John Lewis NN-GT578SBJQ OEM 27L JLFSMWG002, Service Manual

Page 1: ...pt to service or repair the product or products dealt with this service information by anyone else could result in serious injury or death There are special components used in this equipment which are important for safety These parts are marked by in the schematic diagrams circuit board diagrams exploded views and replacement parts lists It is essential that these critical parts are replaced with ...

Page 2: ...ide 17 13 Parts List 23 14 Exploded View 25 15 Door Assy 26 16 Escutcheon Base 27 17 Packing and Accessories 28 18 Digital Programmer Circuit 29 Power source 240V AC Single Phase 50Hz Power requirements Microwave 1260W Grill 1360W Convection 1470W Convection Grill 2770W Micro Grill Combi 2430W Micro Convection Combi 2550W Micro Grill Convection Combi 2550W Output IEC60705 Microwave 1000W Grill 130...

Page 3: ...ction 17 Combi Yes Sensor Reheat Sensor Cook Sensor Combi Weight Defrost 3 Weight Combi 8 Weight Reheat 4 Weight Cook 2 Memory Cook Weight Crisp Stage Cooking 3 stage Delay Stand Yes More Less No Kg lb oz Yes Clock 12h Word Prompt English Step by Step No ...

Page 4: ...nacrunch Program Pads 14 Start Pad Press to start operating the oven If during cooking the door is opened or Stop Cancel Pad is pressed once Start Pad has to be pressed again to continue cooking 15 Stop Cancel Pad Before cooking one press clears your instructions During cooking one press temporarily stops the cooking program Another press cancels all your instructions and the time of day will appe...

Page 5: ...pair the inverter PCB this can be very dangerous Replace the high volt age inverter circuit as a complete unit Do not adjust or tamper with the pre set volume on the inverter board It is very dangerous to adjust this pre set without proper test equipment Do not operate the microwave oven when the inverter grounding plate and fixing screw is loose It is very dangerous to operate the inverter circui...

Page 6: ...6 5 Schematic Diagram ...

Page 7: ...HE COLOUR O THE CONNECTOR HOUSIN MA NETRON HI H OL TA E IN ER TER CAUTION HEAT SINK HOT LI E ER Y HI H OL TA E AND TEMPERATURE BR BR BR OR 1 C2 PRIMARY LATCH SWITCH TOP WH WH WH SECONDARY LATCH SWITCH OUTSIDE BOTTOM BR N YE YE SHORT SWITCH INSIDE BOTTOM YE BL POWER RELAY RY1 N 2 1 BL SYMBOL COLOUR BL BLUE BK BLACK BR BROWN WH WHITE YE YELLOW N NATURAL R RED R ...

Page 8: ...en 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 auto cooking if the oven temperature is over the predetermined temperature the fan motor rotates to cool the oven and its compo nents Auto weight defrost Auto Weight Cook Category 1st Touch weight Cooking time Defrost Small Pieces Meat 150g 2 ...

Page 9: ...ltage never touch this heat sink when the micro wave oven is plugged into the mains outlet The collec tor of the power device IGBT is directly connected to the aluminium heat sink The aluminium heat sink becomes very hot when the inverter circuit operates Never touch this heat sink during operation and allow time for it to cool down before servicing the microwave oven figure 3HV Inverter warning W...

Page 10: ...r to adjustments and meas urements for the location of these switches 2 When replacing the fuse confirm that it has the appropriate rating for these models 3 When replacing faulty switches be sure the mount ing tabs are not bent broken or deficient in their ability to hold the switches 8 5 Oven cavity aperatures Never insert a wire or any other metal object through the lamp holes or other aperatur...

Page 11: ...rge the high voltage capacitors 2 Remove 2 screws holding the tie bar 3 Unplug the H V Lead wires from the magnetron 4 Remove the 1 screw holding the earth wire to the magnetron 5 Remove the connector CN701 and CN702 from the inverter PCB figure 8 6 Remove the 2 screws holding the inverter support base to the oven chassis 7 Carefully remove the inverter circuit board and sup port base from the ove...

Page 12: ...ote Ground your body to discharge static charges before handling the DPC 1 Carefully remove all solder from the terminal pins of the low voltage transformer power relays using a 30W soldering iron and a solder sucker 2 With all of the terminal pins cleaned and separated from the DPC contacts remove the defective trans former power relays and install the new compo nents making sure that the termina...

Page 13: ... between the door and microwave oven 3 Perform the microwave leakage test figure 11Disassembly of the door figure 12Adjusting the door hinge 9 7 Turntable Motor 1 Remove the motor cover by breaking it off at the 8 spots indicated by the arrows 2 Disconnect the two lead wires connected to the turntable motor 3 Remove the 2 screws holding the turntable motor Note After breaking off the motor cover m...

Page 14: ...r to these leads 3 Test the continuity of the short switch with the door open and the door closed using a ohm meter set to the lowest resistance scale 10 3 Magnetron Continuity checks can only indicate an open filament or a shorted magnetron To diagnose an open filament or shorted magnetron 1 Dissconnect the high voltage lead wires from the magnetron input terminals 2 Check the continuity across t...

