SERVICE MANUAL STAINLESS STEEL EM-SL20NECO MICROWAVE OVEN .

FILE No.SERVICE MANUALSTAINLESS STEELMICROWAVE OVEN WITH 50wC/Kg/KgProduct Code No.EM-SL20NECO1-437-574-25FOREWORDRead this manual carefully, especially precaution on microwave energy, and follow the procedurestrictly. Careless servicing and testing may expose yourself to the microwave energy leakage.PRECAUTIONSPRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOIDPOSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY(a) Do not operate or allow the oven to be operated with the door open.(b) Make the following safety checks on all ovens to be serviced before activating the magnetron orother microwave source, and make repairs if necessary:(1) Interlock operation, (2) proper door closing, (3) seal and sealing surfaces (arcing, wear, andotherdamage), (4) damage to or loosening of hinges and latches, (5) evidence of dropping orabuse.(c) Before turning on microwave power for any service test or inspection within themicrowave generating compartments, check the magnetron, wave-guide or transmission line,and cavity for proper alignment, integrity, and connections.(d) Any defective or misadjusted components in the interlock, monitor, door seal, and microwavegeneration and transmission systems shall be repaired, replaced, or adjusted by proceduresdescribed in this manual before the oven is released to the owner.REFERENCE No. SM-2400005

TABLE OF CONTENTSAdjustment Procedures.1Circuit Diagram. 4Specifications. 2Test Procedures and Troubleshooting. 5-12Power Output Measurement. 2Disassembly Instructions. 13-14Precautions and Repair Service Tips.2Exploded View and Parts list.15-19Oven Control Panel.3Control Circuit Board.20Overall Circuit Diagrams. 21CAUTIONMICROWAVE ENERGYPERSONNEL SHOULD NOT BE EXPOSED TOTHE MICROWAVE ENERGY WHICH MAY RADIATE FROM THE MAGNETRON OR OTHERMICROWAVE GENERATING DEVICE IF IT ISIMPROPERLY USED OR CONNECTED. ALLINPUT AND OUTPUT MICROWAVE CONNECTIONS, WAVE GUIDES, FLANGES, AND GASKETS MUST BE SECURE. NEVER OPERATETHE DEVICE WITHOUT A MICROWAVE ENERGY ABSORBING LOAD ATTACHED. NEVERLOOK INTO AN OPEN WAVE GUIDE ORANTENNA WHILE THE DEVICE IS ENERGISED.Lever Stopper1. ADJUSTMENT PROCEDURESTO AVOID POSSIBLE EXPOSURE TO MICRO-WAVEENERGY LEAKAGE, THE FOLLOWING ADJUSTMENT OF THE INTERLOCK SWITCHES SHOULDBE MADE ONLY BY AUTHORISED SERVICEPERSONNELScrewPositionsDoor LatchPRIMARY INTERLOCK SWITCH, DOOR SENSINGSWITCH AND INTERLOCK MONITOR SWITCHADJUSTMENT(Figure 1)Door SensingSwitch(1) Loosen 2 screws securing the lever stopper.(2) Adjust the lever stopper position so that it is pushedup and pull forward until there is about zero gap.2-1. Between the lever and the switch body onthe door sensing switch.2-2. Between the lever and the switch bodyon the interlock monitor switch.2-3. Between the latch lever and the switch bodyon the primary interlock switch.when the door latch is securely locked.(3) Tighten the lever stopper screws securely.(4) Make sure the interlock monitor is closed afterthe primary interlock switch opens when the door isopened very slowly, according to “CHECKOUTPROCEDURE FOR SWITCHES” on page 8.(5) Make sure the interlock monitor is open beforethe primary interlock and secondary interlockswitches close when the door is closed very slowly,according to “CHECKOUT PROCEDURE FORSWITCHES” on page 8.(6) Make sure the microwave energy leakage is belowthe limit of the regulation (5mW/cm2) whenmeasured with a detector. ( All serviceadjustments must be made for minimum energyleakage readings.)LeverInterlock MonitorSwitchLatch LeverPrimary InterlockSwitchFigure 1-1-

