R-8740 (serv.man10). Component replacement and adjustment procedure — Sharp Home Appliance Service Manual (repair manual)

Model
R-8740 (serv.man10)
Pages
5 Few pages! See other manuals at the bottom of the first or last page.
Size
488.66 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Component replacement and adjustment procedure
File
r-8740-sm10.pdf
Date

View Sharp R-8740 (serv.man10) Service Manual online

R-8740M  - 28
WARNING: Avoid possible exposure to microwave energy. Please follow the instructions below before
operating the oven.
1. CARRY OUT 3D CHECKS.
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 damage
(dents, cracks, signs of arcing etc.).
Carry out any remedial work that is necessary before oper-
ating 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.
Please refer to ‘OVEN PARTS, CABINET PARTS, DOOR PARTS’, when carrying out any of the following removal
procedures:
OUTER CASE REMOVAL
6. Lift the entire case from the oven.
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 backplate.
4. Remove the screws from rear and along the side edge of
case.
5. Slide the entire case back about 3cm to free it from
retaining clips on the cavity face plate.
CONTROL PANEL REMOVAL
1. CARRY OUT 3D CHECKS
2. Remove outer wrap.
3. Disconnect wiring panel.
4. Lift up the control panel assembly and pull it forward. Now
the control panel assembly is free.
HIGH VOLTAGE TRANSFORMER REMOVAL
1. CARRY OUT 3D CHECKS
2. Disconnect the filament leads of high voltage transformer
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 voltage
transformer.
5. Remove the two (2) screws and one (1) washer holding
the transformer to base plate.
6. Remove the transformer.
7. Now the high voltage transformer is free.
7. Discharge the H.V. capacitor before carrying out any
further work.
8. Do not operate the oven with the outer case removed.
N.B.; Step 1, 2 and 6 form the basis of the 3D checks.
CAUTION:
DISCHARGE HIGH VOLTAGE CAPACITOR
BEFORE TOUCHING ANY OVEN COMPONENT OR
WIRING.
HIGH VOLTAGE COMPONENTS REMOVAL
(HIGH VOLTAGE CAPACITOR AND HIGH VOLTAGE RECTIFIER ASSEMBLY)
To remove the components, proceed as follows.
1. CARRY OUT 3D CHECKS
2. Disconnect all the leads and terminals of high voltage
rectifier assembly from the high voltage capacitor.
3. Remove one (1) screw holding earth side terminal of high
voltage rectifier assembly and remove capacitor holder.
4. Remove one (1) screw holding capacitor holder to oven
cavity.
5. Release the capacitor holder from the duct.
CAUTION: WHEN REPLACING HIGH VOLTAGE
RECTIFIER ASSEMBLY, ENSURE THAT
THE CATHODE (EARTH) CONNECTION IS
SECURELY FIXED TO THE CAPACITOR
HOLDER WITH AN EARTHING SCREW.
6. Remove the capacitor from the capacitor holder.
7. Now high voltage rectifier assembly and capacitor should
be free.
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
R-8740M  - 29
MAGNETRON REMOVAL
6. Remove the magnetron from the waveguide with care so
the magnetron antenna is not hit by any metal object
around the antenna.
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 magnetron to
waveguide, when removing the screws hold the
magnetron to prevent it from falling.
REMOVAL
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.
Disconnect the wire leads from the fan duct.
5.
Remove the one (1) screw holding the capacitor holder
to the oven cavity back plate.
6.
Release the tabs of the capacitor holder from the fan
duct.
7.
Remove the one (1) screw holding the fan duct to the
oven cavity back plate.
8.
Remove the fan duct from the oven.
9.
Remove the fan duct from the fan motor shaft according
the following procedure.
1) Hold the edge of the rotor of the fan motor by using
a pair of groove joint pliers.
CAUTION:
• Make sure that no swarf from the rotor enters
the gap between the rotor & stator of the fan
motor.
• Avoid touching the coil of the fan motor with
the pliers as the coil may become cut or
damaged.
• Avoid deforming the bracket whilst using the
pliers.
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.
CAUTION:
• Do not reuse the removed fan blade as the
fixing hole may be oversize.
10. Remove the two (2) screws and nuts holding the fan
motor to the fan duct.
11. Now, the fan motor is free.
INSTALLATION
1.
Install the fan motor to the fan duct with the two (2)
screws.
2.
Install the fan blade to the fan motor shaft according the
following procedure.
1)
Hold the centre of the bracket which supports the shaft
of the fan motor on the 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 strongly when installed
because the bracket may be deformed.
Make sure that the fan blade rotates smoothly
after installed.
Make sure that the axis of the shaft is not
slanted.
3.
Install the fan duct to the oven cavity back plate with the
one (1) screw.
4.
Insert the tabs of the capacitor holder to the fan duct.
5.
Install the capacitor holder to the oven cavity back plate
with the one (1) screw.
6.
Install the noise filter to the fan duct and the chassis
support with the one (1) screw.
7.
Re-connect the wire leads to the fan motor.
Rear view
Side view
CAUTION: WHEN REPLACING THE MAGNETRON,
BE SURE THE R.F. GASKET IS IN PLACE
AND THE MAGNETRON MOUNTING
