Panasonic NN-A850CB Service Manual Download Page 3

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Inverter Gounding

Figure 2

Inverter PCB layout

2. Feature Chart

Function

NN-A880WB NN-A850WB

NN-A850CB

Microwave

Grill

Convection

Combination

YES

Sensor reheat

Sensor cook

Sensor combination

Weight defrost

Weight combination

Weight reheat

Weight cook

Stage cooking

Delay/Stand

YES

More/Less

YES

Kg-> lb/oz

YES

Clock

12H

Word prompt

English

Step by Step

LED

Summary of Contents for NN-A850CB

Page 1: ... Number MOP00090015C2 Microwave Oven NN A880WB NN A850WB NN A850CB SPECIFICATIONS 1995 Matsushita Electric Industrial Co Ltd All rights reserved Unauthorized copying and distribution is a violation of law 1 ...

Page 2: ... 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 t...

Page 3: ... 6 6 Grill 3 3 Convection 17 17 Combination YES YES Sensor reheat 2 Sensor cook 2 Sensor combination 4 Weight defrost 3 3 Weight combination 8 12 Weight reheat 2 Weight cook 2 Stage cooking 3 3 Delay Stand YES YES More Less YES NO Kg lb oz YES YES Clock 12H 12H Word prompt English English Step by Step LED LED 3 ...

Page 4: ...3 Control Panel 4 Operation And Digital Programmer Circuit Test Procdure 4 ...

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Page 7: ...5 Schematic Diagram 7 ...

Page 8: ...ply 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 ...

Page 9: ...art 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 a...

Page 10: ... Whole Chicken 1000 18m 20s 8 Chicken Portions 300 9m 30s 9 Beef Lamb 500 14m 40s 10 Casserole 800 56m 40s 11 Chilled Crispy Top 300 10m 12 Frozen Crispy Top 300 14m 13 Chilled Pizza 200 7m 40s 14 Frozen Pizza 200 10m 15 Bake Pastry 600 15m 16 FruitCrumble 500 18m 20s 7 4 Convection Cooking 1 The digital programmer circuit operates the power relays RY3 RY5 and RY6 in the sequence as shown in the f...

Page 11: ...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 th...

Page 12: ...ropower ON OFF OUTPUT ON OFF Grill 1 66 0 Medium 600W 66 0 Grill 2 48 18 Low 440W 66 0 Grill 3 36 30 Simmer 440W 45 21 Warm 440W 24 42 Grill Convection And Microwave Combination Duty Cycles Convection Heater Grill Heater Micropower 100 250 C ON OFF OUTPUTON OFF Grill 1 66 0 Medium 600W 66 0 Grill 2 48 18 Low 440W 66 0 Grill 3 36 30 Simmer 440W 45 21 Warm 440W 24 42 Figure 1 12 ...

Page 13: ...Convection and microwave duty cycles Figure 2 Grill and microwave duty cycles 13 ...

Page 14: ...gth of time it will take to cook the food NOTE Auto sensor cooking is successful with the foods and recipes found in the auto sensor cooking guide Because of the vast differences in food composition items not mentioned in the cooking guide should be prepared in the microwave oven using the power select and time features Please consult variable power microwave cook book for procedures Explanation o...

Page 15: ...xample 1 If the t1 time is measured to be 2 minutes and 40 seconds and the auto sensor program is selected is sensor reheat Fish Program 4 T2 T1 x K 2 min and 40 sec X 0 3 48 sec Catergory P1 POWER P2 POWER K FACTOR STANDARD 1 Chilled meal HIGH HIGH 1 6 2 Frozen meal MED HIGH 0 9 Figure 1 Auto sensor cooking 8 Cautions to Be Observed When Troubleshooting Unlike many other appliances the microwave ...

Page 16: ...minium heat sink is also energized with high voltage HOT so do not touch when the AC input terminal is connected The power devices Collector is directly connected to the aluminium heat sink The aluminium heat sink may be HOT due to heat energy therefore extreme care should be taken during servicing Figure 1 HV Inverter warning WARNING FOR INVERTER POWER SUPPLY U GROUNDING Check the high voltage in...

Page 17: ...of the magnetron filament terminals to the chassis ground with an insulated handle screwdriver to discharge Please be sure to touch the chassis ground side first and then short to the output terminals Figure 3 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...

Page 18: ...e 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 8 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 anten...

Page 19: ...ease use caution when unpacking installing or moving the unit as some exposed edges may be sharp to touch and cause injury if not handled with care 9 Parts Replacement Procedure 9 1 Magnetron 1 Discharge the high voltage capacitors on the inverter circuit 2 Remove the five screws shown in figure 1 3 Disconnect the two high voltage leads from the magnetron 4 Remove the four screws holding the magne...

Page 20: ...1 Discharge the high voltage capacitors 2 Unplug the H V Lead wires from the magnetron 3 Remove the connector CN701 and CN702 from the inverter PCB 4 Remove the two screws holding the inverter base to the chassis See figure 3 5 Remove the one screw holding the inverter earth wire to the oven chassis 20 ...

