LG MH-794GS User manual

MICROWAVE/
GRILL OVEN
SERVICE MANUAL
MODEL : MH-794GS
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS
IN THIS MANUAL.
August, 1999
P/NO. 3828W5S1308 Printed in Korea

This device is to be serviced only by properly qualified service personnel.
Consult the Service Manual for proper service procedures to assure continued safety operation and for precautions
to be taken to avoid possible exposure to excessive microwave energy.
SAFETY PRECAUTIONS
2
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 com-
partments, 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 should be performed on each oven prior to release to the owner.
CAUTION
MICROWAVE RADIATION
SPECIAL FUNCTION
Auto Cancel Function:
If you don’t touch start key for 4 min. 15 sec after setting and power the oven display will be
changed to initial condition.
DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE
GENERATOR OR OTHER PARTS CONDUCTING MICROWAVE ENERGY.

TABLE OF CONTENTS
3
(Page)
SAFETY PRECAUTIONS Inside front cover
SPECIFICATIONS 4
CAUTIONS 5
INSTALLATIONS 6
OPERATING INSTRUCTIONS 7
FEATURES 7
CONTROL PANEL 7
AUTO MOVING HEATER GUIDE 8
OPERATING SEQUENCE 9
SCHEMATIC DIAGRAM 11
CIRCUIT DESCRIPTION 12
SERVICE INFORMATION 13
TOOLS AND MEASURING INSTRUMENTS 13
MICROWAVE LEAKAGE TEST 13
MEASUREMENT OF MICROWAVE POWER OUTPUT 15
DISASSEMBLY AND ADJUSTMENT 15
INTERLOCK CONTINUITY TEST 20
COMPONENT TEST PROCEDURE 21
TROUBLE SHOOTING GUIDE 25
EXPLODED VIEW 31
REPLACEMENT PARTS LIST 38
MICOM CONTROLLER SCHEMATIC DIAGRAM 40
MICOM CONTROLLER P.C.B LAYOUT 41
TACT SWITCH BUTTON POSITION 42
MICOM CONTROLLER P.C.B PARTS LIST 43
PACKING AND ACCESSORIES 46

SPECIFICATIONS
4
ITEM DESCRIPTION
MODEL MH-794GS
Power Requirement 230V AC 50Hz
Single phase, 3 wire grounded
Microwave 1200W
Grill 1150W
Combination 2300W
Power Output 900W full microwave power(IEC705)
Microwave Frequency 2,450MHz
Magnetron 2M214 - 39F
Timer 99min. 90sec.
Outside Dimensions 556mm(W) X 322mm(H) X 435mm(D)
Cavity Dimensions 374mm(W) X 235mm(H) X 406mm(D)
Net Weight 17.5kg(approx.)
Shipping weight 19.5kg(approx.)
Control Complement Microwave Power for Variable Cooking
Power level
HIGH.............................................Full power throughout the cooking time(100%)
MED-HIGH....................................approx. 80% of Full power
MEDIUM.......................................approx. 60% of Full power
DEFROST ....................................approx. 40% of Full power
LOW .............................................approx. 20% of Full power
• Grill
• Combination 1, 2 & 3
Name plate Location
Accessories Owner's manual
Rotating ring Ass'y
Glass Tray
Grill rack
Shaft
This microwave oven is designed for household use only.
It is not recommended for commercial purpose.

