Panasonic NN-J993 User manual

OrderNo. MOD0311270C3
MicrowaveOven
NN-J993
SPECIFICATIONS
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1. FEATURE CHART
2. CONTROLPANEL
3. OPERATIONAND DIGITALPROGRAMMER
CIRCUITTEST
4. SCHEMATICDIAGRAM
5. DESCRIOTIONOFOPERATING SEQUENCE
6. STEAMFUNCTION(STEAM&MICRO POWER AND
Reheat withSTEAM.)
7. CAUTIONS TO BE OBSERVED WHENCAUTIONS
TO BE OBSERVED WHEN TROUBLESHOOTING
8. DISASSEMBLYAND PARTSREPLACEMENT
PROCEDURE
9. COMPONENTTESTPROCEDURE
10. MEASUREMENTSAND ADJUSTMENTS
11. TROUBLESHOOTING GUIDE (NEWH.V.)
12. HOWTO CHECK THE SEMICONDUCTORS USING
ANOHMMETER
13. EXPLODED VIEWAND PARTSLIST
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4 SCHEMATIC DIAGRAM
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5 DESCRIPTION OF
OPERATING SEQUENCE
5.1. Variable power cooking
control
HIGH VOLTAGE INVERTER POWER SUPPLY (U) controls
output power by the signal from Digital programmer Circuit
(DPC). Power relay 2 stays on while 1000W to 300W selection
but the inverter drive signal to control it‘s output power 150 W
and 100 W will be ON-OFF controlled.
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.
5.2. Defrost
When auto weight defrost is selected and the start Pad is
tapped:
1. The digital programmer circuit determines the power level
and cooking time to complete cooking and indicates the
operating stage in the display window. Table shows the
corresponding cooking time for respective serving by
categories.
2. When cooking time in the display window has elapsed, the
oven turns off automatically by a control signal from the digital
programmer circuit.
5.3. Convection Grill Cooking
Control
The digital programmer circuit controls the ON-OFF time of the
heater in order to control oven cavity temperature.
1. After the start pad is tapped with the desired Bake-Broil
program set, an high level signal comes out Micro-Computer
circuit and is applied to gate of triacs, D222 and D223.
2. When triacs turns on, power source voltage is applied the
heater and the heater turns on.
3. When the oven temperature reaches the set temperature,
the digital programmer circuit senses the temperature through
oven temp sensor and stops supplying high level signal to the
triacs and the heater turns off.
4. After the heater turns off, the oven temperature will continue
increasing a while and then decrease as shown in Figure.
When the oven temperature drops below the set temperature,
the digital programmer circuit senses the signal and starts
supplying an high level signal to the trialc again.
Defrost
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5.4. Combination cooking control
Combination cooking is accomplished by microwave and
convection cooking being done alternately during one
combination cooking cycle. One combination cooking cycle is
22 seconds.
1. During combination cooking, the digital programmer circuits
ON-OFF time of both heater and magnetron shown in Figure.
NOTE 1: Note that the heater may not be on during a heater
on period if the preporgrammed oven temperture has been
reached. This is due to the fact that the oven is keeping the
preporgrammed oven temperature constant, so of course
5.5. Sensor reheating
The temperature of the foods being heated is detected by an
infrared (IR) sensor and you do not have to set the temperature
or time.
5.5.1. How to read temperature by IR
sensor
IR sensor can read food temperature without touching, IR rays
emitted from food. IR sensor to generate temperature related
electric signal output and micro-computer to convert actual
temperature.
5.5.2. Operation
IR sensor is mounted top back of oven cavity through the hole.
It scans all over cooking shelf. IR sensor has 8 eyes and can be
the heater will only be on when it is needed and off when
it is not needed.
