National NN-C781JF User manual

Service Manual
ORDER NO. SIMMC 0110022C3
E1
Microwave Oven
© 2001 Shanghai Matsushita Microwave
Oven Co.,Ltd
All rights reserved. Unauthorized copying
and distribution is a violation of law.
Specifications:
Power Source:
Power Requirement: Microwave
Heater
Output: Microwave (ICE 705)
Heater
Microwave Frequency:
Timer:
Outside Dimensions:
Oven Cavity Dimensions:
Weight:
Output power: IEC705-88 Test Procedure
Specifications subject to change without notice.
Specifications:
Models:
240V AC Single Phase, 50Hz .......... For KNQ Models
230V-240V AC Single Phase, 50Hz . For MNQ, YNQ Models
220V AC Single Phase, 50Hz .......... For HNE, TNE, YKE, KKE, ZPE Models
220V AC Single Phase, 50/60Hz ..... For SNM Models
120V AC Single Phase, 60Hz .......... For WNT Models
1260W
1550W
1000W
1515W
2450MHz
30min (HIGH) / 99min. 59sec
400mm (W) x 520mm (D) x 312mm (H)
373mm (W) x 373mm (D) x 206mm (H)
15.5kg
NN-C781JF
NN-C781JF
®

WARNING
CONTENTS
(Page) (Page)
- 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 compartments,
check the magnetron, waveguide 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 trans-
mission 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.
WARNING
This service information is designed for experienced repair technicians only and is not designed for use by the general public. It does not
contain warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product.
Products powered by electricity should be serviced or repaired only by experienced professional technicians. Any attempt to service or repair
the product or products dealt with in this service information by anyone else could result in serious injury or death.
1.This product should be serviced only by trained, qualified personnel.
2.Check for radiation leakage before and after every servicing according to the “procedure for measuring radiation leakage.”
3.If the unit cannot be repaired on site, advise the customer not to use until unit is repaired.
4.There are special components used in the microwave oven which are important for safety. These parts are marked with
a on the replacement parts list. It is essential that these critical parts should be replaced only with the manufacture’s
specified parts to prevent microwave leakage, shock, fire, or other hazards. Do not modify the orginal design.
This service manual covers products for following markets.
When troubleshooting or replacing parts, please refer to the country/area identifications shown below for your
applicable product specification.
HNE ......................................... For Hong Kong KKE .................................... For UAE, Egypt, Iran
YNQ ......................................... For Singapore KNQ ................................... For Kuwait, Doha, Quatar
MNQ ......................................... For Malaysia Oman, Bahrain, Pakistan
TNE .......................................... For Thailand, Indonesia SNM ................................... For Saudi Arabia
YKE .......................................... For Others ZPE .................................... For CIS Countries
WNT ......................................... For Tai Wan
FEATURE CHART ............................................................................... 4
CONTROL PANEL ............................................................................... 4
OPERATION AND DIGITAL PROGRAMMER
CIRCUIT TEST PROCEDURE ............................................................ 5
SCHEMATIC DIAGRAMS .................................................................... 7
DESCRIPTION OF OPERATING SEQUENCE ................................... 9
CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING ......... 11
DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE ........... 13
COMPONENT TEST PROCEDURE .................................................... 17
MEASUREMENTS AND ADJUSTMENTS ........................................... 20
PROCEDURE FOR MEASURING MICROWAVE ENERGY LEAKAGE ... 21
TROUBLESHOOTING GUIDE ............................................................ 22
EXPLODED VIEW AND PARTS LIST .................................................. 28
SCHEMATIC DIAGRAM &
PARTS LIST OF DIGITAL PROGRAMMER CIRCUIT ......................... 34
!
!

DANGER OF HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LIVE) OF THE INVERTER POWER SUPPLY (U)
INVERTER WARNING
This Inverter board looks like a regular PCB. However, this PCB drives the magnetron tube with extremely high voltage
and high current.
IT HAS: 1. Very high voltage and high current circuits.
It functions the same as the high voltage transformer and high voltage capacitor in ordinary microwave ovens.
2. Aluminum heat sink is energized with very high voltages and high heat energy.
3. Very high voltage may remain in circuitry even when oven is off. High voltage may remain in the capacitors
on the board.
DO NOT:
1. Do not touch circuitry because it has very hot (high voltage) circuitry. Even when replacing board, extreme
care should be taken to avoid possible electric shock hazards. High voltage may remain in circuit.
2. Do not touch aluminum heat sink because it is very hot in high voltage and also very hot in high heat energy.
3. Do not try to adjust or tamper with preset volume on the Inverter board because it is very dangerous to
adjust without proper test equipment.
4. Do not test oven while Inverter grounding plate or screws are loose. It is very dangerous to operate H.V.
Inverter Circuit (U) with loose mounting screws or if improperly grounded.
5. For USA only:
Do not try to repair Inverter PCB because it is very dangerous to repair it. Replace as whole High Voltage
Inverter Circuit unit and return fully re-packed with original shipping box and shipping materials.
INVERTER POWER SUPPLY
- 3 -
*
*
*
*
*
HEAT SINK
(RECTIFIER BRIDGE)
CHOKE COIL
CURRENT
TRANSFORMER
SAND BAR
RESISTOR
HIGH VOLTAGE
TRANSFORMER
PCB
FILM CAPACITORS
VARISTOR
PRIMARY WINDINGS
SECONDARY
WINDINGS
HIGH VOLTAGE
DIODES
DO NOT TOUCH
GROUND
METAL
RELEASE TAB
TO MAKE FLAT
NEW H.V.

