Panasonic NN-GF668M EPG User manual

© 2008 Panasonic Home Appliances Microwave
Oven (Shanghai) Co., Ltd. All rights reserved.
Unauthorized copying and distribution is a violation
of law.
NN-GF668M
EPG (Continental Europe)
SPG (Norway, Finland, Sweden, Denmark)
Microwave Oven
ORDER NO.PHAMO0806026C2

2
NN-GF668M

3
NN-GF668M

1 FEATURE CHART 5
2 CONTROL PANEL 5
3 SCHEMATIC DIAGRAM 6
4 DESCRIPTION OF OPERATING SEQUENCE 7
4.1. Variable power cooking control 7
4.2. Inverter power supply circuit 7
4.3. Auto Weight cooking 7
4.4. Grill cooking control 7
4.5. Combination cooking control 7
5 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING
8
5.1. Check the grounding 8
5.2. Inverter warnings 8
5.3. Part replacement 9
5.4. When the 15A fuse is blown due to the malfunction of the
short switch 9
5.5. Avoid inserting nails, wire etc. through any holes in the
unit during operation 9
5.6. Verification after repair 9
5.7. Sharp edges 9
6 DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE
10
6.1. Magnetron 10
6.2. Digital programmer circuit (D.P.C) AU, (D.P.C.) DU,
membrane sheet, low voltage transfarmer and power relay
11
6.3. H.V. Inverter 12
6.4. Fan motor 13
6.5. Upper heaters 14
6.6. Door assembly 14
6.7. Stirrer motor 15
7 COMPONENT TEST PROCEDURE 16
7.1. Primary, Secondary Latch Switch interlocks & Power
Relay RY1 16
7.2. Short Switch 16
7.3. Magnetron 16
7.4. Inverter power supply (U) 17
7.5. Temperature thermistor 17
8 MEASUREMENTS AND ADJUSTMENTS 18
8.1. Adjustment of Primary latch switch, Secondary latch
switch and Short switch. 18
8.2. Measurement of microwave output 18
9 TROUBLESHOOTING GUIDE 19
9.1. (Troubleshooting) Oven stops operation during cooking
20
9.2. (Troubleshooting) Other problems 21
9.3. Troubleshooting of inverter circuit (U) and magnetron 22
9.4. Trouble related to Digital Programmer Circuit 23
9.5. SIMPLE WAY OF H.V. INVERTER/MAGNETRON
TROUBLESHOOTING 23
9.6. How to check the semiconductors using an OHM meter
24
9.7. H.V. INVERTER MAIN PARTS LIST (Z606Y6Y40BP) 24
10 EXPLODED VIEW AND PARTS LIST 25
10.1. EXPLODED VIEW 25
10.2. PARTS LIST 26
10.3. ESCUTCHEON BASE ASSEMBLY 28
10.4. DOOR ASSEMBLY 29
10.5. WIRING MATERIALS 30
10.6. PACKING AND ACCESSORIES 31
11 DIGITAL PROGRAMMER CIRCUIT 32
11.1. SCHEMATIC DIAGRAM 32
CONTENTS
Page Page
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1 FEATURE CHART
2 CONTROL PANEL
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4.1. Variable power cooking
control
High Voltage Inverter Power Supply (U) controls output power
by the signal from Digital Programmer Circuit (D.P.C.). Power
relay always stays 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.
Variable Power Cooking
POWER SETTING OUTPUT
POWER(%)
APPROX.
MANUAL MICROWAVE
DUTY
ON(SEC) OFF(SEC)
HIGH 100% 22 0
MEDIUM 60% 22 0
LOW 45% 22 0
DEFROST 30% 16 6
SIMMER 25% 15 7
WARM 10% 8 14
4.2. Inverter power supply circuit
The Inverter Power Supply circuit powered from the line
voltage, 230V 50Hz AC input supplies 4,000V DC to the
magnetron tube, and functions in place of the H.V. transformer,
the H.V. capacitor and H.V. diode.
