6.1. Adjustment of primary latch switch, secondary latch switch
and monitor interlock switch.
6.2. Measurement of microwave output
7 PROCEDURE FOR MEASURING MICROWAVE ENERGY
LEAKAGE
7.1. Equipment
7.2. Procedure for measuring radiation leakage
7.3. Record keeping and notification after measurement
7.4. At least once a year, have the radiation monitor checked
for calibration by its manufacturer.
8 TROUBLESHOOTING GUIDE
8.1. (Troubleshooting) Oven stops operation during cooking
8.2. (Troubleshooting) Other problems
8.3. Troubleshooting of inverter circuit (U) and magnetron
8.4. SIMPLE WAY OF H.V. INVERTER/MAGNETRON
TROUBLESHOOTING
8.5. H.V.INVERTER BOARD MAIN PARTS LIST
(F606Y8M00AP)
8.6. How to check the semiconductors using an OHM meter
9 EXPLODED VIEW AND PARTS LIST
9.1. EXPLODED VIEW
9.2. PARTS LIST
9.3. WIRING MATERIALS
9.4. DOOR ASSEMBLY
9.5. ESCUTCHEON BASE ASSEMBLY
9.6. PACKING AND ACCESSORIES
10 DIGIT AL PROGRAMMER CIRCUIT
10.1. NN-SD698S
10.2. NN-ST678S
10.3. NN-ST658W
10.4. PARTS LIST
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1 SCHEMATIC DIAGRAM
NN-SD698S / NN-ST678S / NN-ST658W
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2 DESCRIPTION OF OPERATING SEQUENCE
2.1. Variable power cooking
control
High Voltage Inverter Power Supply (U) controls output power
by the signal from Digital Programmer Circuit (DPC). Power
relay always stay on, but PWM (Pulse Width Modulation) signal
controls microwave output power.
NOTE:
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.
POWER SETTINGOUTPUT
HIGHP10100%220
MEDIUM-HIGHP770%220
MEDIUMP660%220
MEDIUM-LOWP330%220
DEFROSTP330%220
Variable Power Cooking
POWER(%)
APPROX.
P990%220
P880%220
P550%220
P440%220
P220%157
P110%814
MANUAL MICROWAVE
DUTY
ON(SEC)OFF(SEC)
2.2. Inverter power supply circuit
The Inverter Power Supply circuit powered from the line
voltage, 120V 60Hz AC input supplies 4,000V DC to the
magnetron tube, and functions in place ofthe H.V. transformer,
the H.V. capacitor and H.V. diode.
1. The AC input voltage 120V 60Hz is rectified to DC voltage
immediately.
2. DC voltage will be supplied to the switching devices called
IGBT. These devices are switched ON-OFF by the 20 to 40
kHz PWM (pulse width modulation) signal from the
microcomputer in the DPC.
3. This drives the High voltagetransformer to increase voltage
up to 2,000V AC.
4. Then the half-wave doubler voltage rectifier circuit,
consisting of the H.V. diodes and capacitors, generates the
necessary 4,000V DC needed for the magnetron.
5. Output power of the magnetron tube isalways monitored by
the signal output from the current transformer built into the
inverter circuit.
6. This signal is fed back to the microcomputer in the DPC to
determine operating conditions and output necessary to
control PWM signal to the Inverter Power Supply for control
of the output power.
2.3. Inverter defrost
When the Auto Control feature is selected and the Start pad is
tapped:
1. 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.
Inverter Turbo Defrost
SELECTED WEIGHTCOOKING TIME
1.0 LB5 min.00 sec.
2. When cooking time in the display window has elapsed, the
oven turns off automatically by a control signal from the
digital programmer circuit.
2.4. Sensor cooking
Auto sensor cooking 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.
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Explanation of the Auto Sensor Cooking process
1. During the first 10 second period there is no microwave
activity. When calculating the T2 time by using the
formula below make sure this 10 seconds 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 themicrowave
oven to switch to T2 time after the 10second period.