FEATURE CHART
- 4 -
CONTROL PANEL
NN-C781JF
FEATURE
Three Stage Cooking
Grill
Convection Bake
Combination
Turbo Defrost
Sensor Reheat
One Touch Cook (weight)
Sensor Cook
Child Safety Lock
Delay Start
Timer/Stand
Digital Clock
MODEL NN-C781JF
Pull Door Handle:
Pull to open the door. Opening the door during cooking will stop the cooking process without cancelling the program. Cooking
resumes as soon as the door is closed and Start Pad is pressed. The oven lights will turn on and stay on whenever the door is
opened. It is quiet safe to open the door at any time during a cooking program and there is no risk of microwave exposure.
Beep Sound:
When a pad is pressed correctly, a beep will be heard. If a pad is pressed and no beep is heard, the unit has not accepted the
instruction. The oven will beep twice between programmed stages. At the end of any complete program, the oven will beep five
times.
Display Windows
Grill Pad
Time Pads
Turbo Defrost Pad
Recipe Stores Pads
Timer Pad
Start Pad
Micro Power Pad
One tap allows oven to begin
functioning. If door is opened or
STOP/RESET Pad is pressed once
during oven operation, START Pad
must again be pressed to restart
oven.
Auto Menu/Sensor Cook Pads
Sensor Reheat Pad
Conv.Bake Pad
Combination Pad
More/Less Pads
Clock Pad
Auto Menu/Auto Cook Pads
Before cooking: One tap clears your instructions.
During cooking: One tap temporarily stops the cooking
process. Another tap cancels all your instructions and
time of day or colon appears on the display window.
Stop/Reset Pad

- 5 -
OPERATION AND DIGITAL PROGRAMMER CIRCUIT TEST PROCEDURE
1. Press Grill pad.
2. Set for 30 minutes by pressing
pads.
3. Press Start Pad.
4. When cooking time has elapsed.
Oven beeps 5 times and shuts off.
7. When 1st stage cooking time has
elapsed. Oven beeps twice and
automatically switches to 2nd
stage cooking.
8. When 2nd stage cooking time has
elapsed, oven beeps 5 times and
shuts off.
3. Grill
OPERATION SCROLL DISPLAY
OPERATION SCROLL DISPLAY
2. Press Micro Power pad once
to set High power.
(1st stage)
3. Set for 5 seconds by pressing
pads.
4. Press Micro Power pad 4 times
to set Medium power.
(2nd stage)
5. Set for 1 minute by pressing
pads.
6. Press Start pad.
OPERATION SCROLL DISPLAY
1. Plug the power supply cord into
wall outlet.
2. Press Start pad twice to select
English.
3. Press Clock pad.
4. Enter time of day (TOD) by press-
ing appropriate pads.
5. Press Clock pad. TOD has now
been resistered into the digital
programmer circuit and will count
up by minutes.
2. Time Cooking for Two Stage
OPERATION SCROLL DISPLAY
1. Place a water load in the oven.
88.88
11 25
11: 25
1 00
min s
HIGH
5
s
MEDIUM
1. To Set Clock
1. Press Combination pad.
2. Set for 2 hours by pressing
pad.
3. Press Start pad.
4. When cooking time has elapsed.
Oven beeps 5 times and shuts off.
4. Combination
OPERATION SCROLL DISPLAY
4
10 110 1
10 110 1
10 110 1
ENGLISH
GRILL 1
30 00
min s
30 00
min s
5
s
Time of day or colon if set appears
in the display.
1 00
min s
Time of day or colon if set appears
in the display.
10 110 1
10 110 1
Time of day or colon if set appears
in the display.
2H 00
2H 00
COMB 1
Power connected, then scroll display “ 88.88 ” . Press Start pad once for
Chinese only. Press twice for both Chinese and English sisplay. Press 3 times
for English only. Press 4 times for BAHASA only.
CHINESE
CHINESE + ENGLISH
ENGLISH
BAHASA
S
S

