John Lewis NN-CT878SBJQ, JLFSMWC003 Service Manual
HAD0901001C2
Microwave Oven
NN-CT878SBJQ
JLFSMWC003
32L OEM
United Kingdom
NN-CT878SBJQ JLFSMWC003 32L OEM
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1 Contents
1 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Inverter Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Feature Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
4 Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
5 Operation And Digital Programmer Circuit Test Procedure . . . . . . . . . . . . . . . . . . . 5
6 Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7 Wiring Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8 Description of the Operation Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9 Cautions to be Observed when Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10 Part Replacement Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11 Component Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
12 Measurements and Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
13 Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
14 Digital Programmer Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
15 Description of Operating instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
16 Exploded View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
17 Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
18 Door Assy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
19 Escutcheon Base. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
20 Packing and Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
21 Digital Programmer Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
22 Key Board Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
© Panasonic Home Appliance Division. 2008
Unauthorized copying and distribution is a
violation of law.
NN-CT878SBJQ JLFSMWC003 32L OEM
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2 Inverter Warning
The inverter board looks like a regular PCB, however, this PCB
drives the magnetron tube using very high voltages and current.
It has
1. Very high voltage and high current
2. An Aluminium heat sink that becomes very hot
3. The capacitors on the inverter circuit will contain a high
voltage charge even when the oven is not operating.
Do not
1. Do not touch the circuitry as it contains very high voltages. When replacing the board please take extreme
care to avoid possible electric shock. High voltages may
remain in the circuit.
2. Do not touch the aluminium heat sink as it will become
very hot. It also contains high voltages.
3. Do not attempt to repair the inverter PCB as this can be
very dangerous. Replace the high voltage inverter circuit
as a complete unit. Return the old unit fully repacked
in the original shipping box and completed paper
work.
4. Do not adjust or tamper with the preset volume on the
inverter board. It is very dangerous to adjust this preset
without proper test equipment.
5. Do not test the oven while the inverter grounding strip or
screws are loose. It is very dangerous to operate the
inverter circuit board without a proper ground connection.
Inverter Grounding
Figure 1
Inverter PCB layout
Figure 2
3 Feature Chart
Function NN-A883
Microwave 6
Grill 3
Convection 17
Combination YES
Sensor reheat 2
Sensor cook 2
Sensor combination 4
Sensor crisp Weight defrost 3
Weight combination 8
Weight reheat Weight cook Memory cook Weight crisp Stage cooking 3
Delay/Stand YES
More/Less YES
Kg-> lb/oz YES
Clock 12H
Word prompt English
Step by Step LED
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4 Control Panel
Potatoes
Micro Power
Grill 1-2-3
Convection
Turbo-Bake
Combination
CHAOS
g/
lb
oz
Delay/
Stand Clock more less
Stop/Cancel
Start
Reheat
Meal
Pastry/
Cake
Crispy
Top
Meat
Chicken
Roast Veg
Veg/Fish
JLFSMWC003
AUTO SENSOR
SENSOR COMBI
AUTO WEIGHT
10
min
1
min10sec
1
h
(1) Display Window
(2) Time Pads
(3) Auto Sensor Microwave
Programs
(4a) Auto Sensor Combination
Programs
(4b) Auto Weight Combination
Programs
(5) Auto Weight Defrost Programs
(6) Microwave Power Pad
(7) Grill Pad
(8) Convection Pad
(9) TURBO-BAKE Pad
(10) Combination Pad
(11) Delay/Stand Pad:
This can be used to delay a
cooking program for up to 9 hrs
99 mins., or used to time or for
standing (non-cooking) time.
(12) Clock Pad:
Refer to page 15 for setting the
clock.
(13) lb/oz Conversion Pad
(14) More/Less Pads
(15) Stop/Cancel Pad:
Before Cooking:
one press clears your instructions.
During Cooking:
one press temporarily stops the
cooking program. Another press
cancels all your instructions and
the time of day will appear in the
display.
(16) Start Pad:
Press to start operating the oven.
If during cooking the door is
opened or Stop/Cancel Pad is
pressed once, Start Pad has to
be pressed again to continue
cooking.
(17) Door Release Pad
(1)
(2)
(15)
(12)
(13)
(14)
(16)
(6)
(7)
(8)
(9)
(10)
(5)
(11)
(3)
(4a)
* The design of your control panel may
vary from the panel displayed (depending
on colour and shape of pads or buttons),
but the words relating to the pads will be
the same, and function in the same way.