3. T2 time When the steam escapes from the cooking
container placed in the oven, the steam sensor detects
it and the microprocessor calculates 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 T2time, can
be calculated 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
microprocessor 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
varies 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 Oatmeal:
T2 = T1 × K
= 2 min. and 40 sec. × 0.1
= 160sec. × 0.1
= 16 sec.
CategoryP1
Power
OatmealHIGHHIGH0.1
P2
Power
K Factor
Standard
2.5. Sensor reheat
Auto Sensor Reheat is a quick and easy way to reheat
refrigerated 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.
CategoryP1
Power
Sensor ReheatHIGHMEDIUM0.3
P2
Power
K Factor
Standard
2.6. Steam sensor and digital
programmer circuit
In order to determine if the steam sensor function of the digital
programmer circuit is working, 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
for cooking (T2).
6. The remaining cooking time (T2) appears in display
window. If the following cooking time appears, Steam
Sensor function is normal.
T1 TIMET2 TIME (Remainingcooking time)
1 Min. 30 Sec. ~ 4 Min.27 Sec. ~ 1Min.12 Sec.
2.7. Thermistor
The thermistor which fixed on magnetron detects magnetron
temperature and make power down when the temperature
becomes abnormal high. A normal thermistor´s resistance
values for temperature ranges between 75-85 degree F is from
37kΩ to 57kΩ.
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3 CAUTIONS TO BE OBSERVED WHEN
TROUBLESHOOTING
Unlike many other appliances, the microwave oven is a high
voltage, high current device. It is free from danger in ordinary
use, though extreme care should be taken during repair.
CAUTION
Servicemen should remove their watches and rings
whenever working close to or replacing the magnetron.
3.1. Check the grounding
Do not operate on a two wire extension cord. The microwave
oven is designed to be grounded when used. It is imperative,
therefore, to ensure the appliance is properly grounded before
beginning repair work.
3.2. Inverter warnings
WARNING HIGH VOLTAGE AND HIGHTEMPERATURE
(HOT/LIVE) OF THE INVERTERPOWER SUPPLY (U)
The High Voltage Inverter Power Supply generates very
high voltage and current for the magnetron tube. Though it
is free from danger in ordinary use, extreme care should be
taken during repair.
The aluminum heat sink is also energized with high voltage
(HOT), do not touch when the AC input terminals are
energized. The power device Collector is directly connected
to the aluminum heat sink.
The aluminum heat sink may be HOT due to heat energy,
therefore, extreme care should be taken during servicing.
Grounding of the inverter circuit board
WARNINGDISCHARGETHEHIGHVOLATGE
CAPACITORS
For about 30 seconds after the oven is turned off, an
electric charge remains in the high voltage capacitors of 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 be sure
to contact the chassis ground side first and then short to the
output terminal.
H.V. Inverter warning
WARNING FOR INVERTER POWER SUPPLY (U)
GROUNDING
Check the High Voltage Inverter Power Supply circuit
grounding. The high voltage inverter power supply circuit
board must have a proper chassis ground. The inverter
grounding plate must be connected to the chassis. If the
inverter board is not grounded it will expose the user to very
high voltages and cause extreme DANGER! Be sure that
the inverter circuit is properly grounded via the inverter
grounding plate.
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Discharging the high voltage capacitors
WARNING
There is high voltage present with high current capabilities
in the circuits of the primary and secondary windings, choke
coil and heat sinkof the inverter. It is extremely dangerous
to work on or near these circuits with the oven energized.
DO NOT measure the voltage in the high voltage circuit
including the filament voltage of the magnetron.
WARNING
Never touch any circuit wiring with your hand or with an
insulated tool during operation.
3.3. Part replacement.
When troubleshooting any part or component is to be replaced,
always ensure that the power cord is unplugged from the wall
outlet.
3.4. When the 20A fuse is blown
due to the malfunction of the
monitor interlock switch:
WARNING
When the 20A 120V fuse is blown due to the malfunction of
the monitor interlock switch, replace all of the components
(primary latch switch, monitor interlock switch and power
relay RY1).
1. This is mandatory. Refer to “measurements and
adjustments” for the location of these switches.
