Panasonic NN-GD371S User manual

© Panasonic Home Appliances Microwave Oven
(Shanghai) Co., Ltd. 2011.
NN-GD371S
NN-GD361M
NN-GD351W
BPQ (U.K.)
EPG (Continental Europe)
WPG (Switzerland)
Microwave Oven
ORDER NO.PHAMOS1106061CE

2
NN-GD371S / NN-GD361M / NN-GD351W

3
NN-GD371S / NN-GD361M / NN-GD351W

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. Inverter defrost, Auto menu & Auto reheat 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 10A 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) 10
6.3. Low voltage transformer and/or power relays (RY1) 11
6.4. DC fan motor 11
6.5. Door assembly 12
6.6. Turntable motor 13
6.7. Quartz heater 14
6.8. H.V. Inverter Power Supply 14
7 COMPONENT TEST PROCEDURE 16
7.1. Primary, Secondary Latch Switch interlocks & Power
Relay RY1 16
7.2. Short switch & monitor 16
7.3. Magnetron 16
7.4. DC fan motor 16
7.5. Inverter power supply (U) 17
7.6. 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
19
9.2. Troubleshooting of inverter circuit (U) and magnetron 21
9.3. Simple way of H.V. Inverter/magnetron troubleshooting
22
9.4. How to check the semiconductors using an OHM meter
22
9.5. H.V. INVERTER MAIN PARTS LIST (Z606YBA00GP) 23
10 EXPLODED VIEW AND PARTS LIST 24
10.1. EXPLODED VIEW 24
10.2. PARTS LIST 25
10.3. ESCUTCHEON BASE ASSEMBLY 26
10.4. DOOR ASSEMBLY 28
10.5. WIRING MATERIALS 29
10.6. PACKING AND ACCESSORIES 30
11 DIGITAL PROGRAMMER CIRCUIT 31
11.1. SCHEMATIC DIAGRAM 31
CONTENTS
Page Page
4
NN-GD371S / NN-GD361M / NN-GD351W

1 FEATURE CHART
2 CONTROL PANEL
5
NN-GD371S / NN-GD361M / NN-GD351W

3 SCHEMATIC DIAGRAM
6
NN-GD371S / NN-GD361M / NN-GD351W

4.1. Variable power cooking
control
High Voltage Inverter Power Supply (U) controls output power
by the signal from Digital Programmer Circuit (DPC). Power
relay always 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)
950W 100% 22 0
270W 30% 14 8
600W 70% 22 0
440W 50% 22 0
300W 30% 22 0
100W 10% 13 9
4.2. Inverter power supply circuit
The Inverter Power Supply circuit powered from the line
voltage, 230-240V 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 230-240V 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. Inverter defrost, Auto menu &
Auto reheat
When the Auto Control feature is selected and the Start button
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.
Weight Deforst (Meat Items) for BPQ models:
SELECTED WEIGHT COOKING TIME
1000 g 20 min.00 sec.
Weight Deforst (Small Piece) for EPG &WPG models:
SELECTED WEIGHT COOKING TIME
1000 g 19 min.00 sec.
Weight Cook (Fresh Vegetables)
For BPQ models:
SELECTED WEIGHT COOKING TIME
200 g 5 min.40 sec.
For EPG & WPG models:
SELECTED WEIGHT COOKING TIME
200 g 4 min.56 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 DESCRIPTION OF OPERATING SEQUENCE
7
NN-GD371S / NN-GD361M / NN-GD351W

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/LINE) 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.
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 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
earth bracket.
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.
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 CAUTIONS TO BE OBSERVED WHEN
TROUBLESHOOTING
8
NN-GD371S / NN-GD361M / NN-GD351W

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 10A fuse is blown
due to the malfunction of the
short switch:
WARNING
When the 10A 250V fuse is blown due to the malfunction of
the interlock monitor switch, replace all of the components
(primary latch switch, secondary latch switch, short 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.
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 nor 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
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.
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.
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.
9
NN-GD371S / NN-GD361M / NN-GD351W

6.1. Magnetron
1. Discharge the high voltage capacitor.
2. Remove 1 screw holding front plate bracket on cavity top
plate.
3. Remove 2 screws holding air guide A on cavity top plate
and on magnetron.
4. Remove 1 screw holding air guide A on the wave guide,
then remove the air guide A.
5. Remove 1 screw holding thermistor on the magnetron.
6. Remove 2 screws holding the 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.
CAUTION
When replacing the magnetron, be sure the antenna gasket is in
place.
6.2. Digital programmer circuit
(D.P.C)
CAUTION:
Be sure to ground any static electric charge built up in
your body before handling the D.P.C..
1. Disconnect all connectors from D.P.C. board.
6 DISASSEMBLY AND PARTS REPLACEMENT
PROCEDURE
10
NN-GD371S / NN-GD361M / NN-GD351W

2. Disconnect 1 grounding connector from cavity front plate.
3. Disconnect connector CN701 from H.V. inverter.
6.3. Low voltage transformer
and/or power relays (RY1)
CAUTION:
Be sure to ground any static electric charge built up in
your body before handling the DPC.
1. 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.
NOTE:
Do not use a soldering iron or desoldering tool of
more than 30 watts on D.P.C. contacts.
2. 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.
6.4. DC fan motor
1. Disconnect DC fan motor connect CN15 from DPC board
DU.
2. Remove 2 screws holding orifice assy and detach the orifice
assy from oven assy.
3. Remove 2 screws holding DC fan motor(U) on orifice assy
and detach the fan motor from orifice assy.
11
NN-GD371S / NN-GD361M / NN-GD351W

