LG MC-805A User manual

MICROWAVE/GRILL
CONVECTION OVEN
SERVICE MANUAL
MODEL : MC-805A/MC-805AR
CAUTION
BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.

SPECIFICATIONS
1-1
ITEM DESCRIPTION
MODEL MC-805A/MC-805AR
Power Requirement 230V AC50Hz
Single phase, 3 wire grounded
Microwave 1350W
Grill 1250W
Convection 1350W (MAX. 2550W)
Combination 2650W
Power Output 850W full microwave power(IEC705)
Microwave Frequency 2,450MHz
Magnetron 2M214 - 39F, 2M254J, 2M218J
Timer 90min.
Outside Dimensions 530(W) X 322 X 500mm
Cavity Dimensions 348(W) X 232 X 374mm
Net Weight 23.0kg
Shipping weight 25.5kg
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
• Convection - Max. 250°C
• Grill
• Combination
Name Plate Location
Accessories Owner's manual Glass tray
Rotating ring Convection rack
Grill rack Metal tray
Rotisserie-Bar MC-805AR ONLY
Rotisserie-Handle
This microwave oven is designed for household use only.
It is not recommended for commercial purpose.
Back Side

OPERATING INSTRUCTIONS
4-1
1. CLOCK: To set the time of day.
2. MICRO POWER: To select micro power cooking and
cooking power levels.
3. Grill: To select grill cooking.
4. CONVECTION: To select convection cooking.
5. COMBINATION: To select combination cooking.
6. WEIGHT: To set weight of food auto weight defrost.
- TIME: To set cooking times.
7. DISPLAY WINDOW: Used to show Time of day,
Cooking of day, Cooking power level, Cooking
category.
8. AUTO WEIGHT DEFROST: To select auto weight
defrost.
9. AUTO COOK: To select auto cook.
10. MORE/LESS: To select convection temperature, and
change cooking time.
11. AUTO ROAST
12. STOP/CLEAR: Stops the oven and clear all entries
except the time of day.
- CHILD LOCK
13. START/QUICK START: To quickly set the cooking
time directly.
Control panel
Glass tray
Rotating ring
Shaft
Metal tray
Convection rackGrill rack
ROTISSERIE-BAR
FOR MC-805AR ONLY
ROTISSERIE-HANDLE
Oven front plate
Window door screen
Door seal
Latch
2
8
10
11
9
12
13
7
3
1
6
4
5
1.
1.
2.
2.
3.
3.
4.
4.
Features
Control Panel

The following is a description of component functions
during oven operation.
1. SETTING THE CLOCK
2. MICROWAVE COOKING
3. MULTI STAGE COOKING
4. GRILL COOKING
5. CONVECTION COOKING
To pre-heat
To cook
6. COMBINATION COOKING
7. AUTO WEIGHT DEFROST
8. AUTO ROAST
9. AUTO COOK
10. CHILD LOCK
This oven has a CHILD LOCK feature.
To Set CHILD LOCK
To Cancel CHILD LOCK
11. QUICK START
12. MORE AND LESS
Operating Sequence
4-2
Clock
Desired
minute Start
Desired
hour
Stop/Clear
Stop/Clear
Stop/Clear
Desired
power
level
Desired
cooking
time Start
Stop/Clear Grill Desired cooking
time
Desired
cooking
time
Start Stop/Clear Stop/Clear
(Touch and Hold)
Stop/Clear Stop/Clear
(Touch and Hold)
Stop/Clear Start
Stop/Clear More
Less
Desired auto cook
Stop/Clear
Stop/Clear
Desired
defrost
category Food
weight Start
Stop/Clear Desired auto roast
category Food
weight Start
Stop/Clear Desired auto cook
category Food
weight Start
Desired power level
(20%, 40% or 60%) Desired
cooking
time Start
Stop/Clear
Desired convection
temp(40oC, 100oC~250oC)
Start
Stop/Clear
Desired convection
temp
(40oC, 100oC~250oC)
Start
Desired convection
temp(40oC, 100oC~250oC)
Grill
Desired
power level
Desired
power level Desired
cooking
time Start
Desired
cooking
time
Stage 1
OR
Stage 2

