removal pg. 32
[11] Cooling Fan Removal pg. 32
[12] Turntable Motor Removal pg. 33
[13] Antenna (Stirrer) Motor Removal pg. 33
[14] Stirrer Cover and Antenna Installation pg. 33
[15] Oven Lamp Removal pg. 33
[16] Positive Lock Connector Removal pg. 33
[17] Right Panel Assembly and Power
Unit Removal pg. 33
[18] Door Switch Removal pg. 34
[19] Door Switch Adjustment pg. 34
[20] Door Replacement pg. 34
[21] Door Disassembly pg. 35
[22] Cooktop Lamp Socket Removal pg. 36
CHAPTER 12.
CIRCUIT DIAGRAMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
[1] Pictorial Diagram pg. 37
[2] Power Unit Circuit pg. 38
[3] Keypad Unit and Display Circuit pg. 39
[4] Printed Wiring Board (PWB) pg. 40
PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
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PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID
POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE
ENERGY
(a) Do not operate or allow the oven to be operated with the door open.
(b) Make the following safety checks on all ovens to be serviced before activating the magnetron or other
microwave source, and make repairs as necessary: (1) interlock operation, (2) proper door closing, (3)
seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and
latches, (5) evidence of dropping or abuse.
(c) Before turning on microwave power for any service test or inspection within the microwave generating
compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,
integrity, and connections.
(d) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave
generation and transmission systems shall be repaired, replaced, or adjusted by procedures described
in this manual before the oven is released to the owner.
(e) A microwave leakage check to verify compliance with the Federal Performance Standard should be
performed on each oven prior to release to the owner.
Before servicing an operative unit, perform a microwave emission check as per the Microwave
Measurement Procedure outlined in this service manual.
If microwave emissions level is in excess of the specified limit, contact ELECTROLUX HOME
PRODUCTS, INC. immediately.
If the unit operates with the door open, service person should 1) tell the user not to operate the
oven and 2) contact ELECTROLUX HOME PRODUCTS, INC. and Food and Drug Administration's
Center for Devices and Radiological Health immediately.
Service personnel should inform ELECTROLUX HOME PRODUCTS, INC. of any certified unit
found with emissions in excess of 4mW/cm . The owner of the unit should be instructed not to use
the unit until the oven has been brought into compliance.
BEFORE SERVICING
2
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CHAPTER 1. WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts may result in a severe, possibly
fatal, electrical shock.
(Example)
High Voltage Capacitor, High Voltage Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..
Read the Service Manual carefully and follow all instructions.
[1] Before Servicing
1. Disconnect the power supply cord , and then remove outer
case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
WARNING: RISK OF ELECTRIC SHOCK. DISCHARGE THE HIGH-
VOLTAGE CAPACITOR BEFORE SERVICING.
The high-voltage capacitor remains charged about 60 seconds after
the oven has been switched off. Wait for 60 seconds and then shortcircuit the connection of the high-voltage capacitor (that is the connecting lead of the high-voltage rectifier) against the chassis with the use
of an insulated screwdriver.
Whenever troubleshooting is performed the power supply must be
disconnected. It may, in some cases, be necessary to connect the
power supply after the outer case has been removed, in this event,
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5) Ensure that these leads remain isolated from other components
and oven chassis by using insulation tape.
6) After that procedure, reconnect the power supply cord.
[2] When the testing is completed,
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.
[3] After repairing
1. Reconnect all leads removed from components during testing.
2. Reinstall the outer case (cabinet).
3. Reconnect the power supply cord after the outer case is installed.
4. Run the oven and check all functions.
Microwave ovens should not be run empty. To test for the presence of
microwave energy within a cavity, place a cup of cold water on the
oven turntable, close the door and set the power to HIGH and set the
microwave timer for two (2) minutes. When the two minutes has
elapsed (timer at zero) carefully check that the water is now hot. If the
water remains cold carry out Before Servicing procedure and reexamine the connections to the component being tested.
When all service work is completed and the oven is fully assembled,
the microwave power output should be checked and microwave leakage test should be carried out.
Don't Touch !
Danger High Voltage
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CHAPTER 2. MICROWAVE MEASUREMENT PROCEDURE
[1] Requirements:
1. Microwave leakage limit (Power density limit):
Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven should not exceed 1mW/
cm2 at any point 5cm or more from the external surface of the oven, measured prior to acquisition by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm
2
at any point 5cm or more from the external surface of the oven.
