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R-953/963M - 11

Fuse F8A blows when the door is opened.
Home fuse blows when power cord is plugged into wall outlet.
Fuse 20A blows when power cord is plugged into wall outlet.
Nothing appears in display when power cord is plugged into wall outlet 
and the door is opened and closed.
Display does not operate properly when STOP/CLEAR key is touched.
Oven lamp does not light when door is opened. (Display operates.)
Oven does not start when the START key is touched. (Display operates.)
Oven lamp does not light  and turntable motor does not operate.
Fan motor does not operate. (Oven lamp lights.)
Convection fan motor does not operate. (Fan motor operates.)
Turntable motor does not operate. (Oven lamp lights.)
Oven or any electrical parts (except fan motor) does not stop when 
cooking time is 0 or STOP/CLEAR key is touched.
Oven stops after 4 minutes and 15 seconds since START key is 
touched. (Except Microwave mode and Dual cook mode)
Display operates properly but all electrical parts do not operate.
Oven goes into cook cycle but shuts down before end of cooking cycle.
After cooking, the temperature of oven cavity is higher than 120ßC but 
fan motor does not operate.
The oven stops 1 minute after starting.
Oven seems to be operating but little or no heat is produced in oven 
load. (Microwave power control is set at 100%)
Oven does not seem to be operating properly during variable cooking 
condition except 100% cooking condition.
Oven goes into cook cycle but shuts down before end of cooking cycle.
Convection cooking mode does not heat.
Oven seems to be operating but the temperature in the oven cavity is 
lower or higher than preset one. 

Grill heating element does not operate.

Oven goes into cook cycle but shuts down before end of cooking cycle.
Oven seems to be operating but little or no heat is produced in oven 
load. (Microwave power does not seem to be generated properly)
Oven seems to be operating but the temperature in the oven cavity is 
lower or higher than preset one. 
Convection heating elements do not heat.

Grill heating element does not heat.

Oven is in sensor cooking condition but AH sensor doesnot stop cooking 
cycle, or oven stop soon and display shows "ERROR".

OFF

CONDITION

COOKING

CONDITION

(COMMON MODE)

MICROWAVE

COOKING

CONDITION

GRILL COOKING

CONDITION

CONVECTION

COOKING

CONDITION

DUAL COOKING

CONDITION

(COMMON MODE)

DUAL COOKING

CONDITION

(MICRO./CONV.)

DUAL COOKING

CONDITION

(MICRO./GRILL)

SENSOR

 COOKING

CONDITION

CONDITION

PROBLEM

BLOCKED 

COOLING FAN

BLOCKED 

CONVECTION FAN

NO POWER AT WALL OUTLET

HOME FUSE OR BREAKER

MIS-ADJUSTMENT OF SWITCHES

BLOCKED VENTILATION OPENINGS

OPENED WIRE HARNESS

SHORTED WIRE HARNESS

OVEN LAMP OR SOCKET

POWER SUPPLY CORD

AH SENSOR

FOIL PATTERN ON P.W.B.

RELAY RY8

RELAY RY7

RELAY RY6

RELAY RY5

RELAY RY4

RELAY RY3

RELAY RY2

RELAY RY1

KEY UNIT

TOUCH CONTROL PANEL

TC TRANSFORMER

CONVECTION HEATING ELEMENT

GRILL HEATING ELEMENT

FUSE F8A

FUSE 20A

NOISE FILTER

DAMPER MOTOR

CONVECTION FAN MOTOR

FAN MOTOR

TURNTABLE MOTOR

THERMAL CUT-OUT 170

ß

C (CONV.)

THERMAL CUT-OUT 170

ß

C (GRILL)

THERMAL CUT-OUT 125

ß

C 

THERMISTOR

DAMPER SWITCH

MONITOR SWITCH

STOP SWITCH

MONITORED LATCH SWITCH SW1

HIGH VOLTAGE CAPACITOR

H.V. HARNESS

H.V. RECTIFIER ASSEMBLY

HIGH VOLTAGE  TRANSFORMER

MAGNETRON

A B C

D E E E E F G G G H H H H

TEST PROCEDURE

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

I

J K L L

M N O O O O O O O O P Q

R-953/963M - 12

The power output of this oven is rated using the method specified by  IEC 60705. Full details of how
to curry out this procedure can be found in the Sharp Technical Training notes which is available from
Sharp Parts Centre (part number SERV-LITMW01).

The IEC60705 procedure must be carried out using laboratory-type procedures and equipment.
These requirements make the procedure unsuitable for routine performance checks.

