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R-334 - 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 below.

CARRY OUT 4R CHECKS

Temperature of ”ON” condition (closed circuit) ...................................................................

 This is not resetable type

Temperature of ”OFF” condition (open circuit) ....................................................................................

 Above 125

°

C

Indication of ohmmeter (When room temperature is approx. 20

°

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
restricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.

An open circuit thermal cut-out (OVEN) indicates that the foods in the oven 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 3D CHECKS

1. If the special fuse F1 is blown, there could be shorts or grounds in electrical parts or wire harness.

Check them and replace the defective parts or repair the wire harness.

2. If the special fuse F1 is blown, there could be a short in the asymmetric rectifier or there is a ground

in wire harness.  A short in the asymmetric rectifier may have occurred due to short or ground in H.V.
rectifier, magnetron, power transformer or H.V. wire. Check them and replace the defective parts or
repair the wire harness.

3. If the fuse  F1  8A is blown when the door is opened, check the primary latch switch and monitor switch.

If the fuse F1  8A is blown by incorrect door switching replace the defective switch(s) and the fuse
F1  8A.

CARRY OUT 4R CHECKS

CARRY OUT 3D CHECKS

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

Between N and L

>100M

Ω

 ohm

Between terminal N and WHITE

Short circuit

Between terminal L and RED

Short circuit

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

CARRY OUT 4R CHECKS

L(min)

Cx 

±

 20%

Cy 

±

 20%

1mH

0.22

µ

F

0.0033

µ

F

RED

WHT

L

L

L

F8A

N

Cx

Cy

R2

R1

R1 = 10M

Ω

 

±

 5%

R2 = 680K

Ω

 

±

 5%

R-334 - 18

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 218

Ω

Turntable motor

Approximately 15.5k

Ω

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS

1. CARRY OUT 3D CHECKS
2. Disconnect the leads from the primary of the power transformer. Make sure that the leads remain

isolated from other oven components and chassis. (Use insulation tape if necessary.)

3. Connect a voltmeter, set to 250V AC, across the motor terminals. (Refer to the relevant motor test

procedure or pictorial diagram for the correct terminal numbers.)

4. Arrange the meter in a position where it can be read during the test.

(Do not touch the meter, meter leads or oven circuitry while the oven is active.)

5. Close the oven door.
6. Set the power level to HIGH and set the relevant timer for about three (3) minutes.
7. Note the reading on the meter and carefully observe the motor under test to see if it is turning.
8. CARRY OUT 3D CHECKS
9. Remove test meter leads.
10. Reconnect the leads to the primary of the power transformer.

If a reading of the line voltage was obtained (step 7) but the motor was not turning then it is faulty and
should be replaced. If the meter indicated that no supply was present then the wiring to the motor should
be checked for continuity.

Do not touch the electrical parts and the printed wiring board to prevent an electric

shock. Because the control unit is " TRANSLESS CIRCUIT " and all electrical parts
are used at A.C. line voltage.

The touch 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, the touch control panel assembly is in one unit and troubleshooting by unit
replacement is described according to the symptoms indicated.
Control Panel.

The following symptoms indicate a defective control unit.

1.  Tact Switch.

The following symptoms indicate a defective tact switch. Replace the tact switch.

a) When touching a tact switch, a certain tact switch produces no signal at all.
b) When touching a tact switch, sometimes a tact switch produces no signal.

2. In connection with tact switches.

a) When touching a tact switch, a certain group of tact switch do not produce a signal.
b) When touching a tact switch, no tact switch produce a signal.

3. Display problems.

a) At a certain digit, all or some segments do not light up.
b) At 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.

R-334 - 19

e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
h)  When touching a tact switch, the control unit does not respond.

4. Other possible problems caused by defective control unit.

a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.

1. Disconnect the oven from the power supply.
2. Discharge the high voltage capacitor.
3. Remove the control unit from the control panel.
4. By using an ohmmeter, check the tact switch operation.
5. 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.

Remove the outer case and check voltage between Pin No 5 of the 3 pin connector (A) and common
terminal of the relay (RY2) on the control unit with an A.C. voltmeter.
The meter should indicate rated voltage, if not check oven circuit.

RY1 and RY2 Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.

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

control unit or relay is defective.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

Approx. 24.0V D.C.

Oven lamp / Turntable motor / Cooling fan motor

RY2

Approx. 12.0V D.C.

Power transformer

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.

STEPS

OCCURRENCE

CAUSE OR CORRECTION

1

The rated voltage is not applied between Pin

Check supply voltage and oven power cord.

No. 5 of the 3 pin connector (A) and the

common terminal of the relay RY2.

2

Only pattern at "a" is broken.

*Insert jumper wire J1 and solder.

3

Pattern at "a" and "b" are broken.

*Insert the coil RCILF2003YAZZ between "c" and "d".

NOTE: *At the time of making these repairs,

make a visual inspection of the
varistor. Check for burned damage.
If any abnormal condition is detected,
replace the defective parts.

1

5

RY2

(J1)

CN-A 

RY1

D1

VRS1

D71

ZD71

R-334 - 20

The touch control section consists of the following circuits
as shown in the touch control panel circuit.

The principal functions of these circuits and their related
signals are explained below.

Tact Switch
Signals generated in the LSI are sent to the tact switches
through R60, R61,R62 and R63.
When a tact switch is touched, a signal is completed
through the tact switch and passed back to the LSI
through R81 to perform the function that was requested.

Control Unit
Control unit consists of LSI, ACL circuit, indicator circuit,
power source circuit, relay circuit, buzzer circuit, synchro-
nizing signal circuit and back light circuit.

This circuit generates a signal which resets the LSI to
the initial state when power is supplied.

This circuit consists of 4-digits, 12-segments and
3-common electrodes using a Liquid Crystal Display.

This circuit generates voltage necessary in the control
unit from the AC line voltage.

Symbol

Voltage

Application

VC

+5V

LSI(IC1)

To drive the magnetron, fan motor, turntable motor and
light the oven lamp.

The buzzer is responsive to signals from the LSI to emit
audible sounds (key touch sound and completion sound).

The power source synchronizing signal is available in
order to compose a basic standard time in the clock
circuit. It accompanies a very small error because it
works on commercial frequency.

A switch to "tell" the LSI if the door is open or closed.

The encoder converts the signal generated by LSI into
the pulse signal, and the pulse signal is returned to the
LSI.

A circuit to drive the back light (Light emitting diodes
LED1-LED3)