- 6 -
1. Press Clock pad 3 times
continuously.
Note: To cancel demonstration
mode, press Clock pad 3
times continuously.
OPERATION SCROLL DISPLAY
OPERATION SCROLL DISPLAY
1.Set the weight for 1 kg by press-
ing 1.0 kg pads.
2. Press Start pad.
3. When cooking time has elapsed.
Oven beeps 5 times and shuts off.
1.0 KG
5. Turbo Defrost
14 36
min s
DEMO MODE
Time of day or colon if set appears
in the display.
OPERATION SCROLL DISPLAY
1. Set the weight for 500g by
pressing Roast Beef pad.
2. Press Start pad.
3. When cooking time has elapsed.
Oven beeps 5 times and shuts off.
500 G
14 00
min s
8. To Set Child Safety Lock
OPERATION SCROLL DISPLAY
1. Press Start pad 3 times
continuously. “LOCK” appears
in the display
LOCK
9. To Reset Child Lock
OPERATION SCROLL DISPLAY
1. Press Stop/Reset pad 3 times
continuously.
Time of day or colon if set appears
in the display.
10. Demonstration Mode
The domonstration mode designed for retail store display. It is not
designed for home use. Cooking will not operate during
demonstration mode.
To set demonstration mode.
1. Pour 150±15cc (4.5±1/2ozs) of
room temperature water in a oven
glassware or ceramic utensil.
Place the oven glassware or
ceramic utensil in the center of the
oven.
2. Tap Sensor Reheat pad.
3. Tap Start pad.
4. The steam sensor detects steam
about 1.5 to 4 minutes after the
Start Pad is tapped.
Sensor Brown Cooking (T1)
automatically switches to time
cooking (T2).
“AUTO” disappeares with beep
sounds and the remainder of
cooking time appears in display
window.
NOTE: Cooking time will vary
depending on the water
temperature, the shape
of beaker or the power
source voltage.
5. When the balance of cooking
time has elapsed, oven stops
and beeps five times.
OPERATION SCROLL DISPLAY
11. Sensor Cooking
Note: Make sure that the control panel is installed before Sensor
Cooking tast since Auto Sensor function does not operate
properly without the outer panel.
18
s
48
s
6. One Touch Cooking
7. Convection Bake
OPERATION SCROLL DISPLAY
1. Press Conv. Bake pads twice.
2. Press Start pad.
3. When cooking time has elapsed.
Oven beeps 5 times and shuts off.
160˚C
P

V-16G-3C26-M
BL
BL
W
W
(W)
L-3C2-2
BL
BR
B
(W)
BR
B
BL
(BL)
L-2C2-2
BR
W
(Y)
W
B
BR
(R)
BR
POWER RELAY 4 (RY4)
POWER RELAY 1
(
RY1
)
HIGH VOLTAGE INVERTER
SCHEMATIC DIAGRAM
- 7 -
NN-C781JF (EXCEPT ZPE & WNT)
WIRING DIAGRAM
NEW H.V.
CAUTION: H.V.
(S-5G0)
CAUTION
HIGH VOLTAGE AREA
10A
FUSE
50Hz
AC 220V-240V
SW0 SW1
DIGITAL PROGRAMMER CIRCUIT
STEAM SENSOR
TEMP SENSOR
INVERTER
MAGNETRON
2M261-M32F
THERMAL CUTOUT
(HEATER)
PRIMARY LATCH
SWITCH
SECONDARY LATCH
SWITCH
SHORT SWOTCH
GROUNDING
CHASSIS GROUND
FUSE
FAN MOTOR
CONVECTION
MOTOR
TURNTABLE MOTOR
OVEN LAMP
HEATER
POWER RELAY
SWITCHING POWER
SUPPLY
3.3µF
NEW H.V.
NOTE: Door closed.
Unit is not operating.
Ground
Chassis

V-16G-3C26-M
BL
BL
W
W
(W)
L-3C2-2
BL
BR
B
(W)
BR
B
BL
(BL)
L-2C2-2
BR
W
(Y)
W
B
BR
(R)
BR
POWER RELAY 4 (RY4)
POWER RELAY 1
(
RY1
)
HIGH VOLTAGE INVERTER
SCHEMATIC DIAGRAM
- 8 -
NN-C781JF (ZPE, WNT)
WIRING DIAGRAM
NEW H.V.
CAUTION: H.V.
(S-5G0)
CAUTION
HIGH VOLTAGE AREA
AC 220V, 50Hz
AC 120V, 60Hz
SW0 SW1
DIGITAL PROGRAMMER CIRCUIT
STEAM SENSOR
TEMP SENSOR
INVERTER
MAGNETRON
2M261-M32G
THERMAL CUTOUT
(HEATER)
PRIMARY LATCH
SWITCH
SECONDARY LATCH
SWITCH
SHORT SWOTCH
GROUNDING
CHASSIS GROUND
FUSE
FAN MOTOR
CONVECTION
MOTOR
TURNTABLE MOTOR
OVEN LAMP
HEATER
POWER RELAY
SWITCHING POWER
SUPPLY
NEW H.V.
NOTE: Door closed.
Unit is not operating.
Ground
Chassis