1. The AC input voltage 230V 50Hz 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 voltage transformer 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 is always 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.
4.3. Auto Weight cooking
When the Auto Weight feature is selected and the [Start] button
is pressed:
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 (Small pieces)
SELECTED WEIGHT COOKING TIME
1.0 kg 18 min. 25 sec.
Auto Reheat Cup
SELECTED WEIGHT COOKING TIME
15.0 g 1 min. 10 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.
4.4. Grill cooking control
Grill cooking is accomplished by upper heaters only. One grill
cooking cycle is 33 seconds.
1. During grill cooking, the digital programmer circuit controls
power relay RY4´s ON-OFF time. In all three grill cooking
categories, power relay RY1 always stay ON, but RY4´s
ON-OFF time are shown in Figure.
GRILL
CATEGORY
GRILL (RY4) MICROWAVE
(RY1)
ON (sec.) OFF (sec.)
1 33 0 ON
2 24 9 ON
3 18 15 ON
4.5. Combination cooking control
Combination cooking is accomplished by microwave and grill
cooking.
When setting combination cooking it is possible to firstly set
either the grill level or microwave power.
NOTE:
For EPG model, there are 4 microwave power levels
(Medium, Low, Simmer, Warm) available in combination
mode, but for SPG model, there are only 3 microwave
power levels (Low, Simmer and Warm) available in
combination mode.
NOTE:
After grill cooking or combination cooking, fan moter rotates
for 1~3 minutes to cool oven and electric components.
4 DESCRIPTION OF OPERATING SEQUENCE
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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.
5.1. 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.
5.2. Inverter warnings
WARNING HIGH VOLTAGE AND HIGH TEMPERATURE
(HOT/LIVE) OF THE INVERTER POWER 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.
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
reinforcement and grounding bracket 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 reinforcement and grounding
bracket A.
Grounding of the inverter circuit board
WARNING DISCHARGE THE HIGH VOLATGE
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.
5 CAUTIONS TO BE OBSERVED WHEN
TROUBLESHOOTING
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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 sink of 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.
5.3. Part replacement
When troubleshooting any part or component is to be replaced,
always ensure that the power cord is unplugged from the wall
outlet.
5.4. When the 15A fuse is blown
due to the malfunction of the
short switch
WARNING
When the 15A 250V fuse is blown due to the malfunction of
the short 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.
3. When replacing faulty switches, be sure the mounting
tabs are not bent, broken or deficient in their ability to
hold the switches.
5.5. 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 holes or gaps, because such
objects may work as an antenna and cause microwave
leakage.
5.6. Verification after repair
1. After repair or replacement of parts, make sure that the
screws of the oven, etc. are neither loose 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.
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/cm2. After repair or
exchange, it is very important to check if the magnetron
and the door hinges are correctly installed.
3. After repair or replacement of parts, make sure that all
the water pipes and tubes are properly connected,
otherwise the water might invade the electric parts and
will cause short circuit even result in electric shock.
5.7. 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.
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6.1. Magnetron
1. Discharge the high voltage capacitor (see page 8 for
instructions).
2. Remove 2 screws holding the inverter
reinforcement/grounding bracket A on oven cavity.
3. Remove 2 screws holding the inverter reinforcement
bracket B on oven cavity.
4. Remove 1 screw holding oven thermistor on cavity top
plate.
5. Release lead wire harness from locking tabs on inverter
bracket A.
6. Disconnect 2 high voltage lead wires from magnetron
filament terminals.
7. Remove 1 screw holding thermistor on magnetron.
8. Remove 2 screws holding air guide A on magnetron, then
remove air guide A.
9. Remove 4 screws holding air guide B on magnetron, wave
guider & on base plate respectively, then remove air guide
B.
