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R-212M 9

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 .......................... 2.4 ohms approximately
b. Secondary winding .................... 130 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 10M

Ω

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.

R-212M 10

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.

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

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.

following table.

CARRY OUT 3D CHECKS.

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

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

2. If the fuse F1 is blown when the door is opened, check the monitored latch switch and monitor switch.

If the fuse F1 is blown by incorrect door switching replace the defective switch(es) and the  fuse F8A.

CARRY OUT 4R CHECKS.

R-212M 11

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 360 

Ω

Turntable motor

Approximately 12 - 15 k

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 high voltage transformer. Make sure that the leads

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

3. Connect the 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) minute.
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 the test meter leads.
10.Reconnect the leads to the primary of the high voltage 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 the no supply was present then the winding to the motor
should be checked for continuity.

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 obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.

F1: FUSE

    F8A

N

L

0.22

µ

/AC250V 

680K/ 0.5W 

10M/ 0.5W 

NOISE 
SUPPRESSION COIL 

0.0033

µ

/ 250V

0.0033

µ

/ 250V

NOISE FILTER

RED

WHT

R-212M 12

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.

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.

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.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

Approx. 12.0V D.C.

Oven lamp / Turntable motor / Fan motor

RY2

Approx. 11.0V D.C.

High voltage transformer

CARRY OUT 4R CHECKS.