R-21ATP - Sharp Home Appliance Service Manual (repair manual). Page 12

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test across the two terminals as described in the below.

Table: Thermal Cut-out Test

Temperature of "ON"

Temperature of "OFF"

Indication of ohmmeter

Parts Name

 condition  (closed circuit).

condition (open circuit).

(When room temperature

(˚C)

(˚C)

is approx. 20˚C.)

Thermal cut-out 125˚C

This is not resetable type.

Above 125˚C

Closed circuit

Thermal cut-out 145˚C

This is not resetable type.

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 or a fault condition within the magnetron or HV. circuit.

An open circuit thermal cut-out (OVEN) indicates that the food in the oven cavity may catch fire, this may
be due to over heating produced by improper setting of the cooking timer or failure of the control panel.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

If the fuse M10A is blown when the door is opened, check the 1st. interlock switch, monitor switch and
monitor resistor.

If the fuse M10A is blown, there could be a short or ground in electrical parts or wire harness. Check
them and replace the defective parts or repair the wire harness.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as described
in the following table.

Between N and L

Approx. 680 k

Ω

Between terminal N and WHITE

Short circuit

Between terminal L and RED

Short circuit

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

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.

Table: Resistance of Motor

Motors

Resistance

Fan motor

Approximately 219 

Ω

Antenna motor

Approximately 11 k

Ω

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

FUSE
M10A

N

L

DISCHARGE RESISTOR 680 k

Ω

NOISE SUPPRESSION COIL 

NOISE FILTER

LINE BYPASS
CAPACITOR
0.0033

µ

F/ AC 250V

DISCHARGE
RESISTOR 10M

Ω

LINE BYPASS
CAPACITOR
0.0033

µ

F/ AC 250V

LINE CROSS CAPACITOR 0.068

µ

F/ AC 250V

CARRY OUT 3D CHECKS.