2. SPECIFICATIONS - EM-SL20NRated Power Consumption. Micro 1450 10%WGrill 1100 5/-10%WDual 2500 5/-10%W(After 15mins.)Microwave Output. 900W( Adjustable 90Wthrough 900W )Frequency. 2,450MHz 50MHzPower Supply. 230V,50HzRated Current.Micro 6.3 10% AmpsGrill 4.75 5/-10% AmpsDual 10.9 5/-10% Amps(After 15mins.)Safety Devices. Thermal Protector forMagnetron and Cavity,Open at 122 CThermal Protector forHeater, Open at 150 CFuse (Cartridge Type 8A)Primary Interlock SwitchDoor Sensing SwitchInterlock Monitor SwitchTimer. Electronic DigitalOverall Dimensions.490(W)x378(D)x322(H)mmOven Cavity Size.304(W)x304(D)x248(H)mmTurntable Diameter.262mmNet Weight.Approx. 19.0Kg.4.PRECAUTIONS AND REPAIR SERVICE TIPSPRELIMINARYA.SINCE NEARLY 4,000 VOLTS EXIST INSOME CIRCUITS OF THIS MICROWAVEOVEN, REPAIRS SHOULD BE CARRIEDOUT WITH GREAT CAREB.TO AVOID POSSIBLE EXPOSURE TOMICROWAVE ENERGY LEAKAGE, THEFOLLOWING PRECAUTIONS MUST BETAKEN BEFORE SERVICING.(1)Before the power is applied.(a)Open and close door several times to make surethe primary interlock switch, the door sensing switch,and the interlock monitor switch operate properly.(Listen for the clicking sound from switches). Makesure the interlock monitor switch is closed after theprimary interlock switch is opened, when the door isopened. (See pages 1 and 7).(b)Make sure the perforated screen and the dielectricchoke of the door are correctly mounted.(2)After the power is applied.(a)Open and close the door to see if the interlockmechanism operates properly.(b)Check microwave energy leakage with a leakagedetector and confirm the energy leakage is below5mW/cm2.3. POWER OUTPUT MEASUREMENT(1) Prepare 1000cc tap water in a wide mouthed Pyrexcontainer.(2) Stir thoroughly and note initial water temperature T1( C).(3) Place container in centre of oven and operate for 60seconds at full power.(4) Remove container, stir thoroughly and note finalwater temperature T2 ( C).(5) Calculate power output 70 x Temp. rise (T2-T1).NOTE: This is only an approximate test method, notIEC705 test method to which the microwave oven hasbeen tested and rated.(3)Do not operate the unit until it is completelyrepaired, if any of the following conditions exists.(a)Door does not close firmly against the cavity front.(b)The hinge is broken.(c)The choke dielectric or the door seal is damaged.(d)The door is bent or warped, or there is any othervisible damage to the oven that may causemicrowave energy leakage.NOTE: Always keep the seal clean(e)Make sure there are no defective parts in themicrowave generating and transmission assembly.(especially waveguide).(4)Following items should be checked after the unit isrepaired.(a)The interlock monitor switch is connectedcorrectly and firmly.(b)The magnetron gasket on the magnetron isproperly positioned.(c)Wave guide and oven cavity are intact ( no leakageof microwave energy).(d)The door can be properly closed and the safetyswitches work properly.(e)The oven must be stopped when the door isopened or the time is up.The oven must not be operated with any of the abovecomponents removed or bypassed.-2-

5. OVEN CONTROL re 1KEYS:1. Display Window2. Function and Accessary Indicator3. Kitchen Timer Display4. Auto Program Key5. Auto-Defrost6. Kitchen Timer Key7. More/Less Key8. Personal Menu Keys9. MIcro Power10. Delay Start11. Quick Start12. Clear/Stop13. Start14. Rotary DialNotes :A "beep tone" sounds when a "pad" on the control panel is touched, to indicate a setting hasbeen entered.When setting the controls you can keep your finger on a key until the desired setting is reached.-3-

6.CIRCUIT DIAGRAMEM-SL20N230V 50HzOVEN CONDITIONDOOR : OPENL1,L2 1mHC1 0.22 FC2,C3 4700PFR 1MC1RTOUCH 22ûC)GM3FUSE (8A T)BMRL4CONTROLCIRCUITBOARDRL3HT(150ûoC)RL2HIR (25 )SC321NCCOMNOSC2HIGH VOLTAGE TRANSFORMERCOMMAGNETRON 2M-253H(IF)-NH.V. FUSE 0.75A1.14 FHIGH VOLTAGE RECTIFIERHIGH VOLTAGE CONDENSER2x500PF/2x1.5uHSC1 : PRIMARY INTERLOCK SWITCHSC2 : DOOR SENSING SWITCHSC3 : INTERLOCK MONITOR SWITCHMTCO/CFTCO : MAGNETRON/CAVITY FIRETHERMAL CUT OUTHT : HEATER THERMOSTATRL1 : MAIN RELAYRL2 : POWER CONTROL RELAYRL4 : GRILL HEATER RELAYBM : BLOWER MOTORGM : GEAR MOTORL: CAVITY LAMPST : STEP DOWN TRANSFORMERIR : INRUSH RESISTOR- The parts marked withare supplied witha high voltage which exceeds 250V.- The parts marked withhave special characteristics important for macrowave leakage.When replacing any of these parts use onlymanufacturer's specified parts.-4-

