Sharp R-1880LS Service Manual page 25

PROCEDURE
LETTER
I BLOWN MONITOR FUSE
1. Disconnect the power supply cord, and then remove outer case.
. Open the door and block it open.
3. Discharge high voltage capacitor.
4. If the monitor 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 monitor fuse.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE PRIMARY INTERLOCK
If the monitor fuse is blown by improper switch operation, the monitor fuse and monitor switch must be
replaced with "monitor fuse and monitor switch assembly" part number FFS-BA018/KiT, even if the monitor
switch operates normally. The monitor fuse and monitor switch assembly is comprised of a 0 ampere fuse
and switch.
5. Reconnect all leads removed from components during testing.
6. Re-install the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
J TEMPERATURE FUSE TEST
MAGNETRON TEMPERATURE FUSE
1. Disconnect the power supply cord, and then remove outer case.
. Open the door and block it open.
3. Discharge high voltage capacitor.
4. A continuity check across the temperature fuse terminals should indicate a closed circuit. If the temperature of
the magnetron reaches approximately 30
indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially the cooling
fan air guide.
5. Reconnect all leads removed from components during testing.
6. Re-install the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE,
K HOOD THERMAL CUT-OUT TEST
1. Disconnect the power supply cord, and then remove outer case.
. Open the door and block it open.
3. Discharge high voltage capacitor.
4. A continuity check across the thermal cut-out terminals should indicate an open circuit unless the temperature
of the thermal cut-out reaches approximately 140
close. The thermal cut-out opens automatically at approximately 113
5. Reconnect all leads removed from components during testing.
6. Re-install the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
L THERMISTOR TEST
Disconnect connector-E from the control unit. Measure the resistance of the thermistor with an ohmmeter. Con-
nect the ohmmeter leads to Pin No's E-3 and E-4.
If the meter does not indicate above resistance, replace the thermistor
TEST PROCEDURES
RELAY, SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR
SWITCH FOR PROPER OPERATION.
REPLACE THE TEMPERATURE FUSE.
Room Temperature
68F (0 C) - 86 F(30 C)
O O O O
COMPONENT TEST
O F(150 O C), the temperature fuse opens. An open temperature fuse
O F(60 O C) or more. At that temperature, the contacts will
O
Resistance
Approx. 360 k ohm - 15 k ohm
5
F(45 O C).
R-1880LS/LST