10. Disconnect 2 lead wires from fan motor terminals.
11. Disconnect all connectors from D.P.C. board LU.
6 DISASSEMBLY AND PARTS REPLACEMENT
PROCEDURE
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12. Release locking tabs of inverter reinforcement/grounding
bracket A hanging on both sides of oven cavity, then
withdraw the inverter reinforcement/grounding bracket A
outside slightly.
NOTE:
Pay attention to the sharp edges of inverter
reinforcement/grounding bracket A.
13. Hold the inverter reinforcement/grounding bracket A, then
remove 4 screws holding 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.
6.2. Digital programmer circuit
(D.P.C) AU, (D.P.C.) DU,
membrane sheet, low voltage
transfarmer and power relay
CAUTION:
Be sure to ground any static electric charge built up in
your body before handling the DPC.
1. Disconnect all wiring connectors from D.P.C. board DU
(relay board).
2. Remove 1 screw holding escutcheon base on cavity front
plate.
3. Open the door of oven, slide the escutcheon base upward
and out slightly.
4. Forcibly pull out rotary dial directly.
5. Disconnect flat cable connecting between D.P.C. board AU
and DU from connector CN13 on D.P.C. board DU by
pulling upward slightly.
6. Remove 3 screws holding D.P.C. board DU (relay board) on
escutcheon base.
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7. Remove 3 screws holding grounding panel on escutcheon
base.
8. Remove 11 screws holding D.P.C. board AU (display &
rotary dial board) on escutcheon base.
9. Using solder wick or a desoldering tool and 30W soldering
iron carefully to 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.
10. 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, then resolder all terminal contacts
carefully.
To replace membrane sheet
11. Use tools such as kinfe etc. to lift the edge of escutcheon
sheet and peel off escutcheon sheet completely from
escutcheon base.
NOTE:
1. The membrane sheet 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 membrane sheet, make sure
that the surface of escutcheon base is clean.
6.3. H.V. Inverter
1. Discharge high voltage remaining in high voltage capacitor.
2. Remove 2 screws holding the inverter
reinforcement/grounding bracket A on oven cavity.
3. Remove 2 screws holding inverter reinforcement bracket B
on cavity top plate.
4. Remove 1 screw holding oven thermistor on cavity top
plate.
5. Release lead wire harness from locking tabs on Inverter
bracket A.
6. Disconnect 2 lead wires from fan motor terminals.
7. Disconnect all connectors from D.P.C. board LU.
8. Disconnect a big connector from the main harness which
connecting to D.P.C. board LU.
9. Disconnect 2 high voltage lead wires from magnetron
filament terminals.
10. Unplug connector CN701 & CN702 from H.V. Inverter
board.
11. Remove 1 screw holding inverter air guide bracket on
reinforcement bracket B, then release locking tabs, detach
air guide bracket.
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12. Release catch hook from Inverter bracket A.
13. Remove 2 screws holding H.V. Inverter on Inverter bracket.
6.4. Fan motor
1. Disconnect 2 lead wires from fan motor terminals.
2. Remove 4 screws holding air guide B on magnetron & on
base plate respectively, then remove air guide B.
3. Remove 2 screws holding fan motor and detach fan motor
from oven assy.
4. Remove fan blade from fan motor shaft by pulling it straight
out.
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6.5. Upper heaters
1. Disconnect lead wires from both sides of upper heaters.
2. Remove 2 screws holding heater support from the right side
of microwave oven.
3. Remove the heater by pulling it out.
6.6. Door assembly
1. Remove left and right door key springs from door arm with
plier.
NOTE:
Support door before removing door springs.
2. When mounting the door to the oven, be sure to adjust the
door parallel to the cavity front plate by moving hinges back
or forward.
3. 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.
4. Be sure the gap between left or right portion of door
assembly and cavity front plate will be 0.7±0.3mm.
5. Always perform the microwave leakage measurement test
after installation and adjustment of door assembly.
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6.7. Stirrer 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 from stirrer motor terminals.
3. Remove 2 screws holding stirrer motor.
NOTE:
After reinstalling the new stirrer 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 screw.