DESCRIPTION OF OPERATING SEQUENCE
1. Variable power cooking control
HIGH-VOLTAGE INVERTER POWER SUPPLY (U) controls output
power by the signal from Digital Programmer Circuit (DPC). Power relay
1 stays on but the inverter drive signal to control it’s output power.
NOTE 1: The ON/OFF time ratio does not correspond with the
percentage of microwave power since approximately 2
seconds are required for heating of magnetron filament.
NOTE 2: If microwave cooking is over 3 minutes, fan motor rotates for
1 minute after cooking to cool oven and electric components.
2. Inverter Power Supply Circuit NEW H.V.
This Inverter Power Supply Circuit supplies 4,000V DC to the magnetron
tube from the line voltage, 220-240V 50Hz / 120V 60Hz AC input. functions
as the H.V. transformer, the H.V.capacitor and H.V.Diode.
(A) The AC input voLtage 220-240V 50Hz / 120V 60Hz is rectified to DC
voltage immediately.
(B) DC voltage will be supplied to the switching devices called IGBT.
These devices will be switched ON-OFF by the 20 to 40 kHz PWM.
(pulse width modulation) signal from the microcomputer in the DPC.
(C) This drives the High voltage transformer to increase up to 2,000V
AC and approximately 3V AC by means of transformer.
(D) Then the half-wave doubler voltage rectifier circuit, consisting of the
HV diodes and Capacitors, generates the necessary 4,000V DC
needed for the magnetron.
(E) Output power of the magnetron tube is always monitored by the
signal output from the current transformer built into the inverter
ciruit.
(F) Then this signal will be fed back to the microcomputer in the DPC to
determine operating conditions and output necessary to control PWM
signal to the inverter Power Supply to control output power.
3. Turbo Defrost Control
When this Auto Control feature is selected and the Start Pad is tapped:
(A) The digital programer circuit determines the power level and
cooking time to complete cooking and indicates the operating state
in the display window. Table shows the corresponding cooking
times for respective serving by categories.
(B) When cooking time the display window has elapsed, the oven
tums off automatically by a control signal from the digital
programmer circuit.
4. Convection Cooking Control
The digital programmer circuit controls the ON-OFF time of the heater
in order to control oven cavity temperature.
(A) After the start pad is tapped with the desired Bake/Broil program
set, an 12V DC singal comes out of the digital programmer circuit
and is applied to coil of power relay (RY4).
(B) When the contacts of power relay 4 close, power source voltage
is applied to the heater and the heater turns on.
(C) When the oven temperature reaches the set temperature, the
digital programmer circuit senses the temperature through oven
temp sensor and stops supplying and 12V DC signal to the coil of
power relay 4 and the heater turns off.
(D) After the heater turns off, the oven temperature will continue
increasing a while and then decrease as shown in Figure. When
the oven temperature drops below the set temperature, the digital
programmer circuit senses the signal and starts supplying an 12C
DC signal to the coil of power relay again.
- 9 -
POWER SETTING
OUTPUT
POWER(%)
APPROX.
Variable Power Cooking
HIGH
MEDIUM-HIGH
MEDIUM
MEDIUM-LOW
LOW
DEFROST
100%
70%
55%
30%
10%
30%
stay ON
stay ON
stay ON
15s ON / 7s OFF
8s ON / 14s OFF
16s ON / 6s OFF
stay ON
stay ON
stay ON
ON / OFF
ON / OFF
ON / OFF
INVERTER
CONTROL
SIGNAL
RY-1
OVEN TEMP
HEATER
(RY4)
CONVECTION
FAN MOTOR
(RY5)
OVEN TEMP
SELECTED OVEN TEMP
START
ON OFF ON OFF ON
ON
Turbo Defrost
WEIGHT
SELECTED
1.0KG
COOKING TIME
14min. 36 sec.
Convection Cooking

5. Combination Cooking
Combination cooking is accomplished by microwave and convection
cooking being done alternately during one combination cooking cycle.
One combination cooking cycle is 22 seconds.
(A) During combination cooking, the digital programmer circuit
controls ON-OFF time of both power relay 1 and 4 as shown in
Figure.
(B) When the power relay 1 (RY1) is turned on, heater turns off and
after the power relay 1 turns off, power relay 4 turns on.
NOTE 1: Note that the heater may not be on during a heater on
period if the preprogrammed oven temperature has been
reached. This is due to the fact that the oven is keeping the
preprogrammed oven temperature constant, so of course
the heater will only be on when it is needed and off when it
is not needed.
NOTE 2: As for temperatures of combination cooking for
convection, the temperatures by each program are
preprogrammed in the microprocessor as shown in Figure.
- 10 -
Combination
No.
1
2
3
Microwave (RY 1)
ON (SEC) OFF (SEC)
8
5
12
14
17
10
OVEN TEMP
HEATER
(RY4)
CONVECTION
FAN MOTOR
(RY5)
FAN MOTOR
(RY3)
MICROWAVE
(RY1)
SELECTED OVEN TEMP
START
8S
OFF
8S
ON
STOP
14S
ON
ON
14S
OFF
ON/OFF
EX COMEINATION 1

CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING
Unlike many other appliances, the microwave oven is high-voltage, high
current equipment. Though it is free from danger in ordinary use, extreme
care should be taken during repair.
1. Check the grounding
Do not operate on a 2-wire extension cord. The microwave oven is
designed to be used when grounded. When it is inoperative, make
sure it is grounded properly before beginning repair work.
2. Inverter Warnings
CAUTION
Servicemen should remove their watches whenever
working close to or replacing the magnetron.
DANGER OF HIGH VOLTAGE AND HIGH
TEMPERATURE (HOT/LIVE) OF THE INVERTER
POWER SUPPLY (U)
This High Voltage Inverter Power Supply circuit supplies
very high voltage and very high current for the magnetron
tube. Though it is free from danger in ordinary use, extreme
care should be taken during repair. As you can see, it looks
like a TV flyback transformer, however the current is
extremely large and so danger exists because of its high
current and high voltages.
The aluminum heat sink is also energized with high voltage
(HOT), so do not touch when AC input terminal is connected
to the power line because one of the IGBT switching power
devices (Collector) is directly connected to the Aluminum
heat sink.
The Aluminum heat sink may be HOT from heat energy;
therefore, extreme care should be taken during servicing
and replacing.
WARNING OF INVERTER POWER SUPPLY (U)
GROUNDING
Check the High Voltage Inverter Power Supply circuit grounding.
This High Voltage Inverter Power Supply circuit board must have
a proper chassis ground by the grounding bracket to the chassis
ground; otherwise, this H.V. Inverter circuit board will expose
very high voltage and cause extreme DANGER! Be sure to have
proper grounding by the grounding plate and screws.
WARNING OF DISCHARGING HIGH VOLTAGE
CAPACITORS
Warning about the electric charge in the high voltage capacitors.
For about 30 seconds after the oven is turned off, an electric charge
remains in the high voltage capacitors in the inverter power supply
circuit board.
When replacing or checking parts, remove the power plug from
the outlet and short the Inverter output terminal of the magnetron
filament terminals to the chassis ground with an insulated handle
screwdriver to discharge. Please make sure to touch chassis
ground side first then short to the output terminals.
WARNING
There is high-voltage present, with high-current capabilities in the
circuits of the primary, and secondary windings, choke coil and
heat sink of the Inverter. It is extremely dangerous to work on or
near these circuits with oven energized.
DO NOT measure the voltage in the high voltage circuit including
filament voltage of magnetron.
WARNING
Never touch any circuit wiring with your hand nor with an
insulated tool during operation.
3. When parts must be replaced, remove the power
plug from the outlet.
4.When the 10 Amp fuse is blown due to the operation
of short switch:
(A) This is mandatory. Refer to “Measurements and Adjustments”
for these switches.
(B) When replacing the fuse, confirm that it has the appropriate
rating for these models.
(C) When replacing faulty switches, be sure mounting tabs are
not bent, broken or otherwise deficient in their ability to hold
the switches.
5.Avoid inserting nails, wire, etc. through any holes in
the unit during operation.
Never insert a wire, nail or any other metal object through the
lamp holes on the cavity or any other holes or gaps, because
such objects may work as an antenna and cause microwave
leakage.
INVERTER
GROUND WIRE
Touch chassis side first then short to the high voltage diode terminal.
- 11 -
NEW H.V.
WARNING
When the 18 Amp. fuse if blown due to the operation of
short switch, you must replace Primary latch switch and
short switch. Also replace power relay B (RY1) when the
continuity check reads shorted contacts (1-2).
HIGH
VOLTAGE
CAPACITORS
SHORT FOR
DISCHARGE
HIGH VOLTAGE
CAPACITORS
DANGER OF HIGH VOLTAGE
AND HIGH TEMPERATURE
HOT/LIVE OF HEAT SINK
HIGH VOLTAGE REMAINS
IN HIGH VOLTAGE CAPACITORS
SHORT FOR
DISCHARGING
HIGH VOLTAGE
REMAINS IN
HIGH VOLTAGE
CAPACITORS
CHOKE COIL
CURRENT
TRANSFORMER
VR 701
* DO NOT
ADJUST
GROUNDING
HOLE

6.Confirm after repair
(A) After repair or replacement of parts, make sure that the screws of the
oven, etc. are neither loose nor missing.
Microwaves might leak if screws are not properly tightened.
(B) Make sure that all electrical connections are tight before inserting the
plug into the wall outlet.
(C) Check for microwave energy leakage. (Refer to procedure for measuring
microwave energy leakage.)
CAUTION
MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM THE
MICROWAVE GENERATOR OR OTHER PARTS CONDUCTING
MICROWAVE ENERGY.
IMPORTANT NOTICE
1. The following components have potentials above 250V while the
appliance is operating..
h Magnetron
h High voltage transformer (Located on Inverter (U))
h High voltage diodes (Located on Inverter (U))
h High voltage capacitors (Located on Inverter (U))
Pay special attention on these portions.
2. When the appliance is operated with the door hinges or magnetron
fixed incorrectly, the microwave leakage can reach more than
5mW/cm2. After repair or exchange, it is very important to check if
magnetron and the door hinges are correctly fixed.
NEW H.V.
- 12 -
*
*
*
*

