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Model
R-874 (serv.man3)
Pages
13
Size
429.78 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Control pannel assembly, component replacement procedure and leakage measurement
File
r-874-sm3.pdf
Date

Sharp R-874 (serv.man3) Service Manual ▷ View online

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.
CAUTION:
• Do not hit the fan blade when installing be-
cause the bracket may be deformed.
• Make sure that the fan blade rotates smoothly
after installation.
• Make sure that the axis of the shaft is not
slanted.
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
Figure C-1(a). Turntable motor cover removal
Figure C-1(b). Turntable motor cover re-install
Rear view
Side view
TURNTABLE MOTOR REPLACEMENT
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,
CONVECTION FAN MOTOR REMOVAL
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 
  COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
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.
Figure C-3. Oven lamp
Removal
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.
Re-install
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.
POWER SUPPLY CORD REPLACEMENT
TOP HEATING ELEMENT REMOVAL
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.
POSITIVE LOCK
®
  CONNECTOR REMOVAL
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).
Figure C-2.  Positive lock
®
connector
BULB
LOCK
Terminal
Push
Pull down
1
2
Lever
Positive lock®
connector
Figure C-4 (a) Replacement of Power Supply Cord
Figure C-4(b). Power Supply Cord Replacement
1. CARRY OUT 3D CHECKS.
2. Remove the turntable motor cover from the base plate,
referring to "TURNTABLE MOTOR REPLACEMENT".
BOTTOM HEATING ELEMENT REMOVAL
3. Disconnect the wire leads from the bottom heating
element.
POWER
SUPPLY CORD
MOULDING
CORD STOPPER
OVEN CAVITY
BACK PLATE
SQUARE HOLE
OVEN LAMP SOCKET REMOVAL
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
  COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
R-874 S/MANUAL
11/7/01, 10:59 am
27
R-874M - 28
4. Remove the two (2) nuts holding the bottom heating
element to the oven cavity.
5. Remove the heater cover and the heater packing from
the bottom heating element.
6. Remove the bottom heating element from the oven
cavity .
1. CARRY OUT 3D CHECKS.
2. Remove the control panel assembly referring to "CON-
TROL PANEL ASSEMBLY REMOVAL".
3. Remove the open lever from the oven cavity front plate
by removing the control panel assembly.
4. Disconnect the leads from all switches.
5. Remove the two (2) screws holding the latch hook to
the oven cavity.
6. Remove the latch hook.
7. Remove the switch(es) from the latch hook by pushing
the retaining tab backwards slightly and turning the
switch(es) on the post.
8. Now the switch(es) is free.
Figure C-5. Switches
MONITORED LATCH SWITCH,  MONITOR SWITCH AND STOP SWITCH REMOVAL
If the monitored latch switch, stop switch and monitor
switch do not operate properly due to a mis-adjustment,
the following adjustment should be made.
1. CARRY OUT 3D CHECKS.
2. Loosen the two (2) screws holding the latch hook to
the oven cavity front flange.
3. With the door closed, adjust the latch hook by moving
it back and forward or up and down. In and out play of
the door allowed by the latch hook should be less than
0.5 mm. The horizontal position of the latch hook
should be placed where the monitor switch has acti-
vated with the door closed. The vertical position of the
latch hook should be placed where the monitored latch
switch and stop switch have activated with the door
closed.
4. Secure the screws with washers firmly.
5. Make sure of the all switches operation. If the latch
head has not pushed the plungers of the monitor
switch with door closed, adjust the latch hook position.
At that time, the latch head should have pushed the
plungers of the monitored latch switch and stop switch.
If the latch head has not pushed the plungers of the
monitored latch switch and stop switch with door
closed, loose two (2) screws holding latch hook to
oven cavity front flange and adjust the latch hook
position.
After adjustment, make sure of following:
1. In and out play of door remains less than 0.5 mm when
latched position. First check the latch hook position,
pushing and pulling upper portion of the door toward
MONITORED LATCH SWITCH,  STOP SWITCH AND MONITOR SWITCH ADJUSTMENT
the oven face. Then check the lower latch hook posi-
tion, pushing and pulling lower portion of the door
toward the oven face. Both results (play of the door)
should be less than 0.5mm.
2. The stop switch  interrupt the circuit before the door
can be opened.
3. When the door is opened the contacts (COM-NC) of
the monitor switch and monitored latch switch close.
And the contacts (COM-NO) of their switches open.
4. When the door is closed the contacts (COM-NC) of the
monitor switch and monitored latch switch open. And
the contacts (COM-NO) of their switches close.