NOTE:
Do not remove the two screws holding the left and
right hinges on the bottom of cavity front plate.
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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 nor advisable to attempt 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).
7.1. 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 Closed Door Opened
Primary Latch Switch 0Ω(Close) Ω(Open)
Secondary Latch Switch 0Ω(Close) Ω(Open)
Power Relay RY1 Ω(Open) Ω(Open)
7.2. Short 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 short switch with door opened and
closed positions using lowest scale of the ohm meter.
Normal continuity readings should be as follows.
Door Opened Door Closed
0Ω(Close) Ω(Open)
7.3. 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.
7 COMPONENT TEST PROCEDURE
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7.4. Inverter power supply (U)
DO NOT try to REPAIR H.V. Inverter power supply (U).
Replace complete H.V. Inverter(U) Unit.
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 Clock button once.
b. Press Delay/Stand button once.
c. Press Start button once.
d. Press Microwave Power button once.
5. Program oven at High power for 1 minute and press [Start]
button.
a. After approximately 23 seconds, oven stops operating.
b. During oven operation, the input current is
approximately 0.5 to 1A. If both a and b are OK,
proceed to test 2.
INPUT CURRENT FAILURE CODE
Unplug CN703 0.5 to 1A Oven stops in 23
seconds after started.
Test 2
Continued from Test 1
1. Unplug the oven’s AC power supply cord from outlet.
2. Unplug 3 pin connector CN701. CN703 remains unplugged.
3. Plug in the oven’s AC power supply cord into outlet.
4. Program DPC.
a. Press Clock button once.
b. Press Delay/Stand button once.
c. Press Start button once.
d. Press Microwave Power button once.
5. Program oven at High power for 1 minute and press [Start]
button.
a. After approximately 3 seconds, oven stops operating.
b. During oven operation, the input current is
approximately 0.4A.
INPUT CURRENT FAILURE CODE
Unplug CN701 0.4A Oven stops in 3
seconds after started.
If both a and b check OK, the Inverter Power Supply (U) can be
determined to be OK.
7.5. 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.
TEMP MAGNETRON
THERMISTOR
OVEN THERMISTOR
100°C 30-60KΩ10-20K
Ω
25°C 700K-1.5MΩ100K-300K
Ω
If the resistance reading is out of the range stated here, the
thermistor is detective and must be replaced.
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8.1. Adjustment of Primary latch
switch, Secondary latch
switch and Short switch.
1. Mount the Primary latch switch, the Secondary latch switch
and the Short switch to the door hook assembly as shown
in illustration.
NOTE:
No specific individual adjustments during
installation of the Primary latch switch, Secondary
latch switch or Short 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 all latch
switches work properly after adjustment is completed.
Completely tighten the screws holding the door hook
assembly to the oven assembly.
3. Reconnect the short switch and check the continuity of the
monitor circuit and all latch switches again by following the
component test procedures.
4. The Primary latch switch must be ON when the space
between upper portion of door A and cavity front plate is
2~4mm, if the door gap is greater than 4mm, the Primary
latch switch must be OFF.
If alignment is poor, oven may not operate after grill use.
8.2. 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 litre 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.
1. Fill the beaker with exactly one litre 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 ceramic plate.
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 OUTPUT TEMPERATURE RISE
900W Min.8.0°C
1000W Min.8.5°C
8 MEASUREMENTS AND ADJUSTMENTS
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9 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. 230V 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.
Self diagnostic display
Oven has self diagnostic function but it will not be activated in normal operation mode.
To show self diagnostic result, please take the following steps.
1. Firstly, you must program the DPC into TEST MODE (Plug-in oven →press Clock button once →press Delay/Stand button
once →press Start button once →press Microwave Power button once.)
2. Error code list
H** Hardware problem, oven itself has problem.
U** Usage problem such as run out of water and oven itself works well.
