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8

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

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.

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 .......................... 2.8 ohms approximately
b. Secondary winding .................... 189 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.
CARRY OUT 4R CHECKS.

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 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, 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 10MΩ

resistance.

F. When the internal wire is opened in the high voltage capacitor, the 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.

CARRY OUT 3D CHECKS.

9

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 "ON"

Temperature of "OFF"

Indication of ohmmeter (When room

Parts Name

condition (closed circuit).

condition (open circuit).  temperature is approx. 20˚C.)

Thermal cut-out 95˚C (MG.)

 Below 75˚C

Above 95˚C

Closed circuit.

Thermal cut-out 125˚C (OVEN)

This is not resetable type. Above 125˚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 overheating produced by improper setting of the cooking time or failure of the control panel.

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 

Ω

Turntable motor

Approximately 12 k

Ω

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 monitored latch switch and monitor
switch.
If the fuse T6.3A is blown by incorrect door switching, replace the defective switch(s) 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 noise filter.
Using an ohmmeter, check between the terminals as described in
the following table.

Between N and L

Open circuit

Between terminal N and WHITE

Short circuit

Between terminal L and RED

Short circuit

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

CARRY OUT 4R CHECKS.

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

10

1. CARRY OUT 3D CHECKS.
2. Remove the control unit from the control panel.
3. By using an ohmmeter, check the tact switch operation.
4. When the tact switch is not depressed, an ohmmeter should indicate an open circuit. When the tact

switch is depressed, an ohmmeter should indicate a short circuit. If improper operation is indicated,
the tact switch is probably defective and should be checked.

5. CARRY OUT 4R CHECKS after test.

The control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike
conventional microwave ovens, proper maintenance can not be performed with only a voltmeter and
ohmmeter.
In this service manual, troubleshooting by replacement is described according to the symptoms
indicated.
1. Control Panel

The following symptoms indicate a defective control unit.

1-1  In connection with LEDs

a) At a certain LED, all or some LEDs do not light up.
b) At a certain LED, brightness is low.
c) Only one LED does not light up.
d) All or some LEDs continue to light up.
e) A certain group of LEDs do not light up.
f) The LEDs flicker.

1-2  Tact switch

a) When touching a tact switch, a tact switch produces no signal.

1-3  Other possible troubles caused by defective control unit.

a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.
c) Cooking time can not be set.
d) Power level can not be set.

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.

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin Nos. 3 and 5 of the 3 pin connector (A) on the
control unit with an A.C. voltmeter.
The meter should indicate 230-240 volts, if not check oven circuit.

Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.

DC. voltage indicated .......... Defective relay.
DC. voltage not indicated .... Check diode which is connected to the relay coil. If diode is good,

control unit is defective.

11

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

Approx. -11.4V D.C.

Oven lamp / Turntable motor / Fan motor

RY2

Approx. -11.0V D.C.

High voltage transformer

CARRY OUT 4R CHECKS.

To protect the electronic circuits, this model is provided with a fine foil pattern added to the input circuit
on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.

CARRY OUT 3D CHECKS.

STEPS

OCCURRENCE

CAUSE OR CORRECTION

1

The rated AC voltage is not present at

Check supply voltage and oven power cord.

Power terminal of CPU connector (CN-A).

2

The rated AC voltage is present at primary

Low voltage transformer or secondary circuit defective.

side of low voltage transformer.

Check and repair.

3

Only pattern at “a” is broken.

*Insert jumper wire J1 and solder.

µ

(CARRY OUT 3D CHECKS BEFORE REPAIR)

4

Pattern at “a” and “b” are broken.

*Insert the coil RCILF2003YAZZ between “c” and “d”.
(CARRY OUT 3D CHECKS BEFORE REPAIR)

NOTE: *At the time of these repairs, make a visual

inspection of the varistor for burning dam-
age and examine the transformer with
tester for the presence of layer short cir-
cuit (check primary coil resistance).
If any abnormal condition is detected,
replace the defective parts.

CARRY OUT 4R CHECKS.

(J1)

CN - A

1

5

1

P

T1

VRS1

RY1