2. Safety interlock switches:
Primary interlock relay and door sensing switch shall prevent microwave radiation emission in excess of the requirement as above mentioned.
Secondary interlock switch shall prevent microwave radiation emission in excess of 5 mW/cm
2
at any point 5cm or more from the external surface
of the oven.
[2] Preparation for testing:
Before beginning the actual measurement of leakage, proceed as follows:
1. Make sure that the actual instrument is operating normally as specified in its instruction booklet.
Important:
Survey instruments that comply with the requirement for instrumentation as prescribed by the performance standard for microwave ovens, 21 CFR
1030.10(c)(3)(i), must be used for testing.
2. Place the oven tray in the oven cavity.
3. Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5°C (68°F) in the center of the oven cavity.
The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-1/2 in.) and made of an electrically
nonconductive material such as glass or plastic.
The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any leakage is measured accurately.
4. Set the cooking control on Full Power Cooking Mode.
5. Close the door and select a cook cycle of several minutes. If the water begins to boil before the survey is completed, replace it with 275 ml of cool
water.
[3] Leakage test:
Closed-door leakage test (microwave measurement):
1. Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door and the body of the oven.
2. Move the probe slowly, not faster than 1 in./sec. (2.5 cm/sec.) along the gap, watching for the maximum indication on the meter.
3. Check for leakage at the door screen, sheet metal seams and other accessible positions where the continuity of the metal has been breached (eg.,
around the switches, indicator, and vents).
While testing for leakage around the door, pull the door away from the front of the oven as far as is permitted by the closed latch assembly.
4. Measure carefully at the point of highest leakage and make sure that the highest leakage is no greater than 4mW/cm
2
.
NOTE: After servicing, record data on service invoice and microwave leakage report.
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CHAPTER 3. FOREWORD AND WARNING
[1] FOREWORD
This Manual has been prepared to provide Electrolux Home Products Service Personnel with Operation and Service Information for the ELECTROLUX OVER THE RANGE MICROWAVE OVENS, PLBMV188HC, GLBM188HS and GLBM188HB.
It is recommended that service personnel carefully study the entire text of this manual so that they will be qualified to render satisfactory customer
service.
Check the interlock switches and the door seal carefully. Special attention should be given to avoid electrical shock and microwave radiation hazard.
[2] WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is not any other visible damage with the oven.
Servicing and repair work must be carried out only by trained service personnel.
[3] DANGER
Certain initial parts are intentionally not grounded and present a risk of electrical shock only during servicing. Service personnel - Do not
contact the following parts while the appliance is energized;
High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness;
If provided, Vent Hood, Fan assembly, Cooling Fan Motor.
All the parts marked “ “on parts list are used at voltages more than 250V.
Removal of the outer wrap gives access to voltage above 250V.
All the parts marked “*“on parts list may cause undue microwave exposure, by themselves, or when they are damaged, loosened or removed.
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CHAPTER 4. PRODUCT DESCRIPTION
[1] SPECIFICATIONS
ITEM DESCRIPTION
Power Requirements
120 Volts / 14.3 Amperes
60 Hertz
Single phase, 3 wire grounded
Power Output
1000 W nominal of RF microwave energy (IEC Test procedure)
Operating frequency of 2450 MHz
Case Dimensions
Width 29 15/16"
Height 17 1/16"
Depth 18 15/32" (Not including the door handle)
Cooking Cavity Dimensions
(1.8 Cubic feet)
Width 22 1/2" NOTE: Internal capacity is calculated by measuring maximum width, depth and height.
Height 10 1/16" Actual capacity for holding food is less.
Depth 14 31/32"
Hood lamp 20W x 2 incandescent
Hood fan Approx. 300 C.F.M.