- 13 -
DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE
1. Magnetron
1. Discharge the high voltage capacitors.
2. Remove A screw holding magnetron on bracket.
3. Remove 2 high voltage lead wires.
4. Remove circulation fan motor bracket and belt. (2 screws)
5. Remove air guide. (2 screws)
6. Remove 4 screws holding magnetron.
NOTE: After replacement of the magnetron, tighten mounting
screws properly making sure there is no gap between the
waveguide and the magnetron to prevent microwave
leakage.
NOTE: Magnetron used for this modes is unique type for inverter
power supply system. Make sure to use the one as listed in
the part list.
CAUTION
When replacing the magnetron, be sure the antenna
gasket is in place.
REMOVE
BRACKET
DISCHARGE
HIGH VOLTAGE
CAPACITORS
REMOVE
GROUND
WIRE
08-180M
08-155M
08-150M
2. Digital Programmer Circuit (DPC) and membrane key
board.
NOTE: Be sure to ground any static electric charge built up on
your body, before handling the DPC.
1. Disconnect all connectors from D.P.C.
2. Remove 2 screws holding escutcheon base and slide the
escutcheon base upward slightly with door closed.
3. Release CN5 connector’s lock of DPC by pushing both levers to
inside and pull them upward, and remove flat cable of membrane
key board.
4. Remove 3 screws holding DPC.
To replace membrane key board
5. Remove escutcheon bracket from escutcheon base by freeing 5
catch hooks on the escutcheon base.
6. On some models, the key board is not replaced with individual
parts. Instead, the entire escutcheon base assembly must bu
replaced. Refer to parts list.
NOTE
Magnetron used for this model is unique type for inverter
power supply system. Make sure to use the one as
listed in the part list.

- 14 -
3. Inverter Power Supply (U)
1. Discharge high voltage capacitors.
2. Remove 2 screws holding magnetron bracket. (Remove grounding
wire)
3. Remove 3 screws holding inverter and fan motor assembly.
4. Unplug 3 connectors of inverter PCB.
5. Remove 2 screws holding inverter PCB on to bracket.
NOTE: Do not pull by lead wires but make sure to pull housing
unless PCB or lead wire may break.
08-154M
08-153M
GROUND
METAL
RELEASE TAB
TO MAKE FALT
GROUND METAL
RELEASE TAB
TO MAKE FALT
08-149M
GROUND WIRE
GROUND METAL
08-181M

- 15 -
PUSH
DOOR ARM
DOOR
DOOR
SPRING
LEFT
HINGE
CATCH HOOKS
HINGE PIN HINGE PIN
CUT
TURNTABLE
MOTOR
4. Door assembly
1. Remove door spring right side.
NOTE: Please hold door unless door become fall down.
2. Remove door arm lever by pushing tab and turn clock wise.
3. Remove door spring left.
4. Insert flat blade screw driver to release hinge pin from left hinge.
5. Slide out left hinge pin to release the door.
6. Slide out door arms from the oven to disconnect door assembly.
7. Remove door arms from the door assembly.
To remove door C
8. Release catch hooks from hinge pin side.
To remove door E
9. Remove screws holding door E to door A assembly.
After replacement of the defective component parts of the
door, reassemble it and follow the instructions below for
proper installation and adjustment so as to prevent an
excessive microwave leakage. Adjustment of the door
assembly.
10. When mounting the door to the oven, be sure to adjust, the
door parallel to the oven face plate by moving hinges back or
front.
NOTE: Upper portion of door A should farmly touch to oven
face plate without pushing.
5. Turntable motor
1. Breaking off at 5 spots indicated by allow with a cutter or like.
2. Remove 2 screws holding motor cover.
3. Disconnect 2 lead wires from turntable motor.
4. Remove 2 screws holding turntable motor.
NOTE: Make sure to remove sharp barrs at 5 spots to avoid
possible injury.

- 16 -
6. Heater
1. Remove belt.
2. Remove 2 lead wires from heater.
3. Remove 2 screws holding heater and oven temperature
sensor.
4. Turn right to release hooks to remove heater assembly.
5. Remove a screw to release heater.
EXHAUST GUIDE
SENSOR MOUNTING PLATE
HOOK
HOOK
SENSOR MOUTING PLATE
METAL
SURFACE
SURFACE OF LEAD WIRE
(WHITE SURFACE)
METAL SIDE
TO DETECT
STEAM
FROM OVEN
CAVITY
7. Steam sensor
1. Remove 1 screw holding steam sensor unit.
2. Disconnect CN2 connector from digital programmer circuit
board.
3. Remove exhaust guide from steam sensor unit.
4. Remove catch hooks on sensor mounting plate and air guide.
5. Remove steam sensor from sensor mounting plate.
NOTE: When installing the steam sensor, make sure that the
direction of steam sensor is as shown in figure.
TO RELEASE
HEATER UNIT
BELT

