LG MB-308DDD User manual

MICROWAVE/ GRILL OVEN
SERVICE MANUAL
MODEL: MB-308DDD
CAUTION
BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.

5-1
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
NECESSARY MEASURING INSTRUMENTS
●TESTER (VOLTS-DC, AC, Multimeter)
●Microwave survey meter
— Holaday HI-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)
SERVICE INFORMATION
Tools and Measuring Instruments
CAUTIONS
●Be sure to check a microwave emission prior to ser-
vicing the oven if the oven is operative prior to ser-
vicing.
●If the oven operates with door open, the service
personnel 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 radi-
ation 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 radia-
tion leakage.
NOTE: The standard is 5 mW/cm2while in the cus-
tomer's home. 4 mW/cm2stated here is manufac-
turer's own voluntary standard for units in cus-
tomer's home.
EQUIPMENT
●Microwave Survey Meter
●600cc glass beaker
●Glass thermometer 100°C
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 electro-
magnetic radiation monitor by holding the probe
perpendicular to the surface being measured.
Microwave Leakage Test
Move probe along shaded area.
Probe scanning speed;
Less than 2.5 cm/sec

5-2
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 adjusted.
Special care should be taken in measuring the fol-
lowing parts. (Shaded area of below Fig.)
— Around the magnetron
— The waveguide
MEASUREMENT WITH A FULLY ASSEM-
BLED OVEN
●After all components, including the outer panels,
are fully assembled, measure for microwave ener-
gy 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 panels removed — less than
5 mW/cm2.
Leakage for a fully assembled oven ("Before the latch
switch (primary) interrupted") with the door in a slight-
ly 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, oth-
erwise 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 NOTIFICATION
AFTER MEASUREMENT
●After adjustment and repair of any microwave ener-
gy interruption or microwave energy blocking
device, record the measured values for future refer-
ence. Also enter the information on the service
invoice.
●Should the microwave energy leakage not be more
than 4 mW/cm2after 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.
WARNING: AVOID CONTACTING ANY
HIGH VOLTAGE PARTS

5-3
●Microwave power output measurement is made
with the microwave oven supplied at its rated volt-
age 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
190 mm.
●The oven and the empty vessel are at ambient tem-
perature 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 shelf 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 temperature and the ambient tem-
perature is 5°K.
●The microwave power output P in watts is calculat-
ed from the following formula:
P=
is measured while the microwave generator is
operating at full power. Magnetron filament heat-up
time is not included. (about 2 sec.)
●The water is stirred, to equalize temperature
throughout the vessel, prior to measuring the final
water temperature.
●Stirring devices and measuring instruments are sel-
ected in order to minimize addition or removal of
heat.
Measurement of Microwave Power Output
4187 ( ∆ T)
T
Water Load
Turn Table
A. OUT CASE REMOVAL
1) Disconnect power supply cord from the outlet.
2) Remove the screws from the rear section. The out
case must be moved backward to the lifted off.
B. POWER SUPPLY CORD.
1) Remove the out case.
2) Disconnect two terminals from the noise filter assy
and remove one screw of the earth terminal.
CAUTION: DISCHARGE HIGH VOLTAGE
CAPACITOR BEFORE SERVICING
(refer to page 2-1)
C. CONTROL PANEL ASSEMBLY
1) Disconnect the leadwire from the PCB SUB ASM.
2) Remove one screw of the control panel.
3) Lift control panel assembly from the oven by the
tab unhooked.
Disassembly and Adjustment

5-4
D. DOOR GROSS ASSEMBLY REMOVAL
1) Remove screws of the hinge-L.
2) Open door and remove door assembly from hinge-U.
NOTES
1. After replacing the door, be sure to check that the
primary switch, monitor switch and secondary
switch operates normally.
2. After replacing the door, check for microwave
energy leakage with a survey meter.
Microwave energy must be below the limit of
4mW/cm2., (With a 275ml water load).
NOTE:
Do not lose the spacer at the lower hinge and upper
hinge. When mounting the door assembly to the oven
assembly, be sure to adjust the door assembly paral-
lel to the chassis by moving the upper hinge and
lower hinge. Also adjust so that the door has no play
between the inner door surface and oven frame
assembly. If the door assembly is not mounted prop-
erly, 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 H.V capacitor.
3) Remove the screws holding the high voltage trans-
former to the base plate.
F. FAN MOTOR ASSEMBLY REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from fan motor, noise filter
asm and H.V capacitor.
3) Remove the two screws holding the suction guide
assembly to the oven cavity and remove the high
voltage diode earth screw.
4) Remove the two screws holding the fan motor
assembly to the suction guide asm.
G. HIGH VOLTAGE CAPACITOR AND
DIODE REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from fan motor, noise filter
asm and H.V capacitor.
3) Remove the screws holding the suction guide
assembly to the oven cavity and remove the high
voltage diode earth screw.
4) Remove the screw holding the high voltage capac-
itor bracket and terminal of high voltage diode.
Fan Motor Asm
Suction
Guide
H.V. Capacitor
H.V. Transformer