Control Complement
Touch Control System
Clock (1:00 - 12:59)
Timer (0 - 99 minutes 99 seconds)
Microwave Power for Variable Cooking
Repetition Rate;
Full power throughout the cooking time
Approx. 90% of FULL Power
Approx. 80% of FULL Power
Approx. 70% of FULL Power
Approx. 60% of FULL Power
Approx. 50% of FULL Power
Approx. 40% of FULL Power
Approx. 30% of FULL Power
Approx. 20% of FULL Power
Approx. 10% of FULL Power
No power throughout the cooking time
Light Hi/Lo/Off pad
Vent Hi/Lo/Off pad
Sensor Cook pad
Sensor Reheat pad
Auto Cook pad
Auto Defrost pad
Timer on-off pad
User Pref pad
Keep Warm pad
Melt Soften pad
Snacks Menu pad
Popcorn pad
Veggies pad
Baked Potato pad
Power level pad
Turntable on-off pad
STOP/Clear pad
START/Enter pad
Add 30 Sec pad
Number pads
(Quick start pads)
Oven Cavity Light 20W x 1 incandescent light bulb
Safety Standard
UL Listed.
FCC Authorized
DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J
Weight Approx. 61 lbs.
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CHAPTER 5. GENERAL INFORMATION
[1] GROUNDING INSTRUCTIONS
This oven is equipped with a three prong grounding plug. It must be plugged into a wall receptacle that is properly installed and grounded in accordance with the National Electrical Code and local codes and ordinances.
In the event of an electrical short circuit, grounding reduces the risk of electric shock by providing an escape wire for the electric current.
WARNING:
Improper use of the grounding plug can result in a risk of electric shock.
Electrical Requirements
The oven is equipped with a 3-prong grounding plug. DO NOT UNDER ANY CIRCUMSTANCES CUT OR REMOVE THE GROUNDING PIN FROM
THE PLUG.
The power supply cord and plug must be connected to a separate 120 Volt AC, 60 Hz, 15 Amp. or more dedicated line, using a grounded receptacle.
The receptacle should be located inside the cabinet directly above the Microwave Oven/Hood system mounting location.
[2] OVEN DIAGRAM
1. OVEN
1. Microwave oven door with see-through window
2. Door hinges
3. Waveguide cover: DO NOT REMOVE.
4. Turntable motor shaft
5. Microwave oven light
It will light when microwave oven is operating or door is open.
6. Rack holders
7. Safety door latches
The microwave oven will not operate unless the door is securely
closed.
8. Handle
9. Light Hi/Lo/Off pad
Press the Light Hi/Lo/Off pad once for high, twice for low and three
times to turn off the light.
10.Vent Hi/Lo/Off pad
Press the Vent Hi/Lo/Off pad once for high speed, twice for low
speed and three times to turn off the fun.
11.Control panel
12.Time display: Digital display, 99 minutes, 99 seconds
13.Ventilation openings
14.Removable turntable
The turntable will rotate clockwise or counterclockwise.
Only remove for cleaning.
15.Removable turntable support
First, carefully place the turntable support in the motor shaft in the
center of the microwave oven floor. Then, place the turntable on the
turntable support securely.
16.Rack for 2-level cooking/ reheating
17.Light cover
18.Grease filters
19.Menu label
3-Pronged Plug
Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
BOTTOM VIEW
FRONT VIEW
(Front of microwave oven)
(Rear of microwave oven)
13
8
7
1
2
6
6
4
3
5 7
19
16
14
11
9 10
17
18
12
15
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5 – 2
[3] CONTROL PANEL
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CHAPTER 6. OPERATION
[1] DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during oven operation.
1. OFF CONDITION
Closing the door activates the door sensing switch and secondary
interlock switch. (In this condition, the monitor switch contacts are
opened.)
When oven is plugged in, 120 volts A.C. is supplied to the control unit.
(Figure O-1).
1. The display will show “ENJOY YOUR OVEN PRESS CLEAR”.
To set any program or set the clock, you must first touch the Clear
Off pad. The display will clear, and “ : " will appear
2. COOKING CONDITION
Program desired cooking time touching the NUMBER pads. When the
START pad is touched, the following operations occur:
1. The contacts of relays are closed and components connected to
the relays are turned on as follows.
(For details, refer to Figure O-2)
2. 120 volts A.C. is supplied to the primary winding of the power transformer and is converted to about 3.3 volts A.C. output on the filament winding, and approximately 2000 volts A.C. on the high
voltage winding.
3. The filament winding voltage heats the magnetron filament and the
H.V. winding voltage is sent to a voltage doubler circuit.
4. The microwave energy produced by the magnetron is channelled
through the waveguide into the cavity feed box, and then into the
cavity where the food is placed to be cooked.
