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Panasonic INVERTER NN-A750WB Manual

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Order Number MOP00080014C2
Microwave Oven
NN-A750WB / NN-A720MB / NN-A770SB
27L
WHITE SILVER STAINLESS
United Kingdom
SPECIFICATIONS
Specification
1

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Summary of Contents for Panasonic INVERTER NN-A750WB

  • Page 1 Order Number MOP00080014C2 Microwave Oven NN-A750WB / NN-A720MB / NN-A770SB WHITE SILVER STAINLESS United Kingdom SPECIFICATIONS Specification...
  • Page 2 Power Source 240VAC Single phase, 50Hz Power Requirements Micro 1260W Grill 1360W Conv 1470w Combi 2770W Output (IEC705-88) Micro 1000W Grill 1300W Conv 1400W Microwave 2450MHz Frequency 99 Minutes 99 Seconds Timer Oven Cavity Size Outside Dimensions 510mm(W) x 477mm(D) x 314mm(H) Inside Dimensions 359mm(W) x 352mm(D) x 217mm(H) Weight...

  • Page 3: Inverter Warning

    1. 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.

  • Page 4: Feature Chart

    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 with out a proper ground connection. Figure 1 Inverter Power Supply Diagram Figure 2 Inverter Layout 2.

  • Page 5: Control Panels

    Function Microwave Grill Convection Combination Weight Defrost Weight Combination Weight Reheat Weight Cook Stage Cooking 3 Stage Delay / Stand Kg lb./oz. Clock 12 Hour Word Prompt English 3. Control Panels...

  • Page 6: Operation And Digital Programmer Circuit Test Procedure

    4. Operation And Digital Programmer Circuit Test Procedure 4.1. Setting The Clock 1. Plug the power supply cord into the wall outlet 2. Press the clock pad 3. Enter the time of the day...
  • Page 7 4. Press the clock pad 4.2. Microwave Cooking 1. Place a water load in the oven 2. Press Micro power once to set high power 3. Set time at 5 sec. by pressing 1 sec. pad 5 times 4. Press Micro power pad 3 times to set medium power 5.
  • Page 8 6. Press the start pad 7. When the first stage cooking has elapsed oven automatically switches to second stage 8. When second stage cooking has elapsed oven bleeps 5 times and shuts off 4.3. Auto Weight Defrost 1. Select the desired program 2.
  • Page 9 4. Press Start 4.4. Delay Stand 1. Set power level and time 2. Press Stand 3. Set standing time 4. Press Start 4.5. Delay Start 1. Press delay 2. Set delay time 3. Set power level and time...
  • Page 10 4. Press start pad 4.6. Grill Operation 1. Select grill power press once for grill 1 2. Set cooking time 3. Press start 4.7. Convection Operation 1. Press convection pad to select oven temperature 2. Press start to preheat 3. Press time pads to enter cooking time...
  • Page 11 4. Press start pad 4.8. Turbo Bake Operation 1. Press turbo bake pad to select oven temperature 2. Press grill pad to select grill power 3. Press start to preheat 4. Press time pads to enter cooking time 5. Press start...
  • Page 12 4.9. Combination Cooking (Convection And Microwave) 1. Press combination pad 2. Press convection pad to select oven temperature 3. Select micro power 4. Press start if preheating 5. Set cooking time 6. Press start pad...
  • Page 13 4.10. Combination Cooking (Grill And Microwave) 1. Press combination pad 2. Press grill pad to select oven temperature 3. Select micro power 4. Set cooking time 5. Press start pad 4.11. Combination Cooking (Turbo Bake And Microwave)
  • Page 14 1. Press combination pad 2. Press convection pad to select oven temperature 3. Select micro power 4. Press start if preheating 5. Set cooking time 6. Press start pad...

  • Page 15: Schematic Diagram

    4.12. Auto Weight Cook Programs 1. Select the desired auto weight cook program 2. Press to select grams or pounds and ounces 3. Enter the weight by pressing the up and down pads 4. Press Start 5. Schematic Diagram...

  • Page 17: Wiring Diagram

    6. Wiring Diagram...
  • Page 18 7. Description of Operating instruction 7.1. 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.
  • Page 19 Duty ON/OFF ON Time OFF Time Grill 1 33” 0” Grill 2 24” 9” Grill 3 18” 15” 7.3. 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.
  • Page 20 Category 1st Touch Cooking Weight Time 1.Curry 300g 3m 30s 2.Chinese Style 200g 2m 10s 3.Pasta 250g 2m 55s 4.Casserole 300g 3m 15s 5.Fresh Fish 100g 1m 30s 6.Fresh Vegetables 100g 2m 20s 7.Chilled Crispy Top 300g 8.Frozen Crispy Top 300g 9.Jacket Potatoes 200g...
  • Page 21 Convection Cooking Duty Cycles 7.5. 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 operators the power relays as shown in the figures below.
  • Page 22 Convection Heater Micropower 100 - 250 C OUTPUT ON Medium 600W 440W Simmer 440W Warm 440W Grill And Microwave Combination Duty Cycles Grill Heater Micropower OUTPUT ON Grill 1 Medium 600W Grill 2 440W Grill 3 30 Simmer 440W Warm 440W Grill Convection And Microwave Combination Duty Cycles Convection Grill Heater...
  • Page 23 Convection And Microwave Duty Cycles Figure 2 Grill and Microwave Duty Cycles Figure 3...