NOTE 2: As for temperatures of combination cooking for
convection, the temperatures by each program are
preporgrammed in the microprocessor as shown in Figure.
read oven shelf front to back at the time. Then IR sensor is
design to scan right to left to cover all over shelf. (19 points)
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6.1. Water supply
As showing in figure, water in water tank will be pumped up and
supply to the steam generation heater located inside back
bottom of oven cavity.
6.2. Operation
When pushing start bottom, oven preheat will start and then
water supply begins. It will take about 2 minutes for pre-
heating. When preheat is completed, it will turn into actual
cooking process. During heating, temperature sensor located
on steam sensor monitoring steam heater temperature and
when it exceeds 95C, then additional water to supply to
maintain moisture/steam within oven cavity.
6 STEAM FUNCTION
(STEAM & MICRO POWER AND Reheat with STEAM.)
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Unlike many other appliances, the microwave oven is high-
voltage, high-current equipment. Though it is free from danger
in ordinary use, extreme care should be taken during repair.
7.1. Check the grounding
Do not operate on a 2-wire extension cord. The microwave
oven is designed to be used when grounded. It is imperative,
therefore, to make sure it is grounded properly before
beginning repair work.
7.2. Inverter Warnings (NEW H.V.)
7.3. When parts must be replaced,
remove the power plug from
the outlet.
7.4. When the 10A/18A 250V fuse
is blown due to the operation
of short switch:
1. This is mandatory. Refer to “Adjustments and Measurement”
for these switches.
2. When replacing the fuse, confirm that it has the appropriate
7 CAUTIONS TO BE OBSERVED WHEN
TROUBLESHOOTING
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rating for these models.
3. When replacing faulty switches, be sure mounting tabs are
not bent, broken or therwise deficient in their ability to hold the
switches.
7.5. 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 other holes gaps, because such
objects may work as an antenna and cause microwave
leakage.
7.6. Confirm after repair
1. After repair or replacement of parts, make sure that the
screws of the oven, etc. are neither loose nor misssing.
microwaves 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.
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8 DISASSEMBLY AND PARTS REPLACEMENT
PROCEDURE
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8.1. Inverter PCB
* When removing cabinet, unplug and wait for 30 seconds then
discharge high voltage remaining in high voltage capactior.
1. Remove frame (Remove 2 screws to slide out.).
2. Remove outer cabinet (9 screws).
Including 3 screws on left side as below.
3. Remove a screw on air guide C.
4. Disconnect 2 lead wires on magnetron.
5. Disconnect 4 pin (pump) connector.
6. Remove ceramic cover from oven cavity.
7. Remove back panel (3 screws).
8. Remove air guide E.
10. Turn up side down oven.
11. Remove door spring and door arm.
When re-assemble oven make sure to snap in holder.
13. a. Remove base cover first (3 screws).
b. Do not remove one each hinge screw which direct mount to
oven cabity unless you must re-adjust door again.
c. Remove noise filtor unit mounting 7 screws and release one
lead wire connector).
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14. Carefully pull up base plate from front side, bent holding tab
as shown in figure.
15. Stand base plate by holding tabs
Warning: Any lead wire should not be caught by base.
16. Discharging high voltage by shorting high voltage terminal
to chassis ground.
WARNIG: Touch chassis side first.
17. Release 2 tabs to open air guide.
18. Inverter PCB
1. Release CN701/CN702/CN703 connectors
2. Remove 2 screws
3. Remove 2 tabs to remove inverter
WARNING: Make sure put back grounding screw when re-
assemble
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8.2. Steam heater
1. Follow inverter PCB removing steps 1-16.
2. Release 2 lead wire from thermal cutout.
3. Relese steam heater terminal lead wire (2).
4. Release antenna motor lead wire connector
5. Remove steam thermistor (1 screw)
6. Remove bracket.
7. Remove steam heater.
8.3. DPC
1. Follow inverter PCB removing steps 1-16 first.
2. Remove all wiring connectors.
a. Remove 13 connectors.
b. Remove grounding lead wire (2 screws).
c. Release tabs to remove PCB.
