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11

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 windings. The following readings should be
obtained:

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.

a. Primary winding ------------- approximately 1.2 

Ω

b. Secondary winding ---------- approximately 75 

Ω

c. Filament winding ---------------------- less than 1 

Ω

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

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

CARRY OUT 4R CHECKS.

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

12

3. CARRY OUT 4R CHECKS.

CAUTION: IF THE temperature fuse INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE,

REPLACE temperature fuse.

Open

Close

Display or

temperature

temperature

Condition

Check point

Magnetron tem-
perature fuse (Up-
per) TF1

Magnetron tem-
p e r a t u r e   f u s e
(Lower) TF2

Exhaust tempera-
ture fuse TF3

150˚C

120˚C

Non resetable
type

Non resetable
type

EE1

EE3

EE2

Oven shut
off

Magnetron MG1 Failure:
Test magnetron MG1 and Blower motor.

Magnetron MG1, MG2 Failure: Test magnetron MG1,
MG2. Check blower motor and ventilation opening.

Magnetron MG2 Failure:
Test magnetron MG2 and Blower motor.

Food has been burned in oven.
Temperature of oven inside is very high.

CARRY OUT 3D CHECKS.

If the weak point F3 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.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

If the fuse F1 F10A (or F2 F10A) is blown when the door is opened, check the interlock switch SW1
(or SW2) and monitor switch SW3 (or SW4).
If thefuse F1 F10A (or F2 F10A) is blown by incorrect door switching replace the defective switch(s)
and the fuse F1 F10A (or F2 F10A).

CARRY OUT 4R CHECKS.

CAUTION: Only replace fuse F1 F10A (or F2 F10A) with the correct value replacement.

1. CARRY OUT 3D CHECKS.
2. A continuity check across the temperature fuse terminals should indicate a closed circuit unless the

temperature of the temperature fuse reaches specfied temperature as shown below.

1. CARRY OUT 3D CHECKS.
2. Follow the procedures below for each thermistor.

2-1. THERMISTOR TEST
Disconnect the connector of the thermistor from the switch harness. Measure the resistance of the
magnetron thermistor with an ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.

Resistance:

Approx. 500 k

Ω -- 1 MΩ

If the meter does not indicate above resistance, replace the thermistor.
3. CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals.

Resistance of Blower motor should be approximately 60

Ω.

Resistance of Antenna motor should be approximately 8.8 k

Ω.

13

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

If incorrect readings are absorbed, replace the noise filter.

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

Approx. 680 k

Ω

Between terminal N and WHIT

Short circuit

Between terminal L and BLK

Short circuit

CARRY OUT 3D CHECKS.

If the high voltage fuse F4 (or F5) is blown, there could be a short in the  high voltage rectifier or the magnetron
MG1 (or MG2). Check them and replace the defective parts and the high voltage fuse F4 (or F5).

CARRY OUT 4R CHECKS.

F3 : WEAK POINT

NOISE FILTER

NOISE SUPPRESSION COIL

DISCHARGE RESISTOR 680 k

Ω 1/2W

DISCHARGE RESISTOR 10 M

Ω 1/2W

LINE CROSS CAPACITOR 0.22

µF/ AC250V

LINE CROSS CAPACITOR 

10000 pF/ AC250V

LINE CROSS CAPACITOR 

10000 pF/ AC250V

L

BLK

WHT

N

The touch control panel consists of circuits including semiconductors such as LSI 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 three
units, Control Unit,  Switch Unit and Encoder Unit troubleshooting by unit replacement is described
according to the symptoms indicated.
1. Switch Unit    Note : Check the lead wire harness connections among big and small switch units

and control unit before replacement.

The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the buttons, a certain button produces no signal at all.
b) When touching the buttons, sometimes a button produces no signal.

2. Encoder        Note : Check the lead wire connection between encoder and control unit before

replacement.

The following symptoms indicate a defective encoder. Replace the encoder.
a) When rotating the encoder, the cooking time can not be entered.

3. Control Unit

The following symptoms may indicate a defective control unit. Replacing the control unit. Before
replacing the control unit, perform the switch unit test (Procedure N) to determine if control unit is
faulty.

3-1 Programming problems.

a) When touching the buttons, a certain group of buttons do not produce a signal.

3-2 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.
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.

3-3 Other possible problems caused by defective control unit.

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

14

1. CARRY OUT 3D CHECKS.
2. Remove the switch unit from the control panel, referring to control panel removal.
3. To test the switches (SW1-SW5) on the switch unit, check between the terminals of the connector

CN-F as described in the following table by using ohmmeter when the switches are released and
depressed.

Switches

Terminals

Released

Depressed

SW1

F1 - F4

O.C.

S.C.

SW2

F1 - F5

O.C.

S.C.

SW3

F2 - F4

O.C.

S.C.

SW4

F2 - F5

O.C.

S.C.

SW5

F3 - F4

O.C.

S.C.

4. If incorrect readings are obtained, replace the defective switch.
5. CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

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

RY1, RY3 and RY4 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 ............................. Defective relay.
DC. voltage not indicated ....................... Check diode which is connected to the relay coil. If

diode is good, control unit is defective.

RY1

APPROX. 25.9V D.C.

Oven lamp, Blower motor and Antenna motors

RY3

APPROX. 25.0V D.C.

High voltage transformer (MG1)

RY4

APPROX. 25.0V D.C.

High voltage transformer (MG2)

CARRY OUT 4R CHECKS.

To protect the electronic circuits, this model is provided with a fine fuse added to the primary on
the PWB. If the fuse 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

Touch control transformer or secondary circuit defective.

side of touch control transformer.

Check and repair.

3

Fuse on the PWB is open.

Replace the fuse with new one.
(CARRY OUT 3D CHECKS BEFORE REPAIR)

NOTE: *At the time of these repairs, make a visual inspection of the varistor for burning damage

and examine the transformer with tester for the presence of layer short-circuit (check
primary coil resistance). If any abnormal condition is detected, replace the defective parts.

CARRY OUT 4R CHECKS.

O.C. ----- Open Circuit
S.C. ----- Short Circuit