DOWNLOAD Sharp R-874 (serv.man3) Service Manual ↓ Size: 429.78 KB | Pages: 13 in PDF or view online for FREE

R-874M - 24

9. Discharge the H.V. capacitor before carrying out any

further work.

10.Do not operate the oven with the outer case removed.
N.B.; Step 1, 2 and 9 form the basis of the 3D checks.

CAUTION: DISCHARGE HIGH VOLTAGE CAPACI-

TOR BEFORE TOUCHING ANY OVEN
COMPONENT OR WIRING.

CAUTION: WHEN THE OUTER CASE CABINET IS

RE-INSTALLED, INSTALL IT BEFORE THE
BACK PLATE IS INSTALLED, OR THE
OUTER CASE CABINET WILL BE DE-
FORMED.

1. Disconnect oven from power supply.
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 push the door open
button 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 dam-

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

Carry out any remedial work that is necessary before
operating 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 or 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.

Please refer to ‘OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS’, when carrying out any
of the following removal procedures:

To prevent an electric shock, take the following
manners.
1. Before wiring,

1) Disconnect the power supply.
2) Open the door and wedge the door open.
3) Discharge the 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, High voltage transformer, High volt-
age capacitor and High voltage rectifier assem-
bly.

2) Hot parts:

Top heating element, Bottom heating element,

Oven lamp, Magnetron, High voltage transformer
and Oven cavity.

3) Sharp edge:

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

4) Movable parts (to prevent a fault)

Fan blade, Fan motor, Switch, Open lever, Open
button,Turntable motor, Convection motor.

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

is locked. And make sure that the wire leads should
not  come off even if the wire leads is pulled.

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

correctly, referring to the Pictorial Diagram.

voltage capacitor.

3. Disconnect the high voltage wire B from the magnetron.
4. Remove one (1) screw holding earth side terminal of

the high voltage rectifier assembly.

To remove the outer case proceed as follows.
1. Disconnect oven from power supply.
2. Open the oven door and wedge it open.
3. Remove the two (2) screws holding the back plate to

the oven cavity rear plate. Remove the back plate

4. Remove the one (1) screw holding the air duct assem-

bly to the oven cavity rear plate.

5. Remove the air duct assembly
6. Remove the eight (8) screws from rear and along the

side edge of case.

7. Slide the entire case back about 3 cm to free it from

retaining clips on the cavity face plate.

8. Lift the entire case from the oven.

To remove the components, proceed as follows.
1. CARRY OUT 3D CHECKS.
2. Disconnect the filament lead of the high voltage trans-

former and the high voltage wire A from the high

R-874 S/MANUAL

11/7/01, 10:59 am

24

R-874M - 25

1. CARRY OUT 3D CHECKS.
2. Disconnect the filament leads of high voltage trans-

former from high voltage capacitor and the magnetron.

3. Disconnect the H.V. wire A from the high voltage

transformer.

4. Disconnect the main wire harness from the high volt-

age transformer.

5. Remove the two (2) screws and one (1) washer holding

the transformer to the base plate.

7. Remove the transformer.
8. Now the high voltage transformer is free.

1. CARRY OUT 3D CHECKS.
2. Disconnect the H.V. wire B and filament lead of the

transformer from the magnetron.

3. Remove the one (1) screw holding the chassis support

to the magnetron.

4. Move the air intake duct to left.
5. Carefully remove four (4) screws holding the magnetron

to the waveguide, when removing the screws hold the

magnetron to prevent it from falling.

6. Remove the magnetron from the waveguide with care

so the magnetron antenna is not hit by any metal object
around the antenna.

CAUTION: WHEN REPLACING THE MAGNETRON,

BE SURE THE R.F. GASKET IS IN PLACE
AND THE MAGNETRON MOUNTING
SCREWS ARE TIGHTENED SECURELY.

adhesive on the control panel frame surfaces com-
pletely with a soft cloth soaked in alcohol.

2. When attaching the key unit to the control panel frame,

adjust the upper edge and right edge of the key unit to
the correct position of  control panel frame.

3. Stick the key unit firmly to the control panel frame by

rubbing with soft cloth not to scratch.