2. When replacing the fuse, confirm that it has the
appropriate rating for these models.
3. When replacing faulty switches, be sure the mounting
tabs are not bent, broken or deficient in their ability to
hold the switches.
3.5. Avoid inserting nails, wire etc.
through any holes in the unit
during operation.
3.6. Verification after repair
1. After repair or replacement of parts, make sure that the
screws of the oven, etc. are neither loosen or missing.
Microwave energy might leak if screws are not properly
tightened.
2. Make sure that all electrical connections are tight before
inserting the plug into the wall outlet.
3. Check for microwave energy leakage. (Refer to procedure
for measuring microwave energy leakage).
CAUTION OF MICROWAVE RADIATION LEAKAGE
USE CAUTION NOT TO BECOME EXPOSED TO
RADIATION FROM THE MICROWAVE MAGNETRON OR
OTHER PARTS CONDUCTING MICROWAVE ENERGY.
IMPORTANT NOTICE
1. The following components have potentials above 2000V
while the appliance is operated.
• Magnetron
• High voltage transformer (Located on inverter (U))
• High voltage diodes (Located on inverter (U))
• High voltage capacitors (Located on inverter (U))
Pay special attention to these areas.
2. When the appliance is operated with the door hinges or
magnetron installed incorrectly, the microwave leakage
can exceed more than 5mW/cm
exchange, it is very important to check if the magnetron
and the door hinges are correctly installed.
2
. After repair or
3.7. Sharp edges
CAUTION
Please use caution when disassembling or reassembling
internal parts. Some exposed edges may be sharp to the
touch and can cause injury if not handled with care.
Never insert a wire, nail or any other metal object through the
lamp holes on the cavity or any holes or gaps, because such
objects may work as an antenna and cause microwave
leakage.
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4 DISASSEMBLY AND PARTS REPLACEMENT
PROCEDURE
4.1. Magnetron
1. Discharge high voltage charge.
2. Remove 1 screw holding air guide A on the oven cavity.
3. Remove 1 screw holding air guide A on the magnetron.
4. Remove 1 screw holding air guide B.
5. Remove 1 screw holding themistor.
6. Disconnect 2 high voltage lead wires from magnetron
filament terminals.
7. Remove 4 screws holding the magnetron.
NOTE:
After replacement of the magnetron, tighten mounting
screws properly in an x pattern, making sure there is no
gap between the waveguide and the magnetron to
prevent microwave leakage.
CAUTION
When replacing the magnetron, be sure the antenna gasket is in
place.
4.2. Digital programmer circuit
(D.P.C)
CAUTION:
Be sure to ground any static electric charge built up in
your body before handling the DPC.
1. Disconnect all connectors from D.P.C.
2. Remove 1 grounding screw.
3. Remove 1 screw holding escutcheon base and slide the
escutcheon base upward slightly.
4. Remove all screws holding D.P.C. board on escutcheon
base.
5. Separate D.P.C board from tabs on the escutcheon base
and remove D.P.C board.
To replace membrane key board
6. Use tools such as kinfe etc. to lift the edge of escutcheon
sheet and peel off escutcheon sheet & key board
membrane completely from escutcheon base.
NOTE:
1. The membrane key board is attached to the
escutcheon base with double faced adhesive tape.
Therefore, applying hot air such as using a hair
dryer is recommended for smoother removal.
2. When installing the new key board membrane, make
sure that the surface of escutcheon base is clean to
prevent a malfunction or shorted contacts.
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4.3. Low voltage transformer
and/or power relays (RY1,
RY2)
CAUTION:
Be sure to ground any static electric charge built up in
your body before handling the DPC.
1. Replace D.P.C. board.
(A) Using solder wick or a desoldering tool and 30W
soldering iron carefully remove all solder from the terminal
pins of the low voltage transformer and/or power relays.
CAUTION:
Do not use a soldering iron or desoldering tool of
more than 30 watts on D.P.C. contacts.
