R-657SL (serv.man7). Test Procedures - Sharp Home Appliance Service Manual (repair manual). Page 3

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R657(W)
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If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (MG) indicates that the magnetron has overheated, this may be due to resistricted ventilation, cooling fan failure.
An open circuit thermal cut-out (OVEN) indicates that the oven cavity has overheated, this may be due to no load operation.
CARRY OUT 4R CHECKS.
[7] G: BLOWN FUSE 20A
CARRY OUT 3D CHECKS.
If the fuse 20A 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: Only replace fuse with the correct value replacement.
[8] H: BLOWN FUSE F8A (NOISE FILTER)
CARRY OUT 3D CHECKS.
1. If the fuse F8A 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.
2. If the fuse F8A is blown when the door is opened, check the monitored latch switch, monitor switch, relay RY1 and relay RY3.
If he fuse F8A is blown by incorrect door switching replace the defective switch(es) and the noise filter.
3. If the fuse F8A is blown, there could be shorts in the asymmetric rectifier or there is a ground in wire harness. A short in the asymmetric rectifier
may be occurred due to short or ground in H.V. rectifier, magnetron, high voltage transformer or H.V. wire. Check them and replace the defective
parts or repair the wire harness.
CARRY OUT 4R CHECKS.
[9] I: 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. 
If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
[10] J: 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.
[11] K: GRILL HEATING ELEMENTS TEST
CARRY OUT 3D CHECKS.
Before carrying out the following tests make sure the heating element is cool completely. 
1. Resistance of heating element.
Disconnect the wire leads to the heating element to be tested. Using ohmmeter with low resistance range. Check the resistance across the termi-
nals of the heating element as described in the following table.
MEASURING POINT 
INDICATION OF OHMMETER
Between N and L 
Approx. 680 k
Ω
Between terminal N and WHITE 
Short circuit
Between terminal L and RED 
Short circuit
Table: Resistance of Motor
Motors
Fan motor
Turntable motor
RMOTEA405WRZZ
RMOTDA265WRZZ
RMOTDA173WRE0
RMOTDA253WRZZ
Resistance at 20
°C
Approximately  388
Ω
Approximately   14.7k
Ω
Approximately   12.2k
Ω
Approximately   14.5k
Ω
Table: Resistance of heater
Parts name
Resistance
Grill heating elements
Approximately 61
Ω 
20A
F8A
WHT
RED
R2
N
Cx
R1
Cy
L
L
L
L (min) Cx ± 20% Cy ± 20% R2 ± 20% R1 ± 5%
1.0mH
0.22uF
680k
10M
4700pF
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