• DO NOT operate on a 2-wire extension cord during
repair and use.
• NEVER TOUCH any oven components or wiring
during operation .
• BEFORE TOUCHING any parts of the oven, always
remove the power plug from the outlet.
• For about 30 seconds after the oven stop, an electric
charge remains on the high voltage capacitor. When
replacing or checking, you must discharge the
capacitor by shorting across the two terminals with an
insulated screwdriver.
• Remove your watches whenever working close to or
replacing the Magnetron.
• NEVER operate the oven with no load.
• NEVER damage the door seal or front plate of the
oven cavity.
• NEVER put iron tools on the magnetron.
• NEVER put anything into the latch hole and the
interlock switches area.
• Proper operation of the microwave oven requires that
the magnetron be assembled to the waveguide and
cavity. Never operate the magnetron unless it is
properly installed.
• Be sure that the magnetron gasket is properly installed
around the dome of the tube whenever installing the
magnetron .
CAUTIONS
5
Unlike other appliances, the microwave oven is
high-voltage and high-current appliance.
Though it is free from danger in ordinary use,
extreme care should be taken during repair.
ANTENNA
GASKET
FILAMENT
TERMINAL
COOLING FIN
MAGNETRON
CHASSIS
GROUND
MICROWAVE RADIATION
Personnel should not be exposed to the
microwave energy which may radiate from the
magnetron or other microwave generating device if
it is improperly used or connected.
All input and output microwave connections, wave-
guide,flange and gasket must be secure never
operate the device without a microwave energy
absorbing load attached.
Never look into an open waveguide or antenna
while the device is energized.
MAGNETRON
THE OVEN IS TO BE SERVICED ONLY
BY PROPERLY QUALIFIED SERVICE
PERSONNEL.

Installing microwave oven
1. Empty the microwave oven and clean inside it with
a soft, damp cloth. Check for damage such as
misaligned door, damage around the door or dents
inside the cavity or on the exterior.
2. Put the oven on a counter, table or shelf that is
strong enough to hold the oven, food and utensils
you put in it. (The control panel side of the oven is
the heavy side. Use care when handling.)
3. Do not block the vent and the air intake openings.
Blocking vent or air intake openings can cause
damage to the oven and poor cooking results.
Make sure the microwave oven legs are in place to
ensure proper air flow.
4. The oven should not be installed in any area where
heat and steam are generated, because they may
damage the electronic or mechanical parts of the
unit.
Do not install the oven next to a conventional
surface unit or above a conventional wall oven.
5. Use the microwave oven in an ambient temperature
of less than 104°F (40°C).
6. Place the microwave oven on a sturdy and flat
surface, at least 10cm(4 inches) from the wall.
7. Place the microwave oven as far away as possible
from TV, RADIO, COMPUTER etc, to prevent
interference.
8. This oven must be plugged into a 15A outlet.
9. Do not touch the front glass during or after cooking
of the Grill, Convection and Combination mode.
This glass is very hot during heater operating.
10. Do not operate oven at microwave and combination
mode with the Convection rack or Grill rack placed
in the cavity when the oven is empty.
Earthing Instructions
This microwave oven is designed to be used in a fully
earthed condition.
It is imperative, therefore, to make sure it is properly
earthed before servicing.
WARNING-
THIS APPLIANCE
MUST BE EARTHED
IMPORTANT
As the colours of the wires in the mains lead of this
appliance may not correspond with the coloured
markings identifying the terminals in your plug, proceed
as follows.
The wire which is coloured green-and-yellow must be
connected to the terminal in the plug which is marked
with the letter Eor by the earth symbol (b) or coloured
green or green-and yellow.
The wire which is coloured blue must be connected to
the terminal in the plug which is marked with the letter N
or coloured black.
The wire which is coloured brown must be connected
to the terminal in the plug which is marked with the
letter Lor coloured red.
INSTALLATIONS
6
BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.
The wires in this mains lead are coloured in
accordance with the following code:
Green-and-yellow: Earth
Blue: Neutral
Brown: Live

OPERATING INSTRUCTIONS
7
Features
Control Panel
Oven front face
Rotating ring ASS'Y
Latch Shaft
DisplayWindow
Grill Rack
Control Panel
Window Door Screen
Door Seal
GlassTray
В
p
e
м
я
COOKING MODE
¥ Set the cooking mode
(Microwave, Grill, Combination)
TEMPERATURE
Used to set the desired
temperature of food.
STOP / CLEAR
Stop the oven and clear all
entries except time of day.
DIAL KNOB
¥ Used to set cooking time,
sensor cook menus and
sensor reheat menus.
¥ Select cooking mode.
NOTE: A beep sounds when a button on the control panel
is touched, to indicate a setting has been entered.
DEF 1
¥ To defrost
SENSOR REHEAT MENUS
¥ Dinner Plate
¥ Chilled Meal
¥ Soup / Sauce
SENSOR COOK MENUS
¥ Potato
¥ Fresh Vegetable
¥ Frozen Vegetable
¥ Pasta
¥ Fresh Fish
CLOCK / KITCHEN TIMER
Set the clock or timer
DISPLAY INDICATOR- Shows:
Time of Day,
Cooking power Level,
Cooking Category.
TEMPERATURE INDICATOR
Shows the current and set
temperature.
MORE / LESS
To change auto cook time
under 1kg of frozen food
DEF 2
¥ To defrost over 1kg of frozen food.
START /QUICK START
¥ Used to start cooking
and set the cooking
time quickly and directly.
¥ Set the cooking mode.