(B) With all the terminal pins cleaned and separated from
D.P.C. contacts, remove the defective transformer/power
relays, Replace components making sure all terminal pins
are inserted completely resolder all terminal contacts
carefully.
4.4. Fan motor
1. Disconnect 2 lead wires from fan motor terminals.
2. Remove 2 screws at location on oven attaching orifice
assembly.
3. Remove orifice assembly from oven assembly.
4. Remove fan blade from the fan motor shaft by pulling it
straight out.
5. Remove 2 screws holding fan motor to orifice.
4.5. Door assembly
1. Remove door C from door E by carefully pulling outward,
starting from upper right hand corner using a flat blade
screwdriver.
2. Separate door E from tabs on door A and remove door A.
3. Open Door E at the opening angle of approximately
10°(Note: The door cannot be removed if the opening
angle is greater than 10°).
4. Remove the door E from its hinges by pushing the door E
upward and out.
5. Remove door screen B from door A.
6. Remove door key and door key spring.
7. Replace other components.
To re-install components:
1. Place the door’s lower hinge pin into the bottom hinge
hole.
2. Use your left index finger to support the door’s lower
hinge pin while guiding the door’s upper hinge pin into
the top hinge hole.
3. Lower your finger to seat the door onto the hinges.
NOTE:
Adjust so that the upper portion of the door will
touch firmly to the oven cavity front plate, without
pushing the door. If the door assembly is not
mounted properly, microwave power may leak from
the clearance between the door and oven.
NOTE:
Alwaysperformthemicrowaveleakage
measurement test after installation and adjustment
of door assembly.
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4.6. Turntable motor
1. Remove the motor cover by breaking off at the 8 spots
indicated by arrows with a cutter or the like.
NOTE:
After removing the motor cover, be sure that cut
portions are properly trimmed or bent to the inside
so that no sharp edges will be exposed to outside.
2. Disconnect 2 lead wires connected to the turntable motor.
3. Remove the turntable motor by removing screw.
4.7. Steam sensor
1. Disconnect connector CN2 from digital programmer circuit
board.
2. Disengage catch hooks on sensor cover C from orifice.
3. Remove steam sensor from orifice.
NOTE:
When installing the steam sensor, make sure that
the direction of steam sensor is as shown in figure.
NOTE:
After reinstalling the new turntable motor and
reconnecting the 2 lead wires, reinstall the motor
cover by rotating it around 180, tucking the 2 tabs
under the base in the 2 provided slots, then screw
the single tab to the base using a 4mm × 6mm
screw.
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4.8. Inverter power supply
CAUTIONS
1. Always leave the grounding plate in place.
2. Always securely tighten the ground screw through the bottom of the
chassis (base).
3. Securely connect 3 lead wire connectors.
4. Make sure the heat sink has enough space (gap) from the oven.
Take special care not to dress any lead wire over the aluminum heat
sink because it is hot.
1. Discharge high voltage charge.
2. Remove the H.V.lead wire from magnetron terminals.
3. Disconnect 2 connectors from CN701 & CN702 on
H.V.Inverter(U).
4. Remove 1 screw holding grounding plate to the base.
6. Press 1 encircled locking tab and then slide 4 locking tabs
of Inverter bracket at the bottom of the base in direction of
arrows.
7. Remove 1 screw holding H.V.Inverter to Inverter bracket.
5. Bend back 1 locking metal tab on the base.
8. Remove 1 screw holding grounding plate to H.V. Inverter.
9. Seperate H.V. Inverter from Inverter bracket by freeing 3
catch hooks on the Inverter bracket.
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5 COMPONENT TEST PROCEDURE
WARNING
1. High voltage is present at the output terminals of the High Voltage
Inverter (U) including aluminum heat sink during any cook cycle.
2. It is neither necessary noradvisabletoattempt measurement of the
high voltage.
3. Before touching any oven components, or wiring, always unplug
the power cord and discharge the high voltage capacitors (see page
8).
5.1. Primary, Secondary Latch
Switch interlocks & Power
Relay RY1
1. Unplug lead connectors to Power Relay RY1 and verify
open circuit of the Power Relay RY1 1-2 terminals.
