R-86STMA (serv.man8). Test Procedures - Sharp Home Appliance Service Manual (repair manual). Page 3

R86STMA

8 – 3

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.

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 excessive heat / fire
inside the oven.

CARRY OUT 4R CHECKS.

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.

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.

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.

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.

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 (MG) 125

°C

This is not resetable type.

Above 125

°C

Closed circuit

Thermal cut-out (OVEN) 145

°C

Bellow  115

°C.

Above 145

°C

Closed circuit

Table: Resistance of Motor

Motors

Fan motor

Turntable motor

Convection fan motor

RMOTDA255WRZZ

RMOTDA189WRE0

Resistance

Approximately  399

Ω

Approximately 14.5k

Ω

Approximately 12k

Ω

Approximately 288k

Ω

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

F8A

20A

WHT

RED

R1

R2

N

Cx

Cy

L

L

L

L (min) Cx ± 20% Cy ± 20%

R1

R2

1.0mH

0.22 uF

4700pF 10 M

680k