1. CARRY OUT 3D CHECKS.
2. Disconnect the wire leads and the connectors from the

control unit.

3. Lift up the control panel assembly and pull it forward.

Now the control panel assembly is free.

NOTE:
1. Before attaching a new key unit, wipe off remaining

2) Remove the fan blade assembly from the shaft of

the fan motor by pulling and rotating the fan blade
with your hand.

3) Now, the fan blade is free.

12.Remove the two (2) screws and nuts holding the fan

motor to the fan duct.

13.Now, the fan motor is free.

1. Install the the fan motor to the fan duct with the two (2)

screws and nuts.

2. Install the fan blade to the fan motor shaft according to

the following procedure.

1. CARRY OUT 3D CHECKS.
2. Remove the one (1) screw holding the noise filter to the

chassis support.

3. Release the noise filter from the tabs of the fan duct.
4. Remove the one (1) screw holding the chassis support

to the oven cavity front flange.

5. Remove the chassis support from the oven cavity.
6. Disconnect the wire leads from the fan duct.
7. Remove the one (1) screw holding the capacitor holder

to the oven cavity back plate.

8. Release the tabs of the capacitor holder from the fan

duct.

9. Remove the one (1) screw holding the fan duct to the

oven cavity back plate.

10.Remove the fan duct from the oven.
11.Remove the fan duct from the fan motor shaft accord-

ing to the following procedure.
1) Hold the edge of the rotor of the fan motor by using

a pair of groove joint pliers.

5. Remove one (1) screw holding fan duct to the oven

cavity rear plate.

6. Remove one (1) screw holding capacitor holder to the

oven cavity rear plate.

7. Release the capacitor holder from the fan duct.
8. Remove the high voltage capacitor from the capacitor

holder.

9. Disconnect the high voltage wire B and the high voltage

rectifier assembly from the high voltage capacitor.

10.Disconnect the high voltage rectifier assembly from the

high voltage wire B.

11.Now, the high voltage rectifier assembly and the high

voltage capacitor should be free.

CAUTION: WHEN REPLACING HIGH VOLTAGE

RECTIFIER ASSEMBLY, ENSURE THAT
THE CATHODE (EARTH) CONNECTION
IS SECURELY FIXED TO THE CAPACI-
TOR HOLDER WITH AN EARTHING
SCREW.

R-874 S/MANUAL

11/7/01, 10:59 am

25

R-874M - 26

1) Hold the centre of the bracket which supports the

shaft of the fan motor on a flat table.

2) Apply the screw lock tight into the hole  (for shaft) of

the fan blade.

3) Install the fan blade to the shaft of fan motor by

pushing the fan blade with a small, light weight, ball
peen hammer or rubber mallet.

3. Insert the tabs of the capacitor holder to the fan duct.
4. Install the fan duct to the oven cavity back plate with the

one (1) screw.

5. Install the capacitor holder to the oven cavity back plate

with the one (1) screw.

6. Re-install the chassis support to the oven cavity with the

one (1) screw.

7. Install the noise filter to the fan duct and the chassis

support with the one (1) screw.

8. Re-connect the wire leads to the fan motor.

Shaft

Table

Center of 
bracket

Coil

Gap

Rotor

Bracket

Stator

Groove joint pliers

Shaft

Axis

Stator

Rotor

These are the position 
where should be 
pinched with pliers

Removal
1. Disconnect the oven from the power supply.
2. Remove the turntable from the oven cavity.
3. Turn the oven over.
4. Cut the four (4) bridges holding the turntable motor

cover to the base plate with cutting pliers as shown in
Figure C-1(a).

CAUTION: DO NOT DROP THE TURNTABLE MOTOR

COVER INTO THE OVEN AFTER CUTTING
THE BRIDGES. BECAUSE IT WILL DAM-
AGE THE WIRE LEADS OF THE MOTOR
AND IT IS DIFFICULT TO REMOVE IT OUT
OF THE OVEN.

5. Remove the turntable motor cover from the base plate.
6. Disconnect the wire leads from the turntable motor.
7. Remove the one (1) screw holding the turntable motor

to the turntable motor angle.

8. Remove the turntable motor from the turntable motor

angle. Now, the turntable motor is free.