2. Unplug lead connectors to Primary Latch Switch and
Secondary Latch Switch.
3. Test the continuity of switches at door opened and closed
positions with ohm meter (low scale).
Normal continuity readings should be as follows.
Door ClosedDoor Opened
Primary Latch Switch0Ω (Close)Ω(Open)
Secondary Latch Switch0Ω (Close)Ω(Open)
Power Relay RY1Ω (Open)Ω(Open)
5.3. Magnetron
Continuity checks can only indicate an open filament or a
shorted magnetron. To diagnose for an open filament or
shorted magnetron.
1. Isolate magnetron from the circuit by disconnecting the
leads.
2. A continuity check across magnetron filament terminals
should indicate one ohm or less.
3. A continuity check between each filament terminal and
magnetron case should read open.
5.2. Monitor Interlock Switch
1. Unplug lead wires from Inverter Power Supply (U) primary
terminals.
2. Connect test probes of ohm meter to the disconnected
leads that were connected to Inverter Power Supply (U).
3. Test the continuity of Monitor Interlock Switch with door
opened and closed positions using lowest scale of the ohm
meter.
Check continuity between switch terminals, by tapping an
appropriate pad on the key board. The contacts assignment of
the respective pads on the key board is as shown in digital
programmer circuit.
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5.5. Inverter power supply (U)
Ω
Ω
DO NOT try to REPAIR H.V. Inverter power supply (U).
Replace complete H.V. Inverter(U) Unit.
NN-SD698S / NN-ST678S / NN-ST658W
5. Program oven at High power for 1 minute and press [Start]
pad.
a. After approximately 3 seconds, oven stops operating.
b. Duringovenoperation,theinputcurrentis
approximately 0.4A.
INPUT CURRENTFAILURE CODE
Unplug CN7010.4AOven stops in 3
seconds after started.
If both a and b check OK, the Inverter Power Supply (U) can be
determined to be OK.
5.6. Temperature thermistor
These sensor monitors the heat produced by the heater circuit
and maintains the magnetron temperature which user had
selected. Normal room temperature 10°C to 30°C, the reading
across the temperature thermistor should be as follows.
TEMPMAGNETRON THERMISTOR
100°C30-60K
25°C700K-1.5M
WARNING: HIGH VOLTAGE
Test if failure codes H95, H97 or H98 appear when performing
the following procedure. It is recommended to use an AC line
input current ammeter for testing.
Test 1
1. With the oven unit’s AC power supply cord is unplugged
from the wall outlet, unplug the 2 pin H.V. connector CN703
from the magnetron tube.
2. Place 1 liter of water load into oven cavity.
3. Plug in the oven’s AC power supply cord into outlet.
4. Program DPC.
a. Press Timer/Clock
b. Press Start
c. Press Power Level
pad twice.
pad once.
pad once.
5. Program oven at High power for 1 minute and press [Start]
pad.
a. After approximately 37 seconds, oven stops operating.
b. Duringovenoperation,theinputcurrentis
approximately 0.5 to 1A. If both a and b are OK,
proceed to test 2.
INPUT CURRENTFAILURE CODE
Unplug CN7030.5 to 1AOven stops in 37
seconds after started.
If the resistance reading is out of the range stated here, the
thermistor is detective and must be replaced.
Test 2
Continued from Test 1
1. Unplug the oven’s AC power supply cord from outlet.
3. Plug in the oven’s AC power supply cord into outlet.
4. Program DPC.
a. Press Timer/Clock
b. Press Start
c. Press Power Level
pad twice.
pad once.
pad once.
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6 MEASUREMENTS AND ADJUSTMENTS
6.1. Adjustment of primary latch
switch, secondary latch switch
and monitor interlock switch.
1. Mount the Primary latch switch, the Secondary latch switch
and the Monitor interlock switch to the door hook assembly
as shown in illustration.
NOTE:
Nospecificindividualadjustmentsduring
installation of the Primary latch switch, Secondary
latch switch or Monitor interlock switch to the door
hook are required.