  • Page 24: Cautions To Be Observed When Troubleshooting

    Grill, Convection And Microwave Duty Cycles 8. Cautions to Be Observed When Troubleshooting Unlike many other appliances, the microwave oven is a high voltage, high current is device. Though it is free from danger in ordinary use, extreme care should be taken during repair. Caution Servicemen should remove their watches whenever working close to or replacing the magnetron.
  • Page 25 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 inverter power supply circuit grounding. This high voltage inverter power supply circuit board must have a proper chassis ground, the inverter grounding bracket must be connected to the chassis.
  • Page 26 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 the inverter.
  • Page 27 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 antenna and cause microwave leakage.

  • Page 28: Parts Replacement Procedure

    9. Parts Replacement Procedure 9.1. Magnetron 1. Discharge the high voltage capacitors on the inverter circuit. 2. Remove the screw holding the air guide 3. Remove the two screws holding the tie bar 4. Remove the oven lamp and lead wire harness cables form the air guide A.
  • Page 29 4. Remove the one screw holding the earth wire to the magnetron 5. Remove the connector CN701 and CN702 from the inverter PCB 6. Remove the two screws holding the inverter base to the chassis (See figure 2) 7. Carefully remove the inverter PCB and support base from the oven.
  • Page 30 Disconnecting the PCB lock connector 9.3. Digital Programmer Circuit (DPC) and membrane key board. NOTE: Ground any static electric built up on your body before handling the DPC. 1. Disconnect all connectors from the DPC. 2. Remove the two screws holding the escutcheon base and slide the escutcheon base upward slightly.
  • Page 31 3. When replacing the silver escutcheon sheet (NN-A720MB) ensure that the escutcheon sheet is earthed to the back-plate via the earth strip. Figure 4 Removal of DPC AU and DPC DU Figure 5 Grounding of the silver escutcheon 9.4. Low voltage transformer and/or power relays (RY1) Note Be sure to ground your body to discharge any static before handling the DPC.
  • Page 32 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. Remove two screws and remove the tie bar 2. Disconnect the two lead wires from the fan motor terminals 3.
  • Page 33 these hooks during disassembly. 4. Remove the door key and spring form 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 excessive microwave leakage.
  • Page 34 by the arrows. 2. Disconnect the two lead 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.
  • Page 35 One screw to remove the grill bracket Figure 12 Removing the grill element 9.9. Convection Element And Circulation Fan Motor 1. Remove the four screws A holding the rear heater cover. 2. Remove the wire terminals from the thermal cutout, circulation fan motor and the convection elements.

  • Page 36: Component Test Procedure

    8. Remove the three screws F to release the circulation fan motor assembly. Figure 13 Disassembly of the rear convection assembly 9.10. Temperature Sensor 1. Remove lead wire plug from connector CN7 2. Remove 1 screw holding temperature sensor 3. Replace temperature sensor and lead wire as a complete unit. Figure 14 Removing the temperature sensor unit 10.
  • Page 37 Caution 1. High voltage is present at the high voltage terminal of the inverter unit, including the aluminium heat sink. 2. It is not necessary or advisable to attempt 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.
  • Page 38 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 circuit by disconnecting the HV leads 2. A continuity check across the magnetron filament terminals should indicate one ohm or less 3.

  • Page 39: Measurements And Adjustments

    Figure 3 10.6. Inverter Power Supply Unit Warning Do not attempt to make any measurements in the high voltage circuitry of the inverter or magnetron. See troubleshooting of the inverter circuit and magnetron on Figure 4 to determine if the inverter power supply is still functioning.
  • Page 40 ability to hold the switches. - Refer to the schematic and wiring diagram to ensure proper connection 11.1. Installation of primary latch switch, secondary latch switch and short switch. 1. When mounting the primary latch switch, secondary latch switch and short switch to the door hook assembly. Follow the instructions in figure 1.

