Sharp R-307KW Service Manual - Page 13

RC30H7KAWPTER 7. TROUBLESHOOTING GUIDEService Manual R307KW Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected. When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter which will be found in the "Test Procedure "section. IMPORTANT: 4) Disconnect the leads to the primary of the power transformer. If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, primary interlock relay (RY2), door sensing switch and secondary interlock switch before replacing the monitor fuse. If monitor fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA037WRKZ as an assembly. IMPORTANT: Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases, be necessary to connect the power supply cord after the outer case has been removed, in this event, 1) Disconnect the power supply cord, and then remove outer case. 2) Open the door and block it open. 3) Discharge high voltage capacitor. 5) Ensure that the leads remain isolated from other components and oven chassis by using insulation tape. 6) After that procedure, reconnect the power supply cord. When the testing is completed, 1) Disconnect the power supply cord, and then remove outer case. 2) Open the door and block it open. 3) Discharge high voltage capacitor. 4) Reconnect the leads to the primary of the power transformer. 5) Reinstall the outer case (cabinet). 6) Reconnect the power supply cord after the outer case is installed. 7) Run the oven and check all functions. [1] TROUBLESHOOTING CHART TTEST PROCEDURE RE CK A B C D E F F G H RE RE CK I J CK CK CK K L M N POSSIBLE CASE AND DEFECTIVE PARTS SHORT IN POWER CORD SHORT OR OPENED WIRING MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR TEMPERATURE FUSE or THERMAL CUT-OUT PRIMARY INTERLOCK SYSTEM SECONDARY INTERLOCK SWITCH MONITOR SWITCH MONITOR FUSE OVEN LAMP COOLING FAN MOTOR TURNTABLE MOTOR NOISE FILTER TOUCH CONTROL PANEL WRONG OPERATION LOW VOLTAGE DIRTY OVEN CAVITY KEY UNIT (MEMBRAINE SWITCH RELAY (RY1) DEFROST FOIL PATTERN ON PWB CONDITION PROBLEM Home fuse or circuit breaker blows when power cord is plugged into wall receptacle Monitor fuse blows when power cord is plugged into wall receptacle. OFF All letters and indicators do not appear in dis- CONDITION play when power cord is first plugged into wall outlet. Display does not operate properly when STOP/CLEAR pad is touched. (Buzzer should sound and ":" or time of day should appear in display.) Oven lamp does not light when door is opened. Oven lamp does not go out when door is closed. Oven lamp lights but fan motor and turntable motor do not operate. Oven does not go into cook cycle when START pad is touched COOKING CONDITION Oven seems to be operating but little or no heat is produced in oven load. (Food incompletely cooked or not cooked at all at end of cook cycle.) Oven goes into a cook cycle but extremely uneven heating is produced in oven load (food). Oven does not cook properly when programmed for Cooking Power P-50 mode. (Operates properly on Cooking Power P-HI (HIGH) mode.) Oven goes into DEFROST but food is not defrosted well. 7 - 1