NN-SD297SR - Panasonic

1 Panasonic Home Appliances microwave Oven(Shanghai) Co., Ltd. (CANADA) microwave OvenPlease file and use this manual together with the service manual for Model NN-S262SF ( )ORDER 1 SCHEMATIC DIAGRAM 5 NN-SD297SR /BR/WR, P295 SFR/W FR 5 SD277SR/BR/WR 6 NN-SA247SR, S245 WFR 7 NN-S255 WFR 8 2 DESCRIPTION OF OPERATING SEQUENCE 9 Variable power cooking control 9 Inverter power supply circuit 9 Inverter defrost 9 Sensor cooking (Only for sensor models) 9 Sensor reheat (Only for sensor models) 10 3 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING 11 Check the grounding 11 Inverter warnings 11 Part replacement. 12 When the 20A fuse is blown due to the malfunction of themonitor interlock switch: 12 Avoid inserting nails, wire etc. through any holes in theunit during operation.

2 12 Verification after repair 12 Sharp edges 12 4 COMPONENT TEST PROCEDURE 13 Primary, Secondary Latch Switch interlocks & PowerRelay RY1 13 Monitor Interlock Switch 13 Magnetron 13 Inverter power supply (U) 14 Humidity sensor 14 5 MEASUREMENTS AND ADJUSTMENTS 15 Adjustment of primary latch switch, secondary latch switchand monitor interlock switch. 15 Measurement of microwave output 15 6 PROCEDURE FOR MEASURING microwave ENERGYLEAKAGE 16 Equipment 16 Procedure for measuring radiation leakage 16 Record keeping and notification after measurement 16 At least once a year, have the radiation monitor checkedfor calibration by its manufacturer. 17 7 TROUBLESHOOTING GUIDE 18 Troubleshooting of inverter circuit (U) and magnetron 18 SIMPLE WAY OF INVERTER/MAGNETRONTROUBLESHOOTING 19 BOARD MAIN PARTS LIST(F606Y8X00AP)

3 19 8 EXPLODED VIEW AND PARTS LIST 20 EXPLODED VIEW 20 PARTS LIST 21 DOOR ASSEMBLY 23 ESCUTCHEON BASE ASSEMBLY 24 PACKING AND ACCESSORIES 28 WIRING MATERIALS 30 9 DIGITAL PROGRAMMER CIRCUIT 31 NN-SD297SR /BR/WR CPH 31 NN-P295 SFR/WFR CPH 33 NN-SD277SR/BR/WR CPH, S255 WFR CPH 35 NN-SA247SR CPH, S245 WFR CPH 37 PARTS LIST 39 CONTENTS Page Page4NN-SD297SR1 SCHEMATIC NN-SD297SR /BR/WR, P295 SD277SR/ NN-SA247SR, Variable power cookingcontrolHigh Voltage Inverter Power Supply (U) controls output powerby the signal from Digital Programmer Circuit (DPC). Powerrelay always stay on, but PWM (Pulse Width Modulation) signalcontrols microwave output :The ON/OFF time ratio does not correspond with thepercentage of microwave power since approximately 2seconds are required for heating of Power CookingPOWER SETTINGOUTPUTPOWER(%) MICROWAVEDUTYON(SEC)OFF(SEC)HIGHP10100%2 20P990%220P880%220 MEDIUM-HIGHP770%220 MEDIUMP660%220P550%220P440%220 MEDIUM-LOWP330%220P220%157P110%814 DEFROSTP330% Inverter power supply circuitThe Inverter Power Supply circuit powered from the linevoltage, 120V 60Hz AC input supplies 4,000V DC to themagnetron tube, and functions in place ofthe transformer,the capacitor and diode.

4 1. The AC input voltage 120V 60Hz is rectified to DC voltageimmediately. 2. DC voltage will be supplied to the switching devices calledIGBT. These devices are switched ON-OFF by the 20 to 40kHz PWM (pulse width modulation) signal from themicrocomputer in the DPC. 3. This drives the High voltage transformer to increase voltageup to 2,000V AC. 4. Then the half-wave doubler voltage rectifier circuit,consisting of the diodes and capacitors, generates thenecessary 4,000V DC needed for the magnetron. 5. Output power of the magnetron tube is always monitored bythe signal output from the current transformer built into theinverter circuit. 6. This signal is fed back to the microcomputer in the DPC todetermine operating conditions and output necessary tocontrol PWM signal to the Inverter Power Supply for controlof the output Inverter defrostWhen the Auto Control feature is selected and the Start buttonis tapped: 1.

5 The digital programer circuit determines the power level andcooking time to complete cooking and indicates theoperating state in the display window. Table shows thecorresponding cooking times for respective serving Turbo DefrostSELECTED WEIGHTCOOKING LB5 sec. 2. When cooking time in the display window has elapsed, theoven turns off automatically by a control signal from thedigital programmer Sensor cooking (Only forsensor models)Auto sensor cooking without setting a power level or selectinga time. All that is necessary is to select an Auto SensorProgram before starting to Auto Sensor CookingAs the food cooks, a certain amount of steam is the food is covered, this steam builds up and eventuallyescapes from the container. In Auto Sensor Cooking, acarefully designed instrument, called the humidity sensorelement, senses this escape of steam. Then, based uponthe Auto SensorProgram selected, the unit willautomatically determine the correct power level and theproper length of time it will take to cook the :Auto Sensor Cooking is successful with the foods andrecipes found in the Auto Sensor Cooking of the vast differences in food composition,items not mentioned in the Cooking Guide should beprepared in the microwave oven using power selectand time features.