Page 15: ...n on elemtext to determine if the inverter power supply is still functioning HEAT SINK RECTIFIER BRIDGE CHOKE COIL SAND BAR RESISTOR CURRENT TRANSFORMER HIGH VOLTAGE TRANSFORMER PRESET VOLUME 4 DO NOT ADJUST FILM CAPACITORS HIGH VOLTAGE DIODES HIGH VOLTAGE CAPACITORS CN 703 CN 702 CN 701 CONTROL BOARD WITH CUSTOM IC PHOTOCOUPLER DANGER HIGH VOLTAGE AND HIGH TEMPERATURE HOT LIVE HEAT SINK HIGH VOLT...

Page 16: ...ted Completely tighten the screws holding the door hook assembly to the oven assembly 4 Reconnect the short switch primary switch and sec ondary latch switches and check the continuity of the monitor circuit and latch switches by following the component test procedures on elemtext 11 2 Measurement of microwave output The output power of the magnetron can be determined by performing the IEC standar...

Page 17: ...y of these components when both legs are soldered into the board may result in a false reading or damage to your meter 6 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 7 Do not touch components on the digital programmer circuit this circuit is sensitive to static electricity 8 When wor...

Page 18: ...t including the mag netron filament circuit NOTE A large contact resistance lowers the magnetron filament volt age reducing the magnetron output or causing intermittent operation 3 Defective high voltage component Inverter circuit or Magnetron 4 Open or loose wiring of power relay RY1 5 Defective primary latch switch 6 Defective power relay RY1 or DPC AU or DPC DU Adjust door and latch switches Ch...

Page 19: ...ere is no microwave oscil lation Symptom Cause Correction 1 Microwave output is low Oven takes a long time to cook food 1 Decrease in power source volt age 2 Open or loose wiring of magne tron filament circuit causing inter mittent oscillation 3 Ageing of magnetron Consult electrician Refer to output test procedures Change magnetron 2 Loud Buzzing noise can be heard 1 Loose fan or fan motor 3 Turn...

Page 20: ...ot oscillate H97 H98 appears in the display window Check magnetron filament continuity Check Inverter input AC voltages at CN702 Check Inverter control signal at CN701 Pin 1 and 2 Magnetron DPC board Power relay Loose relay wiring Latch switch DPC board H V Inverter NOTE DANGER HIGH VOLTAGE Open 0V 0V Unplug CN702 and test for 3 VAC acorss the lead wire connector AC 240V Approx AC 3V Unplug CN702 ...

Page 21: ...V line Abnormal 0V IC10 Normal 12V Step 3 3 IC 1 pin 73 Emitter of Q10 Abnormal ZB10 Q10 Ribbon cable Normal 5V Step 4 4 IC 1 pin 27 pin 15 of IC220 Abnormal IC 220 Normal IC1 CX1 NOTE The procedure for repairing the fuse pattern on the DPC is as follows 1 Fuse pattern PF2 open circuit a Remove the jumper wire PF2 b Move the jumper wire PF3 into the postion of PF2 and solder inplace Replace the DP...

Page 22: ...rom the following test 1 Unplug CN702 connec tor and measure the voltage between the terminlas Abnormal 1 Latch switch 2 DPC Power relay Normal Step 2 2 Unplug CN703 connec tor and measure the voltage at Pin 1 Abnormal DPC Normal 1 Magnetron 2 Inverter circuit Diode Transistor Digital transistor A C C C C B B E E E E B B A K K Forward Forward Forward Forward Reverse Reverse Reverse Reverse A K B E...

Page 23: ...ver A 1 20 E630H8000BP Convection Heater Unit 1 21 E22394V00BP Circulation Fan 1 22 E41634V00BP Fan Spacer C 1 23 XNG4EVSL Nut 1 24 E64174V00BP Heater Bracket A 1 25 XTWANE 4 8BN Screw 1 26 E00069000EP Warning Label 1 27 E10594V00BP Back Plate Cover B 1 28 XTWANE 4 8BN Screws 2 29 E22594V00BP Adiabatic Material D 1 30 E030A7N20BJ Lead Wire Harness 1 31 E67597550GP 10A Fuse 1 32 ANE6230P10GN 16A Fu...

Page 24: ...able Motor 1 72 E01506R30EP Outer Panel Warning Label 1 73 XTWA 4 12CF Screw 1 74 XTWA 4 12DF Screw 1 75 E30074L00GP Lower Hinge 1 76 AEE2177 F80 Pulley Shaft Washer 1 77 E21315870GP Pulley Shaft 1 78 XST4 W5V Screw 1 79 E20554L00GS Cover A 1 80 E30064N30BP Upper Hinge 1 81 XTWA 4 12CF Screws 2 82 E200A4N30BP Oven cavity 1 83 E64604N70UP Heater Support Bracket 1 84 E64604N30BP Heater Support Brack...