5. Upon completion of the cooking time, the power transformer, oven
lamp, etc. are turned off, and the generation of microwave energy
is stopped. The oven will revert to the OFF condition.
6. When the door is opened during a cook cycle, monitor switch, door
sensing switch, secondary interlock switch, and primary interlock
relay are activated with the following results. The circuits to the
antenna motor, the cooling fan motor, the turntable motor, and the
high voltage components are de-energized, and the digital read-out
displays the time still remaining in the cook cycle when the door
was opened.
7. The monitor switch is electrically monitoring the operation of the
secondary interlock switch and door sensing switch is mechanically
associated with the door so that it will function in the following
sequence.
1) When the door opens from a closed position, the primary inter-
lock relay, door sensing switch and secondary interlock switch
open their contacts, and then the monitor switch contacts close.
2) When the door is closed from the open position, the monitor
switch contacts open first. Then the contacts of the secondary
interlock switch and door sensing switch close. And contacts of
the relay (RY1) open.
If the secondary interlock switch and primary interlock relay (RY2)
fail with the contacts closed when the door is opened, the closing of
the monitor switch contacts will form a short circuit through the
monitor fuse, secondary interlock switch, relay (RY1) and primary
interlock relay (RY2), causing the monitor fuse to blow.
3. POWER LEVEL P-0 to P-90 COOKING
When Variable Cooking Power is programmed, the 120 volts A.C. is
supplied to the power transformer intermittently through the contacts of
relay (RY2) which is operated by the control unit within an interval sec-
ond time base. Microwave power operation is as follows:
NOTE: The ON/OFF time ratio does not correspond with the percent-
age of microwave power, because Approx. 2 seconds are
needed for heating of the magnetron filament.
4. POWER OUTPUT REDUCTION
If the oven is set for over 40 minutes at 80%, 90% or 100% power
level, after the first 40 minutes the power level will automatically adjust
itself to 70% power to avoid overcooking.
5. VENTILATION METHODS HOT AIR EXHAUST
1. VERTICAL VENTING
For this venting method, hot air rising from the conventional range
below is drawn in by the hood fan motor through the grease filters
at the right and left sides of the base cover, up through the right and
left sides of the oven cavity, then discharged vertically at rear center top of the oven, into the customer's vent system.
RELAY CONNECTED COMPONENTS
RY1 Oven lamp / Fan motor / Antenna motor
RY2 Power transformer
RY3 Turntable motor
VARI-MODE ON TIME OFF TIME
100% power 32 sec. 0 sec.
Approx. 90% power 30 sec. 2 sec.
Approx. 80% power 26 sec. 6 sec.
Approx. 70% power 24 sec. 8 sec.
Approx. 60% power 22 sec. 10 sec.
Approx. 50% power 18 sec. 14 sec.
Approx. 40% power 16 sec. 16 sec.
Approx. 30% power 12 sec. 20 sec.
Approx. 20% power 8 sec. 24 sec.
Approx. 10% power 6 sec. 26 sec.
0% power 0 sec. 32 sec.
HOOD FANMOTOR
AIR FLOW
HOOD
INTAKE
DUCT
TO DUCT
TO DUCT
GREASE
FILTER
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2. HORIZONTAL VENTING
The air handing is the same as VERTICAL VENTING except that
the final air discharge is directed horizontally out from the top rear
of the oven into the customer's vent system.
3. RE-CIRCULATION (INSIDE VENTING)
The air handing is the same as VERTICAL VENTING except that
the final air discharge is directed horizontally through the upper
front of the oven into the kitchen. In this case, the charcoal filter
must be used which have already been installed in the oven.
6. SENSOR COOKING CONDITION
Using the SENSOR function, food is cooked without figuring time,
power level or quantity. When the oven senses enough steam from the
food, it relays the information to its microprocessor which will calculate
the remaining cooking time and power level needed for best results.
When the food is cooked, water vapor is developed. the sensor
“senses” the vapor and its resistance increase gradually. When the
resistance reaches the value set according to the menu, supplementary cooking is started. The time of supplementary cooking is determined by experiment with each food category and inputted into the
LSI. An example of how sensor works: (Potatoes)
1. Potatoes at room temperature. Vapor is emitted very slowly.
2. Heat Potatoes. Moisture and humidity is emitted very rapidly. You
can smell the aroma as it cooks.
