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Panasonic NN-CT878SBPQ, Service Manual, Page: 1 / 35

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Panasonic NN-CT878SBPQ Service Manual Download Page 1

HAD0712001C2

Microwave Oven

NN-CT878SBPQ

32L

United Kingdom

Chaos

Defrost

Vegetables

Potatoes

Fish

Pizza

Chicken

Meat

Crispy Top

Bake

10

min

1

min

10

sec

1

h

Micro Power

Grill 1-2-3

Convection

Combination

Turbo-Bake

Memory

Timer

Start

Stop / Cancel

less

more

NN-CT878S

Power source

240V AC Single Phase 50Hz

Power requirements

Microwave 1220W

Grill 1560W

Convection 1350W

Combi 2870W

Output (IEC60705)

Microwave 1000W

Grill 1500W

Convection 1250W

Microwave frequency

2450Mhz

Timer

99 min 99 second

Oven cavity size

32L

Outside dimensions

530mm(W) x 508mm(D) X 344MM (H)

Inside dimensions

350mm(W) X 360mm(D) x 250mm(H)

Weight

21Kg

© 2007 Matsushita Electric Industrial Co., Ltd. All rights reserved.
Unauthorized copying and distribution is a violation of law.

Summary of Contents for NN-CT878SBPQ

Page 1: ...er source 240V AC Single Phase 50Hz Power requirements Microwave 1220W Grill 1560W Convection 1350W Combi 2870W Output IEC60705 Microwave 1000W Grill 1500W Convection 1250W Microwave frequency 2450Mhz Timer 99 min 99 second Oven cavity size 32L Outside dimensions 530mm W x 508mm D X 344MM H Inside dimensions 350mm W X 360mm D x 250mm H Weight 21Kg 2007 Matsushita Electric Industrial Co Ltd All rig...

Page 2: ...e 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 Description of Operating instruction 35 15 Exploded View 36 16 Parts List 37 17 Door Assy 39 18 Escutcheon Base 40 19 Packing and Accessories 41 20 Trim Kit 43 21 Digital Programmer Circuit 44 22 ...

Page 3: ...er 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 a...

Page 4: ...NN CT878SBPQ 4 4 Control Panel ...

Page 5: ...NN CT878SBPQ 5 5 Operation And Digital Programmer Circuit Test Procedure ...

Page 6: ...NN CT878SBPQ 6 ...

Page 7: ...NN CT878SBPQ 7 ...

Page 8: ...NN CT878SBPQ 8 6 Schematic Diagram ...

Page 9: ...NN CT878SBPQ 9 7 Wiring Diagram Wiring Harness ...

Page 10: ... 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...

Page 11: ...ng 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 tempera ture is higher than the predetermined temperature the fan motor rotates to cool the electronic compon...

Page 12: ...is completed When the oven temperature drops below the selected tempera ture 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 con trol the grill elements With convection grill and micro power combination The grill elements and convection ele...

Page 13: ...NN CT878SBPQ 13 8 5 1 convection and microwave duty cycles Figure 1 ...

Page 14: ...NN CT878SBPQ 14 8 5 2 grill and microwave duty cycles Figure 2 ...

Page 15: ...NN CT878SBPQ 15 Figure 3 8 5 3 Grill Convection and microwave duty cycles ...

Page 16: ... columns in figure 1 indicate when the humid ity sensor heater is on 2 During the 30 second period there is no microwave activ ity When calculating the T2 time by using the formula below make sure this 30 seconds is subtracted from the T0 time 3 T1 time T0 time 30 seconds 4 T2 time when the steam escapes from the cooking con tainer placed in the oven the humidity sensor detects it and the micropro...

Page 17: ...ger in ordinary use extreme care should be taken during repair As you can see it looks like a TV flyback transformer however the current is extremely large and is therefore dangerous due to this high current and high voltage The aluminium heat sink is also energized with high voltage HOT so do not touch when the AC input terminal is con nected The power devices Collector is directly connected to t...

Page 18: ...scharge Please be sure to touch the chassis ground side first and then short to the output terminals 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 circ...

Page 19: ...ter repair or replacement of parts make sure that the screws of the oven etc are neither loose nor missing Microwaves might leak if screws are not properly tight ened 2 Make sure that all electrical connections are tight before inserting the plug into the wall outlet 3 Check for microwave energy leakage Refer to proce dure for measuring microwave energy leakage CAUTION MICROWAVE RADIATION DO NOT B...