Auto Moving Heater Guide
8
GRILL HEATER POSITION
• Cooking • Cooking Stop • Next Cook Setting
• Door Open • Door Closed ater cook
• Cooking End is ended and food is
removed
DEF
Microwave Cook
1. Jacket
Potato
2. Fresh
Vegetable
3. Frozen
Vegetable
4. Rice •Grill heater will not move.
5. French Fish
Grill Cook
Combination Cook
French Fries
Chicken Legs •Grill heater will move to •Grill heater will move
the cooking position. to the backside.
•Grill heater will stay at
the cooking position.
COOK
CATEGORY
Sensor
Cook
(M/W)
Sensor
Reheat
•Grill heater will stay at
the cooking position.
• When the cook is
ended,the food must
be removed.
• When the cook is ended
and you want to cook the
next cooking, the food
must be removed before
setting the next cooking.

Operating Sequence
9
The following is a description of component functions during oven operation.
Plug the power
cord into an
electric outlet
Clock
M/W Cook
Grill Cook
Combi. Cook
Sensor Cook
Auto Roast
Cook
DEF1
DEF2
2times Set the
correct hour Set the correct minute
Stop/
Clear Desired power level Set the
correct minute
Stop/
Clear Desired cooking time
twice
Stop/
Clear Desired
cooking time
3 times Set Combi.
1,2or3
Stop/
Clear Desired
Sensor Cook
Stop/
Clear Desired auto
roast cook Desired food weight
Stop/
Clear Set Defrost

Operating Sequence
10
The following is a description of component functions during oven operation.
Programme
Desired
Cooking
Stop/
Clear
Stop/
Clear
Stop/Clear
Touch and Hold
Stop/Clear
Stop/Clear
Touch and Hold
Stop/
Clear
Stop/
Clear
Child Lock
Quick Start
More and
Less
Temp
To Set CHILD LOCK
• "L" appears on the display
and you can't input any key.
• "L" disappears on the display.
To Cancel CHILD LOCK
To Set MORE/LESS

SCHEMATIC DIAGRAM
11

GENERAL DETAILS
•The low voltage transformer supplies the necessary
voltage to the micom controller when power cord is
plugged in.
•When the door is closed, the primary switch is ON, the
secondary switch is ON, and the monitor switch opens
(contact COM and NO).
WHEN SELECTING COOKING
POWER LEVEL AND TIME
•The micom controller memorizes the function you set.
•The time you set appears in the display window.
•Each indicator light turns on to indicate that the stage
has been set.
WHEN TOUCHING THE START PAD
•The coil of the relay is energized by the micom
controller.
•Power input is supplied to the high voltage transformer
through the fuse to the primary switch and relay 2.
•Turntable rotates.
•The fan motor rotates and cools the magnetron by
blowing the air(coming from the intake on the
baseplate).
•The air is also directed into the oven to exhaust the
vapor in the oven through the upper plate.
•Cooking time starts counting down.
•3.2 volts AC is generated from the filament winding of
the high voltage transformer. This 3.2 volts is applied
to the magnetron to heat the magnetron filament
through two noise-preventing choke coils.
•A high voltage of approximately 2100 volts AC is
generated in the secondary of the high voltage
transformer which is increased by the action of the
high voltage diode and charging of the high voltage
capacitor.
•The negative 4,000 Volts DC is applied to the filament
of the magnetron.
WHEN THE OVEN IS SET AT ANY
LEVEL EXCEPT MAXIMUM
•The micom controller controls the ON-OFF time of
relay 5 by the applied signal to vary the average
output power of microwave oven as POWER LEVEL.
(refer to page 1-1)
•One complete cycle of relay 5 is 22 seconds.
WHEN THE DOOR IS OPENED
DURING COOKING
•Both the primary switch and relay 2 are cut off primary
winding voltage of the high voltage transformer.
•ON-OFF of relay 2 is coupled electrically with opening
and closing of the secondary switch.
•When the door is opened, the secondary switch is
opened and when the door is closed, the secondary
switch is closed.
•The cooking time stops counting down.
•Relay stops functioning.
•As the door is opened, if the contact of primary switch
and secondary switch fail to open, the fuse opens due
to the large current surge caused by the monitor
switch activation, which in turn stops magnetron
oscillation.
WHEN TOUCHING THE START KEY
WITH THE GRILL COOKING
FUNCTION SELECTED
•The contacts of the primary switch and the secondary
switch close the circuit.
•A.C. voltage is applied to the grill heater through oven
thermal cut-out as shown by the solid line.
•Turntable rotates.
•Rotisserie Motor rotates.
•The fan motor rotates.
•The air is also directed into the oven to exhaust the
vapor in the oven through the back plate and upper
plate.
Circuit Description
12
PRIMARY
SWITCH
RELAY 2
H.V.
TRANS-
FORMER
MONITOR
SWITCH
L
N
FUSE
SECONDARY
SWITCH
MICOM CONTROLLER
PRIMARY
SWITCH
MONITOR
SWITCH
L
N
FUSE
H.V.
TRANS-
FORMER
RELAY 2 SECONDARY
SWITCH
MICOM CONTROLLER
L
N
E
N
LG-Y GRILL
HEATER
RELAY 3
OVEN THERMAL
CUT-OUT

