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11

Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be tested using
an ohmmeter set to its highest range. Connect the ohmmeter across the terminals A + B of the asymmetric
rectifier and note the reading obtained. Reverse the meter leads and note this second reading. If an open
circuit is indicated in both directions then the asymmetric rectifier is good. If an asymmetric rectifier is
shorted in either direction, then the asymmetric rectifier is probably faulty and must be replaced with the
high voltage rectifier. When the asymmetric rectifier is defective, check whether magnetron, high voltage
rectifier, high voltage wire or filament winding of the power transformer is shorted.

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 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 readings 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.

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

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

Table: Thermal Cut-out Test

PARTS NAME

THERMAL CUT-OUT

THERMAL CUT-OUT

THERMAL CUT-OUT

   Condition

125

°

C (MAG)

150

°

C (GRILL)

160

°

C (OVEN)

Temperature of ”ON” condition

This is not resetable type

130

°

C

This is not resetable type

(closed circuit)

Temperature of ”OFF” condition

Above 125

°

C

Above 150

°

C

Above 160

°

C

(open circuit)

Indication of ohmmeter (When room

Closed circuit

Closed circuit

Closed circuit

temperature is approx. 20

°

C.)

If incorrect readings are obtained replace the thermal cut-out.

12

An open circuit thermal cut-out (MG) indicates that 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 unproper setting of the cooking timer or failure of the control panel.

An open circuit thermal cut-out (GRILL) indicates that the oven cavity has overheated, this may be due to
no load operation.

CARRY OUT 3D CHECKS

If the fuse 13A  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.

CARRY OUT 4R CHECKS

CARRY OUT 3D CHECKS

1. If the fuse M8A  is blown when the door is opened, check the primary latch switch, monitor switch and

monitor resistor.
If the fuse  M8A is blown by incorrect door switching replace the defective switch(s) and the fuse  M8A.

2. If the fuse M8A  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 occured 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.

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

Approx. 680K ohm

Between terminal N and WHITE

Short circuit

Between terminal L and RED

Short circuit

R1: 10M ohm 

±

 20%

R2: 680K ohm 

±

 20%

L(min)

Cx 

±

 20%

Cv 

±

 20%

1.0mH

0.22

µ

F

0.0047

µ

F

RED

WHT

L

L

R1

L

F6.3A

R2

N

Cx

Cy

M8A

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

CARRY OUT 4R CHECKS

CARRY OUT 3D CHECKS

Disconnect the leads from the monitor resistor.
Using an ohmmeter and set on a low range.
Check between the terminals of the monitor resistor as described in the following table.

13

If incorrect readings are obtained, replace the monitor resistor.

CARRY OUT 4R CHECKS

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 200

Ω

Turntable motor

Approximately 15.5k

Ω

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS

Table: Resistance

Resistor

Resistance

Monitor resistor

 Approx. 0.8

Ω

CARRY OUT 3D CHECKS

Before carrying out the following tests make sure the heating element is cool completely.
1. Resistance of heating element

Disconnect the wire leads to the heating element to be tested. Using ohmmeter with low resistance
range. Check the resistance across the terminals of the heating element as described in the following
table.

Table: Resistance of heating element

Parts name

Resistance

Grill heater

Approximately 29

Ω

 x 2 = 58

Ω

2. Insulation resistance

Disconnect the wire leads to the heater element to be tested, Check the insulation resistance
between the element terminal and cavity using a 500V - 100M

Ω

 insulation tester. The insulation

resistance should be more than 10M

Ω

 in the cold start.

If the results of above test 1 and/or 2 are out of above specifications, the heater is probably faulty and
sholud be replaced.

CARRY OUT 4R CHECKS

The touch control panel consists of circuits including semiconductors such as LSI, ICs, 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, and troubleshooting by replacement is described according to the symptoms indicated.
1.  Key Unit

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 a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.

2.  Control Unit

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

14

2-1  In connection with pads.

a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.

2-2  In connection with indicators

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.
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) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtainned.

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. Close the door.
4. Reconnect the supply.
5. Check  the 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 indicat 240 volts, if not check oven circuit.

6. RY1, RY2 AND RY3 TEST
    These 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. 25.0V.D.C.

  Oven lamp / Turntable motor / Cooling fan motor

  RY2

  Approx. 25.0V.D.C.

  Power transformer

  RY3

  Approx. 25.0V.D.C.

  Grill heater

 CARRY OUT 4R CHECKS

If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon is making
good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are
closed closed when the door is closed and open when the door is open. If the door sensing switch (stop
switch) is good, disconnect the flat ribbon cable that connects the key unit to the control unit and make sure
the door sensing switch is closed (either close the door or short the door sensing switch connecter). Use
the Key unit matrix indicated on the STOP/CLEAR pad making momentary contact. If the control unit
responds by clearing with a beep the key unit is faulty and must be replaced. If the control unit does not

respond, itis a faulty and
must be replaced. If a spe-
cific pad does not re-
spond, the above method
may be used (after clear-
ing the control unit) to
determine if the control
unit or key pad is at fault.

KEY UNIT

G-8

G-7

G-6

G-5

G-4

G-3

G-2

G-1

G-9

G-10

G-11

G-12

10

SEC.

1

MIN.

10

MIN.

STOP

CLEAR

DUAL

COOK

GRILL

AUTO

MINUTE

START

AUTO

DEFROST

AUTO

COOK

MORE

LESS

g • oz

Kg • Lb

AUTO

START

Kg / Lb

POWER

LEVEL

TIMER
/HOLD

INSTANT

COOK