Page 20: ...g the magnetron as shown in figure 2 NOTE After replacing the magnetron tighten the mount ing screws making sure that there is no gap between the waveguide and the magnetron to prevent microwave leak age Caution When replacing the magnetron ensure that the antenna gasket is in place Note The magnetron used for this model is unique for the inverter power supply system Make sure to use the magnetron...

Page 21: ...ort base from the oven 7 Remove the air guide E by un clipping the catch hooks 8 Remove the four screws holding the PCB to the inverter support base Caution when replacing the inverter power supply U 1 Make sure that grounding plate is in place 2 Securely tighten the grounding screw through the side of the chassis Base 3 Securely connect the 3 lead wire connectors 4 Make sure that the heat sink ha...

Page 22: ... with double faced adhesive tape Therefore apply ing hot air such as using a hair dryer is recommended for smoother removal 2 When installing a new escutcheon key board make sure that the surface of the escutcheon base is cleared suffi ciently so that problems such as shorted contacts and uneven surfaces can be avoided 10 4 Low voltage transformer and or power relays Note Be sure to ground your bo...

Page 23: ...ove the door key and spring from the door E After replacement of the defective component parts of the door reassemble it and follow the instructions below for proper installation and adjustment so as to prevent exces sive microwave leakage 1 When mounting the door to the oven be sure to adjust the door parallel to the bottom line of the oven face plate by moving the upper hinge in the direction ne...

Page 24: ...3 Disconnect the cables to the grill heater 4 Remove the grill cover by removing the 5 screws in figure 11 5 Remove the two screws holding the grill heater Figure12 6 Loosen the 2 screws holding the ceramic grill holders turn the holders to release the grill element 7 Remove the heater bracket D by using a flat blade screw driver to lever back the tabs 8 The grill element can now be removed from i...

Page 25: ...NN CT878SBPQ 25 Removing the screws holding the grill heater Figure 11 Removing the grill element Figure 12 ...

Page 26: ...Remove the power cord 5 Remove the wire terminals from the circulation fan motor and the convection heater element 6 Remove the four screws from the oven base Figure 15 7 Carefully place the oven onto its base and remove the backplate 8 Remove the nut holding the circulation fan Figure 16 9 Remove the circulation fan by removing the three screws Figure 16 10 Remove the convection element by removi...

Page 27: ...NN CT878SBPQ 27 Removing the oven back plate Figure 14 Removing the base plate Figure 15 ...

Page 28: ...NN CT878SBPQ 28 Removing the circulation motor Figure 16 ...

Page 29: ... Monitor Cir cuit 1 Unplug the lead wires from the HV inverter primary termi nals 2 Connect the test probes of the ohm meter to these leads 3 Test the continuity of the short switch with the door open and the door closed using the lowest ohm scale 11 3 Magnetron Continuity checks can only indicate an open filament or a shorted magnetron To diagnose an open filament or shorted magnetron 1 Isolate t...

Page 30: ...eplaced NOTE When measuring the resistance of the thermistor dis connect the connector from the digital programmer circuit NOTE If the microwave oven has been operated allow to cool to room temperature before attempting to measure the ther mistor resistance 11 8 Humidity sensor and digital programmer circuit 1 Check the resistance across the sensor heater terminals Normal cold resistance should re...

Page 31: ...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 primary switch and second ary latch switches and check the continuity of the monitor circuit and latch switches by following the component test procedures on page 29 12 2 Measurement of microwave output The output power of the mag...

Page 32: ...NN CT878SBPQ 32 13 Troubleshooting Guide ...

Page 33: ...NN CT878SBPQ 33 Fuses are not blown Fuses are blown Checking the semiconductors using a resistance meter ...

Page 34: ...ternate way to troubleshoot oven with AC Ampere meter used H95 H97 H98 H99 appears in display window a short time after start key is pressed and no microwave oscillation with AC Ampere meter used for troubleshooting Alternative method for toubleshooting the inverter circuit ...

Page 35: ...lay 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 Auto Weight Defrost Category 1st Touch Weight Cooking Time Bread 100g 45s Meat Items 200g 3m 40s Meat Joints 400g 6m 20s Category 1st Touch W...

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