Sharp R-200BK Service Manual page 15

PROCEDURE
LETTER
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-BA020WRK0, even if the
monitor switch operates normally. The C/T fuse and monitor switch assembly is comprised of a 13
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 the oven overheated, Replace the oven C/T fuse and check the inside of the
oven cavity, the proper setting of cooking time and the proper operation of control unit. Also check for
proper air flow through the ovens venting system. Especially check the cooling fan for proper operation
and the air guide for restriction.
CAUTION: IF THE C/T FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE, REPLACE
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 CONTROL PANEL ASSEMBLY TEST
WARNING : Do not touch the electrical parts and the printed wiring board to prevent an electric
The 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 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. Control Panel
The following symptoms indicate a defective control unit.
1-1 In connection with LEDs
a) At a certain LED, all or some LEDs do not light up.
b) At a certain LED, brightness is low.
c) Only one LED does not light up.
d) All or some LEDs continue to light up.
e) A certain group of LEDs do not light up.
f) The LEDs flicker.
1-2 Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock is not possible.
c) Cooking time can not be set.
When 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 all leads removed from components during testing.
5) Re-install the outer case (cabinet).
6) Reconnect the power supply cord after the outer case is installed.
7) Run the oven and check all function.
TEST PROCEDURES
THE C/T FUSE.
shock. Because the control unit is "TRANSLESS CIRCUIR" and many electrical parts
are used at A.C. line voltage.
COMPONENT TEST
13
R-200BK
R-200BW