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R1900M

9 – 1

R1900M

Service Manual

 

Please refer to “OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS”, when carrying out any of the following removal proce-
dures:

To remove the components, procedure as follows.

1. Disconnect the oven form the power supply.

2. Open the door and wedge it open.

3. Remove the eleven (11) screws from the rear and along side the

edge of the outer case.

NOTE: Do not lose the support angle at this time.

4. Slide the case back about 1 inch (3 cm) to free it from the oven cav-

ity.

5. Lift entire case from the unit.

6. DISCHARGE TWO HIGH VOLTAGE CAPACITORS BEFORE

7. Now, outer case is free.

NOTE: Step 1, 2 and 6 form the basis of the 3D checks. 

8. Remove the four (4) screws holding the magnetron exhaust cover

to the rear cover.

NOTE: The magnetron exhaust cover can not be removed from the

rear cover.

9. Disconnect the connector of the fan motor from the connector of

harness.

Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following parts may result
in severe, possibly fatal, electric shock.
(Example)
High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..

1. Disconnect the power supply cord.
2. Make sure that a definite "click" can be heard when the

microwave oven door is unlatched. (Hold the door in a
closed position with one hand, then pull the door handle
lever with the other, this causes the latch leads to rise, it is
then possible to hear a "click" as the door switches
operate.)

3. Visually check the door and cavity face plate for damage

(dents, cracks, signs of arcing etc.).

Carry out any remedial work that is necessary before operat-

ing the oven.

Do not operate the oven if any of the following conditions exist;
1. Door does not close firmly.

2. Door hinge, support or latch hook is damaged.
3. The door gasket or seal is damaged.
4. The door is bent or warped.
5. There are defective parts in the door interlock system.
6. There are defective parts in the microwave generating

and transmission assembly.

7. There is visible damage to the oven.

Do not operate the oven:
1. Without the RF gasket (Magnetron).
2. If the wave guide or oven cavity are not intact.
3. If the door is not closed.
4. If the outer case (cabinet) is not fitted.

tions.
1. Before wiring,

1) Disconnect the power supply cord.
2) Open the door block it open.
3) Discharge the two high voltage capacitor and wait for

60 seconds.

2. Don't let the wire leads touch to the following parts;

1) High voltage parts:

Magnetron, Power transformer, High voltage
capacitor, High voltage rectifier assembly and High
voltage wire.

2) Hot parts:

Oven lamp, Magnetron, Power transformer and

3) Sharp edge:

Bottom plate, Oven cavity, Waveguide flange Chassis
support and other metallic plate.

4) Movable parts (to prevent a fault)

Blower fan blade, Blower fan motor, Switches, Switch
levers, Antenna motor and Stirrer antennas.

3. Do not catch the wire leads in the outer case cabinet.
4. Insert the positive lock connector until its pin is locked and

make sure that the wire leads do not come off even if the
wire leads are pulled.

5. To prevent an error function, connect the wire leads

correctly, referring to the Pictorial Diagram.

Oven cavity.

R1900M

9 – 2

10.Remove the six (6) screws holding the rear cover and exhaust

cover to the bottom plate, power supply cord angle, intake duct and
exhaust duct.

11.Remove the rear cover with the fan motor and exhaust cover from

the oven cavity.

12.Now, the rear cover with the fan motor and exhaust cover is free.

NOTE: Do not forget to re-connect the wire leads to the exhaust fan

when the rear cover and outer case cabinet are reinstalled.

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Disconnect the main wire harness from power transformers (1)

and/or (2).

4. Disconnect wire leads of power transformers (1) and/or (2) from

magnetrons (1) and/or (2).

5. Disconnect wire leads of power transformers (1) and/or (2)from

high voltage capacitors (1) and/or (2).

6. Remove two (2) screws holding each power transformer (1) and/or

(2) to base plate.

7. Remove the power transformers (1) and/or (2) from base plate.

8. Now, power transformers (1) and/or (2) are free.

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Disconnect the connector of the magnetron thermistor assembly

from the connector of the harness.

4. Remove the magnetron thermistor assembly from magnetrons.

5. Disconnect wire leads from magnetrons (1) and/or (2).

6. Remove the two (2) screws holding the bottom cover to the bottom

plate assembly.

7. Remove the bottom cover from the bottom plate assembly.

8. Remove the four (4) screws holding each magnetron (1) and/or (2)

to upper and/or lower waveguide. When removing the screws, hold
the magnetron to prevent it from falling.