NOTE: The following test method gives an indication of the output power only, it cannot be used to

establish the actual/rated output power. If the true output power is required, then the IEC60705
test method must be used.

Alternative simplified method:
1. Place 2  litres of cold water (between 12

°

C and 20

°

C) in a suitable container.

2. Stir the water and measure the temperature in 

°

C. Note temperature as T1.

3. Place the container in the microwave and heat the water for 1 minute and 40 seconds on full power.
4. When the 1 min. 40 sec. is completed, remove the  container and stir the water. Note the water

temperature as T2.

5. Calculate the output power using the following formula:

R.F. Power Output = (T2 - T1) x 90.

±

MICROWAVE LEAKAGE TEST

This oven should be tested for microwave leakage on completion of any repair or adjustment, following
the procedure described in the Sharp Technical Training notes (part number SERV-LITMW01). The
maximum leakage permitted in BS EN 60335-2-25 is 50mW/cm

2 

(equivalent to 5mW/cm

2

), however it

is not normal to detect any significant leakage, therefore, any leakage which is detected should be
investigated.

It is essential that only leakage detectors with current calibration traceable to National Physical
Laboratories are used.

Suitable leakage detectors: CELTEC A100

APOLLO X1

CARRY OUT 3D CHECKS.
Disconnect the leads to the primary winding of the high voltage  transformer. Disconnect the filament
and secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set on a low
range,  it is possible to check the continuity of all three winding. The following readings should be
obtained:-

a. Primary winding ................................... approximately 2 

Ω

b. Secondary winding .......................... approximately 127 

Ω

c. Filament winding .........................................  less than 1 

Ω

If the readings obtained are not stated as above, then the high voltage transformer is probably faulty
and should be replaced.
CARRY OUT 4R CHECKS.

R-953/963M - 13

CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier  can be tested
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more than 100 k

Ω

 in the other direction.

CARRY OUT 4R CHECKS.

ASYMMETRIC RECTIFIER TEST

CARRY OUT 3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be tested
using an ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and
note the reading obtained. Reverse the meter leads and note this second reading. If an open circuit is
indicated in both directions then the asymmetric rectifier is good. If the asymmetric rectifier is shorted
in either direction, then the asymmetric rectifier is probably faulty and must be replaced with high voltage
rectifier. When the asymmetric rectifier is defective, check whether magnetron, high voltage rectifier,
high voltage wire or filament winding of the high voltage transformer is shorted.

CARRY OUT 4R CHECKS.

NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF

THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BECAUSE
OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.

CARRY OUT 3D CHECKS.

A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest

resistance range.

C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10M

Ω

after it has been charged.

D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 M

Ω

 because of its internal 10M

Ω

resistance.

F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is

normal.

If incorrect reading are obtained, the high voltage capacitor must be replaced.

CARRY OUT 4R CHECKS.

If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in
the following table.

Table: Terminal Connection of Switch

Plunger Operation

COM to NO

COM to NC

Released

Open circuit

Short circuit

Depressed

Short circuit

Open circuit

COM; Common terminal,
NO;

Normally open terminal

NC;

Normally close terminal

R-953/963M - 14

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

Temperature of

Temperature of

Indication of ohmmeter

        Parts Name

 "ON" condition

"OFF"condition

(When room temperature

(closed circuit).

(open circuit).

is approx. 20˚C.)

Thermal cut-out 125˚C

This is not resetable

Above 125˚C

Closed circuit

Thermal cut-out 170˚C (GRILL)

Below 155˚C.

Above 170˚C

Closed circuit

Thermal cut-out 170˚C (CONV.)

Below 155˚C.

Above 170˚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 (GRILL) indicates that the oven cavity has overheated, this may be due
to no load operation.

An open circuit thermal cut-out (CONV.) indicates that the convection fan motor winding has over
heated, this may be due to resisted ventilation or locked cooling fan or locked convection fan motor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.
Disconnect the connector B from CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to Pin No's C1 and C3 of the thermistor harness.

Room Temperature

Resistance

20˚C - 30˚C

Approximately 359.9 k

Ω

 - 152 k

Ω

If the meter does not indiicate above resistance, replace the thermistor.

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.

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.

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

Table: Resistance of Motor

Motors

Resistance

Fan motor

Approximately

293 

Ω

Turntable motor

Approximately

15 k

Ω

Convection fan motor

Approximately

288 

Ω

Damper motor

Approximately

11 k

Ω