SCREWS ARE TIGHTENED SECURELY.
FAN MOTOR REPLACEMENT
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
Coil
Gap
Rotor
Bracket
Stator
Groove joint pliers
Shaft
Axis
Stator
Rotor
These are the position 
where should be pinched 
with pliers
Shaft
Table
Center of
bracket
R-8740M  - 30
OVEN LAMP SOCKET REMOVAL
1. CARRY OUT 3D CHECKS
2. Remove wire leads as positive lock connector
    removal below.
3. Lift up the oven lamp from its retaining clips.
4. Now, the oven lamp is free.
POSITIVE LOCK
®
 CONNECTOR REMOVAL
1. CARRY OUT 3D CHECKS.
2. Pushing the lever of positive lock
®
 connector.
3. Pull out the positive lock
®
 connector.
CAUTION:
WHEN YOU (SERVICE ENGINEERS) CON-
NECT THE POSITIVE LOCK
®
 CONNECTORS
TO THE TERMINALS, CONNECT THE POSI-
TIVE LOCK
®
  SO THAT THE LEVER FACE
YOU (SERVICE ENGINEERS).
CONVECTION FAN MOTOR REMOVAL
CONVECTION FAN MOTOR
7. Remove the one (1) nut holding the convection fan,
washers, pipe and auxiliary fan to the convection fan
motor shaft.
8. Remove the two (2) screws holding the convection motor
mounting plate to the convection fan duct.
9. Remove the pin on the convection fan motor shaft.
10. Remove the two (2) screws holding the convection motor
mounting plate to the convection fan motor.
11. Now, the convection fan motor is free.
1. CARRY OUT3DCHECKS.
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 convection fan
duct 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 is free.
Figure C-4 (a) Replacement of Power Supply Cord
Figure C-2 Positive lock
®
 connector
Terminal
Push
Pull down
1
2
Lever
Positive lock®
connector
POWER SUPPLY CORD REPLACEMENT
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 rear cabinet, 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.
OVEN CAVITY
BACK PLATE
SQUARE HOLE
MOULDING
CORD
STOPPER
POWER SUPPLY
CORD
GROMMET
MOULDING
Lock
Socket
Bulb
POWER SUPPLY CORD
OVEN CAVITY
BACK PLATE
BROWN WIRE
BLUE WIRE
NOISE FILTER
CHASSIS SUPPORT
Figure C-4(b). Power Supply Cord Replacement
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
R-8740M  - 31
1. CARRY OUT 3D CHECKS
2. Disconnect the wire leads to the grill heating element.
3. Remove the two(2) screws holding the exhaust duct
assembly to the oven cavity.
4. Push the two tabs holding the grill heating element
assembly to the oven cavity.
5. Release the grill heating element assembly from the
1. CARRY OUT 3D CHECKS.
2. Remove the control panel assembly referring to
"CONTROL PANEL REMOVAL".
3. Disconnect the leads from all switches.
4. Remove the two (2) screws holding the latch hook to the
oven cavity.
5. Remove the latch hook.
6. Push the retaining tab slightly and remove the switch.
If the monitored switch, stop switch and monitor switch do not
operate properly due to a mis-adjustment, the following
before the door can be opened.
3. The monitor switch contacts of (COM.- NC.) close when
the door is opened and the monitored latch switch contacts
of (COM.- NO.) open and  contacts of (COM.- NC.) close
when the door is opened.
4. 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. Switch Adjustment
adjustment should be made.
1. CARRY OUT 3D CHECKS
2. Loosen the two (2) screw holding the latch hook to the
oven cavity front flange.
3. With the door closed, adjust 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 latch head has pushed the plungers of the
monitor switch with the door closed. The vertical position
of the latch hook should be placed where the latch head
has pushed the plungers of the monitored latch switch
and stop switch with the door closed.
4. Secure the screws firmly.
5. Make sure all of the switches operate. 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 the two (2) screws holding latch hook to the oven
cavity front flange and adjust the latch hook position.
After adjustment, make sure of the following:
1. In and out play of door remains less than 0.5 mm when
latched position. First check latch hook position, pushing
and pulling upper portion of door toward the oven face.
Then check the lower latch hook position, pushing and
pulling lower portion of door toward the oven face. Both
results (plays of the door) should be less than 0.5mm.
2. The monitored switch and stop switch interrupt the circuit
1. CARRY OUT 3D CHECKS.
2. Remove the fan duct from the oven cavity, referring to
"FAN MOTOR REPLACEMENT".
3. Disconnect the wire leads from the bottom heating
element.
BOTTOM HEATING ELEMENT REMOVAL
4. Remove the two (2) nuts holding the bottom heating
element to the oven cavity right wall.
5. Remove the two (2) nuts holding the bottom heating
element to the heater cover with the heat sealed spring
at the oven cavity left wall.
6. Remove the bottom heating element from the oven
cavity.
LATCH
HEADS
LATCH HOOK
MONITORED LATCH
SWITCH
STOP SWITCH
OPEN LEVER
DOOR OPEN BUTTON
MONITOR 
SWITCH
oven cavity by sliding the cover.
6. Now the grill heating element assembly is free.
Figure C-5. Switches
GRILL HEATING ELEMENT ASSEMBLY REMOVAL
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
MONITOR SWITCH
MONITORED LATCH SWITCH
TAB
TAB
STOP SWITCH
MONITORED LATCH  SWITCH, STOP SWITCH AND MONITOR SWITCH ADJUSTMENT
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