6.1. Cooking Sequence.
1. Operate the oven in sensor cooking mode by referring to the operation manual.
NOTE: The oven should not be operated on Sensor Cooking immedi-
ately after plugging in the unit. Wait two minutes before cooking on Sensor Cooking.
2. The coil of shut-off relays (RY1 and RY3) are energized, the oven
lamp, turntable motor and cooling fan motor are turned on, but the
power transformer is not turned on.
3. After about 32 seconds, the relay (RY2) is energized.
The power transformer is turned on, microwave energy is produced
and first stage is started.
The 32 seconds is the cooling time required to remove any vapor
from the oven cavity and sensor.
NOTE: During this first stage, do not open the door or touch Clear Off
pad.
4. When the sensor detects the vapor emitted from the food, the display switches over to the remaining cooking time and the timer
counts down to zero.
At this time, the door may be opened to stir food, turn it or season,
etc.
5. When the timer reaches zero, an audible signal sounds.The shutoff relay (RY1 and RY3) and relay (RY2) are generalized and the
power transformer, oven lamp, etc. are turned off.
6. Opening the door or touching the STOP CLEAR pad, the time of
day will reappear on the display and the oven will revert to an OFF
condition.
HOOD FANMOTOR
AIR FLOW
HOOD
INTAKE
DUCT
TO DUCT
GREASE
FILTER
HOOD FANMOTOR
AIR FLOW
HOODEXHAUST
LOUVER
CHARCOAL
FILTER
HOOD
INTAKE
DUCT
M
IC R OW AV E
MICROWAVE
HUMIDITY SENSOR
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[2] OVEN SCHEMATIC
Figure O-1. Oven Schematic-Off Condition
Figure O-2. Oven Schematic-Cooking Condition
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED
2. CLOCK APPEARS ON DISPLAY
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
2. COOKING TIME PROGRAMMED.
3. VARIABLE COOKING CONTROL "P-HI".
4. START PAD TOUCHED.
NOTE: " " indicates components with potentials above 250
V
BLK
RED
B
LK
B
RN
MAGNETRON
TEMP.FUSE
WHT
2
3
6 3 2 4 5 1
RY5
C1
HOOD FAN
MOTOR
WHT
RY6
RY7
BLK
WHT
WHT
WHT
BRN
WHT
WHT
N. O.
OVEN
LAMP
RELAY
COM.
GRY
GRY
GRY
GRY
CONTROL
UNIT
DOOR UNIT
WHT
ANTENNA
MOTOR
YLW
WHT
YLW
RED
N.C
.
RED
RED
RED
WHT
WHT
E1
D40
20W
20W
E2
RED
GRN
DOOR SENSING
SWITCH
WHT
RY1
BRN
RE
D
RE
D
A1
T1
VRS1
RY8
A5
A3
B3
C7
B1
C5
C3
HUMIDITY SENSOR
F3
F2
F1
BLK
PRIMARY
INTERLOCK
RELAY
LOW VOLTAGE
TRANSFORMER
RY2
COM.
N.O.
RE
D
R
E
D
BLK
B
LK
B
LK
BRN
RY3
TURNTABLE
MOTOR
RELAY
C9
1
1
1
1
6
12
CN-L
CN-J
CN-G
11
11
FAN
MOTOR
WHT
YLW
YLW
GRY
WHT
MONITOR
SWITCH
WHT
GRY
SECONDARY INTERLOCK
SWITCH
OVEN
LAMP
20W
TURNTABLE
MOTOR
TTM
FM
ATM
OL
CL
CL
HM
COM.
HIGH
VOLTAGE
RECTIFIER
HIGH
VOLTAGE
CAPACITOR
0.94uF
2300VAC
POWER
TRANSFORMER
NOTES:
1. Circuits subject to change without notice
2. The neutral wire(White or Gray wire) must be connected to the prescribed tab terminal of the lamp socket.
3. Only certain models use the humidity sensor.
4. The neutral wire(White/Gray wire) must be connected to the winding end tab terminal of the power transformer
primary winding.
