G: Thermal Cut-Out Test; H: Motor Winding Test; I: Noise Filter Test; J: Blown Fuse (F1) 20A - Sharp R-890SLM Service Manual

[7] G: THERMAL CUT-OUT TEST

CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a continuity test across the two
terminals as described in the below.
Parts Name
Thermal cut-out 125°C
Thermal cut-out 145°C
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, or exces-
sive heat / fire inside the oven.
CARRY OUT 4R CHECKS.

[8] 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.
Table: Resistance of Motor
Motors
Fan motor
Turntable motor
Convection fan motor
If incorrect readings are obtained, replace the motor.
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.
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.
[10] J: 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.

[11] K: BLOWN FUSE F8A

CARRY OUT 3D CHECKS.
1. If the fuse F8A is blown when the door is opened, check the monitored latch switch and monitor switch.
2. If the fuse F8A is blown by incorrect door switching replace the defective switch(es) and the noise filter (fuse F8A).
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.
Service_R-890SLM.indd 17
Table: Thermal Cut-out Test
Temperature of "ON" condition
(closed circuit).
This is not resetable type.
Below 115°C.
Resistance
Approximately 399Ω
Approximately 14.7kΩ
Approximately 288kΩ
INDICATION OF OHMMETER
Approximately 680kΩ
Short circuit
Short circuit
Temperature of "OFF" condition
(open circuit).
Above 125°C
Above 145°C
L
20A
Cx
N
F8A
L (min) Cx ± 20%
1.0mH
8 - 3
R-890SLM
Indication of ohmmeter (When
room temperature is approx. 20°C.)
Closed circuit
Closed circuit
WHT
L
R1
L
RED
R2 Cy
Cy ± 20% R1 R2
0.22 uF 4700pF 10 M 680k
4/25/09 10:55:18 AM