  • Page 41: Troubleshooting Guide

    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 Caution 1. Do not try to repair this H.V. Inverter power supply. Replace as a whole unit.
  • Page 42 6. When checking the continuity of the switches on the H.V. inverter, disconnect one lead wire from these parts and then check the continuity with the AC plug removed. To do otherwise may result in a false reading or damage to your meter. When disconnecting a plastic connector from a terminal, you must hold the plastic connector and not the lead wire, otherwise the lead wire may become open circuit.
  • Page 43 Troubleshooting (Fuse is blown) Figure 3 Troubleshooting (Other problems) Figure 4 Troubleshooting Inverter by Input out voltage...
  • Page 44 Figure 5 Troubleshooting Inverter by Microwave Oven Input Current 13. Digital Programmer Circuit Troubleshooting Guide...

  • Page 45: Main Parts List

    Figure 2 How to test the semiconductors 14. Main Parts List...
  • Page 46 1. Part numbers are indicated on most mechanical parts. 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 parts.
  • Page 47 Ref. No. Part No. Part Name & Description Remarks E09020000AA Cushion Rubber E20994N30BP Reinforcement Bracket A E40474N30BP Air Guide A E610T6700BP Lamp Assembly E22364V00BP Right Hand Heater Panel XTW4 +12T Screw E31374830AP Hook Spacer B E31384830AP Hook Spacer C E61425180AP Secondary Latch Switch L-3C2-2 E61785180AP...

  • Page 48: Exploded View

    Ref. No. Part No. Part Name & Description Remarks E40244V00BP Exhaust Guide A XTWANE 4+8BN Screw E09230000AL Cushion Rubber XTWANE 4+8BN Screw E605A-1960 Temperature Sensor E900C6520BP Power cord E030E4N30BP H.V Lead Wire E90314V00BP Holder E90314VOOBP Holder E67579000BP Heater bracket D E203B4V00SBP Heater Cover NN-A770SB...

  • Page 51: Door Assembly

    16. Door Assembly...

  • Page 54: Escutcheon Base

    Ref. No. Part No. Part Name & Description Remarks E302A4V00SBP Door A Assembly NN-A770SB E30014V00HBP Door A NN-A750WB E30014V00NBP Door A NN-A720WB E30214000AP Door Key Spring E30184L00GS Door Key E31464V00BP Door Screen B E302K4V00BP Door E E30854V00BP Door Screen C NOTE: When ordering any Door component also order door C as this part may become damaged during disassembly.

  • Page 57: Packing And Accessories

    Ref. No. Part No. Part Name & Description Remarks E800S4V00SBP Escutcheon Assembly ! NN-A770SB E80074L00SGS Spring NN-A770SB E80724L10HBP Door opening button NN-A750WB E80724L10NBP Door opening button NN-A720MB E80724V00SBP Door opening button NN-A770SB E80378A0AG Door button spring NN-A770SB E83374V00HBP Escutcheon sheet NN-A750WB E83374V00NBP Escutcheon sheet...
  • Page 59 Ref. No. Part No. Part Name & Description Remarks E06435870GS Rubber foot E060V8020BP Wire rack low E06435870SP Rubber foot BLACK E060V6520BP Wire rack high E01084V00BP Tray packing E06014N30BP Glass tray E06015020GP Enamel tray E290D4N00BP Roller ring E01695750BP Service center list E00034V00BP Operating instructions and cook book E01134N30BP...

  • Page 60: Digital Programmer Circuit

    Trim Model No. Top and Bottom Strip REF NO. 1 Side Strip REF NO 2. Set Microwave Ovcen Model No. NN-TKA70 E1603A510HBP E1601A510HBP NN-A750WB E1603A510HBP E1601A510HBP NN-TKA70 E1603A510NBP E1601A510NBP NN-A720MB INSTALLATION GUIDE E000QA820BP 20. Noise filter component parts Ref. No. Part No.
  • Page 61 DPC Schematic 1...

  • Page 63: Key Board Matrix

    DPC Schematic 2 22. Key Board Matrix 23. Digital programmer circuit parts list 23.1. E603L4L00BP DPC AU...
  • Page 64 Ref. No. Part Name Description Remarks R180 ERDS2TJ361T Carbon Resistor 360R D40,D41 AESS133T-77 Diode D180-D182 AESQTLGE260T Green LED CX320 EFOMC8004T4 Ceramic Resonator SW40-SW63 EVQ11L05R Push Switch C110 C20 C40 AECU1F103Z50 Chip Capacitor 10nF -C48 C441 C220 C221 AECU1F104Z25 Chip Capacitor 100nF C222 C224 R111-113 R20...
  • Page 65 Remarks Part No. Description Ref. No. AEEMXF00D04W 4 Pin Connector C25(COVER) A6219-1850 Capacitor Cover (small) RY2 RY3 RY6 AEBGG5N1A12 12 V Relay RY1 RY4 RY5 AEGG5G1A12 12 V Relay AEEM19FEBVKN 19 Pin Connector AEEMXD55511W 11 Pin Connector IC25 AEICP25011HL Photocoupler IC AESTS1WBA60B Diode Bridge (600V) ECA2WHG100E...

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