SCHEMATIC DIAGRAM
4-3
FOR MODEL:MC-805A
FOR MODEL:MC-805AR

•As the door is closed, the contact of MONITOR
SWITCH opens. This switch creates the short circuit to
blow 10 A fuse during operation under abnormal
condition.(ie, should the contacts of primary fail to open
the circuit)
•The latches are secured by latch board. The oven light
turns on while the oven is in operation.
WHEN COOKING POWER LEVEL AND
COOKING TIME ARE SET
•The contacts of the primary switch and the secondary
switch close the circuit.
•230V A.C. is applied to the high voltage transformer
through power control switch as shown by the solid
line.
•Turntable and circulation motor rotate.
•The fan motor rotates and cools the magnetron by
blowing the air (coming from the intake on the
backplate) over the magnetron.
•The air is also directed into the oven to exhaust the
vapor in the oven through the base plate and back
plate.
•3.5V A.C. is generated from the filament winding of the
high voltage transformer. This 3.5V is applied to the
magnetron to heat the magnetron filament through two
noise preventing choke coils. A high voltage of
approximately 2100V A.C. is generated in the
secondary of the high voltage transformer which is
increased by the action of the diode and charging of
the high voltage capacitor. The negative D.C. voltage is
then applied to the filament of the magnetron.
WHEN THE DOOR IS OPEN DURING
COOKING
•Both primary switch and secondary switch open to cut
off the primary winding voltage to the high voltage
transformer to stop microwave oscillation.
•Turntable and fan motor stop.
•As the door is opened, if the contact of primary switch
and relay 2 and/or secondary switch fail to open, the
10A 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 CONVECTION/GRILL
COOKING FUNCTION SELECTED.
•The contacts of the primary switch and the secondary
switch close the circuit.
•230V A.C. is applied to the grill heater through grill
thermostat as shown by the solid line.
•Turntable rotate.
•The fan motor and circulation motor rotate.
•The air is also directed into the oven to exhaust the
vapor in the oven through the base plate and back
plate.
Circuit Description
4-4
FUSE
10A
PRIMARY
SWITCH
N
L
RELAY 2
H.V.T
MONITOR
SWITCH
FUSE
10A
PRIMARY
SWITCH
N
L
RELAY 2
H.V.T
MONITOR
SWITCH
CONVECTION
HEATER
RELAY 4
L
N
E
N
LG-Y
RELAY 3
GRILL
HEATER
OVEN THERMOSTAT
L
N
E
N
LG-Y
RELAY 3
GRILL
HEATER
OVEN THERMOSTAT

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
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
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/cm2while in the
customer’s home. 4 mW/cm2stated 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 (31/2in.)
• 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
electromagnetic radiation monitor by holding the probe
perpendicular to the surface being measured.
Tools and Measuring Instruments
5-1
Microwave Leakage Test
SERVICE INFORMATION
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
adjusted.
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 NOTIFICATION
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/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.
5-2
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 190
mm.
• The oven and the empty vessel are at ambient
temperature prior to the start of the test.
• The initial temperature (±1) 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 temperature is 5°K.
A. OUT CASE REMOVAL
1) Disconnect power supply cord from the outlet.
2) Remove the screws from the rear and side 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 5)
C. REMOVING CONTROL PANEL
ASSEMBLY AND PCB ASSEMBLY
1) Disconnect the leadwire from the PCB SUB ASM.
2) Remove the screws for the earth and securing the
control panel.
3) Lift control panel assembly 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
operating at full power. Magnetron filament heat-up
time is not included.
• 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.
4) Remove three screws securing the PCB SUB ASM
from the control panel.
5) Remove the digitron window.
NOTE : Remove the leadwire and connector VERY
CAREFULLY. Be sure to grasp the connector
and not the wires.
Measurement of Microwave Power Output
5-3
Disassembly and Adjustment
Water Load
Turn Table
4187 X (∆T) + 0.88 X (T2 - T0) X M
T
• T2: Temperature after heating
• T0: Temperature of bowl
• M: Weight of bowl

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 with
the screwdriver.
3) Lift up and push the door.
NOTES
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 4 mW/cm
2
. (with a 275 ml water load)
3. When mounting the door assembly to the oven
assembly, 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.
5-4
Door seal plate
Remove the choke cover cap
Remove door

E. MAGNETRON REMOVAL
1) Disconnect the leadwire from high voltage
transformer 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 microwave
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, tighten
the mounting screws properly making sure there is no
gap between the waveguide and the magnetron.
5-5
Wave Guide
Magnetron
Noise Filter Ass'y
Fan Motor
Guide Suction
H.V Capacitor
H.V.C Bracket
H.V Diode
C. Protector
Air Duct
Oven Lamp