Re-install
1. Remove the any sharp edges on the turntable motor

cover and the base plate with the cutting pliers.

2. Re-install turntable motor by locating shaft onto turnta-

ble motor shaft to the turntable motor angle with the
one (1) screw.

3. Re-connect the wire leads to the turntable motor.
4. Insert the two (2) tabs of the turntable motor cover into

the slits of the base plate as shown in Figure C-1(b).

5. Re-install the turntable motor cover to the base plate

with the screw (LX-EZA045WRE0) as shown in Figure
C-1(b).

1. CARRY OUT 3D CHECKS.
2. Remove the two (2) screws holding the back plate to

oven cavity.

3. Disconnect the wire leads from the convection motor.
4. Remove the two (2) screws holding the rear heat cover

to the oven cavity from out-side.

5. Remove the four (4) screws holding the convection fan

duct to the oven cavity.

6. Now, the convection fan duct assembly is free.
7. Remove the one (1) nut holding the convection fan,

washers, pipe and the cooling fan to the convection
motor shaft.

8. Remove the three (3) screws holding the rear heat

cover to the convection fan duct.

9. Remove the two (2) screws holding the convection

motor to the rear heat cover.

10.Remove the pipe, washers and the cooling fan from the

convection motor shaft.

11.Remove the ring on the convection motor shaft.
12.Now, the convection motor is free.

Cutting pliers

Bridges

Bridges

Turntable motor 
cover

Screw; 
LX-EZA045WRE0 

Turntable motor cover

Base plate  

Tabs 

Slits 

R-874 S/MANUAL

11/7/01, 10:59 am

26

R-874M - 27

1. CARRY OUT 3D CHECKS.
2. Remove the wire leads as Positive lock

®

 connector

removal above.

3. Lift up the oven lamp from its retaining clips.
4. Now, the oven lamp is free.

1. CARRY OUT 3D CHECKS.
2. Remove the one (1) screw holding the green/yellow

wire to the cavity back plate.

3. Disconnect the leads of the power supply cord from the

noise filter, referring to the Figure C-4(a).

4. Release the power supply cord from the rear cabinet.
5. Now, the power supply cord is free.

1. Insert the moulding cord stopper of power supply cord

into the square hole of the power angle, referring to the
Figure C-4(b).

2. Install the earth wire lead of power supply cord to the

oven cavity with one (1) screw and tight the screw.

3. Connect the brown and blue wire leads of power supply

cord to the noise filter correctly, referring to the Pictorial
Diagram.

1. CARRY OUT 3D CHECKS.
2. Remove the two (2) screws holding the two (2) termi-

nals of the main wire harness to the top heating
element.

3. Remove the two (2) screws holding the two (2) grill

heater angles to the top of the oven cavity.

4. Remove the two (2) grill heater angles from the oven

cavity.

5. Remove the top heating element from the top of the

oven cavity.

6. Now the top heating element is free.

1. CARRY OUT 3D CHECKS.
2. Push the lever of positive lock

®

 connector.

3. Pull down on the positive lock

®

 connector.

CAUTION: WHEN YOU (SERVICE ENGNEERS) CON-

NECT THE POSITIVE LOCK

®

 CONNEC-

TORS TO THE TERMINALS, CONNECT
THE POSITIVE LOCK

®

 SO THAT THE LE-

VER FACES YOU (SERVICE ENGNEERS).

BULB

LOCK

Terminal

Push

Pull down

1

2

Lever

Positive lock®

connector

1. CARRY OUT 3D CHECKS.
2. Remove the turntable motor cover from the base plate,

referring to "TURNTABLE MOTOR REPLACEMENT".

3. Disconnect the wire leads from the bottom heating

element.

POWER
SUPPLY CORD

MOULDING
CORD STOPPER

OVEN CAVITY
BACK PLATE

SQUARE HOLE

Power supply cord

Green/ Yellow
wire

Brown wire

Oven cavity back plate 

Blue wire

Noise filter

Screw

L

TP

  F2 F 8 A

TL

RED

F1 20 A

WHT

N

R-874 S/MANUAL

11/7/01, 10:59 am

27