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Panasonic NN-L750WB Service Manual
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Panasonic NN-L750WB Service Manual

Panasonic NN-L750WB Service Manual

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Order Number MOP00100019C2
Microwave Oven
NN-L750WB / NN-L760WB
27L
WHITE
EPG Continental Europe
UPG France
SPECIFICATIONS
1

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Summary of Contents for Panasonic NN-L750WB

  • Page 1 Order Number MOP00100019C2 Microwave Oven NN-L750WB / NN-L760WB WHITE EPG Continental Europe UPG France SPECIFICATIONS...
  • Page 3 2000 Matsushita Electric Industrial Co., Ltd. All rights reserved. Unauthorized copying and distribution is a violation of law.

  • Page 4: 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 5: Feature Chart

    Inverter Power Supply Diagram Figure 2 Inverter Layout 2. Feature Chart NN-750WB NN-750WB NN-760WB NN-760WB Function Microwave Grill Convection Combination Weight Defrost Weight Combination Weight Reheat Weight Cook Weight Crisp Stage Cooking 1 Stage 1 Stage 1 Stage 1 Stage Delay / Stand Clock 24 Hour...

  • Page 6: Operation And Digital Programmer Circuit Test Procedure

    4. Operation And Digital Programmer Circuit Test Procedure 4.1. Word Prompting 4.2. Setting the Clock...
  • Page 8 4.3. Child Safety Lock 4.4. Microwave Cooking and Defrost...
  • Page 11 4.5. Grill Operation 4.6. Convection with Preheating...

  • Page 13: Convection Without Preheating

    4.7. Convection without Preheating...
  • Page 15 4.8. Combination Cooking (Grill and Microwave)
  • Page 17 4.9. Combination Cooking (Convection and Microwave)
  • Page 19 4.10. Combination Cooking (Convection and Grill)
  • Page 21 4.11. Combination Cooking (Convection, Grill and Microwave)

  • Page 23: Auto Defrost

    4.12. Auto Defrost...

  • Page 25: Auto Weight Programs

    4.13. Auto Weight Programs...
  • Page 27 4.14. Auto Weight Program Panacrunch (NN-L760WB)
  • Page 29 5. Schematic Diagram 6. Wiring Diagram...

  • Page 30: Variable Power Cooking Control

    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 31: Convection Cooking

    1st Touch Cooking Weight Time Small Pieces 300g 5m 51s Big pieces 600g 11m 30s Bread and Rolls 100g 3m 54s Auto weight Cook NN-L750WB/NN-L760WB Category 1st Touch Cooking Weight Time 1.Fresh Fish 300g 2.Fresh Vegetables 500g 12m 35s 3.Chicken 1000g 16m 40s 4.Beef...

  • Page 32: Combination Cooking

    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.
  • Page 33 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 Convection Heater Micropower 100 - 250 C...
  • Page 34 Convection And Microwave Duty Cycles Figure 2 Grill and Microwave Duty Cycles Figure 3...

  • Page 35: 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 36 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 37 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 38 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 39: 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 40 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 41 Disconnecting the PCB lock connector 9.3. Digital Programmer Circuit (DPC) 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 42 iron, carefully remove all solder from the terminal pins of the low voltage transformer and/or power relays. 2. With all of the terminal pins cleaned and separated from the DPC contacts, remove the defective transformer/power relays and install the new components making sure that the terminal pins are inserted completely.
  • Page 43 9.6. Door disassembly 1. Remove door C from door E by carefully pulling outward starting from the upper right hand corner using a flat blade screwdriver. 2. Remove four screws holding the door E to the door A assembly 3. Remove the door screen B by carefully un-clipping the screen from the door A catch hooks.

  • Page 44: Turntable Motor

    Adjusting the door hinge 9.7. Turntable Motor 1. Remove the motor cover by breaking off at the 8 spots indicated 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.

  • Page 45: Quartz Heater

    Two screws to remove the turntable motor 9.8. Quartz Heater 1. Disconnect the lead wires from the heater terminals 2. Remove one screw holding the heater supports 3. Remove the heater Figure 11 One screw to remove the grill bracket Figure 12...
  • Page 46 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. 3. After removing the rear heater cover, remove the three screws B holding the inner heater cover.

  • Page 47: Component Test Procedure

    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 48 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. 10.1. Primary Latch Switch, Secondary Latch Switch and power relay B interlocks.
  • Page 49 2. A continuity check across the magnetron filament terminals should indicate one ohm or less 3. A continuity check between each filament terminal and the magnetron case should read open. 10.4. Push Button Keyboard Check the continuity between the switch terminals, by tapping an appropriate pad on the keyboard.