(4b)
(17)
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5 Operation And Digital Programmer Circuit Test Procedure
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NN-CT878SBJQ JLFSMWC003 32L OEM
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6 Schematic Diagram
NN-CT878SBJQ JLFSMWC003 32L OEM
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7 Wiring Diagram
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8 Description of Operating instruction
8.1. Variable power cooking control
The HIGH VOLTAGE INVERTER POWER SUPPLY controls
the output power by a signal from the digital Programmer circuit
DPC. The power relay (RY1) turns on to supply power to the
inverter circuit. The level of output power is controlled by the
drive signal level from the inverter circuit.
NOTE1: The ON/OFF time ratio does not correspond with
the percentage of microwave power since approximately 2
seconds are required for heating the magnetron filament.
NOTE: 2 If microwave cooking is over 8 minutes on HIGH
power, the fan motor rotates for 1 minute after cooking to
cool the oven and electrical components.
Duty cycles for microwave cooking
8.2. Grill Cooking
The digital programmer circuit controls the grill power by operating the power relay RY4 in the sequence shown in the table
below
Duty cycles for Grill Cooking
8.3. Auto weight defrost, Auto
weight Cook
When an auto control feature is selected and the start pad
pressed:
1. The digital programmer circuit determines the power level
and the cooking time and indicates the operating state in
the display. The table shows the corresponding cooking
times for each category and its respective weight.
2. When the cooking time in the display window has
elapsed, the oven turns off automatically via the control
signal from the digital programmer circuit.
Note: After auto cooking if the oven temperature is
over the predetermined temperature the fan motor
rotates to cool the oven and its components.
Defrost Menu’s
Weight Menu’s
Output Duty ON/OFF
ON time OFF time
High 1000W 22” 0”
Defrost 440W 16” 6”
Medium 600W 22” 0”
Low 440W 22” 0”
Simmer 440W 15” 7”
Warm 440W 8” 14”
Duty ON/OFF
ON Time OFF Time
Grill 1 66” 0”
Grill 2 54” 12”
Grill 3 42” 24”
Category 1st Touch Weight Cooking Time
Turbo Defrost 500g 8m 20s
Category 1st Touch Weight Cooking Time
1. Whole Chicken 1000g 18m 20s
2. Chicken Pieces 300g 9m 30s
3. Beef / Lamb 500g 14m 40s
4.Casserole 800g 56m 40s
5. Pastry 600g 15m 00s
6. Cake 400g 11m 40s
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8.4. Convection Cooking
1. The digital programmer circuit operates the power relays
RY3,RY5 and RY6 in the sequence as shown in the figure
below.
2. When the oven reaches a predetermined temperature the
digital programmer circuit stops supplying power to relay
RY5, resulting in the convection heater turning off.
3. When the temperature drops below the predetermined
temperature, the digital programmer circuit supplies
power to power relay RY5 resulting in the convection
heater turning on.
Note: After the convection process, if the oven temperature is higher than the predetermined temperature, the
fan motor rotates to cool the electronic components and
the oven.
Convection Cooking Duty Cycles
Figure 1
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8.5. Combination Cooking
Combination cooking is achieved by operating the microwave
and heater modes together during one cooking cycle. There
are three combination modes.
1. Combination (convection and microwave)
2. Combination (grill and microwave)
3. Combination (grill, convection and microwave)
The digital programmer circuit operates the power relays as
shown in the figures below.
When the oven temperature reaches the predetermined temperature, the digital programmer circuit stops supplying power
to relay (RY5) resulting in the convection heater turning off.
During this time the digital programmer circuit continues to
operate relay (RY1) so that microwave activity continues at the
duty cycle selected. The inverter control signal level is also
maintained. The microwave activity continues to cycle until the
entire cooking program is completed.
When the oven temperature drops below the selected temperature, the digital programmer circuit operates power relay (RY5)
switching on the heater elements.
In the case of grill combination the sequence applies with the
digital programmer circuit switching power relay (RY4) to control, the grill elements.
With convection, grill and micro power combination. The grill
elements and convection elements are operated alternatively
whilst the oven temperature is above the selected level.
Convection And Microwave Combination Duty Cycles
Grill And Microwave Combination Duty Cycles
Grill Convection And Microwave Combination Duty Cycles
Convection Heater Micropower
100 - 250 C DISPLAY OUTPUT ON OFF
440 360W 66 0
250 360W 48 18
100 360W 21 45
Grill Heater Micropower
ON OFF DISPLAY OUTPUT ON OFF
Grill 1 51 15 440 360W 66 0
Grill 2 42 24 250 360W 48 18
Grill 3 28 38 100 360W 21 45
Convection
Heater
Grill Heater Micropower
100 - 250 C ON OFF OUTPUT ON OFF
Grill 1 51 15 440 360W 66 0
Grill 2 42 24 250 360W 48 18
Grill 3 28 38 100 360W 21 45
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