5. Re-install outer case and check for microwave leakage
around the door with an approved microwave survey
meter. (Refer to Microwave Measurement Procedure.)
Figure C-6 Latch Switches Adjustment
MONITOR SWITCH
STOP SWITCH
MONITORED
LATCH SWITCH
Tab
Post
Post
Post
Tab
Tab
DOOR
LATCH HOOK
MONITOR SWITCH
MONITORED
LATCH SWITCH
 STOP SWITCH
OPEN LEVER
LATCH
HEADS
  COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
R-874 S/MANUAL
11/7/01, 10:59 am
28
R-874M - 29
REMOVAL
1. Disconnect the oven from the power supply.
2. Push the open button and open the door slightly.
3. Insert an putty knife (thickness of about 0.5mm) into the
gap between the choke cover and door frame as shown
in Figure C-7 to free engaging parts.
4. Release choke cover  from door panel.
5. Now choke cover is free.
DOOR REPLACEMENT
  COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
Figure C-7. Door Disassembly
6. Lift the door upwards.
7. Now, door sub assembly is free from oven cavity.
8. Remove the four (4) screws holding the door panel to
the door frame.
9. Release door panel from six (6) tabs of door frame by
sliding door panel upward.
10.Now, door panel is free.
11.Slide latch head upward and remove it from door
frame with releasing latch spring from door frame and
latch head.
12.Now, latch head and latch spring are free.
13.Remove the two (2) screws holding the glass stopper to
the door frame.
14.Remove the glass stopper from the door frame.
15.Slide the front door glass leftwards and then slide
upwards to release the tabs holding it.
16.Now, the front door glass is free
RE-INSTALL
1. Re-install the front door glass to the door frame as
follows.
a) Insert the upper edge of the front door glass into the
six (6) tabs of the door frame.
b) Slide the front door glass downwards and insert the
lower edge of the front door glass into the six (6) tabs
of the door frame.
c) Slide the front door glass rightwards and insert the
right edge of the front door glass into the one (1) tab
of the door frame.
2. Re-install the glass stopper to the door frame as follows.
a) Re-install the glass stopper to the door frame so that
the two (2) holes of the glass stopper meet the two
(2) pins of the door frame.
b) Hold the glass stopper to the door frame with the two
(2) screws.
3. Re-install the latch spring to the latch head. Re-install
the latch spring to the door frame. Re-install latch head
to door frame.
4. Re-install door panel to door frame by fitting six (6) tabs
of door frame to six (6) holes of door panel.
5. Hold the door panel to the door frame with four (4)
screws.
6. Locate door panel hinge pins into cavity hinge location
holes.
7. Re-install choke cover  to door panel by clipping into
position.
Note: After any service to the door;
(A) Make sure that the monitor switch, monitored
latch switch and stop switch are operating prop-
erly. (Refer to chapter "Test Procedures".).
(B) An approved microwave survey meter should be
used to assure compliance with proper micro-
wave radiation emission limitation standards.
(Refer to Microwave Measurement Procedure.)
After any service, make sure of the following :
1. Door latch heads smoothly catch latch hook through
latch holes and that latch head goes through centre of
latch hole.
2. Deviation of door alignment from horizontal line of
cavity face plate is to be less than 1.0mm.
3. Door is positioned with its face pressed toward cavity
face plate.
4. Check for microwave leakage around door with an
approved microwave survey meter.  (Refer to Micro-
wave Measurement Procedure.)
Note:
The door on a microwave oven is designed to act
as an electronic seal preventing the leakage of
microwave energy from oven cavity during cook
cycle. This function does not require that door be
air-tight, moisture (condensation)-tight or light-
tight. Therefore, occasional appearance of mois-
ture, light or sensing of gentle warm air movement
around oven door is not abnormal and do not of
themselves, indicate a leakage of microwave en-
ergy from oven cavity.
Figure C-8. Door Replacement
NOTE: When carrying out any repair to the door,
do not bend or warp the slit choke (tabs on
the door panel assembly) to prevent
microwave leakage.
PIN
PIN
LOWER
OVEN HINGE
UPPER
OVEN HINGE
LOWER
OVEN HINGE
CHOKE COVER
DOOR
PANEL
DOOR SUB 
ASSEMBLY
SLIT CHOKE
10
5
4
12
8
7
9
11
3
2
1
Choke Cover
Door Frame
Putty Knife
6
R-874 S/MANUAL
11/7/01, 10:59 am
29
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