F. NOISE FILTER ASS'Y HIGH VOLTAGE
DIODE, HIGH VOLTAGE CAPACITOR,
AND COOLING FAN MOTOR REMOVAL
1 ) Disconnect lead wires from the noise filter ass'y and
remove screw securing the noise filter earth wire to
the back plate.
2) Push two hook of the guide suction and lift up the rear
of noise filter ass'y.
3) Disconnect lead wires from H.V. capacitor and
remove screw securing the H.V. diode earth wire to
the back plate.
4) Disconnect each lead wires from the AC relay and the
fan motor.
5) Remove two screws securing the guide suction ass'y
to the back plate and lift up the guide suction ass'y.
6) Remove one screw from H.V. capacitor bracket.
7) Pull H.V. capacitor bracket from the guide suction.
8) Remove the fan from the fan motor.
9) Remove two screws securing the fan motor to the
guide suction and lift it up.
G. OVEN LAMP REMOVAL
1) Disconnect the wire leads from oven lamp.
2) Remove one screw securing the Air Duct to the
magnetron.
3) Push hook to Right and Left of Air Duct, with Drive.
4) Lift the oven Lamp up.
H. HIGH VOLTAGE TRANSFORMER
REMOVAL
1) Disconnect the wire leads from the transformer to the
magnetron, C. Protector ASS'Y assembly.
2) Remove four screws securing the H.V. transformer to
the base plate.
3) Lift the H.V. transformer up.
I. C-MOTOR, THERMISTOR AND
SHEATH HEATER REMOVAL
1) Remove the two screws securing the cover assembly
to the oven cavity.
2) Disconnect the leadwire from the circulation motor
terminal and the sheath heater.
3) Remove the screws of the thermistor, guide assy-
chamber and lift up the guide assy-chamber.
4) Remove a hex nut securing the circulation fan to shaft
of the C-motor.
5) Remove screws securing the motor bracket to the
guide assy-chamber.
6) Remove two hex nuts securing the C-motor to the
motor bracket.
5-6
H.V. Transformer

J. TURNTABLE MOTOR REMOVAL
1) Remove the turntable.
2) Remove the turntable shaft VERY CAREFULLY with
a slotted screw driver.
3) Lay the set down on its back.
4) Remove the turntable motor cover. The turntable
motor base cover is easily removed by pinching the
six parts with a wire cutting.
5) Disconnect the lead wires from the turntable motor
terminals.
6) Remove two screws securing the turntable motor to
the oven cavity assembly.
7) Lift the turntable motor and mount turntable motor.
8) After repairing the motor, fit the turntable motor
cover's projecting part to the base plate's slit.
K. 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 play in the door by pushing the door
release button. Door movement should be less than
0.5mm. (1/64inch)
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/secondary
switch operate properly by following the continuity
test procedure.
5-7
PRIMARY
SWITCH
SECONDARY
SWITCH
ADJUSTMENT
DIRECTION
MONITOR
SWITCH

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 button 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
multimeter 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 multimeter leads to the common (COM)
and normally open (NO) terminals of the switch. The
meter should indicate a open condition. When the
door is closed, meter should indicate an 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 multimeter 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 closed circuit.When the monitor switch
operation is abnormal, replace the same type of
switch.
Interlock continuity Test
5-8
COMPONENTS TEST PROCEDURE RESULTS
SWITCHES Check for continuity of the switch
(Wire leads removed) with a Multi-meter
Primary
Switch
Monitor
Switch
Secondary
Switch
NOTE: After checking for the continuity of switches, make sure that are
correctly connected.
Door
open Door close
COM NO
COM
NC
COM
NO
WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION
EMISSION,REPLACE ONLY WITH IDENTICAL REPLACEMENT RARTS.
TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY / SECONDARY SWITCH
TYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH

Component Test Procedure
5-9
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 5)
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)
1. Measure the resistance.
(Multi-meter scale: R X 1)
• Primary winding Approx: 1.4 Ω
• Secondary winding Approx: 90 Ω
• Filament winding Less than: 0.1 Ω
2. Measure the resistance.
(Multi-meter scale: R X 1000)
• Primary winding to ground Normal: ∞.
• Filament winding to ground Normal: ∞.
MAGNETRON 1. Measure the resistance.
(Wire leads removed) (Multi-meter scale: R X 1)
• Between filament terminals Normal: Less than 1 Ω
2. Measure the resistance.
(Multi-meter scale: R X 1000)
• Filament to chassis. Normal: ∞.
Secondary
Winding
Filament
Winding
Terminal
Filament
Winding
Terminal
Primary
Winding

5-10
COMPONENTS TEST PROCEDURE RESULTS
HIGH VOLTAGE
CAPACITOR
Antenna
Gasket
Filament
Terminals
Chassis
Normal : Momentary indicates
several ohms, and
then gradually
returns to infinite.
Normal : ∞.
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.
Measure the resistance.
(Multi-meter scale : R x 1000)
• Terminal to termonal.
Measure the resistance.
(Multi-meter scale : R x 1000)
• Terminal to case.
Measure the continuity (Forward).
(Multi-meter scale : R x 10000)
Measure the continuity (Reverse).
(Multi-meter scale : R x 10000) Normal : ∞.
Abnormal : Continuity.
Normal : Continuity.
Abnormal : ∞.
HIGH VOLTAGE
DIODE
NOTE :
Some inexpensive
meter may indicate
infinite resistance in
both direction.