2. When mounting the door hook assembly to the oven
assembly, adjust the door hook assembly by moving it in
the direction of the arrows 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.
3. Reconnect the monitor interlock switch and check the
continuity of the monitor circuit and all latch switches again
by following the component test procedures.
6.2. 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.
Check the line voltage under load.Low voltage will
lower the magnetron output. Take the temperature
readings and heating time as accurately as possible.
1. Fill the beaker with exactly one liter of tap water.Stir the
water using the thermometer and record the water’s
temperature. (recorded as T1).
2. Place the beaker on the center of glass tray.
Set the oven for High power and heat it for exactly one
minute.
3. Stir the water again and read the temperature of the water.
(recorded as T2).
4. The normal temperature rise at High power level for each
model is as shown in table.
TABLE (1L-1min. test)
RATED OUTPUTTEMPERATURE RISE
1200WMin. 18.5°F(10.3°C)
1300WMin. 19.8°F(11.1°C)
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7 PROCEDURE FOR MEASURING MICROWAVE ENERGY
LEAKAGE
7.2.1. Measurement with the outer panel
removed.
Whenever you replace the magnetron, measure for radiation
leakage before the outer panel is installed and after all
necessary components are replaced or adjusted. Special care
should be taken in measuring around the magnetron.
7.1. Equipment
• Electromagnatic radiation monitor
• Glass thermometer 212°F or 100°C
• 600cc glass beaker
7.2. Procedure for measuring
radiation leakage
Note before measuring:
• Do not exceed meter full scale deflection. Leakage monitor
should initially be set to the highest scale.
• To prevent false readings, the test probe should be held by
the grip portion of the handle only and moved along the
shaded area in Figure no faster than 1 inch/sec
(2.5cm/sec).
• Leakage with the outer panel removed: less than 5mW/cm
• Leakage for a fully assembled oven with door normally
closed: less than 2mW/cm
• Leakage for a fully assembled oven [Before the latch switch
(primary) is interrupted] while pulling the door: less than
2mW/cm
1. Pour 275 ± 15cc (9ozs
water in a beaker which is graduated to 600cc, and place in
the center of the oven.
2. Set the radiation monitor to 2450MHz and use it following
the manufacturer´s recommended test procedure to assure
correct results.
3. When measuring the leakage, always use the 2 inch (5cm)
spacer supplied with the probe.
4. Tap the start button or set the timer and with the magnetron
oscillating, measure the leakage by holding the probe
perpendicular to the surface being measured.
2
.
2
.
s
± 1/2oz) of 20°C ± 5°C (68° ± 9°F)
7.2.2. Measurements with a fully
assembled oven.
After all components, including outer panel are fully assembled,
measure for radiation leakage around the door periphery, the
door viewing window, the exhaust opening, control panel and
air inlet openings.
7.3. Record keeping and
notification after measurement
• After any adjustment or repair to a microwave oven, a
leakage reading must be taken. Record this leakage
reading on the repair ticket even if it is zero.
2
.
A copy of this repair ticket and the microwave leakage
reading should be kept by repair facility.
• Should the radiation leakage be more than 2 mW/cm
determining that all parts are in good condition, functioning
properly, and genuine replacement parts as listed in this
manual have been used.
2
after
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7.4. At least once a year, have the
radiation monitor checked for
calibration by its
manufacturer.
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8 TROUBLESHOOTING GUIDE
DANGER: HIGH VOLTAGES
1. DO NOT RE-ADJUST PRESET CONTROL on the H.V.Inverter (U). It is very dangerous to repair or adjust without proper test equipment
because this circuit generates very large current and high voltage. Operating a misaligned inverter circuit is dangerous.
2. Ensure proper grounding before troubleshooting.
3. Be careful of the high voltage circuitry, taking necessary precautions when troubleshooting.
4. Discharge high voltage remaining in the H.V.Inverter (U).
5. When checking the continuity of the switches or the H.V.Inverter, disconnect one lead wire from these parts and then check continuity with the
AC plug removed. Doing otherwise may result in a false reading or damage to your meter. When disconnecting a plastic connector from a
terminal, you must hold the plastic connector instead of the lead wire and then disconnect it, otherwise lead wire may be damaged or the
connector cannot be removed.
