Panasonic NN-CF771S User manual

© Panasonic Home Appliances Microwave Oven
(Shanghai) Co., Ltd. 2011
NN-CF771S
BPQ (U.K.)
EPG (Continental Europe)
Microwave Oven
ORDER NO.PHAMOS1101010CE

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NN-CF771S

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NN-CF771S

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 Menu cooking 7
4.4. Grill cooking control 7
4.5. Convection & Grill Convection cooking control 8
5 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING
9
5.1. Check the grounding 9
5.2. Inverter warnings 9
5.3. Part replacement. 10
5.4. When the 15A fuse is blown due to the malfunction of the
short switch: 10
5.5. Avoid inserting nails, wire etc. through any holes in the
unit during operation. 10
5.6. Verification after repair 10
5.7. Sharp edges 10
6 DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE
11
6.1. Inverter power supply 11
6.2. Magnetron 12
6.3. Digital programmer circuit (D.P.C) 12
6.4. Low voltage transformer and/or power relays (RY1, RY2,
RY4, RY6) 14
6.5. Fan motor 14
6.6. Quartz heater 15
6.7. Door assembly 15
6.8. Stirrer motor 16
6.9. Convection fan motor and convection heater 16
7 COMPONENT TEST PROCEDURE 19
7.1. Primary, Secondary Latch Switch interlocks & Power
Relay RY1 19
7.2. Short Switch 19
7.3. Magnetron 19
7.4. Inverter power supply (U) 20
7.5. Temperature thermistor 20
8 MEASUREMENTS AND ADJUSTMENTS 21
8.1. Adjustment of primary latch switch, secondary latch switch
and short switch. 21
8.2. Measurement of microwave output 21
9 TROUBLESHOOTING GUIDE 22
9.1. (Troubleshooting) Oven stops operation during cooking
23
9.2. (Troubleshooting) Other problems 24
9.3. Troubleshooting of inverter circuit (U) and magnetron 25
9.4. Simple way of H.V. Inverter/magnetron troubleshooting
26
9.5. How to check the semiconductors using an OHM meter
26
9.6. H.V. INVERTER MAIN PARTS LIST (F606Y6Y40BP) 27
10 EXPLODED VIEW AND PARTS LIST 28
10.1. EXPLODED VIEW 28
10.2. PARTS LIST 29
10.3. ESCUTCHEON BASE ASSEMBLY 31
10.4. DOOR ASSEMBLY 32
10.5. WIRING MATERIALS 33
10.6. PACKING AND ACCESSORIES 34
11 DIGITAL PROGRAMMER CIRCUIT 35
11.1. SCHEMATIC DIAGRAM 35
CONTENTS
Page Page
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1 FEATURE CHART
2 CONTROL PANEL
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3 SCHEMATIC DIAGRAM
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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 Menu cooking
When the Auto Menu 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.
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 DESCRIPTION OF OPERATING SEQUENCE
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4.5. Convection & Grill Convection
cooking control
The digital programmer circuit controls the ON-OFF time of the
heater in order to control oven cavity temperature.
1. After selecting desired oven cavity temperature of
Convection/Grill Convection (the range of selected oven
temp is 100°C-250°C) and pressing [Start] button, a high
level signal comes out of the micro computer and applies to
power relay (RY6).
2. When RY6 are switched to ON, power source voltage is
applied to the convection heater, and the heaters turn on.
3. The digital programmer circuit senses the oven cavity
temperature through oven temp sensor (thermistor). When
the oven temperature reaches the set temperature, DPC
stops supplying high level signal to the power relay, and the
heater turn off.
4. After the convection heater turn off, the oven temperature
will continue increasing for a while and then decrease.
When the oven temperature drops below the set
temperature, the digital programmer circuit senses the
signal and starts supplying a high level signal to RY6 again.
NOTE:
a. If only convection heater works, convection motor
would rotate for over 1 minute after cooking to cool
oven and electric components.
b. After convection or grill convection cooking, fan
motor rotates for 1~6 minutes to cool oven and
electric components.
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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 & 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 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.
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.
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, 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 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.
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.
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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