9. Remove the magnetrons (1) and/or (2) from upper and/or lower

waveguide with care so magnetron antenna is not hit by any metal
object around antenna.

10.Remove the two (2) screws holding the partition plate S to each

magnetron (1) and/or (2).

11.Remove the two (2) partition plate S from each magnetron (1) and/

or (2).

12.Now, the magnetrons (1) and/or (2) are free.

CAUTION: WHEN REPLACING MAGNETRON, BE SURE THE R.F.

GASKET IS IN PLACE AND MOUNTING SCREWS ARE
TIGHTENED SECURELY.

NOTE: Whenever the magnetron is replaced, replace the weak point

for fan motor, too.

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Disconnect the connector of the magnetron thermistor assembly

from the capacitor of the harness.

4. Remove the snap band of magnetron thermistor assembly from the

hole of the partition cover by pulling out.

5. Remove the magnetron thermistor assembly from the two (2) mag-

netrons.

6. Now, the magnetron thermistor assembly is free.

1. Insert the magnetron thermistor assembly to the magnetron as

shown in Figure C-1 and push it until the thermistor assembly
stops.

i)

The tabs of the magnetron thermistor assembly should be
inserted between the 2nd. fin and 3rd. fin.

ii) The thermistor should be inserted between the 1st. fin and 2nd.

fin.

iii) And also the thermistor should be inserted center of the right

and left walls of the magnetron.

2. Re-install the rear cover and outer case cabinet to the oven by

reversing the procedures of “OUTER CASE AND REAR COVER
REMOVAL”.

NOTE: Do not forget to re-connect the wire leads to the fan motor.

Figure C-1. Magnetron thermistor installation

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Remove the two (2) screws holding the capacitor unit angle to the

intake duct assembly or the exhaust duct assembly.

4. Remove one (1) screw holding the capacitor band to capacitor unit

angle. 

5. Remove one (1) screw holding earth side terminals of high voltage

rectifier assembly to the capacitor band.

Magnetron

Magnetron
thermistor
assembly

Center

Right wall

Left wall

Thermistor

1st. fin

2nd. fin

3rd. fin

Tab

Tab

R1900M

9 – 3

6. Remove the capacitor band from the high voltage capacitor.

7. Disconnect all wire leads from the high voltage capacitor.

8. Now, the capacitor (1) or (2) and the high voltage rectifier assembly

are free.

CAUTION: 1) DISCHARGE THE TWO HIGH VOLTAGE CAPACITOR

BEFORE TOUCHING ANY OVEN COMPONENTS OR
WIRING.

2) DO NOT REPLACE ONLY THE HIGH VOLTAGE REC-

TIFIER. IF IT IS DEFECTIVE, REPLACE THE HIGH
VOLTAGE RECTIFIER ASSEMBLY.

3) WHEN REPLACING THE HIGH VOLTAGE RECTIFIER

ASSEMBLY AND THE HIGH VOLTAGE CAPACITOR,
THE EARTH SIDE TERMINAL OF THE HIGH VOLT-
AGE RECTIFIER MUST BE SECURED FIRMLY WITH
A EARTHING SCREW.

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Remove the one (1) screw holding the earth wire of the power sup-

ply cord to the oven cavity.

4. Disconnect the wire leads of the power supply cord from the noise

filter.

5. Remove the one (1) screw holding the power supply cord angle to

the capacitor unit angle.

6. Remove the power supply cord angle with the power supply cord

from the capacitor unit angle.

7. Nip the cord bushing with the bushing pliers and release it from the

power supply cord angle.

8. Remove the cord bushing with the power supply cord from the

power supply cord angle.

9. Remove the cord bushing from the power supply cord.

10.Now, the power supply cord is free.

1. Install the cord bushing to the power supply cord so that the lock tie

on the power supply cord surface comes to the end of the cord
bushing as shown in the.Figure C-2.

2. Install the cord bushing (with the power supply cord) into the hole of

the power supply cord angle with the bushing pliers.

3. Reinstall the power supply cord angle to the capacitor unit angle

with the one (1) screw.

4. Install the earth wire of the power supply cord to the oven cavity

with the one (1) screw.

5. Connect the brown wire lead of the power supply cord to the source

side upper terminal of the noise filter.