6 Please consult Variable PowerMicrowave Cookbook for DESCRIPTION OF OPERATING SEQUENCE9NN-SD297 SRExplanation of the Auto Sensor Cooking process 1. T1 timeThe total amount of time it takes the microwaveoven to switch to T2 time. 2. T2 timeWhen the steam escapes from the cookingcontainer placed in the oven, the humidity sensordetects it and the microprocessor calculates the balanceof cooking time. This T2 time is then shown in thedisplay and begins counting of cooking time (T2 time)The balance of cooking time which is called T2 time,can be calculated by the following time (in sec.) = T1 time X K factorNOTE:ThecoefficientKisprogrammedin tothemicroprocessor memory and they are listed in thefollowing tables along with the P1 and P2 :When "More" or "Less" button is selected, the K factorvaries resulting in T2 time to be increased or of calculating the T2 timeExample 1: If the T1 time is measured to be 2 minutes and40 seconds, and the Auto program selected is Oatmeal:T2 = T1 K= 2 min.

7 And 40 sec. 160sec. 16 Sensor reheat (Only for sensormodels)Auto Sensor Reheat is a quick and easy way to reheatrefrigerated and room temperature press the [Sensor Reheat] button. There is no need toselect power level and cooking :The Auto Sensor Reheat process is same as Auto SensorCooking FactorStandardSensor many other appliances, the microwave oven is a highvoltage, high current device. Though it is free from danger inordinary use, extreme care should be taken during should remove their watches and ringswhenever working close to or replacing the Check the groundingDo not operate on a two wire extension cord. The microwaveoven is designed to be grounded when used. It is imperative,therefore, to ensure the appliance is properly grounded beforebeginning repair Inverter warningsWARNING HIGH VOLTAGE AND HIGHTEMPERATURE(HOT/LIVE) OF THE INVERTERPOWER SUPPLY (U)The High Voltage Inverter Power Supply generates veryhigh voltage and current for the magnetron tube.

8 Though itis free from danger in ordinary use, extreme care should betaken during aluminum heat sink is also energized with high voltage(HOT), do not touch when the AC input terminals areenergized. The power device Collector is directly connectedto the aluminum heat aluminum heat sink may be HOT due to heat energy,therefore, extreme care should be taken during Inverter warningWARNING FOR INVERTER POWER SUPPLY (U)GROUNDINGC heck the High Voltage Inverter Power Supply circuitgrounding. The high voltage inverter power supply circuitboard must have a proper chassis ground. The invertergrounding plate must be connected to the chassis. If theinverter board is not grounded it will expose the user to veryhigh voltages and cause extreme DANGER! Be sure thatthe inverter circuit is properly grounded via the invertergrounding of the inverter circuit board3 CAUTIONS TO BE OBSERVED WHENTROUBLESHOOTING11NN-SD297 SRWARNINGDISCHARGETHEHIGHVOLATGECAPACITO RSFor about 30 seconds after the oven is turned off, anelectric charge remains in the high voltage capacitors of theInverter Power Supply circuit replacing or checking parts, remove the power plugfrom the outlet and short the inverter output terminal of themagnetron filament terminals to the chassis ground with aninsulated handle screwdriver to discharge.

9 Please be sureto contact the chassis ground side first and then short to theoutput the high voltage capacitorsWARNINGT here is high voltage present with high current capabilitiesin the circuits of the primary and secondary windings, chokecoil and heat sinkof the inverter. It is extremely dangerousto work on or near these circuits with the oven NOT measure the voltage in the high voltage circuitincluding the filament voltage of the touch any circuit wiring with your hand or with aninsulated tool during Part troubleshooting any part or component is to be replaced,always ensure that the power cord is unplugged from the When the 20A fuse is blowndue to the malfunction of themonitor interlock switch:WARNINGWhen the 20A 120V fuse is blown due to the malfunction ofthe monitor interlock switch, replace all of the components(primary latch switch, monitor interlock switch and powerrelay RY1). 1. This is mandatory.

10 Refer to measurements andadjustments for the location of these switches. 2. When replacing the fuse, confirm that it has theappropriate rating for these models. 3. When replacing faulty switches, be sure the mountingtabs are not bent, broken or deficient in their ability tohold the Avoid inserting nails, wire any holes in the unitduring insert a wire, nail or any other metal object through thelamp holes on the cavity or any holes or gaps, because suchobjects may work as an antenna and cause Verification after repair 1. After repair or replacement of parts, make sure that thescrews of the oven, etc. are neither loosen or energy might leak if screws are not properlytightened. 2. Make sure that all electrical connections are tight beforeinserting the plug into the wall outlet. 3. Check for microwave energy leakage. (Refer to procedurefor measuring microwave energy leakage).