TROUBLESHOOTING GUIDE
Contents
1. TROUBLESHOOTING GUIDE CAUTION Check grounding before checking for trouble Be careful of the high voltage circuit Discharge high voltage capacitor When checking the continuity of the switches or the high jolage transformer disconnect one lead wire from these parts and then check continuity with the AC plug removed To do otherwise may result in a false reading or damage to your meter When disconnecting a plastic connector from a terminal you must hold the plastic connector instead of the lead wire and then disconnect it otherwise lead wire may be open or the connector cannot by removed Do not touch any parts of the circuitry on the digital programmer circuit since static electric discharge may damage this control panel Always touch yourself to ground while working on this panel to discharge any static charge in your body 220 230 240V AC is present at the shaded area ES3of the digital programmer circuit Terminals of power relay s and primary circuit of low voltage transformer When troubleshooting be cautious of possible electrical POR shock hazard First of all operate the microwave oven following the correct operating procedures in order to find the exact cause of any trouble TROUBLE 1 Oven does not start cooking Oven is dead 1 Open or loose lead wire harness Fuse is OK Open thermal cutout Magnetron Check fan motor when thermal cutout is No display and no operation at all defective2. Open low voltage transformer Defective DPC Oven does not accept key input Program Key input is not in sequence Refer to operation procedure Open or loose connection of membrane key pad to DPC Flat cable Shorted or open membrane key board Defective DPC Refer to DPC troubleshooting Oven lamp and fan motor turn on when Misalignment or loose wiring of Adjust door ang latch switches AD oven is plugged in with door closed NY Defective secondary latch switch Timer starts count down but no microwave 1 Off alignment of latch switches Adjust door and latch switches oscillation Defective primary latch switch Open or loose wiring of power relay RY1 Defective power relay RY1 Defective DPC Open or loose connection of high voltage circuit especially magnetron filament circuit NOTE Large contact resistance will bring lower magnetron filament voltage and causing magnetron to lower output and or intermittent oscillation 7 Defective high voltage component Check high voltage component H V Transformer according to component test procedure H V Capacitor and replace if it is defective H V Diode Magnetron 20 ee Ne A Shorted lead wire harness N Defective short switch Check adjustment of latch switches and door w Defective primary latch switch Shorted H V Capacitor Shorted H V Diode Replace H V Diode and protector diode NOTE D
3. efective D P C g Turntable motor does not rotate 7 Oven return to plugged in mode after 10 seconds elapsed in the auto sensor cooking mode 24 gt SYMPTOM _ CHECK RESULT CAUSE CORRECTIONS L V T Low voltage transformer LVT Abnormal OV secondary voltage Normal Step 3 NOTE FOR ALL MODELS 1 Remove jumper wire PF1 Trouble related to Digital Programmer Circuit NN S687WA amp NN T687SA Models No display when oven is first STEP 2 plugged in Open NOTE Shorted circuit of ZNR Oven Lamp etc Replace DPC IC 1 pin 1 voltage Abnormal ZD1 Q1 Emitter of Q1 Normal 5V Step 4 Procedure of fuse pattern repairing is as follows 1 When the fuse pattern PF2 opens 2 Insert the removed jumper wire PF1 to PF2 position and solder it If both PF1 and PF2 fuse pattern are open please replace DPC 2 When the fuse pattern PF4 opens 1 Remove jumper wire PF3 2 Insert the removed jumper wire PF3 to PF4 position and solder it If both PF4 and PF3 fuse pattern are open please replace DPC NOTE At the time of these repairs make visual inspection of the varistor for burning damage and examine the transformer with tester for the presence of layer short circuit check primary coil resistance if any abnormal condition is detected replace the defective parts No key input 1 Memb
4. efective magnetron Replace magnetron and protector diode NOTE Shorted H V Transformer Replace H V Transformer and protector diode NOTE Shorted Protector diode OiINIOinis XNOTE Be sure to replace protector diode together with those H V Components In this case only D2 of protector diode may be shorted due to faulty H V Component Therefore if protector diode is not replaced together high voltage transformer will bedamaged over heated TROUBLE 3 Other troubles SYMPTOM Microwave output is low Oven takes longer time to cook food CAUSE CORRECTIONS 1 Decrease in power source voltage Consult electrician 2 Open or loose wiring of magnetron filament circuit Intermittent oscillation 3 Aging change of magnetron Check tighten screws on escutcheon base bracket D P C board and temp sensor Oven does not T and return to plugged in mode 3 Defective DPC Refer to DPC troubleshooting 4 Loud buzzing noise can be heard 1 Loose fan and fan motor 2 Loose screws on H V Transformer Oven stops operation during cooking 1 Off alignment of latch switches Adjust door and latch switches 2 Open or loose wiring of primary and secondary latch switch 3 Operation of thermal cutout Magnetron 1 Open or loose wiring of turntable motor 2 Defective turntable motor 1 Open or loose wiring of sensor terminals Sensor Models from DPC 2 Open steam sensor 3 D
5. rane switch continuity eg cue al ee a No beep sound 1 IC 1 pin 23 voltage Honan SS a E ere turn on even though the program 2 has been set and the start pad is short circuit between pin 1 and Still not turn on tapped 1 pin 12 of IC 2 7 RY 2 tums on 1 No microwave oscillation at any power setting while operation at high power Normal Step 2 5 5V 15 5V IC 1 Dark or unclear display 1 Replace display and check oes Missing or lighting of 1 dase IC 1 and check unnecessary segment ORerauon DISPLAY TO BE CONTINUED FOR AUTO SENSOR MODELS Auto Sensor cooking does not Steam sensor terminal voltage by Abnormal OV operate normally using high impedance tester zanas y IC 1 IC 3 Steam sensor does not detect 20kQ V when breathe on metal Nolipats 1030m i steam from foods surface of sensor 22 PRON emt Bom Nu met Trouble related to Digital Programmer Circuit NN S537WA SYMPTOM STEP CHECK l RESULT No display when oven is first plugged in 1 Fuse pattern of DPC STEP 2 Open NOTE Shorted Circuit of ZNR L V T Oven Lamp etc Replace DPC Low voltage transformer LVT _ Abnormal OV LVT secondary voltage Emitter of Q1 Normal 5V gt Step4 4 IC 1 pin 27 voltage l 14 pin of IC 2 No key input 1 Membrane switch continuity Membrane switch No beep sound 1 IC 1 pin 11 voltage 7 Power relay A RY 2 does not
6. turn on BA sen neon he roa a ee 3693 2 short circuit between pin 1 and pin 12 of Still not turn on i me IC 1 pin 8 and pin 9 voltages while Abnormal operation at high power Normal Step 2 8 5V 9 5V 2 Q8 translator f 1 IC 3 pin 9 voltage C11 D11 D14 LVT 2 Replace display and check operation Display HOW TO CHECK THE SEMICONDUCTORS USING AN OHM METER CAUSE CORRECTIONS Oven is dead O Q z M O No microwave oscillation at any power setting Oven function is OK but no display all digits Diode A K ANODE caTHoDE OOOO O FORWARD REVERSE C D a SMALL ee ee A K p _ Transistor NPN Transistor COLLECTOR c DSCerrere B 2SDer BASE ECB EMITTER PNP Transistor E OSA Ga 28B S Bama See ECB oe FORWARD REVERSE Digital Transistor 2 10kQ 30kQ 10kQ 30kQ PNP Transistor gt Cs 50kQ 90kQ ee Oe OE wk akooo o i HU o ECB s9 oh e nN
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