5. Only PLBMZ189HC has the earth wire.
MAGNETRON
POWER UNIT
145ºC
60ºC
120ºC
150ºC
OVEN THERMAL
CUT OUT
HOOD FAN
THERMOSTAT
High
Low
COOK
TOP
LAMP
N.O.
*NOTE 2
*NOTE 3
*NOTE 2
*NOTE 5
*NOTE 4
GRN
CN-M
CN-N
CN-D
GND
120V AC
60Hz
COM
N.O.
RED
YLW
BLK BLK
PPL
BLK
WHT
WHT
NOISE SUPRESSION COIL 1.0mH
LINE BYPASS CAPACITOR
3300pF 250V
FUSE
20A
LINE BYPASS CAPACITOR
3300pF 250V
NOISE FILTER UNIT
RED
BLK
GRY
ORG
SWITCH
UNIT
1
BLK
RED
B
LK
B
RN
MAGNETRON
TEMP.FUSE
WHT
2
3
6 3 2 4 5 1
RY5
C1
HOOD FAN
MOTOR
WHT
RY6
RY7
BLK
WHT
WHT
WHT
BRN
WHT
WHT
N. O.
OVEN
LAMP
RELAY
COM.
GRY
GRY
GRY
GRY
CONTROL
UNIT
DOOR UNIT
WHT
ANTENNA
MOTOR
YLW
WHT
YLW
RED
N.C.
RED
RED
RED
WHT
WHT
E1
D40
20W
20W
E2
RED
GRN
DOOR SENSING
SWITCH
WHT
RY1
BRN
RED
RE
D
A1
T1
VRS1
RY8
A5
A3
B3
C7
B1
C5
C3
HUMIDITY SENSOR
F3
F2
F1
BLK
PRIMARY
INTERLOCK
RELAY
LOW VOLTAGE
TRANSFORMER
RY2
COM.
N.O.
RE
D
RE
D
BLK
BLK
B
LK
BRN
RY3
TURNTABLE
MOTOR
RELAY
C9
1
1
1
1
6
12
CN-L
CN-J
CN-G
11
11
FAN
MOTOR
WHT
YLW
YLW
GRY
WHT
MONITOR
SWITCH
WHT
GRY
SECONDARY INTERLOCK
SWITCH
OVEN
LAMP
20W
TURNTABLE
MOTOR
TTM
FM
ATM
OL
CL
CL
HM
COM.
HIGH
VOLTAGE
RECTIFIER
HIGH
VOLTAGE
CAPACITOR
0.94uF
2300VAC
POWER
TRANSFORMER
NOTES:
1. Circuits subject to change without notice
2. The neutral wire(White or Gray wire) must be connected to the prescribed tab terminal of the lamp socket.
3. Only certain models use the humidity sensor.
4. The neutral wire(White/Gray wire) must be connected to the winding end tab terminal of the power transformer
primary winding.
5. Only PLBMZ189HC has the earth wire.
MAGNETRON
POWER UNIT
145ºC
60ºC
120ºC
150ºC
OVEN THERMAL
CUT OUT
HOOD FAN
THERMOSTAT
High
Low
COOK
TOP
LAMP
N.O.
*NOTE 2
*NOTE 3
*NOTE 2
*NOTE 5
*NOTE 4
GRN
CN-M
CN-N
CN-D
GND
120V AC
60Hz
COM
N.O.
RED
YLW
BLK BLK
PPL
BLK
WHT
WHT
NOISE SUPRESSION COIL 1.0mH
LINE BYPASS CAPACITOR
3300pF 250V
FUSE
20A
LINE BYPASS CAPACITOR
3300pF 250V
NOISE FILTER UNIT
RED
BLK
GRY
ORG
SWITCH
UNIT
1
Page 12
GLBM188HB
[3] DESCRIPTION AND FUNCTION OF COMPONENTS
1. DOOR OPEN MECHANISM
The door is opened by pulling the door handle, refer to the Figure D-1.
Figure D-1. Door Open Mechanism.
2. DOOR SENSING SWITCH, SECONDARY INTERLOCK SWITCH
The secondary interlock switch is mounted in the lower position of the
latch hook, the door sensing switch in the primary interlock system is
mounted in the upper position of the latch hook is mounted on upper
position of the latch hook. They are activated by the latch heads on the
door. When the door is opened, the switches interrupt the circuit to all
components. A cook cycle cannot take place until the door is firmly
closed thereby activating both interlock switches. The primary interlock
system consists of the door sensing switch and primary interlock relay
located on the control circuit board.
