Sharp R-230HW Service Manual - Page 16

R-203HW R-220HW R-230HW TEST PROCEDURES PROCEDURE LETTER H BLOWN C/T FUSE TEST COMPONENT TEST 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. If the C/T fuse is blown when the door is opened, check the primary interlock relay, secondary interlock switch and monitor switch according to the "TEST PROCEDURE" for those switches before replacing the blown C/T fuse. CAUTION: BEFORE REPLACING A BLOWN C/T FUSE, TEST THE PRIMARY INTERLOCK RELAY, SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR SWITCH FOR PROPER OPERATION. If the C/T fuse is blown by improper switch operation, the C/T fuse and monitor switch must be replaced with "C/T fuse and monitor switch assembly" part number FFS-BA030WRKZ, even if the monitor switch operates normally. The C/T fuse and monitor switch assembly is comprised of a 15 ampere fuse and switch. A continuity check across the C/T fuse terminals should indicate a closed circuit unless the temperature of the C/T fuse reaches approximately 248˚F(120˚C). An open C/T fuse indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially the cooling fa air guide. CAUTION: IF THE C/T FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE, REPLACE THE C/T FUSE. 5. Reconnect all leads removed from components during testing. 6. Reinstall the outer case (cabinet). 7. Reconnect the power supply cord after the outer case is installed. 8. Run the oven and check all functions. I TOUCH CONTROL PANEL ASSEMBLY TEST The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control panel assembly is divided into two units, Control Unit and Key Unit, and troubleshooting by unit replacement is described according to the symptoms indicated. Before testing, 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) Disconnect the leads to the primary of the power transformer. 5) Ensure that these leads remain isolated from other components and oven chassis by using insulation tape. 6) After that procedure, re-connect the power supply cord. 1. Key Unit. NOTE ; 1) Check key unit ribbon connection before replacement. 2) Re-install the outer case (cabinet). 3) Reconnect the power supply cord after the outer case is installed. 4) Run the oven and check all functions. The following symptoms indicate a defective key unit. a) When touching the pads, a certain pad produces no signal at all. b) When touching a number pad, two figures or more are displayed. c) When touching the pads, sometimes a pad produces no signal. If the key unit is defective. 1) Disconnect the power supply cord and then remove outer case. 2) Open the door and block it open. 3) Discharge high voltage capacitor. 14