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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.

R-22AT

R-23AM, R-24AT

a. Primary winding

approximately 1.8 

Ω

approximately 1.2 

Ω

b. Secondary winding

approximately 75 

Ω

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 10M

Ω

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.

12

CARRY OUT 3D CHECKS.

If the fuses F3 and/or F4 M8A are blown, there could be shorts in the high voltage transformers T1 and/
or T2 or there is a ground in wire harness. Check and/ or replace the high voltage transformers T1 and/
or T2 or repair the wire harness.

CARRY OUT 4R CHECKS.

fuses F3, F4 M8A

CARRY OUT 3D CHECKS.

If the fuse F1 F13A 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.

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.

If the fuse F2 F6.3A is blown when the door is opened, check the 1st. latch switch SW1, monitor switch
SW4 and monitor resistor R1.
If the fuse F2 F6.3A is blown by incorrect door switching replace the defective switch(s) and the fuse
F2 F6.3A.

CARRY OUT 4R CHECKS.

CAUTION: Only replace fuse F2 F6.3A 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.

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 TF1

Magnetron tem-
perature fuse TF2

Blower motor tem-
perature fuse TF3

Oven temperature
fuse TF4

150˚C

120˚C

120˚C

Non resetable
type

Non resetable
type

Non resetable
type

EE1

EE3

EE2

Oven shut
off

Oven shut
off

Magnetron MG1 Failure:
Test magnetron MG1 and Blower fan motor.

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

Magnetron MG2 Failure:
Test magnetron MG2 and Blower fan motor.

Check blower fan motor and ventilation opening or
rocked rotating of blower fan motor.

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

13

CARRY OUT 3D CHECKS.

Disconnect the leads from the monitor resistor R1. Using an ohmmeter and set on a low range. Check
between the terminals of the monitor resistor R1.

The resistance of monitor resistor R1 should be read approx. 4.3

Ω

.

If incorrect readings are obtained, replace the monitor resistor R1.

CARRY OUT 4R CHECKS.

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

2-1. MAGNETRON THERMISTOR TEST
Disconnect the connector of the magnetron 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.

Room Temp.

59˚F (15˚C)

68˚F (20˚C)

77˚F (25˚C)

Resistance

Approx. 373 k

Ω

Approx. 292 k

Ω

Approx. 231 k

Ω

If the meter does not indicate above resistance, replace the thermistor.

2-2. OVEN THERMISTOR (1) TEST

Disconnect the connector of the oven thermistor (1) from the switch harness. Measure the resistance
of the oven thermistor (1) with an ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.

Room Temp.

59˚F (15˚C)

68˚F (20˚C)

77˚F (25˚C)

Resistance

Approx. 373 k

Ω

Approx. 292 k

Ω

Approx. 231 k

Ω

If the meter does not indicate above resistance, replace the thermistor.

2-3. OVEN THERMISTOR (2) TEST

Disconnect the two connectors of the magnetron thermistor and oven thermistor (2) from the switch
harness. Measure the resistance of the oven thermistor (2) with an ohmmeter. Connect the ohmmeter
leads to the leads of the thermistor.

Room Temp.

59˚F (15˚C)

68˚F (20˚C)

77˚F (25˚C)

 Resistance

Approx. 16 k

Ω

Approx. 13 k

Ω

Approx. 11 k

Ω

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 52

Ω

.

Resistance of Stirrer motor should be approximately 8.8 k

Ω

.

If incorrect readings are obtained, replace the motor.

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.

14

The touch control panel consists of circuits including semiconductors such as LSI, IC, 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 two units,
Control Unit and Key Unit, troubleshooting by unit replacement is described according to the symptoms
indicated.
1. Key Unit     Note : Check key unit ribbon connection before replacement.

The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching the pads, sometimes a pad produces no signal.

2. Control Unit

The following symptoms may indicate a defective control unit. Replacing the control unit. Before

replacing the control unit, perform the key unit test (Procedure P) to determine if control unit is faulty.

2-1 Programming problems.

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

2-2 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.

2-3 Other possible problems caused by defective control unit.

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

The 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.

Between N and L

Approx. 680 k

Ω

Between terminal N and WHIT

Short circuit

Between terminal L and BLK

Short circuit

If incorrect readings are absorbed, replace the noise filter.

CARRY OUT 4R CHECKS.

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.

F1 : FUSE F13A

NOISE FILTER

NOISE SUPPRESSION COIL

DISCHARGE RESISTOR 680 k

Ω

 1/2W

DISCHARGE RESISTOR 10 M

Ω

 1/2W

LINE CROSS CAPACITOR 0.22

µ

F/ AC250V

LINE CROSS CAPACITOR 

10000 pF/ AC250V

LINE CROSS CAPACITOR 

10000 pF/ AC250V

L

BLK

WHT

N