3. MONITOR SWITCH
The monitor switch is activated (the contacts opened) by the latch
head on the door while the door is closed. The switch is intended to
render the oven inoperative, by means of blowing the monitor fuse,
when the contacts of the primary interlock relay (RY2) and secondary
interlock switch fail to open when the door is opened.
Functions:
1. When the door is opened, the monitor switch contact close (to the
ON condition) due to their being normally closed. At this time the
primary interlock relay (RY2), secondary interlock switch are in the
OFF condition (contacts open) due to their being normally open
contact switches. And the contacts of relay (RY1) are in the ON
condition (contacts close).
2. As the door goes to a closed position, the monitor switch contacts
are first opened and then the door sensing switch and the secondary interlock switch contacts close. (On opening the door, each of
these switches operate inversely.)
3. If the door is opened, and the primary interlock relay (RY2) and
secondary interlock switch contacts fail to open, the monitor fuse
blows simultaneously with closing of the monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE TEST
THE DOOR SENSING SWITCH, PRIMARY INTERLOCK
RELAY (RY2), RELAY (RY1), SECONDARY INTERLOCK
SWITCH AND MONITOR SWITCH FOR PROPER OPER-
ATION. (REFER TO CHAPTER “TEST PROCEDURE”).
NOTE: MONITOR FUSE AND MONITOR SWITCH ARE REPLACED
AS AN ASSEMBLY.
4. THERMAL CUT-OUT (CAVITY)
This thermal cut-out is located on the top of the oven cavity. It is
designed to prevent damage to the oven unit if the food in the oven
catches fire due to overheating produced by improper setting of cooking time or failure of control unit. Under normal operation, the thermal
cut-out remains closed. However, the thermal cut-out will open at
293°F (145°C) causing the oven to shut down.
5. TURNTABLE MOTOR
The turntable motor rotates the turntable located on the bottom of the
oven cavity, so that the foods on the turntable cook evenly during
cooking. Turntable will turn in either direction. The turntable motor can
be turned off by touching TURNTABLE ON/OFF pad.
6. COOLING FAN MOTOR
The cooling fan motor drives a blade which draws external cool air.
This cool air is directed through the air vanes surrounding the magnetron and cools the magnetron. This air is channelled through the oven
cavity to remove steam and vapors given off from the heating foods. It
is then exhausted through the exhausting air vents at the oven cavity.
7. HOOD FAN MOTOR
The hood fan motor is a two-speed, single-phase, double pole induction type, requiring a hood fan capacitor. It is located outside the upper
rear part of the oven cavity, is to remove, from around the oven, hot air
rising from the conventional electric or gas range over which it is
installed. This air is then expelled either vertically or horizontally
through the customer supplied duct system, or discharged back into
the kitchen. The automatically operation is medium speed. The manual operation is a three speed (Low/ High).
7.1. THERMOSTAT (60°C ON)
This thermostat is located on the right base plate. It is designed to
automatically turn on the hood fan motor whenever the hot air rising
from the conventional range below causes the temperature at the thermostat to rise to 140°F (60°C) or higher, thus removing this hot air
from around microwave oven. When the temperature around the thermostat drops to 113°F (45°C) or lower, the thermostat shuts off the
hood fan motor.
8. ANTENNA MOTOR
The motor drives the stirrer fan to stir the microwave radiation from the
waveguide.
9. COOK TOP LAMP
The cook top lamp is mounted at the lamp mounting angle on the base
cover. Touch the Light pad once for high, twice for low and four times
to turn off the light.
Secondary
Interlock
Switch
Monitor
Switch
Latch
Hook
Door
Latch
Heads
Door
Sensing
Switch
Page 13
GLBM188HB
GLBM188HB
ServiceManual
CHAPTER 7. TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many of the possible causes of
trouble will require that a specific test be performed. These tests are given a procedure letter which will be found in the "Test Procedure "section.
IMPORTANT:
If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, relay (RY1) primary interlock relay (RY2), door sensing
switch and secondary interlock switch before replacing the monitor fuse. If the monitor fuse is replaced, the monitor switch must also be replaced.