5-5
H. AIR DUCT ASSEMBLY AND OVEN
LAMP REMOVAL
1) Disconnect the leadwire from oven lamp and ther-
mostat.
2) Remove the mounting screw to the magnetron.
3) Bend the air duct flange front with a long nose pli-
ers.
4) Rotate oven lamp anticlockwise and lift it up.
I. MAGNETRON REMOVAL
1) Disconnect the leadwire from high voltage trans-
former and high voltage capacitor.
2) Carefully remove the mounting screws holding the
magnetron and the waveguide.
3) Remove the magnetron assembly until the tube is
clear from the waveguide.
NOTES
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 micro-
wave energy leakage with a survey meter around
the magnetron. Microwave energy must be below
the limit of 5mW/cm2. (With a 275 ml. water load).
Make sure that gasket is rigidly attached to the
magnetron. To prevent microwave leakage, tight-
en 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 screwdriver.
3) Lay the unit down on its back.
4) Remove the Base plate cover.
The Base plate 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 assembly.
7) After repairing the motor, rotate the removed base
plate cover.
8) Fit the base plate cover's projecting part to the
base plate slit.
NOTES
1. Remove the wire leads from the turntable motor
VERY CAREFULLY with long nose pliers.
2. Be sure to grasp the connector, and not the wires
when removing.
Turntable Motor
Wire Leads
Air Duct
Waveguide
Dome
Magnetron
Gasket
Magnetron
Magnetron

5-6
K. PCB ASSEMBLY REMOVAL
1) Remove the control panel assembly from the
cavity.
2) Remove screw which holding the PCB SUB ASM
to the control panel.
3) Disconnect the flat cable from the PCB SUB ASM
and take off the PCB SUB ASM.
L. INTERLOCK SYSTEM
1) INTERLOCK MECHANISM
The door lock mechanism is a device which has
been specially designed to completely eliminate
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 AND
SECONDARY SWITCH 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 playing in the door by pushing the door
release button. Door movement should be less
than 0.5mm. (1/64 inch)
Do not push the door release button while mak-
ing 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.
PRIMARY
SWITCH
SECONDARY
SWITCH
MONITOR
SWITCH
ADJUSTMENT
DIRECTION

5-7
A. PRIMARY INTERLOCK SWITCH TEST
When the door button is slowly depressed with the
door closed, an audible "click" should be heard at the
same time or successively at intervals. When the but-
ton is slowly released, the latches should activate the
switches with an audible "click".
If the latches do not activate the switches when the
door is closed, the switches should be a adjusted in
accordance with 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 an open circuit in the door
open condition. When the door is closed, meter
should indicate a closed circuit. When the secondary
switch operation is abnormal, make the necessary
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 close(NC) 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 the same type of switch.
NOTE: After reparing the door or the interlock
system, it is necessary to do this continuity test
before operating the oven.
Interlock Continuity Test
WARNING: FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION
EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS.
TYPE NO. SZM-V16-FA-63 OR VP-533A- OF FOR PRIMARY SWITCH
TYPE NO. SZM-V16-FA-62 OR VP-532A- OF FOR MONITOR SWITCH
TYPE NO. SZM-V01-FA-33 OR VP-133A- OF FOR SECONDARY SWITCH
COMPONENTS TEST PROCEDURE RESULTS
SWITCHES
(Wire leads removed.)
Check for continuity of the switch
with an Multi-meter
NOTE: After checking for the continuity of switches, make sure that they
are correctly connected.
Primary
Switch
Monitor
Switch
Secondary
Switch
Door Door
open close
COM NO
COM NO
COM
NC

