R-27STMA (serv.man11). Component Replacement And Adjustment Procedure - Sharp Home Appliance Service Manual (repair manual)

r-27stma (serv.man11) service manual
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R-27STMA (serv.man11)
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6
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PDF
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Service Manual
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Device
Home Appliance / Microwave Oven / Component Replacement And Adjustment Procedure
File
r-27stma-sm11.pdf
Date

Read Sharp R-27STMA (serv.man11) Service Manual online

R27STMA
11 – 1
R27STMA
Service Manual
 
CHAPTER 11. 
COMPONENT REPLACEMENT AND ADJUSTMENT PROCE-
DURE
[1] BEFORE OPERATING
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, High Voltage Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..
WARNING:
Avoid possible exposure to microwave energy. Please follow the instructions below before operating
the oven.
1) Disconnect the power supply cord.
2) 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 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 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 trans-
mission 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.
To prevent an electric shock, take the following manners.
1. Before wiring, 
1) Disconnect the power supply cord.
2) Open the door and block it 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 voltage capacitor
and High voltage rectifier assembly.
2) Hot parts:
Oven lamp, Magnetron, High voltage transformer and Oven
cavity.
3) Sharp edge:
Bottom plate, Oven cavity, Waveguide flange and other metallic
plate.
4) Movable parts (to prevent a fault)
Fan blade, Fan motor, Turntable motor and Switch.
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 do not come off even if the wire leads
are pulled.
5. To prevent an error function, connect the wire leads correctly, refer-
ring to the Pictorial Diagram. 
Please refer to ‘OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS’, when carrying out any of the following removal proce-
dures:
[2] OUTER CASE REMOVAL
To remove the outer case, procedure as follows.
1. Disconnect the oven from power supply.
2. Open the oven door and wedge it open.
3. Remove the two (2) screws from right side of the outer case cabi-
net.
4. Remove the five (5) 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.
6. Lift the entire case from the oven.
7. Discharge the H.V. capacitor before carrying out any further work.
8. Do not operate the oven with the outer case removed.
NOTE: Step 1, 2 and 7 form the basis of the 3D checks.
CAUTION: DISCONNECT OVEN FROM POWER SUPPLY BEFORE
REMOVING OUTER CASE.
 