7. TEST PROCEDURES AND TROUBLESHOOTINGFilament WindingsCAUTION- DISCONNECT THE POWER SUPPLYCORD FROM THE WALL OUTLETWHENEVER REMOVING THE CABINETFROM THE UNIT. PROCEED WITH THETESTS ONLY AFTER DISCHARGINGTHE HIGH VOLTAGE CAPACITOR ANDREMOVING THE LEAD WIRES FROMTHE PRIMARY WINDING OF THE HIGHVOLTAGE TRANSFORMER. ( SeeFigure 3 )Secondary WindingPrimary WindingsFigure 4A. TEST PROCEDURECOMPONENTCHECKOUT PROCEDURE1) Check for resistance : Across the filament terminals of thethe magnetron with an ohmmeter on Rx1 scale.RESULTSNormal reading :Less than 1 ohm.Figure 52) Check for resistance : Across the filament terminals ofthe magnetron and the chassis ground with an ohm-meteron highest scale.MAGNETRONFigure 6The chart below shows the firing times of the variable powerrelay for the EM-SL20 model. The table should be used asa means to check the magnetron is operating correctly andproducing any other power setting apart from full power.Power LevelHigh (900W)M-High(750W)Roast (450W)Simmer(300W)Warm (150W)Low (80W)On Time/s% On Time(inc.’ramp up’ time)30.010028.09318.06013.0438.0276.020-5-Normal reading :Infinite ohms

COMPONENTHIGHVOLTAGETRANSFORMERCHECKOUT PROCEDURERESULTS1) Measure the resistance :With an ohmeter on Rx1 scale.a. Primary Winding ;b. Filament Winding ;c. Secondary Winding ;2) Measure the resistance :With an ohm-meter on highest scale.a. Primary winding to ground ;b. Filament winding to ground ;Normal readings :Approximately 1.75 ohms.Less than 1 ohm.Approximately 90.11 ohms.Normal readings :Infinite ohmsInfinite ohmsNote : Remove varnish ofmeasured point.Figure 71) Measure the resistance : Across two terminals with anohm-meter on highest scaleHIGH VOLTAGECAPACITORincludingBLEEDERRESISTORNormal reading :Momentarily indicates severalohms, and gradually returnsto 10 Meg-ohm.Abnormal reading :Indicates continuity or 10MΩfrom the beginning.Figure 8Measure the resistance : Across two terminals with anohm-meter on its highest scale.HIGHVOLTAGEDIODEFigure 9Normal reading :Indicates over 10MΩ in onedirection (forward direction)and infinite ohms in thereverse direction, using meterwhich is provided with a 9-voltbattery.NOTESome digital meters mayshow over even in a forwarddirection because lowmeasuring voltage of meterdoes not allow the metercurrent to pass throughthe high voltage diode.Abnormal reading:Indicates continuity or infiniteohms in both directions.-6-

COMPONENTCHECKOUT PROCEDURERESULTSMeasure the resistance : Across two terminals with anohm-meter on its highest scale.Normal reading :Indicates continuity.HV FUSEAbnormal reading :Indicates infinite ohms.Figure 10CONTROLCIRCUITBOARDCOMPLETEMeasure the voltage : Between test points TP-1,TP-2,and ground (See control circuit board on page 20 ).NOTEProceed with the check of the step down transformer, tosee if any one of the measured values is different from thespecified values-7-Test TP-1 TP-2pointVoltage -5V -15VDC DC

CHECKOUT PROCEDURE FOR SWITCHESDisconnect the lead wires from the switches and check the continuity of the switches, connecting an ohm-meter to itsterminals.SWITCHCHECKOUT PROCEDURESDOOR OPEN DOOR CLOSEPrimary InterlockConnect an ohm-meters leads to terminals "COM"and "NO" of switchDoor SensingInterlock monitorConnect an ohm-meters leads to terminals "COM"and "NC" of switchCAUTION : After checking the switches, make sure that the interlock monitor switch is properly connected according tothe CIRCUIT DIAGRAM on page 4.-8-