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R-234 - 13

6. Measure the final water temperature. (Example: The final temperature T2 = 21

°

C)

7. Calculate the microwave power output P in watts from above formula.

Initial temperature  T1 = 11

°

C

Temperature after (52+ 3) = 55 sec. .............................................................................  T2 = 21

°

C

Temperature difference Cold-Warm ............................................................................  

∆

T1 = 10

°

C

Measured output power
The equation is “P = 80 x 

∆

T” ............................................................... P = 80 x 10

°

C = 800Watts

±

CAUTION: 1

°

C CORRESPONDS TO 80  WATTS. REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

Heat up for 55 sec.

CARRY OUT 3D CHECKS

Disconnect the leads to the primary winding of the power 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 windings. The following readings should be obtained:-

a. Primary winding ............ 2.3 ohms approximately
b. Secondary winding ....... 140 ohms approximately
c. Filament winding ........... less than 1 ohm

If the reading obtained are not as stated above, then the power transformer is probably faulty and should
be replaced.

CARRY OUT 4R CHECKS

1000g

1000g

1000g

R-234 - 14

CARRY OUT 3D CHECKS

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

COM;

Common terminal

NO;

Normally open terminal

NC;

Normally close terminal

Table: Terminal Connection of Switch

Plunger Operation

COM to NO

COM to NC

Released

Open circuit

Short circuit

Depressed

Short circuit

Open Circuit

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

CARRY OUT 4R CHECKS.

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 10 M

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 10 M

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

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.

R-234 - 15

CARRY OUT 3D CHECKS

1. If the fuse F1is 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 F1 is blown, there could be short to  ground in wire harness.  Check them and replace the

defective parts or repair the wire harness.

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 foods in the oven may have caught fire, this
may be due to over heating produced by unproper setting of the cooking timer or failure of the control
panel.

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

Open circuit

Between terminal N and WHITE

Short circuit

Between terminal L and RED

Short circuit

Rx 

±

5%

L(min)

Cx 

±

 20%

Cy 

±

 20%

Ry 

±

5%

680k

Ω

1.0mH

0.22

µ

F

0.0033

µ

F

10M

Ω

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

CARRY OUT 4R CHECKS

Cx

Cy

Rx

Ry

Cy

L

L

RED

WHT

 F8A

L

N

R-234 - 16

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.
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.

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.

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 800W 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.