NECESSARY TOOLS
Tools normally used for TV servicing are sufficient.
Standard tools are listed below.
•Diagonal pliers
•Long nose pliers
•Cross head screwdriver
•Wrench (size 5 mm)
•Nutdriver (size 5 mm)
•Adjustable wrench
•Soldering iron
•Solder
•Vinyl insulation tape
•Polishing cloth
CAUTIONS
❥ Be sure to check a microwave emission prior to
servicing the oven if the oven is operative prior to
servicing.
❥ If the oven operates with door open, the service per-
sonnel should;
—Tell the user not to operate the oven
❥ The service personnel should check all surface and
vent openings for microwave emission testing.
❥ Check for microwave energy leakage after every
servicing. The power density of the microwave
radiation leakage emitted by the microwave oven
should not exceed 4 mW/cm2.
And always start measuring of an unknown field to
assure safety for operating personnel from radiation
leakage.
NOTE: The standard is 5 mW/cm2 while in the
customer’s home. 4 mW/cm2 stated here is
manufacturer’s own voluntary standard for units in
customer’s home.
EQUIPMENT
❥ Microwave Survey Meter
❥ 600cc glass beaker
❥ Glass thermometer 100°C
NECESSARY MEASURING
INSTRUMENTS
•TESTER (VOLTS-DC, AC, Multmeter)
•Microwave survey meter
—Holaday H1-1500, Hi-1501
—Narda 8100, 8200
•Inch scale
•600 cc non conductive material beaker (glass or
plastic), inside diameter: approx. 8.5cm (31/2 in.)
•Cylindrical and made of borosilicate glass vessel max.
thickness: 3mm
outside diameter: approx. 190mm
height: approx. 90mm
•Glass thermometer: 100°C or 212°F (1 deg scale)
MEASURING MICROWAVE ENERGY
LEAKAGE
❥ Pour 275 ± 15cc of 20°C ± 5°C water in a beaker
which is graduated to 600 cc, and place the beaker on
the center of the turntable.
❥ Set the energy leakage monitor to 2,450 MHz and use
it following the manufacturer’s recommended test
procedure to assure correct result.
❥ When measuring the leakage, always use the 2 inch
(5cm) spacer supplied with the probe.
❥ Operate the oven at its maximum output.
❥ Measure the microwave radiation using and elec
tromagnetic radiation monitor by holding the probe per-
pendicular to the surface being measured.
SERVICE INFORMATION
Tools and Measuring Instruments
Microwave Leakage Test
13
Move probe along shaded area.
Probe scanning speed;
Less than 2.5 cm/sec