  • Page 50: Measurements And Adjustments

    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 to determine if the inverter power supply is still functioning. 10.7. Temperature Sensor A temperature sensor is mounted on the oven cavity on the right hand side. The resistance reading across the thermistor should read 300K ohm within a temperature range of 10 to 30 degrees centigrade.

  • Page 51: Measurement Of Microwave Output

    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 the complexity of the IEC test procedures, it is recommended to test the magnetron using the simple method outlined below.

  • Page 52: Troubleshooting Guide

    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. When returning the inverter unit pack in the original inverter box.
  • Page 53 plastic connector from a terminal, you must hold the plastic connector and not the lead wire, otherwise the lead wire may become open circuit. 7. Do not touch any parts of the circuitry on the digital programmer cicruit, since static electric discharge may damage this control panel.
  • Page 54 Troubleshooting (Fuse is blown) Figure 3 Troubleshooting (Other problems) Figure 4...
  • Page 57 Troubleshooting Inverter by Input out voltage Figure 5...
  • Page 60 Troubleshooting Inverter by Microwave Oven Input Current 13. Digital Programmer Circuit Troubleshooting Guide Figure 2...

  • Page 61: Main Parts List

    How to test the semiconductors 14. Main Parts List 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.
  • Page 62 Remarks Ref. No. Part No. Part Name & Description E64174V00BP Heater Bracket A XTWANE 4 + 8BN Screw E00069000EP Warning Label E10594V00BP Back Plate Cover B XTWANE 4+8BN Screws E22594V00BP Adiabatic Material D E030A4V00BP Lead Wire Harness E67597550GP 10A Fuse AEE6230P10GN 16A Fuse E607X4N30BP...
  • Page 63 Remarks Ref. No. Part No. Part Name & Description AEE2177-F80 Pulley Shaft Washer E21315870GP Pulley Shaft XST4 + W5V Screw E20554L00GS Cover A E30064N30BP Upper Hinge XTWA 4+12CF Screws E200A4V00BP Oven cavity E64604N30BP Heater Support Bracket E64604N30BP Heater Support Bracket E03594N30GP Lead Wire Grill Link XTWANE4 + 8BN Screw...

  • Page 67: Escutcheon Base

    Qty Remarks Ref. No. Part No. Part Name & Description E30014V00HBP Door A E30214000AP Door Key Spring E30184L00GS Door Key E31464V00GP 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 69 E01134N80EP Tray styrol NN-L760WBEPG NN-L760WBUPG E01084V00GP Tray packing NN-L750WBEPG NN-L750WBUPG E01084V40UP Tray packing NN-L760WBEPG NN-L760WBUPG E01024V10HEP Carton box NN-L750WB EPG E01024V10HUP Carton box NN-L750WB UPG E01024V40HEP Carton box NN-L760WB EPG E01024V40HUP Carton box NN-L760WB UPG E01054V00BP Lower filler E01066750BP Vinyl Cover...

  • Page 70: Digital Programmer Circuit

    19.1. Noise filter component parts Ref. No. Part No. Part Name & Description Remarks ERG1SJ753P Resistor C1 & C2 QETJ5225KRP2CE Capacitor C3 & C4 ECKMNA472ME Capacitor 4700pF 250V AC SC-08-E203A Inductor 2.4mH E62316010BP Fuse Holder 19.2. Digital programmer Circuit DPC Schematic 2 19.3.
  • Page 71 Ref. No. Part 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-SW47 EVQ11L05R Push Switch C90 C40 C41 C42 AECU1C101J50 100pF Chip Capacitor C20 C80 C81 C110 C441 AECU1F103Z50 10nFChip Capacitor C22 C220 C221 C222 C224...
  • Page 72 Remarks Part No. Description Ref. No. ZD10 AESZMTZ5R6B Zener Diode D221-D224 AESS133T-77 Silicon Diode AESS133T-77 Silicon Diode D220 AESS1N4003E Silicon Diode AESSAK03 Shottky Diode C330 ECBT1H681KB5 Capacitor 680PF C440 ECBT1E103ZF5 Capacitor 10nF R25,R26 ERDS1FJ563T Resistor 56K 1/2 Watt R220,R232 ERDS2TJ103T Resistor R11 R226-R228 ERDS2TJ104T...

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