5-8
Component Test Procedure
CAUTIONS
1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE
OUT CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH
VOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF
THE HIGH VOLTAGE TRANSFORMER. (SEE PAGE 2-1)
2. ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD (1
LITER OF WATER IN CONTAINER) IN THE OVEN.
COMPONENTS TEST PROCEDURE RESULTS
HIGH VOLTAGE
TRANSFORMER
(Wire leads removed)
MAGNETRON
(Wire leads removed)
1. Measure the resistance.
(Multi-meter scale: Rx1)
●Primary winding
●Secondary winding
●Filament winding
2. Measure the resistance.
(Multi-meter scale: Rx1000)
●Primary winding to ground
●Filament winding to ground
1. Measure the resistance.
(Multi-meter scale: Rx1)
●Between filament terminals
2. Measure the resistance.
(Multi-meter scale: Rx1000)
●Filament to chassis.
Approx: 1.0~2.0 Ω
Approx: 80~100 Ω
Approx: 0 Ω
Normal: ∞
Normal: ∞
Normal: Less than 1 Ω
Normal: ∞
Primary
Terminals
Secondary
Terminal
Filament
Winding
Terminal

5-9
COMPONENTS TEST PROCEDURE RESULTS
HIGH VOLTAGE
CAPACITOR
HIGH VOLTAGE
DIODE
NOTE:
Some inexpensive
meter may indicate
infinite resistance in
both direction.
Measure the resistance.
(Multi-meter scale: Rx1000)
●Terminal to terminal.
Measure the resistance.
(Multi-meter scale: Rx1000)
●Terminal to case.
Measure the continuity (Forward).
(Multi-meter scale: Rx10000)
Measure the continuity (Reverse).
(Multi-meter scale: Rx10000)
Normal: Momentary indi-
cates several ohms, and
then gradually returns to
infinite.
Normal: ∞
Normal: Continuity.
Abnormal: ∞
Normal: ∞
Abnormal: Continuity.
NOTE:
When testing the magnetron, be sure to install the magnetron gasket in
the correct position and be sure that the gasket is in good condition.
Antenna
Gasket
Filamet
Terminals
Chassis

5-10
COMPONENTS TEST PROCEDURE RESULTS
Measure the resistance.
(Multi-meter scale: RX1)
Measure the resistance with 500V-100M
ohm insulation resistance meter.
Check for continuity of the switch
with an Multi-meter
NOTE: If the fuse is blown, check primary, the secondary, the monitor
switches, H.V.D and H.V.C before replacing the fuse.
If the fuse is blown by improper switch operation replace the defective
switch and the fuse at the same time.
Replace just the fuse if the switches operate normally.
HEATER ELEMENT
(Wire leads removed.)
MAGNETRON
THERMOSTAT
OVEN
THERMOSTAT
FUSE
(Wire leads removed.)
NOTE : Make sure heater is fully cooled when tested.
Normal :
Gill heater
Approx.55 Ω
(at 20-30°C)
Normal :
more than 0.5M Ω
0°C~Approx150°C Approx150°C
0°C~Approx145°C Approx145°C
Normal Abnormal

5-11
COMPONENTS TEST PROCEDURE RESULTS
Cooking Start OFF
Cooking Start OFF
FAN MOTOR
(Wire leads removed) Measure the resistance. (Multi-meter scale: Rx1)
Measure the resistance.
(Multi-meter scale: Rx1000)
Normal: Approx.
200~300 Ω
Abnormal: ∞or
several ohms.
Normal: Approx.
10~20 KΩ
Abnormal: ∞or
several ohms.
TURNTABLE MOTOR
(Wire leads removed)
RELAY OF P.C.B.
(Disconnect the 5 pin
connector from P.C.B.)
RELAY 2, RELAY 3
OF P.C.B
(Wire leads removed.)
Note: Relay
Relay 1: Fan motor
Turntable motor
Oven lamp
Relay 2: Microwave
Relay 3: Grill
NOTE: ●A MICROWAVE ENERGY TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT
IS SERVICED FOR ANY REASON.
●MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION.
●WHEN REMOVING THE WIRE LEADS FROM THE PARTS, BE SURE TO GRASP
THE CONNECTOR, NOT THE WIRES.
531
CN 2
Relay 1
Relay 2 Relay 3

