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
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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
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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
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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
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NN-GD371S / NN-GD361M / NN-GD351W