Table Of Contents COVER 1 Inverter Warning 2 Feature Chart 3 Control Panels 4 Operation And Digital Programmer Circuit Test Procedure 4.1 Word Prompting 4.2 Setting the Clock 4.3 Child Safety Lock 4.4 Microwave Cooking and Defrost 4.5 Grill Operation 4.6 Convection with Preheating 4.7 Convection without Preheating 4.8 Combination Cooking (Grill and Microwave)
Page 2
5 Schematic Diagram 6 Wiring Diagram 7 Description of Operating instruction 7.1 Variable power cooking control 7.2 Grill Cooking 7.3 Auto weight defrost, Auto weight Cook 7.4 Convection Cooking 7.5 Combination Cooking 8 Cautions to Be Observed When Troubleshooting 8.1 Check the grounding 8.2 Inverter Warnings 8.3 When parts must be replaced, remove the power plug from the outlet.
Page 3
9.5 Fan Motor 9.6 Door disassembly 9.7 Turntable Motor 9.8 Quartz Heater 9.9 Convection Element And Circulation Fan Motor 9.10 Temperature Sensor 10 Component Test Procedure 10.1 Primary Latch Switch, Secondary Latch Switch and power relay B interlocks. 10.2 Short Switch and Monitor Circuit 10.3 Magnetron 10.4 Push Button Keyboard 10.5 Inverter Power Supply...
Page 4
15 Exploded View 16 Door Assembly 17 Escutcheon Base 18 Packing And Accessories 19 Trim Kit Accessories 20 Noise filter component parts 21 Digital programmer Circuit 22 Key Board Matrix 23 Digital programmer circuit parts list 23.1 J603L4V10EP/10UP/40EP/40UP DPC AU 23.2 J603Y4V00BP DPC DU...
Page 5
Service Manual TOP NEXT Order Number MOP00100019C2 Microwave Oven NN-L750WB/NN-L760WB WHITE EPG Continental Europe UPG France...
1 Inverter Warning TOP PREVIOUS NEXT 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.
4 Operation And Digital Programmer Circuit Test Procedure TOP PREVIOUS NEXT 4.1 Word Prompting 4.2 Setting the Clock 4.3 Child Safety Lock 4.4 Microwave Cooking and Defrost 4.5 Grill Operation 4.6 Convection with Preheating 4.7 Convection without Preheating 4.8 Combination Cooking (Grill and Microwave) 4.9 Combination Cooking (Convection and Microwave) 4.10 Combination Cooking (Convection and Grill) 4.11 Combination Cooking (Convection, Grill and Microwave)
7 Description of Operating instruction TOP PREVIOUS NEXT 7.1 Variable power cooking control 7.2 Grill Cooking 7.3 Auto weight defrost, Auto weight Cook 7.4 Convection Cooking 7.5 Combination Cooking •@ TOP PREVIOUS NEXT...
7.1 Variable power cooking control TOP PREVIOUS NEXT 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 signallevel form 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 onHIGH power, the fan motor rotates for 1 minute after cooking to cool...
7.2 Grill Cooking TOP PREVIOUS NEXT 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 Duty ON/OFF ON Time OFF Time Grill 1 33”...
7.4 Convection Cooking TOP PREVIOUS NEXT 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.
7.5 Combination Cooking TOP PREVIOUS NEXT 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 35
Grill Heater Micropower ON OFF OUTPUT ON OFF Grill 1 600W 600W Grill 2 440W 440W Grill 3 250W 440W 100W 440W Grill Convection And Microwave Combination Duty Cycles Convection Heater Grill Heater Micropower 100 - 250 C ON OFF OUTPUT ON OFF Grill 1 600W...
8 Cautions to Be Observed When Troubleshooting TOP PREVIOUS NEXT 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.
8.1 Check the grounding TOP PREVIOUS NEXT Do not operate on a two wire extension cord. The microwave oven is designed to be used when grounded. It is imperative, therefore, to ensure the appliance is properly grounded before beginning repair work. •@ TOP PREVIOUS NEXT...
8.2 Inverter Warnings TOP PREVIOUS NEXT DANGER, HIGH VOLTAGE AND HIGH TEMPERATURE (HOT/LINE) OF THE INVERTER POWER SUPPLY (U) This high voltage inverter power supply handles very high voltage and very high current for the magnetron tube. Though it is free from danger in ordinary use, extreme care should be taken during repair.
Page 39
For about 30 seconds after the oven is turned off, an electric charge remains in the high voltage capacitors in the inverter power supply circuit board. When replacing or checking parts, remove the power plug from the outlet and short the inverter output terminal of the magnetron filament terminals to the chassis ground with an insulated handle screwdriver to discharge.
8.4 When the 10A fuse is blown due to the operation of the short switch: TOP PREVIOUS NEXT WARNING when the 10A 250V fuse is blown due to the operation of the short switch, the primary latch switch and short switch must be replaced. It is also important to change the power relay 1 (RY1) when the continuity test shows shorted contacts.
8.5 Avoid inserting nails, wire etc. through any holes in the unit during operation. TOP PREVIOUS NEXT 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. •@ TOP PREVIOUS NEXT...
8.6 Confirm after repair TOP PREVIOUS NEXT 1. After 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 tightened. 2. Make sure that all electrical connections are tight before inserting the plug into the wall outlet. 3.
8.7 Sharp Edges TOP PREVIOUS NEXT Caution Please 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. •@ TOP PREVIOUS NEXT...