MEASUREMENT WITH THE OUTER
CASE REMOVED
❥ When you replace the magnetron, measure microwave
energy leakage before the out case is installed and
after all necessary components are replaced or adjust-
ed.
Special care should be taken in measuring the
following parts. (Shaded area of below Fig.)
—Around the magnetron
—The waveguide
MEASUREMENT WITH A FULLY
ASSEMBLED OVEN
❥ After all components, including the outer case, are fully
assembled, measure for microwave energy
leakage around the door viewing window, the exhaust
opening and air inlet openings.
❥ Microwave energy leakage must not exceed the
values prescribed below.
NOTES:
Leakage with the outer case removed - less than
5 mW/cm2.
Leakage for a fully assembled oven (“Before the latch
switch (primary) is interrupted”) with the door in a
slightly opened position - less than 4 mW/cm2.
NOTES WHEN MEASURING
❥ Do not exceed meter full scale deflection.
❥ The test probe must be removed no faster than,
1 inch/sec (2.5 cm/sec) along the shaded area,
otherwise a false reading may result.
❥ The test probe must be held with the grip portion of the
handle.
A false reading may result if the operator’s hand is
between the handle and the probe.
❥ When testing near a corner of the door, keep the
probe perpendicular to the surface making sure the
probe horizontally along the oven surface, this may
possibly cause probe damage.
RECORD KEEPING AND NOTIFICA-
TION AFTER MEASUREMENT
❥ After adjustment and repair of any microwave energy
interruption or microwave energy blocking
device, record the measured values for future
reference. Also enter the information on the service
invoice.
❥ Should the microwave energy leakage not be more
than 4 mW/cm2 after determining that all parts are in
good condition, functioning properly and genuine
replacement parts which are listed in this manual have
been used.
❥ At least once a year, have the electromagnetic energy
leakage monitor checked for calibration by its
manufacture.
14
WARNING: AVOID CONTACTING ANY
HIGH VOLTAGE PARTS

❥ Microwave power output measurement is made with
the microwave oven supplied at its rated voltage and
operated at its maximum microwave power setting with
a load of (1000 ± 5)g potable water.
❥ The water is contained in a cylindrical borosilicate
glass vessel having a maximum material thickness of
3 mm and an outside diameter of approximately
190mm.
❥ The oven and the empty vessel are at ambient
temperature prior to the start of the test.
❥ The initial temperature (T1) of the water is (10±2)°C. It
is measured immediately before the water is added to
the vessel. After addition of the water to the vessel, the
load is immediately placed on the center of the
turntable which is in the lowest position and the
microwave power switched on.
❥ The time T for the temperature of the water to rise by a
value ∆T of (10±2)°K is measured, where T is the time
in seconds and ∆T is the temperature rise. The initial
and final water temperatures are selected so that the
maximum difference between the final water tempera-
ture and the ambient temperature is 5°K.
A. OUT CASE REMOVAL
1) Disconnect power supply cord from the outlet.
2) Remove the screws from the rear and along side
egges of the case.
The ouer case must be moved backward to the lifted
off.
B. POWER SUPPLY CORD
1) Remove the out case.
2) Disconnect two terminals, and remove one screw of
the earth terminal.
CAUTION: DISCHARGE THE HIGH VOLTAGE
CAPACITOR BEFORE SERVICING
(refer to page 5)
C. CONTROL PANEL ASSEMBLY
1) Disconnect the leadwire from the PCB SUB ASS'Y.
2) Remove the screws for the earth and securing the
control panel.
3) Lift control panel ASS'Y from the oven by the tab
unhooked.
❥ The microwave power output P in watts is calculated
from the following formula:
P=
is measured while the microwave generator is op
erating at full power. Magnetron filament heat-up
time is not included. (about 3 sec.)
❥ The water is stirred to equalize temperature
throughout the vessel, prior to measuring the final
water temperature.
❥ Stirring devices and measuring instruments are
selected in order to minimize addition or removal of
heat.
Measurement of Microwave Power Output
Disassembly and Adjustment
15
Water Load
Turn Table
4187 X ∆T
T