Test 1
A. Place 1 liter of water load into oven cavity.
B. Unplug 2 pin H.V. lead wire connector CN703 from magnetron
tube.
C. Program oven at High power for 1 minute and press start.
1. After approximately 23 seconds, oven stops.
2. During oven operation, input current is approx. at 0.5 to
1.0A. If both 1 and 2 are OK, please proceed to test 2.
Test 2.
Continued from Test 1
A. Unplug 3 pin connector, CN701 & CN703 remains unplug.
B. Set oven at High power for 1 minute and start.
1. After approximately 3 seconds, oven stops.
2. During oven operation, input current is approximately less
than 0.4A.
If both 1 and 2 are OK, the Inverter Power Supply (U) can be
determined OK.
COMPONENT TEST PROCEDURE
CAUTION
1. High voltage is present at the high voltage terminal of
the High Voltage Inverter (U) including aluminum heat
sink during any cook cycle.
2. It is neither necessary nor advisable to attempt mea-
surement of the high voltage.
3. Before touching any oven components, or wiring,
always unplug the oven from its power source and
discharge the high voltage capacitors.
NEW. H.V.
1. Primary Latch Switch, Secondary (Secondary Latch
Switch and Power Relay B) Interlocks.
(A) Unplug the lead connectors to Power Relay B and verify continuity
of the power relay B 1-2 terminals.
(B) Unplug lead connectors to Primary Latch Switch and Secondary
Latch Switch.
(C) Test the continuity of switches at door opened and closed positions
with ohm meter (low scale).
Normal continuity readings should be as follows.
2. Short Switch & Monitor
(A) Unplug lead wires from Inverter Power Supply (U) primary terminals.
(B) Connect test probes of ohm meter to the disconnected leads which
were connected to Inverter Power Supply (U).
(C) Test the continuity of short switch with door opened and closed
positions using lowest scale of the ohm meter.
Normal continuity readings should be as follows.
Door Closed
0 Ω(close)
0 Ω(close)
5. Inverter Power Supply (U)
DO NOT try to REPAIR this H.V. Inverter power supply
(U).Replace as whole H.V. Inverter(U) Unit.
Primary Latch Switch
Secondary Latch Switch
Power Relay B
Door Closed
∞Ω
Door Opened
0 Ω
- 17 -
3. Magnetron
Continuity checks can only indicate an open filament or a shorted
magnetron. To diagnose for an open filament or shorted magne-
tron.
(A) Isolate magnetron from the circuit by disconnecting the leads.
(B) A continuity check across magnetron filament terminals should
indicate one ohm or less.
(C) A continuity check between each filament terminal and magnetron
case should read open.
ANTENNA
COOLING
FIN
MAGNETRON
CASE
HIGHEST
OHM
SCALE
FILAMENT
TERMINALS
04-031M
0Ω-1Ω
RX1
SCALE
ANTENNA GASKET
HEAT SINK
CHOKE COIL
CURRENT
TRANSFORMER
RESISTOR
SAND BAR
PCB
FILM CAPACITORS
VARISTOR
PRIMARY WINDINGS
SECONDARY
WINDINGS
HIGH VOLTAGE
DIODES
DO NOT TOUCH
SYMPTOM
Oven stops in 23
seconds after
started.
Unplug CN703
INPUT AMPERE
0.5 to 1A
HIGH BOLTAGE
TRANSFORMER
DO NOT TOUCH (HOT/HIGT VOLTAGE)
Door Opened
∞Ω(open)
∞Ω(open)
∞Ω(open)
4. Membrane key board (Membrane switch assembly)
Check continuity between switch terminals, by tapping an appropri-
ate pad on the key board. The contacts assignment of the
respective pads on the key board is as shown in digital programmer
circuit.
∞Ω(open)
SYMPTOM
Oven stops in 3
seconds after
started.
Unplug CN701
INPUT AMPERE
< 0.4A

- 18 -
6. Sensor Cooking
Auto sensor cooking is a revolutionary way to cook by microwave
without setting a power level or selecting a time.
All that is necessary is to select an Auto Sensor Program before starting
to cook.
Understanding Auto Sensor Cooking
As the food cooks, a certain amount of steam is produced. If the food
is covered, this steam builds up and eventually escapes from the
container. In Auto Sensor Cooking, a carefully designed instrument,
called the steam sensor element, senses this escape of steam. Then,
based upon the Auto Sensor Program Selected, the unit will
automatically determine the correct power level and the proper length
of time it will take to cook the food.
NOTE: Auto Sensor Cooking is successful with the foods and
recipes found in the Auto Sensor Cooking Guide. Because
of the vast differences in food composition, items not
mentioned in the Cooking Guide should be prepared in the
microwave oven using power select and time features. Please
consult variable Power Microwave cookbook for procedures.
Explanation of the Auto Sensor Cooking process
1) During the first 10 second period there is no microwave activity,
and when calculating the T2 time by using the formula below make
sure this 10 second is subtracted from the T1 time. In other words T1
time starts at the end of the 10 second period.
2) T1 time... The total amount of time it takes the microwave oven to
switch to T2 time after the 10 second period.
3) T2 time... When the steam escapes from the cooking container placed
in the oven, the steam sensor detects it and the microprocessor cal-
culates the balance of cooking time. This T2 time is then shown in the
display and begins counting down.
Balance of cooking time (T2 time)
The balance of cooking time which is called T2 time, can be calcu-
lated by the following formula.
T2 time (in sec.)=T1 time X K factor
NOTE: Remember, the T1 time starts after the 10 second period.
The coefficient K is programmed Into the mlcroprocessor
memory and they are listed in the following tables along with
the P1 and P2 powers.
NOTE: When "More" or "Less" pad is selected, the K factor varles
resulting In T2 time to be increased or decreased.
Example of calculating the T2 time
Example 1: If the T1 time is measured to be 2 minutes and 40 seconds
after the 10 second period, and the Auto program selected is
Frozen Vegetable:
T2 = T1 X K
=2 min. and 40 sec. X 0.1
=160 sec. X 0.1
=16 sec.
7. Sensor Reheat
Auto Sensor Reheat is a quick and easy way to reheat refrigerator
and room temperature foods.
Simply press the reheat pad. There is no need to select power level
and cooking time.
NOTE: The Auto Sensor Reheat process is same as Auto Sensor
Cooking process.
AUTO SENSOR COOKING/REHEAT PROCESS
Category
Frozen Vegetables
Sensor Cooking
P1
Power
M.HIGH
K Factor
Standard
0.1
P2
Power
LOW
Category
Sensor Recheat
Sensor Reheat
P1
Power
HIGH
K Factor
Standard
0.2
P2
Power
M.HIGH