9 Parts Replacement Procedure TOP PREVIOUS NEXT 9.1 Magnetron 9.2 Inverter power supply (U) 9.3 Digital Programmer Circuit (DPC) 9.4 Low voltage transformer and/or power relays (RY1) 9.5 Fan Motor 9.6 Door disassembly 9.7 Turntable Motor 9.8 Quartz Heater 9.9 Convection Element And Circulation Fan Motor 9.10 Temperature Sensor •@ TOP PREVIOUS NEXT...
9.1 Magnetron TOP PREVIOUS NEXT 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. 5.
9.2 Inverter power supply (U) TOP PREVIOUS NEXT 1. Discharge the high voltage capacitors 2. Remove two screws holding the tie bar. 3. Unplug the H.V. Lead wires from the magnetron 4. Remove the one screw holding the earth wire to the magnetron 5.
Page 48
Disconnecting the PCB lock connector •@ TOP PREVIOUS NEXT...
9.3 Digital Programmer Circuit (DPC) TOP PREVIOUS NEXT 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.
9.4 Low voltage transformer and/or power relays (RY1) TOP PREVIOUS NEXT Note Be sure to ground your body to discharge any static before handling the DPC. 1. Using a solder wick or a de soldering tool and a 30W soldering iron, carefully remove all solder from the terminal pins of the low voltage transformer and/or power relays.
9.5 Fan Motor TOP PREVIOUS NEXT 1. Remove two screws and remove the tie bar 2. Disconnect the two lead wires from the fan motor terminals 3. Disconnect all lead wires from the noise filter 4. Remove the noise filter 5.
9.6 Door disassembly TOP PREVIOUS NEXT 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.
9.7 Turntable Motor TOP PREVIOUS NEXT 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.
9.8 Quartz Heater TOP PREVIOUS NEXT 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 Removing the grill element •@ TOP PREVIOUS NEXT...
9.9 Convection Element And Circulation Fan Motor TOP PREVIOUS NEXT 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.
9.10 Temperature Sensor TOP PREVIOUS NEXT 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 •@ TOP PREVIOUS NEXT...
10 Component Test Procedure TOP PREVIOUS NEXT 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.
10.1 Primary Latch Switch, Secondary Latch Switch and power relay B interlocks. TOP PREVIOUS NEXT 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 latch switch and secondary latch switch. 3.
10.2 Short Switch and Monitor Circuit TOP PREVIOUS NEXT 1. Unplug the lead wires from the HV inverter primary 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.
10.3 Magnetron TOP PREVIOUS NEXT 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.
10.4 Push Button Keyboard TOP PREVIOUS NEXT Check the continuity between the switch terminals, by tapping an appropriate pad on the keyboard. The keypad matrix is shown on Key Board Matrix •@ TOP PREVIOUS NEXT...
10.5 Inverter Power Supply TOP PREVIOUS NEXT Caution DO NOT try to repair this inverter power supply). Replace as a whole H.V. Inverter Unit. Inverter Power Supply Diagram Figure 3 •@ TOP PREVIOUS NEXT...
10.6 Inverter Power Supply Unit TOP PREVIOUS NEXT 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 to determine if the inverter power supply is still functioning.
10.7 Temperature Sensor TOP PREVIOUS NEXT 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. This would be the temperature range within akitchen environment. If the resistance measured is outside this range the thermistor is defective and should be replaced.
11 Measurements and Adjustments TOP PREVIOUS NEXT Warning For continued protection against radiation hazard, replace only with identical parts. When the 10 amp fuse is blown due to the operation of the short switch, you must replace the primary latch switch and short switch. Then follow the installation procedures below. Interlock switch replacement - In replacing faulty switches, be sure mounting tabs are not bent, broken or otherwise deficient in their ability to hold the switches.
11.1 Installation of primary latch switch, secondary latch switch and short switch. TOP PREVIOUS NEXT 1. When mounting the primary latch switch, secondary latch switch and short switch to the door hook assembly. Follow the instructions in figure 1. NOTE: No specific adjustment during the insulation of each switch into the door hook is necessary.
11.2 Measurement of microwave output TOP PREVIOUS NEXT 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.
12 Troubleshooting guide TOP PREVIOUS NEXT 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. 2. Do not adjust the preset volume on the H.V. Inverter. It is very dangerous to repair or adjust without sufficient test equiptment, this circuit handles very high volatge and current 3.
14 Main Parts List TOP PREVIOUS NEXT 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 73
XNG4EVSL 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 Noise Filter E400A4760JP Fan Motor E41444N30BP Upper Orifice E42094N30BP...
15 Exploded View TOP PREVIOUS NEXT •@ TOP PREVIOUS NEXT...
Page 77
16 Door Assembly TOP PREVIOUS NEXT Ref. No. Part No. Part Name & Description Qty Remarks 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.
17 Escutcheon Base TOP PREVIOUS NEXT Ref. No. Part No. Part Name & Description Remarks E80724L10HBP DOOR OPENING BUTTON E80378AOAG DOOR BUTTON SPRING E80344V40HUP ESCUTCHEON BASE NN-L760WBEPG NN-L760WBUPG E80344V10HUP ESCUTCHEON BASE NN-L750WBEPG NN-L750WBUPG E83874L60HUP START/STOP BUTTON E82564L10BP DOOR OPENING LEVER E603Y4V00BP DPC DU E83094L60UP...
20 Noise filter component parts TOP PREVIOUS NEXT Ref. No. Part No. Part Name & Description Remarks ERG1SJ753P Resistor 75KΩ W C1 & C2 QETJ5225KRP2CE Capacitor 2.2μF C3 & C4 ECKMNA472ME Capacitor 4700pF 250V AC SC-08-E203A Inductor 2.4mH E62316010BP Fuse Holder •@ TOP PREVIOUS NEXT...