Use part FFS-BA042WRKZ as an assembly.
IMPORTANT:
Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases, be necessary to connect the power supply
cord after the outer case has been removed, in this event,
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure that the leads remain isolated from other components and oven chassis by using insulation tape.
6. After that procedure, reconnect the power supply cord.
When the testing is completed
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.
Page 14
GLBM188HB
[1] TROUBLESHOOTING CHART
CK = Check / RE = Rep
lace
POSSIBLE CASE AND
DEFECTIVE PARTS
PROBLEM
TEST PROCEDURE
COND
I
TION
O
F
F
C
ONDI
TION
IDLE
CO
NDI
T
ION
CK
LOW VOL
T
AGE
CK
NO
P
O
WE
R
AT O
UTLET
RE
SHORTED IN POWER
CO
RD
CK
OPENED OR SHOR
TE
D W
IRING
C
K
HO
O
D M
O
T
O
R CAPAC
I
T
O
R O
N PWB
RE
COO
K
TOP LAMP
O
R SOCKET
CK
T
URNT
ABLE
O
F
F CO
NDITIO
N
RE
ANTENNA MOTOR
RE
TURNT
AB
LE MOTOR
RE
F
A
N
M
OTOR
RE
OVEN LAM
P
OR SO
CKET
O
FUS
E ON P
.W.B.
N
RELAY ( RY-5
)
N
RELAY (
R
Y
-7,
R
Y
-8)
N
R
E
L
AY
(RY-6)
N
RELAY (
R
Y
-3)
N
RE
LAY (RY-2)
N
RELAY (
R
Y
1
)
M
KE
Y UNIT (
DOO
R)
L
CONT
ROL UNIT
K
HO
O
D F
AN
MOTOR
J
HOO
D T
HERM
OSTA
T 60º
C ON
I
M
ONITOR FUSE
H
M
ONITOR SWITCH
G
P
R
IMARY
INTE
R
LOCK
S
YSTE
M
F
SECON
DARY INTERLOCK S
W
ITCH
E
TEMPERATU
RE FU
S
E OR THERM
A
L
CUT-OUT
D
HIGH VOLTAGE CAPACIT
O
R
C
H.V. RE
CTIFIE
R
B
P
OW
E
R TRA
NSF
O
RME
R
A
MAGNETRON
Q
NOI
SE
FILTER
SENSO
R
C
O
O
KI
NG
CO
N
DI
TION
P
HU
MIDI
T
Y S
E
NSOR
MICROWAVE
COOKING
CONDITION
Home fuse blows when power cord is plugged
into wall receptacle.
Monitor fuse blows when power cord is plugged
into wall receptacle.
Display does not illuminate when power cord is
first plugged into wall receptacle.
Display does not operate properly when
STOP/CLEAR key is touched. (The time of day
should appear on the display with beep sound
during normal condition.)
Oven lamp does not light with door is opened.
Hood fan motor operates when power cord is first
plugged into wall receptacle.
Temperature of oven base seems more than
140ºF (60ºC) because of operation of the range
below. But hood fan motor does not turn on
automatically. (Normally, food fan motor should
be operating at mid speed.)
Cook top lamp does not turn on when LIGHT pad
is pressed.
Hood fan motor does not rotate at all with
touched VENT pad.
Speed of the hood fan motor does not change
when the VENT pad is touched for this function.
Oven lamp does not light in cook cycle. (But it
does light when door is opened.)
Fan motor does not operate. (Oven lamp and
turntable motor operate.)
Turntable motor does not operate (Oven lamp
lights and fan motor operate.)
Oven does not go into cook cycle when START
pad is touched
Oven seems to be operating but little or no heat is
produced in oven load. (Food incompletely
cooked or not cooked at all at end of cook cycle.)
Oven goes into a cook cycle but extremely
uneven heating is produced in oven load (food).
Variable cooking does not operate properly
except Cooking Power 100% mode.
Function of AUTO DEFROST does not operate
properly.
Antenna motor does not operate. (Other parts
operate.)
Oven goes into AUTO DEFROST but food is not
defrosted well.
The oven stops and "ERROR" is displayed or
does not end during Sensor Cooking condition.
(Oven does not shut off after a cup of water is
boiling by Sensor Cooking.)
Oven stops at 32 seconds after starting.
Page 15
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