6. Do not touch any parts of the circuitry on the digital programmer circuit, since static electric discharge may damage this control panel. Always
touch ground while working on this panel to discharge any static charge in your body.
7. 120V AC is present on the digital programmer circuit (Terminals of power relay’s and primary circuit of Digital Programmer Circuit). When
troubleshooting, be cautious of possible electrical shock hazard.
Before troubleshooting, operate the microwave oven following the correct operating procedures in the instruction manual in order
to find the exact cause of any trouble, since operator error may be mistaken for the oven’s malfunction.
8.1. (Troubleshooting) Oven stops operation during cooking
SYMPTOMCAUSECORRECTIONS
1. Oven stops in 3 seconds after
pressing [Start] pad
Oven stops in 37 seconds after
pressing [Start] pad
Oven stops in 10 seconds after
pressing [Start] pad
(Auto sensor cooking)
2. No display and no operation at all.
Fuse is blown.
No 120V AC is supplied to H.V.Inverter (U) CN702
terminals
H.V.Inverter (U) operates by the control signals
from DPC but magnetron is not oscillating
Steam sensor circuit is not functioning1. Steam sensor
Most probably loose connection of connectors, or
door latch mechanism is not adjusted properly
1. Latch Switch
2. Power relay RY1
3. Loose lead wire connector CN701, CN702
4. H.V. Inverter (U)
1. Magnetron
2. Loose lead wire connector CN703
3. H.V. Inverter (U)
2. DPC
3. Open or loose wiring of sensor terminal
from connector CN2 on DPC
1. Allign door, Door Latch Switches
2. Loose wiring connectors
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8.2. (Troubleshooting) Other problems
SYMPTOMCAUSECORRECTIONS
1. Oven is dead.1. Open or loose lead wire harness
Fuse is OK.2. Open thermal cutout / thermistorCheck thermal cutout is defective.
No display and no operation at all.3. Open low voltage transformer
4. Defective DPC
2. No display and no operation at all.
Fuse is blown.
3. Oven does not accept key input
(Program)
4. Fan motor turns on when oven is
plugged in with door closed.
5. Timer starts count down but no
microwave oscillation.
(No heat while oven lamp and fan
motor turn on)
6. Oven can program but timer does not
start countdown.
7. Microwave output is low. Oven takes
longer time to cook food.
8. Fan motor turns on and turntable
motor rotates when door is opened.
9. Oven does not operate and return to
plugged in mode as soon as [Start]
pad is pressed.
10. Loud buzzing noise can be heard.1. Loose fan and fan motor
11. Turntable motor does not rotate.1. Open or loose wiring of turntable motor
12. Oven stops operation during cooking.1. Open or loose wiring of primary and
1. Shorted lead wire harnessCheck adjustment of primary, secondary latch
2. Defective primary latch switch (NOTE 1)
3. Defective monitor interlock switch (NOTE 1)
4. Defective Inverter Power Supply (U)
NOTE 1:
All of these switches must be replaced at the same time.
Check continuity of power relay RY1 contacts (between 1 and 2) and if it has continuity, replace
power relay RY1 also.
1. Key input is not in proper sequenceRefer to operation procedure.
2. Open or loose connection of membrane key
pad to DPC (Flat cable)
3. Shorted or open membrane key board
4. Defective DPCRefer to DPC troubleshooting.
1. Misadjustment or loose wiring of secondary
latch switch
2. Defective secondary latch switch
3. Door switch CN3
1. Off-alignment of primary latch switchAdjust door and latch switches.
2. Open or loose connection of high voltage
circuit especially magnetron filament circuit
NOTE:
Large contact resistance will cause lower
magnetron filament voltage and cause
magnetron to have lower output and/or be
intermittent.
