Sharp R-240B Service Manual page 13

PROCEDURE
LETTER
to resistricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.
An open circuit temperature fuse (OVEN) indicates that the food in the oven cavity may catch fire, this
may be due to overheating produced by improper setting of the cooking time or failure of the control
panel.
H MOTOR WINDING TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals as described in the table below.
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
I FUSE M8A
CARRY OUT 3D CHECKS.
If the fuse M8A is blown when the door is opened, check the 1st latch switch, 2nd latch switch, monitor
switch, relay RY2 and monitor resistor.
If the fuse M8A is blown by incorrect door switching, replace the defective switch(s) and the fuse M8A.
If the fuse M8A is blown, there is a shorts or grounds in electrical parts or wire harness.
Check them and replace the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION:
J NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the noise filter. Using an ohmmeter, check between the
terminals as described in the following table.
MEASURING POINT
Between N and L
Between terminal N and WHITE
Between terminal L and RED
If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
K HIGH VOLTAGE FUSE TEST
CARRY OUT 3D CHECKS.
If the high voltage fuse is blown, there could be a short in the high voltage rectifier or the magnetron.
Check them and replace the defective parts and the high voltage fuse.
CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE HIGH VOLTAGE FUSE WITH THE CORRECT VALUE REPLACE-
TEST PROCEDURES
Table: Resistance of Motor
Motors
Fan motor
Turntable motor
Only replace fuse with the correct value replacement.
MENT.
COMPONENT TEST
Resistance
Approximately 390 ohms
Approximately 12 kohms
INDICATION OF OHMMETER
Open circuit
Short circuit
Short circuit
11
R-240B
NOISE FILTER
L
N
FUSE
LINE CROSS CAPACITOR
M8A
0.068 /AC250V
NOISE SUPPRESSION COIL
LINE BYPASS LINE BYPASS
CAPACITOR CAPACITOR
0.0022 /AC250V 0.0022 /AC250V
WHT RED