TROUBLESHOOTING GUIDE
Contents
1. pe 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 voltage 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 be 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 nang on this panel to discharge any static charge in your body 120V AC is present at the shaded area L of the digital programmer circuit Terminals of power relay s and primary circuit of low voltage transformer When troubleshooting be cautious of possible electrical shock hazard First of all operate the microwave oven following the correct operating procedures in order to find the exact cause of any trouble Oven is dead Fuse is OK No display and no operation at all No display and no operation at all Fuse is blown Oven does not accept key input Program Oven lamp and fan motor turn on when oven is plugged in with door clos2. CHECK RESULT CAUSE CORRECTIONS Membrane switch continuity Membrane switch 1 IC 1 pin 10 voltage while operation Normal 5V gt Step 2 short circuit between pin 1 and pin 12 of Still not turn on 1 IC 1 pin 8 and pin 9 voltages while ee a Replace display and check operation 2 Normal 8 5V 9 5V Step 2 HOW TO CHECK THE SEMICONDUCTORS USING AN OHM METER Diode l A K e ANODE CATHODE l __py A K _p Transistor NPN Transistor COLLECTOR Cc 2SC ences B 2D BASE E ECB EMITTER PNP Transistor E OS Arn 5 2SB acesee c l ECB Digital Transistor 5 PNP Transistor wk Lim ECB 19 B FORWARD REVERSE A K SMALL pe ee FORWARD REVERSE OBE SMALL we Pp BC SMALLEST fai ae FORWARD oee aa ae FORWARD EB 10kKQ 30KQ 10KO 30KQ PCB 50KQ 90KQ_ e CE 40KO 80KQ e
3. Magnetron Open or loose wiring of power relay B Defective primary latch switch Defective power relay B or DPC 47s Refer to operation procedure Refer to DPC troubleshooting Adjust door and latch switches Adjust door and latch switches Check high voltage component according to component test procedure and replace if it is defective Refer to DPC troubleshooting CORRECTIONS _ Oven can program but timer does not start Open or loose wiring of secondary latch Adjust door and latch switches countdown switch Off alignment of secondary latch switch Defective secondary latch switch Microwave output is low Decrease in power source voltage Consult electrician Oven takes longer time to cook food 2 Open or loose wiring of magnetron filament l circuit Intermittent oscillation Aging change of magnetron Fan motor and oven lamp turn on when door is Shorted primary latch switch opened Oven does not operate and return to plugged in Open or loose wiring of temp sensor Check tighten screws on escutcheon base mode Defective temp sensor bracket D P C board and temp sensor Defective DPC i Loud buzzing noise can be heard Loose fan and fan motor Loose screws on H V Transformer Shorted H V Diode Turntable motor does not rotate Open or loose wiring of turntable motor Defective turntable motor Oven stops operation during cooking Open or loose wiring of primary and Adjust door and
4. latch switches secondary latch switch Operation of thermal cutout Magnetron CAUSE CORRECTIONS Oven is dead Open NOTE Shorted Circuit of ZNR N L V T Oven Lamp etc Replace DPC Low voltage transformer LVT Abnormal OV secondary voltage Emitter of Q1 Normal 5V Step 4 14 pin of IC 2 NOTE Procedure of fuse pattern repairing is as follows 1 When the fuse pattern PF2 opens 1 Remove the jumper wire PF1 2 Insert the removed jumper wire PF1 to PF2 position and solder it If both PF1 and PF2 fuse patterns are open please replace DPC 2 When the fuse pattern PF4 opens 1 Remove the jumper wire PF3 2 Insert the removed jumper wire PF3 to PF4 position and solder it If both PF1 and PF2 fuse patterns 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 1G Trouble related to Digital Programmer Circuit SYMPTOM STEP No key input No beep sound Power relay A RY 2 does not turn on even though the program has been set and the start pad is tapped No microwave oscillation at any power setting operation at high power Oven function is OK but no display all digits
5. ed Timer starts countdown but no microwave oscillation No heat while oven lamp and fan motor turn on Open or loose lead wire harness Open thermal cutout Magnetron Open low voltage transformer Defective DPC Shorted lead wire harness Defective primary latch switch NOTE 1 Defective short switch NOTE 1 Shorted H V Capacitor Shorted H V Transformer NOTE 2 NOTE 1 Refer to adjustment instructions CORRECTIONS Check fan motor when thermal cutout is defective Check adjustment of primary secondary latch switch and short switch including door All of these switches must be replaced at the same time Check continuity of power relay B s contacts between 1 and 2 and if it has continuity replace power relay B also NOTE 2 When H V Transformer is replaced check diode and magnetron also Key input is not in sequence Open or loose connection of membrane key pad to DPC Flat cable Shorted or open membrane key board Defective DPC Misadjustment or loose wiring of secondary latch switch Defective secondary latch switch Off alignment of latch switches Open or loose connection of high voltage circuit especially magnetron filament circuit NOTE Large contact resistance will bring lower magnetron filament voltage and cause magnetron to lower output and or have intermittent oscillation Defective high voltage component H V Transformer H V Capacitor H V Diode
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