Samsung MW5490W Service Manual - Page 15

6. Troubleshooting PRECAUTION! 1. CHECK GROUNDING BEFORE CHECKING FOR TROUBLE. 2. BE CAREFUL OF THE HIGH VOLTAGE CIRCUIT. 3. DISCHARGE THE HIGH VOLTAGE CAPACITOR. 4. WHEN CHECKING THE CONTINUITY OF THE SWITCHES OR TRANSFORMER, DISCONNECT ONE LEAD WIRE FROM THESE PARTS AND THEN CHECK CONTINUITY WITHOUT THE POWER SOURCE ON. TO DO OTHERWISE MAY RESULT IN A FALSE READING OR DAMAGE TO YOUR METER. 5. DO NOT TOUCH ANY PART OF THE CIRCUIT OR THE CONTROL CIRCUIT BOARD, SINCE STATIC DISCHARGE MAY DAMAGE IT. ALWAYS TOUCH GROUND WHILE WORKING ON IT TO DISCHARGE ANY STATIC CHARGE BUILT UP. 6-1 Electrical Mulifunction SYMPTOM CAUSE CORRECTIONS Oven is dead. Fuse is OK. No display and no operation at all. 1. Open or loose lead wire harness 2. Open thermal cutout (Magnetron) 3. Open low voltage transformer 4. Defective Ass'y PCB Check fan motor when thermal cutout is defective. Check Ass'y PCB when LVT is defective. No display and no operation at all. Fuse is blown. 1. Shorted lead wire harness 2. Defective primary latch switch (NOTE 1) 3. Defective monitor switch (NOTE1) 4. Shorted HVCapacitor 5. Shorted HVTransformer (NOTE2) Check adjustment of primary, interlock monitor, power relay, door sensing switch. NOTE 1: All of these switches must be replaced at the same time. (refer to adjustment instructions) Check continuity of power relay contacts and if it has continuity, replace power relay also. NOTE 2: When HVTransformer is replaced, check diode and magnetron also. Oven does not accept key input (Program) 1. Key input is not in-Sequence 2. Open or loose connection of membrane key pad to Ass'y PCB 3. Shorted or open membrane panel 4. Defective Ass'y PCB Refer to operation procedure. Replace PCB main. Timer starts countdown but no microwave oscillation. (No heat while oven lamp and fan motor turn on.) 1. Off-alignment of latch switches 2. 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 intermittent oscillation. 3. Defective high voltage components H.V.Transformer H.V.Capacitor H.V.Diode Magnetron 4. Open or loose wiring of power relay 5. Defective primary latch switch 6. Defective power relay or Ass'y PCB Adjust door and latch switches. Check high voltage component according to component test procedure and replace if it is defective. Replace PCB main. Samsung Electronics 6-1