D. DOOR GROSS ASSEMBLY REMOVAL
1) Open the door.
2) Remove the choke cover cap very carefully with a
flat-blade screwdriver.
CAUTION : Be careful not to damage door seal plate
by screwdriver.
3) Lift up and push the door.
NOTE :
1. After replacing the door, be sure to check that the
primary switch, monitor switch, and secondary switch
operate normally.
2. After replacing the door, check for microwave energy
leakage with a survey meter. Microwave energy must
be below the limit of 5 mW/cm.(with a 275 ml water
load)
3. When mounting the door assembly to the oven
asembly, be sure to adjust the door assembly parallel
to the chassis. Also adjust so the door has no play
between the inner door surface and oven frame
assembly. If the door assembly is not mounted
properly, microwaves may leak from the clearance
between the door and the oven.
E. HIGH VOLTAGE TRANSFORMER
REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from magnetron, high
voltage transformer, and capacitor.
3) Remove the screw holding the high voltage
transformer to the baseplate.
F. FAN MOTOR ASSEMBLY
REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from fan motor, noise filter
and high voltage capacitor.
3) Remove the two screws holding the the suction guide
ASS'Y to the oven cavity and remove the high
voltage diode earth screw.
4) Remove the screw of the capacitor bracket.
5) Remove the two screws holding the fan motor ASS'Y
to the suction guide ASS'Y
G. HIGH VOLTAGE CAPACITYOR
AND DIODE REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from fan motor, noise filter
and high voltage capacitor.
3) Remove the screw holding the suction guide ASS'Y
to the oven cavity and remove the high voltage diode
earth screw.
4) Remove the screw holding the high voltage capacitor
bracket.
16
Remove choke cover cap
Fan Motor ASSY
H. V.
Transformer H . V.
Diode
Suction
Guide
H. V.
Capacito
Door seal plate
Remove door

H. AIR DUCT ASSEMBLY REMOVAL
1) Disconnect the leadwire from lamp and MGT ther
mostat.
2) Remove the mounting screw to the cavity.
H. MAGNETRON REMOVAL
1) Disconnect the leadwire from the high voltage
transformer and high voltage capacitor.
2) Carefully remove the mounting screws holding the
magnetron and the waveguide.
3) Remove the magnetron ASS'Y until the tube is clear
from the waveguide.
NOTE:
1. When removing the magnetron, make sure its dome
does not hit any adjacent parts, or it may be
damaged.
2. When replacing the magnetron, be sure to install the
magnetron gasket in the correct position and be sure
that the gasket is in good condition.
3. After replacing the magnetron, check for microwave
leakage with a survey meter around the magnetron.
Microwave energy must be below the limit of 5
mW/cm2.(With a 275 ml. water load).
Make sure that gasket is rigidly attached to the
magnetron. To prevent microwave leakage, tighten
the mounting screws properly, making sure there is
no gap between the waveguide and the magnetron.
J. REMOVING THE TURNTABLE
MOTOR
1) Remove the turntable.
2) Remove the turntable shaft VERY CAREFULLY with
a slotted hand.
3) Lay the unit down on its back.
4) Remove the turntable motor cover. The turntable
base cover is easily removed by pinching the six
parts with a wire cutting.
5) Disconnect the leadwire from the turntable motor
terminals.
6) Remove the screw securing the turntable motor to
the oven cavity ASS'Y
7) After repairing the motor, rotate the removed
turntable motor cover.
8) Fit the turntable motor cover's projecting part to the
base plate slit.
NOTE:
1. Remove the wire lead from tne turntable motor VERY
CAREFULLY.
2. Be sure to grasp the connector, not the wires, when
removing.
17
Waveguide
Magnetron
Gasket
Magnetron
Dome
Waveguide
Bracket
Lamp
Magnetron
Air Duct
Wire Leads
Turntable Motor

K. Auto Moving Heater MOTORE ASS'Y
1. Remove the Screw of the Back and in the Cavity.
2. Remove the Bracket Ass'y.
3. Remove the Joint-spring.
4. Remove the Gasket.
1. Remove the Screw of Back and Cavity on the Right.
2. Remove the H.M.MOTOR ASS'Y.
3. Remove the Washer.
4. Remove the Gasket.
L. Sensor ASS'Y
1. Remove the Screw of the back and on the Cavity.
2. Remove the Screw of the Bracket.
3. Remove the Bracket.
4. Remove the Screw of Sensor Case.
5. Remove the Sensor PCB Ass’y.
18
Heater
Gasket
Joint-Spring
Cover
Terminal
Bracket Ass’y
Motor Ass’y
Bracket
Washer
Gasket
Gear
S/W 1H. M. Motor Ass’y
S/W 2