Error code Cause for error
H99 Inverter on/off control error
H98 Magnetron no oscillation error (It is able to show up both in Test mode and
cooking mode.)
H97 Inverter input error (It is able to show up both in Test mode and cooking
mode.)
H96 Inverter custom IC error
H95 Inverter input failure
H90 Power down controlled by Inverter thermistor
H00 EPROM failure (It is able to show up both in Test mode and cooking mode.)
Usage problem
U40 No load operation, controlled by magnetron thermistor
U65 Power down controlled by Inverter thermistor
NOTE:
If error code “H97” or “H98” was observed, it is necessary to clean up the EPROM though the H.V. Inverter already be
replaced or repaired.
To clean up the EPROM, please take the following steps.
1. Keep pressing Delay/Stand button for more than 2 seconds until buzzer beeps.
2. Press Start button once, one beep sound.
3. The display window will show “EEPEND”.
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9.1. (Troubleshooting) Oven stops operation during cooking
SYMPTOM CAUSE CORRECTIONS
1. Oven stops in 3 seconds after
pressing [Start] button.
No input AC is supplied to H.V.Inverter (U)
CN702 terminals
1. Latch Switch
2. Power relay RY1
3. Loose lead wire connector CN701, CN702
4. H.V. Inverter (U)
Oven stops in 23 seconds after
pressing [Start] button.
H.V.Inverter (U) operates by the control signals
from DPC but magnetron is not oscillating
1. Magnetron
2. Loose lead wire connector CN703
3. H.V. Inverter (U)
2. No display and no operation at all.
Fuse is blown.
Most probably loose connection of connectors, or
door latch mechanism is not adjusted properly
1. Align door, Door Latch Switches
2. Loose wiring connectors
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9.2. (Troubleshooting) Other problems
SYMPTOM CAUSE CORRECTIONS
1. Oven is dead. 1. Open or loose lead wire harness
Check thermal cutout is defective.
Fuse is OK. 2. Open thermal cutout / thermistor
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.
1.
2.
Shorted lead wire harness
Defective primary latch switch (NOTE 1)
Check adjustment of primary, secondary latch
switch and short switch including door.
3. Defective short 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.
3. Oven does not accept key input
(Program)
1. Key input is not in proper sequence Refer to operation procedure.
2. Shorted or open touch switch
3. Defective DPC Refer to DPC troubleshooting.
4. Fan motor turns on when oven is
plugged in with door closed.
1. Misadjustment or loose wiring of secondary
latch switch
Adjust door and latch switches.
2. Defective secondary latch switch
5. Timer starts count down but no
microwave oscillation.
(No heat while oven lamp and fan
motor turn on)
1. Off-alignment of primary latch switch Adjust 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
Check high voltage component according to
component test procedure and replace if it is
defective.
4. Open or loose wiring of power relay RY1
5. Defective primary latch switch
6. Defective DPC or power relay RY1 Refer to DPC troubleshooting
6. Oven can program but timer does not
start countdown.
1. Open or loose wiring of secondary latch switch
2. Off-alignment of secondary latch switch
3. Defective secondary latch switch
7. Microwave output is low. Oven takes
longer time to cook food.
1. Decrease in power source voltage Consult electrician
2. Open or loose wiring of magnetron filament
circuit.(Intermittent oscillation)
3. Aging change of magnetron
8. Fan motor turns on and stirrer motor
rotates when door is opened.
1. Shorted primary latch switch
9. Oven does not operate and return to
plugged in mode as soon as [Start]
button is pressed.
1. Defective DPC Check grounding connector on escutcheon
base.
10. Loud buzzing noise can be heard. 1. Loose fan and fan motor
11. Heater does not turn on. 1. Open or loose wiring of heater
2. Defective heater
3. Defective power relay
4. Defective DPC
12. Oven stops operation during cooking. 1. Open or loose wiring of primary and
secondary latch switch
Adjust door and latch switches.
2. Operation of thermal cutout
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NN-GF668M