Page 21: ...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 has enough space gap from the oven Take care not to touch any lead wire to the aluminium heat sink because it is hot Figure 3 Removal of the inverter PCB Figure 4 Disconnecting the PCB lock connector 9 3 Digital Programmer Circuit DPC and membrane...

Page 22: ...tch hooks on the escutcheon base 2 Peel away the display window from the inside of the base 3 Remove the membrane assembly by pushing from the inside of the base and then peeling away from the outside surface NOTE 1 The escutcheon key board is attached to the escutcheon base with double faced adhesive tape Therefore applying hot air such as using a hair dryer is recommended for smoother removal 2 ...

Page 23: ...at the terminal pins are inserted completely Carefully re solder all terminal contacts carefully Note Do not use a soldering iron or de soldering tool of more than 30 watts on DPC contacts 9 5 Fan Motor 1 Disconnect the two lead wires from the fan motor terminals 2 Remove the power cord by removing the two wires from the noise filter and the ground connection from the oven chassis 3 Remove the noi...

Page 24: ...of the door reassemble it and follow the instructions below for proper installation and adjustment so as to prevent excessive 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 necessary for proper alignment 2 Adjust so that the door has no play between the inner door surfac...

Page 25: ...ad wires connected to the turntable motor 3 Remove the turntable motor by removing the two screws Note After breaking off the motor cover make sure that cut off portions are properly trimmed off or bent inside so that no sharp edges are exposed Note To secure the motor cover use a 4 x 6 screw Figure 8 Removing the Turntable motor cover Figure 9 25 ...

Page 26: ...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 inside the oven Figure 10 Removing the exhaust ...

Page 27: ...screws Figure 13 3 Remove the temperature sensor by removing the two screws Figure 14 4 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 hte oven onto its base and remove the backplate 8 Remove the nut holding the circulation fan Figure 16 9 Remove the circulati...

Page 28: ...10 Remove the convection element by removing the two screws Figure 16 Figure 13 Removing the rear heater cover Figure 14 28 ...

Page 29: ...Removing the oven back plate Figure 15 Removing the base plate Figure 16 29 ...

Page 30: ...tempt to measure this high voltage 3 Before touching any oven components or wiring always unplug the oven from its power source and discharge the high voltage capacitors 10 1 Primary Latch Switch Secondary Latch Switch and power relay B interlocks 1 Unplug the lead connectors to power relay B and verify the continuity of the power relay B 1 2 terminals 2 Unplug the lead connectors to the primary l...

Page 31: ... terminals 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 Door Open Door Closed Monitor switch 0 infinte 10 3 Magnetron Continuity checks can only indicate an open filament or a shorted magnetron To diagnose an open filament or shorted magnetron 1 Isolate the magnetron from the ci...

Page 32: ... keypad matrix is shown on 10 5 Inverter Power Supply Caution DO NOT try to repair this inverter power supply Replace as a whole H V Inverter Unit Figure 3 Inveter power supply diagram 10 6 Inverter Power Supply Unit Warning Do not attempt to make any measurements in the high voltage circuitry of the inverter or magnetron 32 ...

Page 33: ...ss the sensor heater terminals Normal cold resistance should read approximately 4 5 ohms 2 Check the volatge across the sensor heater terminals It should read approximately 2 5VDC 3 In order to determine if the auto cooking by humidity sensor is working perform the following test 1 Place a water load 150cc in the oven 2 Press the auto reheat panel 3 Press the start pad 4 The humidty sensor detects...

Page 34: ...ten the screws holding the door hook assembly to the oven assembly 3 Reconnect the short switch primary switch and secondary latch switches and check the continuity of the monitor circuit and latch switches by following the component test procedures on page 11 2 Measurement of microwave output The output power of the magnetron can be determined by performing the IEC standard test However due to th...

Page 35: ... 4 The normal temperature rise at the high power position for each model is shown in the table Figure 2 Figure 1 Adjustment of latch switch assembly RATED OUTPUT TEMPERATURE RISE 1000W 8 C 12 Troubleshooting Guide 35 ...

Page 36: ...Fuses are not blown Fuses are not blown 36 ...

Page 37: ...Other problems Inverter circuit troubleshooting 37 ...

Page 38: ...Alternative method for toubleshooting the inverter circuit 13 Digital Programmer Troubleshooting Guide 38 ...

Page 39: ...How to check semiconductors 14 Exploded View 39 ...

Page 40: ...ts Please use these part numbers for part orders Do not use the description of the part Important safety notice 1 Components identified by mark have special characteristics important for safety When replacing any of these components use only the manufacturers specified 40 ...