M. PCB ASSEMBLY REMOVAL
1) Remove the control panel assembly from the
cavity.(Refer to control panel assembly removal on
previous page.)
2) Remove screws which hold the PCB SUB ASS'Y to
the control panel.
3) Disconnect the flat cable from the PCB SUB ASS'Y
and take off the PCB SUB ASS'Y.
N. INTERLOCK SYSTEM
1) INTERLOCK MECHANISM
The door lock mechanism is a device which has been
specially designed to eliminate completely microwave
activity when the door is opened during cooking and
thus to prevent the danger resulting from the
microwave leakage.
2) MOUNTING OF THE PRIMARY/MONITOR/
SECONDARY SWITCHS TO THE LATCH BOARD
3) INSTALLATION AND ADJUSTMENT OF THE LATCH
BOARD TO THE OVEN ASSEMBLY
❥ Mount the latch board to the oven assembly.
❥ Adjust the latch board in the arrow direction so the
oven door will not have any play in it when the door
is closed.
❥ Tighten the mounting screw.
❥ Check for play in the door by pushing the door
release button. Door movement should be less
than 0.5mm. (1/64 inch)
Don't push the door release button while making
adjustment. Make sure that the latch moves
smoothly after adjustment are completed and that the
screws are tight. Make sure the primary, monitor, and
secondary switch operate properly by following the
continuity test procedure.
19
PCB SUB ASSY
Control Panel
Knob
Tact switch PCB
Dial
ADJUSTMENT
DIRECTION
MONITOR
SWITCH
PRIMARY
SWITCH
SECONDARY
SWITCH
H. V
DIODE
H. V. CAPACITOR
CIRCUIT PROTECTOR
H. V. TRANSFORVER
MAGNETRON
CAUTION: CHECK THE CORRECT POSITION
PRIMARY

A. PRIMARY INTERLOCK SWITCH
TEST
When the door release button is depressed slowly
with the door closed, an audible click should be
heard at the same time or successively at intervals.
When the button is released slowly, the latches
should activate the switches with an audible click.
If the latches do not activate the switches when the
door is closed, the swithces should be a adjusted in
accordance with the adjustment procedure.
Disconnect the wire lead from the primary switch.
Connect the ohmmeter leads to the common (COM)
and normally open (NO) terminal of the switch. The
meter should indicate an open circuit in the door
open condition.
When the door is closed, the meter should indicate
a closed circuit.
When the primary switch operation is abnormal,
make the necessary adjustment or replace the
switch only with the same type of switch.
B. SECONDARY INTERLOCK SWITCH TEST
Disconnect the wire lead from the secondary switch.
Connect the ohmmeter leads to the common (COM)
and normally open (NO) terminals of the switch. The
meter should indicate a open circuit in the door
open condition. When the door is closed, meter
should indicate a closed circuit. When the sec-
ondary switch operation is abnormal, make the nec-
essary adjustment or replace the switch only with
the same type of switch.
C. MONITOR SWITCH TEST
Disconnect the wire lead from the monitor switch.
Connect the ohmmeter leads to the common (COM)
and normally closed (NO) terminals of the switch.
The meter should indicate closed circuit in the door
open condition. When the door is closed, meter
should indicate an open circuit. When the monitor
switch operation is abnormal, replace with the same
type of switch.
NOTE: After repairing the door or the interlock
system, it is necessary to do this continuity test
before operating the oven.
Interlock continuity Test
20
WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION
EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS.
TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY SWITCH
TYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH
TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR SECONDARY SWITCH
COMPONENTS TEST PROCEDURE RESULTS
SWITCHES Check for continuity of the switch
(Wire leads removed) with an Ohm-meter
Primary
Switch
Monitor
Switch
Secondary
Switch
NOTE: After checking for the continuity of switches, make sure that are
connected correctly.
Door
open Door close
COM NO
COM
NC
COM
NO