3. Defective high voltage component
H.V. Inverter Power Supply (U)
Magnetron
4. Open or loose wiring of power relay RY1
5. Defective primary latch switch
6. Defective DPC or power relay RY1Refer to DPC troubleshooting
1. Open or loose wiring of secondary latch switch
2. Off-alignment of secondary latch switch
3. Defective secondary latch switch
1. Decrease in power source voltageConsult electrician
2. Open or loose wiring of magnetron filament
circuit.(Intermittent oscillation)
3. Aging change of magnetron
1. Low voltage transformer on DPC.
1. Defective DPCCheck grounding connector on escutcheon
2. Defective turntable motor
secondary latch switch
2. Operation of thermal cutout
switch and monitor interlock switch including
door.
Adjust door and latch switches.
Check high voltage component according to
component test procedure and replace if it is
defective.
base.
Adjust door and latch switches.
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8.3. Troubleshooting of inverter circuit (U) and magnetron
This oven is programmed with a self diagnostics failure code system which will help for troubleshooting. H95, H97, H98 and H99
are the provided failure codes to indicate magnetron and inverter circuit problem areas. This section explains failure codes of H95,
H97, H98 and H99. First, you must program the DPC into TEST MODE, press Timer/Clock
→ press Power Level
[Start] pad is pressed and there is no microwave oscillation.
pad once. Program unit for operation. H95, H97, H98, H99 appears in display window a short time after
pad twice → Press Start pad once
Alternate way to troubleshoot oven with AC Ampere meter used
H95, H97, H98, H99 appears in display window a short time after [Start] pad is pressed and no microwave oscillation with AC
Ampere meter used for troubleshooting.
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8.4. SIMPLE WAY OF H.V. INVERTER/MAGNETRON TROUBLESHOOTING
Purpose:
Simple way (3/37 seconds rule) of identifying whether it’s Magnetron, Inverter or others.
Set-up:
The unit under question is connected through the Ammeter as shown below.
Procedure:
Follow the matrix table below to identify the problem source.
Note:
Do not replace both Inverter board and Magnetron simultaneously and automatically without going through this
procedure.
Power will:Ammeter reading is:To do:Remedy:
Shut off in 37 seconds
after “Start”.
1. Between 0.5A and 1.0A.Check and repair open magnetron circuit Open magnetron wiring between Inverter
and magnetron terminal.
2. Between 1.0A and 2.0A.Check continuity of D702 in Inverter PCB.
1. D702 shortedReplace H.V.Inverter(F606Y8M00AP)
2. D702 is OKReplace magnetron
Shut off in 3 seconds
after “Start”
1. Less than 0.5ACheck open circuit: Latch Switch, DPC,
Power Relay and CN701
Replace defective component(s), or
correct switch, cables and connectors.
8.5. H.V.INVERTER BOARD MAIN PARTS LIST (F606Y8M00AP)
mark have special characteristics important for safety.
NN-SD698S / NN-ST678S / NN-ST658W
11F290D9330APROLLER RING(U)1
12F30206G30APDOOR HOOK1SD698S,ST678S
12F30206K50APDOOR HOOK1ST658W
13F3097-5L00LATCH SPRING1ST658W
14F31366G30APHOOK LEVER A1SD698S,ST678S
14F31366K50APHOOK LEVER A1ST658W
15F31376G30APHOOK LEVER B1SD698S,ST678S
15F31376K50APHOOK LEVER B1ST658W
16F31386G30APHOOK LEVER C1SD698S,ST678S
16F31386K50APHOOK LEVER C1ST658W
17F400A5Y00APFAN MOTOR1AC120V,SINGLE PHASE,60Hz
18F40084T00APFAN BLADE1
19F40257D00APGAIR GUIDE A1
20F41445Y00APORIFICE1
42XTCAFA4+12AFMSCREW1FOR CABINET BODY SIDE (SD698S)
42XTCAFA4+12AFSSCREW1FOR CABINET BODY SIDE (ST678S)
42XTCAFA4+12AFWSCREW1FOR CABINET BODY SIDE (ST658W)
43XTTBFE4T12A0SCREW4FOR CABINET BODY
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Ref. No.Part No.Part Name & DescriptionPcs/SetRemarks