6. Connect the blue wire lead of the power supply cord to the source

side lower terminal of the noise filter.

7. Reinstall the rear cover, the magnetron exhaust cover and the

outer case cabinet and check that the oven is operating properly.

Figure C-2(a) Cord bushing position

Figure C-2(b) Wiring to the noise filter

1. CARRY OUT 3D CHECKS.

2. Push the lever of positive lock

 connector, pull down the connector

from terminal. 

3. Now, the connector is free.

CAUTION: THE POSITIVE LOCKR TERMINAL CAN NOT BE

REMOVED BYJUST PULLING ON IT. THE LOCK LEVER
MUST BE RELEASED TO REMOVE THE CONNECTOR
FROM THE TERMINAL.

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Make sure that the connector of the exhaust fan has been discon-

nected from the wire harness.

4. Remove the four (4) screws and the two (2) nuts holding the

exhaust fan.

5. Now, the exhaust fan is free.

Cord bushing

Lock tie

Power supply cord

Green/ Yellow wire of power supply cord

Gray/ White wire

Brown wire of

power supply cord

Blue wire of

power supply cord

Noise filter

Black wire

Terminal

Push

Pull down

1

Lever

Positive lock

R

connector

Figure C-3. How to release the positive lock

R

connector

2

R1900M

9 – 4

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Disconnect the connector of the fan motor from the connector of

the wire harness.

4. Remove the three (3) screws holding the fan motor to the motor fix-

ing angle and magnetron cool duct A.

5. Release the wire leads of the fan motor from the wire holder.

6. Remove the fan motor from the oven cavity.

7. Now, the fan motor is free.

1. CARRY OUT 3D CHECKS.

2. Remove the rear cover. 

3. Disconnect the wire leads from the antenna motor (upper).

4. Remove the one (1) screw holding the antenna motor (upper) to the

oven cavity.

5. Turn and lift up the antenna motor (upper).

6. Now, the antenna motor (upper) is free.

1. Disconnect the oven from the power supply.

2. Remove the two (2) screws holding the motor protect cover to the

bottom plate assembly.

3. Remove the motor protect cover from the bottom plate assembly.

4. Disconnect the wire leads from the antenna motor (lower).

5. Remove the one (1) screw holding the antenna motor (Lower) to

the oven cavity.

6. Now, the antenna motor (lower) is free.

1. CARRY OUT 3D CHECKS.

2. Disconnect all wire leads and connectors from the power unit.

3. Remove the four (4) screws holding the power unit to the PWB

holder.

4. Now, the power unit is free.

1. CARRY OUT 3D CHECKS.

2. Disconnect all connectors from the control unit.

3. Remove the vinyl tape with a cushion attached to the oven cavity

face plate and the control panel case.

4. Remove three (3) screws holding the control panel to the oven cav-

ity face plate.

5. Now the control panel assembly is free.

6. Remove five (5) screws holding the control unit to the panel fixing

plate.

7. Remove the CPU protect sheet from the control unit.

8. Now, the control unit is free.

CAUTION: When installing the control unit into the control panel frame:

1) Be careful not to damage any of the components on the

control unit.

2) When inserting key units ribbon cable through the

frame, ensure it is not pinched or bent.

NOTE: 1) Before attaching a new key unit, remove remaining adhe-

sive on the panel fixing plate surfaces completely with a
soft cloth soaked in alcohol.

2) When attaching the key unit to the panel fixing plate, adjust

the lower edge and left edge of the key unit to the correct
position of panel fixing plate.

3) Stick the key unit firmly to the panel fixing plate by rubbing

with soft cloth to prevent scratching.

4) When the control unit is replaced, set the standard voltage

referring to Special function pages.

5) Attach the vinyl tape and the cushion to the oven cavity

face plate and the control panel case after the control panel
assembly is installed.

1. CARRY OUT 3D CHECKS.

2. Disconnect all wire leads and connectors from the power unit and

the relay unit.

3. Remove the four (4) screws holding the PWB holder to the oven

cavity top plate and the noise filter angle.

4. Remove the PWB holder with the power unit and the relay unit from

the oven cavity.

5. Remove the six (6) screws holding the relay unit to the PWB holder.

6. Remove the relay unit from the PWB holder.

7. Now, the relay unit is free.

Control panel case

Cushion

Vinyl tape
(W 20mm x L 520mm)

Cavity front
plate