- 19 -
8. Steam Sensor and Digital Programmer Circuit
In order to determine if the steam sensor function of the digital
programmer circuit is in working order or not, do the following
test.
1) Place a water load (150 cc) in the oven.
2) Tap Sensor Reheat pad.
3) Tap Start Pad.
4) Steam Sensor detects steam about 1.5 to 4 minutes after the
Start Pad is tapped.
5) T1 time cooking automatically switches to remaining time cooking
(T2).
6) The remaining cooking time (T2) appears in display window. If
the following cooking time appears, Steam Sensor function is
normal.
9. Oven temp sensor thermistor
This sensor monitors the heat produced by the heater circuit and
maintains the oven temperature the user had selected. Normal
room 10˚C to 30˚C. The reading across the oven sensor
thermistor should be within 100K ohm to 300K ohm when
reading in an area with the 50˚F to 90˚F room temperature range.
If the resistance reading is out of the range stated here, the
sensor is detective and must be replaced.
NOTE 1: When measuring resistance disconnect the 3-pin
connector (CN6) from the DPC otherwise a false reading may be
indicated.
NOTE 2: If checking an oven sensor thermistor just after the
microwave oven has been operating, the sensor of course won’t
be room temperature. In this case the sensor must be removed
and allowed to cool down to the 10˚C to 30˚C range.
T2 TIME
18 Sec.~48 Sec.
T1 TIME
1 Min. 30 Sec.~4 Min.
(Remaining cooking time)

- 20 -
WARNING
1. Adjustment of Primary latch switch, Second-
ary latch switch and Short switch.
(A) When mounting Primary latch switch,Secondary latch switch
and short switch to door hook assembly, mount the Primary latch
switch, the Secondary latch switch and the short switch to the
door hook assembly as shown in table.
NOTE: No specific adjustment during installation of
Primary latch switch, Secondary latch switch and
short switch to the door hook is necessary.
(B) When mounting the door hook assembly to the oven assem-
bly, adjust the door hook assembly by moving it in the direction of
arrow in the illustration so that the oven door will not have any
play in it. Check for play in the door by pulling the door assembly.
Make sure that the latch keys move smoothly after adjustment is
completed. Completely tighten the screws holding the door hook
assembly to the oven assembly.
(C) Reconnect the short switch and check the continuity of the
monitor circuit and all latch switches again by following the
components test procedures.
2. Measurement of microwave output
The output power of the magnetron can be determined by performing
IEC standard test procedures. However,due to the complexity
of IEC test procedures, it is recommended to test the magnetron
using the simple method outlined below.
Necessary Equipment:
*1 liter beaker *Glass thermometer
*Wrist watch or stopwatch
NOTE: Check the line voltage under load.Low voltage will
lower the magnetron output. Take the temperature
readings and heating time as accurately as possible.
(A) Fill the beaker with exactly one liter of tap water.Stir the water
using the thermometer and record the beaker’s temperature.
(recorded as T1).
(B) Place the beaker on the center of glass cook plate.
Set the oven for High power and heat it for exactly one minute.
(C) When one minute is elapsed, open the door and take out beaker.
(D) Stir the water again and read the temperature of the beaker.
(recorded as T2).
(E) The normal temperature rise at High power position for each
model is as shown in table.
MEASUREMENTS AND ADJUSTMENTS
*For continued protection against radiation hazard,
replace only with identical replacement parts(For touch
models Part No. ANE6142-1450,Type No.
V-16G-3C26-M for Primary latch switch; Part No.
A61425180AP, Type No. L-3C2-2 for Secondary latch
switch; Part No. A61785180AP, Type No. L-2C2-2 for
short switch and Part. No. AEG5J1EG12B/AEG5J1EG18B,
Type No. G5J-1-TP for power relay B(RY1))
*When the 10 Amp. fuse is blown due to the operation of
the short switch, you must replace power relay B.
Primary
latch switch and the short switch. Then follow the installa-
tion procedures below.
*Interlock switch replacement In replacing faulty
switches, be sure mounting tabs are not bent, broken or
otherwise deficient in their ability to hold the switches.
*Refer to schematic diagram to ensure proper connec-
tion.
TABLE (1L-1min. test)
RATED OUTPUT
1000W (IEC705-88)
TEMPERATURE RISE
Min. 15.4˚F (8.6˚C)
LATCH
SWITCH
PRIMARY
LATCH
SWITCH
SECONDARY
THE GAP SHOULD
BE LESS THAN
0.5mm WHEN DOOR
CLOSED.
SHORT
SWITCH