R-8740 (serv.man8). Test procedure - Sharp Home Appliance Service Manual (repair manual). Page 4

R-8740M  - 17

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.

CARRY OUT 4R CHECKS

Table: Thermal Cut-out Test

Temperature of

Temperature of

Indication of

"ON" condition

"OFF" condition

ohmmeter

Parts Name

(closed circuit).

(open circuit).

(When room

(˚C)

(˚C)

temperature is

approx. 20˚C.)

Thermal cut-out

Below  130˚C

Above 150˚C

Closed circuit

150˚C TC1

Thermal cut-out

This is not resetable

 Above 125˚C

Closed circuit

125˚C TC2

type

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.

CARRY OUT 3D CHECKS

Disconnect the leads from the terminals of
noise filter.
Using an ohmmeter, check between the ter-
minals as described in the following table.

Between N and L

Approx. 680 kΩ

Between terminal N and WHITE

Short circuit

Between terminal L and RED

Short circuit

L (min)

Cx ± 20%

Cy ± 20%

1.0mH

0.22µF

4700pF

Table: Resistance of Motor

Motors

Resistance

Fan motor

Approximately 216 Ω

Turntable motor

Approximately 16 kΩ

Convection fan motor

Approximately 410 Ω

If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (MG)  TC2 indicates that the magnetron has overheated, this may be due
to resistricted ventilation, cooling fan failure.
An open circuit thermal cut-out (OVEN) TC1 indicates that the oven cavity has overheated, this may be
due to no load operation.

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS

If incorrect readings are absorbed, replace the noise filter unit.

CARRY OUT 4R CHECKS

RED

WHT

L

L

R1

L

R2

N

Cx

Cy

R1: 10M ohm ± 20%
R2: 680k ohm ± 20%

F2:F8A

F1:F20A