5-12
WHEN YOU GET A COMPLAINT FROM YOUR CUSTOMER, EVALUATE THE COMPLAINT CAREFULLY.
IF THE FOLLOWING SYMPTOMS APPLY, PLEASE EDUCATE THE CUSTOMER IN THE PROPER USE OF
THE MICROWAVE OVEN. THIS CAN ELIMINATE AN UNNECESSARY SERVICE CALL.
Trouble Shooting
CAUTIONS
1. Check grounding before checking for trouble.
2. Be careful of the high voltage circuit.
3. Discharge the high voltage capacitor. (See page 2-1)
4. When checking the continuity of the switches or of the high voltage transformer, disconnect one lead
wire from these parts and then check continuity with the AC plug removed. To do otherwise may result
in a false reading or damage to your meter.
5. Do not touch any part of the circuitry on the digital programmer circuit since static electric discharge
may damage this control panel.
Always touch yourself ground while working on this panel to discharge any static charge built up in your
body.
CONDITION
Microwave oven
does not work. Inserting many plug into one
plug outlet and using
them at the same time
(causes overloading)
Microwave oven plug is not
inserted tightly.
Output power is too low. Low AC input voltage.
Food temperature is too low.
Using metallic ware and
allowing it to touch the oven
wall.
Sparks occuring.
Inconsistent intensity of
microwave by their charac-
teristics.
Uneven cooking.
Ceramic ware trimed in gold
or silver powder is used.
Avoid using other electrical
appliances when you use the
microwave oven.
Insert microwave oven plug
securely.
Use the microwave oven at
adequate line voltage.
This may not be a defect.
It is possible that the food
should be cooked for a
longer time period.
Do not use metallic ware for
cooking except where noted
in the cooking guide.
1. Wrap the thinner part with
aluminum foil.
2. Use plastic wrap or with a
lid.
3. Stir once or twice while
cooking soup, cocoa or
milk, etc.
Do not use any type of cook-
ware with metallic triming.
CAUSE REMEDY

5-13
1. Incomplete segments.
• Segment missing.
• Partial segment missing.
• Digit flickering (NOTE:Slight flickering is normal.)
2. Colon does not turn on or blink.
3. A distinct change in the brightness of one more numbers in display.
4. One or more digits in the display are not lighting.
5. Display indicates a number different from one touched, for example, key in 5 and 3 appear in the display.
6. Specific numbers (for example 7 or 9) will not display when key pad is touched.
7. Display does not count down with time blinking or up with clock operation.
8. Display obviously jumps in time while counting down.
9. Display counts down too fast while cooing.
10. Each indicator light does not turn on after setting cooking cycle.
11. Display time of day does not reappear when cooking is finished.
12. Beep sound is not heard when correct key is touched.
(TROUBLE 1) The following visual conditions indicate a probable defective control circuit.
CONDITION CHECK RESULT CAUSE REMEDY
1. No input can be
programmed. Certainly.
No certainly.
Defective PCB
assembly.
Loose connec-
tion.
Replace PCB
assembly.
Connect them
tightly.
Check the conn-
ection between
membrane key
assembly and
PCB assembly.
2. Some inputs
cannot be pro-
grammed
3. Display shows a
number or figure
different from one
touched,
4. Random pro-
gramming when
touching other
pads.
5. Display is fixed
some figure and
can not be
accepted any
input.
Everything works
as specified.
Still have trouble.
Defective key
membrane assem-
bly.
Defective PCB
assembly.
Replace key mem-
brane assembly.
Replace PCB
assembly.
Replace key
membrane
assembly and
check operation.

5-14
CONDITION CHECK RESULT CAUSE REMEDY
1. Fuse blows. Continuity.
No continuity.
Continuity. Shorted contact
the primary switch.
Replace primary
and monitor
switch.
No continuity.
Normal. Defective high
voltage capacitor. Replace high volt- age capacitor.
Fuse blows again Defective high vo-
ltage transformer. Replace high vo- ltage transformer.
Malfunciton of the
monitor switch. Replace primary,
and monitor
switch.
Check continuity
of monitor
switch (with
door closed).
Check continuity
of primary
switch (with
door opened).
Disconnect one side of the wire
lead connected from transformer
to the high voltage capacitor and
operate the unit.
Replace fuse
2. Fuse does not
blow. No continuity.
Continuity.
No continuity. Defective power
supply cord. Replace power supply cord.
Defective mag-
netron thermostat. Replace magen- tron thermostat.
Check continuity
of magnetron
thermostat.
Check continuity
of power supply
cord.
(TROUBLE 2) Oven does not operate at all ; Display window does not display any figures
and no input is accepted.
NOTE : • All these switches must be replaced at the same time. Refer to page 5-6, 5-7.