5-11
COMPONENTS TEST PROCEDURE RESULTS
HEATER ELEMENT
(Wire leads removed)
FUSE
(Wire leads removed.)
Normal Abnormal
0°c~Approx 150°C Approx 150°C
OVEN THERMOSTAT
MAGNETRON
THERMOSTAT
Normal :
• Grill heater
Approx. 40.7 Ω
(at 20~30°C)
Normal : more than 0.5M ΩMeasure the resistance with 500V-100M
Ωinsulation resistance meter.
Measure the resistance.
(Multi-meter scale : R x 1)
Check for continuity of the switch with a
Multi-meter.
NOTE : If the fuse is blown, check the primary, the secondary, and 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.
NOTE : Make sure heater is fully cooled when tested.

5-12
COMPONENTS TEST PROCEDURE RESULTS
GRILL HEATER
(Wire leads removed)
SOLENOID
RECTIFIRE ASM:
VOLTAGE FOR
SOLENOID
CIRCULATION MOTOR
(Wire leads removed)
NOTE:
*( ) = WIRE COLOR
Normal : COM-230V : Approx. 150 Ω
COM-24V : Approx. 20 Ω
Abnormal : Infinite or several ohm.
Normal : Approx. 200~300 Ω
Abnormal : Infinite or several
ohm.
Normal : Approx. 134 Ω
Abnormal : Infinite or several ohm.
DC : 24V
24V
(BN)
COM
(YL)
230V(BL)
AC 28V
DC 24V
INPUT
OUT PUT
BN
YL
Measure the resistance.
(Multi-meter scale : R x 1)
Measure the resistance.
(Multi-meter scale : R x 1)

5-13
COMPONENTS TEST PROCEDURE RESULTS
RELAY 3, 4, OF P.C.B
(Disconnect the 7 pin
connector from P.C.B)
See Schematic Dagram on
page 9)
RELAY 2, 3, 4 OF P.C.B
(Wire leads removed.)
RY2 : Microwave
RY3 : Grill
RY4 : Convection
MEMBRANE KEY Check continuity between
switch terminals, by pressing an
appropriate pad on key board.
The contacts assignment of the
respective pads on the key
board is as shown left figures.
Cooking Start OFF
CN2 1
3
5
7Relay 3 Relay 4
Relay 3 Relay 4 Relay 2
1
2
3
4
5
6
7
8
9
10
11
1
2
3
4
5
6
7
8
9
10
11
Membrane
Panel P.C.B
Cooking Start OFF
NOTE : A MICROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS
SERVICED FOR ANY REASON.
MAKE SURE THE WIRE LEADS ARE CORRECT POSITION.
WHEN REMOVING THE WIRE LEAD FROM THE PARTS, BE SURE TO GRASP THE
CONNECTOR, NOT THE WIRES.

Trouble Shooting Guide
5-14
CAUTIONS
1. Check grounding before checking for other trouble.
2. Be careful of the high voltage circuit.
3. When checking the continuity of the switches or transformer, disconnect one lead wire from these parts and
then check continuity without turning the power source on.
4. Do not touch any part of the circuitry on the control circuit board, since static electric discharge may damage
this control circuit.
Always touch yourself to ground while working on this circuit to discharge any static charge built up in your
body.
5. First operate the microwave oven following the correct operating.
6. If the oven become inoperative because of a fuse, check the primary, the secondary and the monitor switches
before replacing the fuse.
CONDITION
The fuse blows when power
cord is plugged into wall
receptacle.
Shorted lead wise assy or
wire hardness.
Defective monitor switch or
out of adjustment. Test procedure switches.
": 0" does not appear in
displasy window when
power cord is first plugged
into wall outlet.
Microwave oven plug is not
inserted tightly.
No power at outlet. Check home fuse.
Replace or repair wiring.
Test procedure tact switch
key.
Defective tact switch key of
P.C.B.
Display does not operate
properly when CLOCK is
touched.
Open wire in power cord,
wiring harness, or wiring
between control panel
assembly units.
Insert microwave oven plug
securely.
Replace lead wire or check
and repair wire hardness.
CAUSE TEST PROCEDURE OR
CORRECTION
Blown fuse. Test procedure fuse.
(TROUBLE 1) Oven does not operate all.
OFF CONDITION