NOTE: One lead wire connector from DPC is not connected
any place, but this is normal, after replacing, make sure not
touching or caught any portion.
8.4. Fan motor
1. Follow inverter PCB removing steps 1-16 first.
2. Remove Fan case.
3. Remove fan motor unit.
a. Remove 2 screws.
b. Release holding tabs.
8.5. Magnetron
1. Follow inverter PCB removing steps 1-16 first.
2. Remove magnetron (3 screws).
8.6. Magnetron Thermistor
1. Follow inverter PCB removing steps 1-16 first.
2. Remove mangetron thermistor.
a. Unsolder lead wire.
b. Remove screw
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8.7. Upper heater
8.7.1. Remove upper heater
1. Remove frame (2 screws).
2. Remove outer cabinet (9+3 screws).
3. Remove lead wire terminal.
4. Remove adiabatic material.
a. Remove 5 screws.
b. Straight vending tabs.
5. Remove upper heater
a. Remove heater terminal board.
b. Cut where marked.
8.7.2. Replace upper heater
1. Place new heater and vend tabs in 90°to secure heater.
2. Secure terminal board.
8.8. Back Heater
1. Remove frame.
2. Remove outer cabinet.
3. Remove back cover.
Slide left to remove.
4. Remove heater.
a. Remove lead wires
b. Straight the tabs.
c. Remove screw.
d. Remove mounting plate.
e. Remove heater.
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8.9. Antenna motor
1. Follow inverter PCB removing steps 1-16 first.
2. Unplug connector.
3. Remove screws.
8.10. Convection fan motor
1. Remove frame.
2. Remove cabinet.
3. Remove back panel.
4. Remove back panel (inner) (11 screws).
5. Remove fan blade (M4 nut + spring washer).
6. Remove IR sensor.
7. Remove barcket.
a. Remove lead wire connector.
8. Remove cooling fan.
9. Remove motor.
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8.11. Oven thermistor
NOTE: If you are doubt about following pocedures please
replace by whole lead wire harness.
Replace thermister.
1. Remove screw.
2. Cut lead wire at 60mm.
3. Cut tube in 35mm.
Do not cut lead wires.
4. 15mm short cut one side lead wire and remove insulation in
7mm.
5. Insert insulation and solder connection of new thermistor.
a. After soldering lead wires make sure isolated by insulation
tube and bind them together.
6. Insert tube for secure insulation.
8.12. Shelf
1. Remove frame
2. Remove outer cabinet
3. Locate oven just off the table and insert screw driver to push
up.
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8.13. Door Parts
1. Remove 2 knobs (E2).
2. Remove knob trim (E5 & E6) by releasing 3 hooks inside hole.
3. Use cutter blade or like to pick up escutchen sheet edge to start peel off where you can find gap between door and escutchen
sheet. Right or left edge is most convenient to start peeling off.
4. To remove escutcheon or printed circuit board remove 4 screw to release from door U.
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9.1. Primary Latch switch,
Secondary (Secondary Latch
Switch and Power Relay 2)
Interlocks.
1. Unplug the lead connectors to Power Relay 2 verify
continuity of the power relay 2 1-2 terminals.
2. Unplug lead connectors to Primary Latch Switch and
secondary Latch Switch.
3. Test the continuity of switches at door opend and closed
positions with ohm meter (low scale).
Normal continuity readings should be as follows.
9.2. Short Switch / Monitor Circuit
1. Unplug lead wires from H. V. Inverter primary terminals.
2. Connect test probes of ohm meter to the disconnected leads
which were connected to H. V. Inverter.
3. Test the continuity of short swich with door opened and
closed positions using lowest scale of the ohm meter.
Nomal continuity readings should be as follows.
9.3. Magnetron (NEW H.V.)
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 berween each filament terminal and
magnetron case should read open.
9 COMPONENT TEST PROCEDURE
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