5-15
CONDITION CHECK RESULT CAUSE REMEDY
1. Setting time
does not count-
down when
touching START
pad.
2. Fan motor or
oven lamp do
not turn on.
No continuity.
Continuity.
Certainly Defective PCB
assembly.
Loose connection.
Replace PCB
assembly.
Connect them
tightly.
No certainly.
AbnormalCheck fan motor. Defective fan motor. Replace fan motor.
AbnormalCheck oven lamp. Defective oven lamp. Replace oven lamp.
Defective sec-
ondary switch. Replace sec- ondary switch.
Check continuity
of secondary
switch (with
door closed).
Check the con-
nection between
3 pin connector
and PCB
assembly.
Normal Defective PCB
assembly. Replace PCB assembly.
(TROUBLE 3) Display shows all figures set, but oven does not start cooking while desired
program times are set and START pad is touched.
(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.
NOTE : Simple test of power output-conducted by heating one liter water for one min. if available.
Minimum 8.5°C temperature rise is normal condition.
CONDITION CHECK RESULT CAUSE REMEDY
Output is low Lower than 90% of
rating voltage.
Normal
Abnormal Defective PCB
assembly. Replace PCB assembly.
Normal
Abnormal
Measure the out-
put power. Defective mag- netron. Replace mag- netron.
Decrease in power
source voltage
with load.
Suggest customer
contact local elec-
tric power utility
co. or qualified
electrician.
Check the
power source
voltage.
Disconnect the
wire leads from
relay 2 and
check on and off
time with multi-
tester.

5-16
CONDITION CHECK RESULT CAUSE REMEDY
No microwave
oscilation. No continuity. Defective PCB
assembly. Replace PCB assimbly.
Continuity.
Disconnect the
wire leads from
relay 2 and check
continuity of relay
2. (Operate the
unit)
(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.
(Display operates properly)
Abnormal Defective H.V.
circuit protector. Replace H.V. circuit protector.
Normal
Check H.V. circuit
protector.
Abnormal Defective high
voltage trans-
former.
Replace high
voltage trans-
former.
Normal
Check high volt-
age transformer.
Abnormal Defective high
voltage capacitor.
Replace high
voltage capacitor.
Normal
Check high volt-
age capacitor.
Abnormal Defective high
voltage diode.
Replace high
voltage diode.
Normal
Check high
voltage diode.
Abnormal Defective
magnetron. Replace magnetron.
Check
magnetron.

5-17
CONDITION CHECK RESULT CAUSE REMEDY
Output is full when
you set lower
power level.
Abnormal. Defective PCB
assembly. Replace PCB assembly.
Disconnect the
wire leads from
relay 2 and check
continuity relay 2.
(Operate the unit)
(TROUBLE 6) Oven does not cook properly when programmed for the set power level
(Operates properly on HIGH)
CONDITION CHECK RESULT CAUSE REMEDY
1. Heater is not
operating. Abnormal. Malfunction the
heater. Replace.
Heater.
Normal.
No continuity. Open or loosen. Replace or
connect tightly.
Wire connection.
(TROUBLE 7) Grill
NOTE • MAKE SURE THE WIRE LEADS CORRECT POSITION.
• WHEN REMOVING THE WIRE LEADS FROM THE PARTS, BE SURE TO GRASP THE CONNECTOR
NOT THE WIRES.
• WHEN REMOVING THE MAGNETRON, BE SURE TO INSTALL THE MAGNETRON GASKET IN THE
CORRECT POSITION AND IN GOOD CONDITION.
2. Lower tempera-
ture in the oven. Abnormal. Malfunction the
heater. Replace.
Heater.
Normal.
Abnormal. Defective PCB
assembly. Replace PCB assembly.
Disconnect the
wire leads from
relay 3 and check
continuity relay 3.
(Operate the unit)

6-1
INTRODUCTION
EXPLODED VIEW
DOOR PARTS
CONTROLLER PARTS
LATCH BOARD PARTS
BASE PLATE PARTS
INTERIOR PARTS
OVEN CAVITY PARTS

6-2
1. DOOR PARTS