6.5. Door assembly
1. Support the door, remove 2 screws holding hinge A.
2. Open the door, remove door(U) and hinge A from cavity.
NOTE:
Support the door before opening.
3. Remove door C from door A (U) & door E by carefully
pulling outward starting from upper right hand corner using
a flat blade screwdriver.
4. Separate door E from tabs on door A (U) and remove door
A (U).
5. Remove door key and door key spring from door E.
6. Replace other components.
To re-install components:
NOTE:
After replacement of the defective component parts
of the door, reassemble it properly and adjustment
so as to prevent an excessive microwave leakage.
Adjustment of the door assembly (Refer page 18).
7. Place the hole of hinge A into the door’s upper hinge pin.
8. Use your left index finger to support the door’s lower hinge
pin while guiding the door’s hinge A into the cavity slot.
Then lower your finger to seat the door onto the hinge.
NOTE:
Door alignment is crucial. If door is misaligned,
apply pressure until alignment is achieved.
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.
12
NN-GD371S / NN-GD361M / NN-GD351W

9. Tighten 2 mounting screws.
Be sure the gap between door E and cavity front plate will
be 0.3~0.7mm.
NOTE:
Always perform the microwave leakage measurement
test after installation and adjustment of door assembly.
6.6. Turntable motor
1. Remove the motor cover by breaking off at the 4 spots
indicated by arrows with a cutter or the like.
NOTE:
After removing the motor cover, be sure that cut
portions are properly trimmed off 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 1 screw.
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 into the 2 provided slots, then screw
the single tab to the base using a 4mm x 6mm
screw.
13
NN-GD371S / NN-GD361M / NN-GD351W

6.7. Quartz heater
1. Disconnect lead wires from both side of heater terminals.
2. Bend back 2 locking tabs from left and right side of upper
heater panel respectively. Then slide the upper heater
panel upward and out.
3. Remove the heater by pulling it out from the cavity left side.
6.8. H.V. Inverter Power Supply
1. Disconnect 2 high voltage lead wires from magnetron
filament terminals.
2. Unplug connector CN701 & CN702 from H.V. Inverter
board.
3. Remove 1 screw holding gro unding plate on the base.
4. Remove 1 screw holding inverter bracket on the base.
5. Slide 2 locking tabs of inverter bracket at the bottom of the
base in direction of arrows.
14
NN-GD371S / NN-GD361M / NN-GD351W

6. Remove 2 screws holding H.V. inverter on the inverter
bracket.
15
NN-GD371S / NN-GD361M / NN-GD351W

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.
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 & monitor
1. Unplug lead wires from Inverter Power Supply (U) primary
terminals.
2. Connect test probes of ohm meter to the disconnected
leads which 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.
7.4. DC fan motor
1. connection
2. Control wire of fan motor should accept PWM control.
Fan motor´s spin speed is controlled by this PWM siginal.
PWM frequency is from 18KHz to 30 KHz. If the PWM
control wire open, fan motor will spin at maximum speed.
7 COMPONENT TEST PROCEDURE
16
NN-GD371S / NN-GD361M / NN-GD351W

7.5. 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 Micro 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 Micro 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.
7.6. Temperature thermistor
The thermistor that is attached to the magnetron detects the
temperature of the magnetron and will stop magnetron
operation when overheating is detected. A normal thermistor´s
resistance is 35KΩto 110KΩfor an ambient temperature range
of 10-30 degree C.
If the resistance reading is out of the range stated here, the
thermistor is detective and must be replaced.
It is also possible to display thermistor level by taking the
following steps.
1. Program the DPC into TEST MODE (Plug-in oven →press
Clock button once →press Delay/Stand button once →
press Start button once →press Micro Power button
once).
2. Program oven at Standing Time for 1 minute and press
[Start] button.
3. Press Micro Power once, the thermistor level reading will
shown on the display.
The normal reading should be in the range of 16-230.
17
NN-GD371S / NN-GD361M / NN-GD351W

8.1. Adjustment of Primary latch
switch, Secondary latch
switch and Short switch.
1. Mount the Primary latch swith, the Secondary latch switch
and the Short switch to the door hook assembly as shown
in ILL.
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 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 short switch and check the coninuity of the
monitor circuit and all latch switches again by following the
component test procedures.
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 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.
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 OUTPUT TEMPERATURE RISE
900W Min.8.0°C
1000W Min.8.5°C
8 MEASUREMENTS AND ADJUSTMENTS
18
NN-GD371S / NN-GD361M / NN-GD351W

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. 230-240V 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.
9.1. (Troubleshooting) Oven stops operation during cooking
SYMPTOM CAUSE CORRECTIONS
1. Oven stops in 3 seconds after
pressing [Start] button
No 230-240V 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
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
19
NN-GD371S / NN-GD361M / NN-GD351W

SYMPTOM CAUSE CORRECTIONS
1. Oven is dead. 1. Open or loose lead wire harness
Fuse is OK. 2. Open thermal cutout / thermistor Check 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.
1. Shorted lead wire harness Check adjustment of primary, secondary latch
switch and monitor interlock switch including
door.
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.
3. Oven does not accept key input
(Program)
1. Key input is not in proper sequence Refer to operation procedure.
2. Open or loose connection of membrane key
button to DPC (Flat cable)
3. Shorted or open membrane key board
4. Defective DPC Refer to DPC troubleshooting.
4. 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
5. 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
6. 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
7. Fan motor turns on and turntable
motor rotates when door is opened.
1. Low voltage transformer on DPC.
8. 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.
9. Loud buzzing noise can be heard. 1. Loose fan and fan motor
10. Turntable motor does not rotate. 1. Open or loose wiring of turntable motor
2. Defective turntable motor
11. 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
12. Heater does not turn on 1. Open or loose wiring of heater
2. Defective heater
3. Defective power relay
4. Defective DPC
20
NN-GD371S / NN-GD361M / NN-GD351W