Sharp R-890SLM Service Manual download pdf (Page 17)

R-890SLM

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[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.

Table: Thermal Cut-out Test

Parts Name

Temperature of “ON” condition

(closed circuit).

Temperature of “OFF” condition

(open circuit).

Indication of ohmmeter (When

room temperature is approx. 20°C.)

Thermal cut-out 125°C This is not resetable type. Above 125°C Closed circuit

Thermal cut-out 145°C Below 115°C. Above 145°C Closed circuit

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 Resistance

Fan motor Approximately 399Ω

Turntable motor

Approximately 14.7kΩ

Convection fan motor Approximately 288kΩ

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 INDICATION OF OHMMETER

Between N and L Approximately 680kΩ

Between terminal N and WHITE Short circuit

Between terminal L and RED

Short circuit

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.

F8A

20A

WHT

RED

L (min) Cx ± 20% Cy ± 20% R1 R2

1.0mH 0.22 uF 4700pF 10 M 680k

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Sharp R-890SLM Service Manual Page 17

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