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7

NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED
TOOL WHILE THE OVEN IS IN OPERATION.

1.

CARRY OUT 3D CHECKS.

2. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity

check across the magnetron filament leads should indicate less than 1 ohm.

3. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament

leads and chassis ground. This test should indicate an infinite resistance. If there is little or no
resistance the magnetron is grounded and must be replaced.

4. Reconnect all leads removed from components during testing.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.

MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (outer case fitted).
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.

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 48 seconds on full

power.

4. When the 1 minute and 48 seconds 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 80.

±

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 50W/m

2 

(equivalent to 5W/

m

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

8

1.

CARRY OUT 3D CHECKS.

2. 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 .......................... 3.3 ohms approximately
b. Secondary winding .................... 207 ohms approximately
c. Filament winding .....................................  less than 1 ohm

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

3. Also, the high voltage transformer has the thermal cut-out in the primary coil. Measure the

resistance of the primary coil. The resistance of the primary coil should be above resistance unless
the temperature of the thermal cut-out in the primary coil reaches approximately 150˚C. The
thermal cut-out resets automatically at 130˚C. If an ohmmeter indicates an open circuit under
normal condition, replace the high voltage transformer because the primary coil (thermal cut-out)
has opened. An open primary coil (thermal cut-out) indicates overheating of the high voltage
transformer. Check for restricted air flow to the high voltage transformer, especially the ventilation
opening.

4. CARRY OUT 4R CHECKS.

HIGH VOLTAGE RECTIFIER TEST

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.

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

THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BE-
CAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIREC-
TIONS.

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 10MΩ

resistance.

F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.

9

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.

Isolate the switch to be tested and using an ohmmeter check between the terminals as described in
the following table.

CARRY OUT 3D CHECKS.

Table: Terminal Connection of Switch

COM; Common terminal

Plunger Operation

COM to NO

COM to NC

NO;

Normally open terminal

Released

O.C.

S.C.

NC;

Normally close terminal

Depressed

S.C.

O.C.

S.C.;

Short circuit

O.C.; Open circuit

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

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the temperature fuse. Then using an ohmmeter, make a
continuity test across the two terminals as described in the below.

Table: 

Temperature Fuse

 Test

Temperature of "ON"

Temperature of "OFF"

Indication of ohmmeter (When room

Parts Name

condition (closed circuit).

condition (open circuit).

 temperature is approx. 20˚C.)

Temperature fuse 120˚C

This is not resetable type.

Above 120˚C

Closed circuit

If incorrect readings are obtained, replace the temperature fuse.

An open circuit temperature fuse (OVEN) indicates that the food in the oven cavity may catch fire, this
may be due to overheating produced by improper setting of the cooking time or failure of the control
panel.

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 400 ohms

Turntable motor

Approximately 14.5 kohms

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

If the fuse T6.3A is blown when the door is opened, check the 1st latch switch, 2nd. interlock relay
control switch, monitor switch and 2nd. interlock relay RY2.

10

FUSE
T6.3A

N

L

LINE CROSS CAPACITOR

0.068

µ/AC250V 

NOISE SUPPRESSION COIL 

LINE BYPASS
CAPACITOR
0.0022

µ/AC250V

LINE BYPASS
CAPACITOR
0.0022

µ/AC250V

NOISE FILTER

WHT

RED

If the fuse T6.3A is blown by incorrect door switching, replace the defective switch(es) and the fuse T6.3A.

If the fuse T6.3A 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.

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.

MEASURING POINT

INDICATION OF OHMMETER

Between N and L

Open circuit

Between terminal N and WHITE

Short circuit

Between terminal L and RED

Short circuit

CARRY OUT 3D CHECKS.
If the high voltage fuse is blown, there could be a short in the high voltage rectifier or the magnetron.
Check them and replace the defective parts and the high voltage fuse.

CARRY OUT 4R CHECKS.

CAUTION: ONLY REPLACE HIGH VOLTAGE FUSE WITH THE CORRECT VALUE REPLACE-

MENT.

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance cannot be performed with only a
voltmeter and ohmmeter.
In this service manual, the touch control panel assembly is divided into two units, Control Unit and
Key Unit, troubleshooting by unit replacement is described according to the symptoms indicated.
1.  Key Unit.  Note : Check key unit ribbon connection before replacement.

The following symptoms indicate a defective key unit. Replace the key unit.

a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.

2. Control Unit.

The following symptoms indicate a defective control unit. Before replacing the control unit, perform
the key unit test (Procedure L) to determine if control unit is faulty. Replace the control unit.

2-1  Programming problems.

a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.

2-2 Display problems.

a) For a certain digit, all or some segments do not light up.
b) For a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.