Page 41: ...P CAM A 1 22 E61425180AP SHUTTER SWITCH 1 23 E22439000BP ADIABATIC MATERIAL A 1 24 E40474V00BP AIR GUIDE E 1 25 E09020000AK CUSHION RUBBER 1 26 E40309000GP AIR GUIDE D 1 27 E030E4V20BP HV LEAD WIRE 1 28 E606Y4V20GP INVERTER 1 29 E66014V00BP INVERTER EARTH BRACKET 1 30 E65854V00BP INVERTER SUPPORT BRACKET 1 31 E01214V20BP ADAPTOR PLATE 1 32 E610T6700BP OVEN LAMP 1 33 E31374830AP HOOK SPACER B 1 34 ...

Page 42: ...IDITY SENSOR 1 NN A880WB 62 E40249000GP EXHAUST GUIDE A 1 63 E202N9000BP UPPER HEATER COVER 1 64 E64179000BP HEATER BRACKET A 1 65 E67579000BP HEATER BRKT D 1 66 E630H9000BP CONVECTION HEATER 1 67 E64189000BP HEATER BRACKET B 1 68 E607F9000BP HEATER COVER 1 69 E22429000BP ADIABATIC MATERIAL 1 70 E20339000BP HEATER COVER B 1 71 E41079000GP EXHAUST GUIDE B 1 72 E09230000AQ CUSHION RUBBER 1 73 E490S8...

Page 43: ... DOOR A ASSYM 1 NN A850CB D2 E30214000AP DOOR KEY SPRING 1 D3 E30188000BP DOOR KEY A 1 D4 E302K9000BP DOOR E 1 D5 E30859000BP DOOR C 1 D6 E30067300AP HINGE 1 When ordering any door component also order door C this part may become damaged during dissassembly of the door 17 Escutcheon Base Assembly 43 ...

Page 44: ...20BP P C B AU 1 NN A880WB E5 E603L4V30BP P C B AU 1 NN A850WB NN A850CB E6 E6629 1600 RIBBON CABLE 1 E7 E82564V20BP DOOR OPENING LEVER 1 E8 E603Y4V20BP P C B DU 1 NN A880WB E8 E603Y4V30BP P C B DU 1 NN A850WB NN A850CB E9 E83264V20BP DISPLAY SHEET 1 E10 E00074V30BP NAME PLATE 1 E11 E83374V20HBP ESCUTCHEON SHEET 1 NN A880WB E11 E83374V30HBP ESCUTCHEON SHEET 1 NN A850WB E11 E83374V30BP ESCUTCHEON SH...

Page 45: ...45 ...

Page 46: ...1 P13 E01136700BP TRAY STYROL 1 P14 E01024V20HBP CARTON BOX 1 NN A880WB P14 E01024V30HBP CARTON BOX 1 NN A850WB P14 E01024V30BP CARTON BOX 1 NN A850CB P15 E01059000BP LOWER FILLER 1 P16 E01069000BP COVER POLYTHENE 1 P17 E01079000BP DOOR SHEET 1 P18 E01926430GP PROTECTOR SHEET 1 NN A850CB P19 E01049000BP UPPER FILLER 1 19 REF No 8 E607X4V20BP Noise Filter U Ref No Part No Description Qty Remarks R1...

Page 47: ...F No 1 Set Side strip REF No 2 Set Microwave Oven Model Number NN TKA80W E1603A510HBP 1 E1601A540HBP 1 NN A880WB NN A850WB NN TKA80C E1603A510BP 1 E1601A540BP 1 NN A850CB Instalation Guide A0003A810BP 21 Digital Programmer Circuit Schematic 47 ...

Page 48: ...48 ...

Page 49: ...22 Key Board Matrix 49 ...

Page 50: ...23 Digital Programmer Circuit Parts 23 1 E603L4V20BP E603L4V30BP DPCAU 50 ...

Page 51: ... Resistor 1 1 1 R502 AERJ3GSYJ272 2 7K Chip Resistor 1 0 R137 R141 AERJ3GSYJ331 330 Chip Resistor 5 0 R514 AERJ3GSYJ364 360K Chip Resistor 1 0 R331 AERJ3GSYJ471 470 Chip Resistor 1 1 R224 R225 AERJ3GSYJ472 4 7K Chip Resistor 2 2 R511 AERJ3GSYJ473 47K Chip Resistor 1 0 R516 AERJ3GSYJ514 510K Chip Resistor 1 0 R508 AERJ3GSYJ562 5 6K Chip Resistor 1 0 R40 R48 AERJ3GSYJ683 68K Chip Resistor 9 9 R515 A...

Page 52: ...SCKTC3199GR NPN Transistor 3 3 C10 EEUFC1C471B 470uF 16 V Elect Capa 1 1 C12 EEUFC1C471B 470uF 16 V Elect Capa 1 0 C12 ECEA1CKA100B 10uF 16V Electrolytic Capacitor 0 1 R27 ERX12SJ1R0E 1R 1 2 Watt Resistor 1 1 L12 ELEKN221KA 220uH 1 0 CN3 AEEMXF00703B 3 Pin Connector Inverter 1 1 CN8 AEEMMF00703W 3 Pin Connector Figaro Sensor 1 0 CN7 AEEMMF00703R 3 Pin Connector OvenThermistor 1 1 CN4 AEEMXF01D05W ...

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