WARNING AGAINST HIGH VOLTAGE:
WARNING FOR WIRING
                                                                                                
REMEMBER TO CHECK 3D
                                                      1) Disconnect the supply.                                                     3)Discharge high voltage capacitor.
                                                      2)Door opened, and wedged open.
R27STMA
11 – 2
[3] HIGH VOLTAGE TRANSFORMER REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the wire leads (main wire harness) from high voltage
transformer.
3. Disconnect the filament lead of high voltage transformer from the
magnetron.
4. Disconnect the filament lead of the high voltage transformer from
high voltage capacitor.
5. Disconnect the high voltage wire of the high voltage transformer
from the high voltage capacitor.
6. Remove the four (4) screws holding the transformer to bottom plate
from below.
7. Remove the transformer. 
[4] HIGH VOLTAGE RECTIFIER ASSEMBLY AND HIGH VOLTAGE CAPACITOR REMOVAL
To remove the components, proceed as follows.
1. CARRY OUT 3D CHECKS.
2. Disconnect the high voltage wire of the high voltage transformer
from the H.V. capacitor.
3. Disconnect the filament lead of the high voltage transformer from
the H.V. capacitor.
4. Remove one (1) screw holding capacitor holder to the oven cavity
back plate.
5. Remove one (1) screw holding earth side terminal of high voltage
rectifier assembly, and remove capacitor holder.
6. Disconnect all the leads and terminals of high voltage rectifier
assembly from high voltage capacitor.
7. Now H.V. rectifier assembly and H.V. 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.
CAUTION: DO NOT REPLACE ONLY HIGH VOLTAGE RECTIFIER.
WHEN REPLACING IT, REPLACE HIGH VOLTAGE REC-
TIFIER ASSEMBLY.
[5] MAGNETRON REMOVAL
1. REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the wire leads from the magnetron.
3. Remove the two (2) screws holding the air duct to the oven cavity.
4. Release the air duct from the oven cavity.
5. Carefully remove the four (4) screws holding the magnetron to the
waveguide flange.
6. Lift up magnetron with care so that the magnetron antenna is not
hit by any metal object around antenna.
7. Now, the magnetron is free.
2. REINSTALLATION
1. Reinstall the magnetron to the waveguide flange with the four (4)
screws.
2. Reinstall the air duct to the oven cavity with the two (2) screws.
3. Reconnect the wire leads to the magnetron. Refer to “PICTORIAL
DIAGRAM”.
4. Reinstall the outer case and check that the oven is operating prop-
erly.
CAUTION: WHEN REPLACING THE MAGNETRON, BE SURE THE
R.F. GASKET IS IN PLACE AND THE MAGNETRON
MOUNTING SCREWS ARE TIGHTENED SECURELY.
[6] POSITIVE LOCK CONNECTOR (NO-CASE TYPE) REMOVAL
1. CARRY OUT 3D CHECKS.
2. Push the lever of positive lock
 connector.
3. Pull down on the positive lock
 connector.
CAUTION: WHEN CONNECTING THE POSITIVE LOCK
 CONNEC-
TORS TO THE TERMINALS, CONNECT THE POSITIVE
LOCK
 SO THAT THE LEVER FACES YOU.
Figure C-1.  Positive lock, connector
[7] TURNTABLE MOTOR REMOVAL
1. REMOVAL
1. Disconnect the power supply cord.
2. Remove turntable and turntable support from oven cavity.
3. Lay the oven on it's backside. Remove the turntable motor cover by
snipping off the material in four corners.
4. Where the corners have been snipped off bend corner areas flat.
No sharp edges must be evident after removal of the turntable
motor cover.
5. Disconnect wire leads from turntable motor.
(See “Positive lock connector removal”)
6. Remove one (1) screw holding turntable motor to oven cavity.
Terminal
Push
Pull down
1
2
Lever
Positive lock¨
connector
R27STMA
11 – 3
7. Remove the TTM packing from the turntable motor.
8. Now, the turntable motor is free.
2. REINSTALL
1. Re-install the TTM packing to the turntable motor.
2. Re-install the turntable motor with the TTM packing with the single
(1) screw to the oven cavity bottom plate.
3. Re-connect the wire leads to the turntable motor.
4. Insert the tab of the turntable motor cover into the hole of the bot-
tom plate.
5. Re-install the turntable motor cover to the bottom plate with one (1)
screw.
                        Figure C-2. TTM packing Installation
[8] COOLING FAN MOTOR REMOVAL
1. REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the wire leads from the fan motor.
3. Remove the two (2) screws holding the fan motor to the oven cavity
back plate.
4. Remove the fan blade from the fan motor shaft according to the fol-
lowing procedure. 
5. Hold the edge of the rotor of the fan motor by using a pair of groove
joint pliers.
CAUTION: MAKE SURE THAT ANY PIECES DO NOT ENTER THE
GAP BETWEEN THE ROTOR AND THE STATOR OF THE
FAN MOTOR. BECAUSE THE ROTOR IS EASY TO BE
SHAVEN BY PLIERS AND METAL PIECES MAY BE PRO-
DUCED.
DO NOT TOUCH THE PLIERS TO THE COIL OF THE
FAN MOTOR BECAUSE THE COIL MAY BE CUT OR
INJURED.
DO NOT DISFIGURE THE BRACKET BY TOUCHING
WITH THE PLIERS.
6. Remove the fan blade from the shaft of the fan motor by pulling and
rotating the fan blade with your hand.
7. Now, the fan blade will be free.
CAUTION: DO NOT RE-USE THE REMOVED FAN BLADE
BECAUSE THE HOLE (FOR SHAFT) MAY BE LARGER
THAN NORMAL.
8. Now, the fan motor is free.
2. INSTALLATION
1. Install the fan blade to the fan motor shaft according to the following
procedure.
2. Hold the center of the bracket which supports the shaft of the fan
motor on the flat table.
3. Apply the screw lock tight into the hole (for shaft) of the fan blade.
4. 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 TRANS-
FORMED.
MAKE SURE THAT THE FAN BLADE ROTATES
SMOOTH AFTER INSTALLED.
MAKE SURE THAT THE AXIS OF THE SHAFT IS NOT
SLANTED.
5. Install the fan motor assembly to the oven cavity back plate with
two (2) screws. 
6. Connect the wire leads to the magnetron and fan motor, referring to
the pictorial diagram.
TTM packing
Turntable motor
Gap
Rotor
Bracket
Stator
Groove joint pliers
Coil
Shaft
Axis
Stator
Rotor
These are the positions
that should be pinched
with pliers.
Shaft
Table
Center of
bracket
Rear View
Side View
R27STMA
11 – 4
[9] POWER SUPPLY CORD REPLACEMENT
1. REMOVAL
1. CARRY OUT 3D CHECKS.
2. Remove the single (1) screw holding the green/yellow wire to the
oven cavity back plate.
3. Disconnect the leads of the power supply cord from the noise filter,
referring to the Figure C-3(a).
4. Release the moulding cord stopper of the power supply cord from
 the square hole of the oven cavity back plate, referring to the Fig-
ure C-3 (b).
5. Now, the power supply cord is free. 
2. REINSTALL
1. Insert the moulding cord stopper of power supply cord into the
square hole of the rear cabinet, referring to the Figure C-3 (b).
2. Install the earth wire lead of power supply cord to the oven cavity
back plate 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.
                    Figure C-3(a) Power Supply Cord Replacement                                      
        Figure C-3(a) Figure C-3(b) Power Supply Cord Replacement
[10] CONTROL PANEL ASSEMBLY REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the leads from the control unit.
3. Remove the one (1) screw holding the control panel to the front
panel of the oven cavity.
4. Lift up the control panel assembly and release it from the oven cav-
ity.
5. Now, the control panel assembly is free.
[11] SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR SWITCH
ADJUSTMENT
1. REMOVAL
1. CARRY OUT 3D CHECKS.
2. Remove the control panel assembly, referring to section of CON-
TROL PANEL ASSEMBLY REMOVAL.
3. Disconnect wire leads from the switches.
4. Remove two (2) screws holding latch hook to oven flange.
5. Remove latch hook assembly from oven flange.
6. Push outward on the two (2) retaining tabs holding switch in place.
7. Switch is now free.
2. REINSTALL
1. Re-install each switch in its place. The secondary interlock switch
and the monitor switch are in the lower position and the door sens-
ing switch is in the upper position
2. Secure latch hook (with two (2) mounting screws) to oven flange.
3. Re-connect wire leads to each switch. Refer to pictorial diagram.
4. Reinstall the control panel assembly to the oven cavity.
5. Reconnect wire leads to the control unit, referring to the pictorial
diagram. 
6. Make sure that the monitor switch is operating properly and check
continuity of the monitor circuit. Refer to chapter “Test Procedure”
and Adjustment procedure.
[12] SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR SWITCH
ADJUSTMENT
1. Adjustment
1. CARRY OUT 3D CHECKS.
If the secondary interlock switch, door sensing switch and monitor
switch do not operate properly due to a misadjustment, the following
adjustment should be made.
2. Loosen the two (2) screws holding latch hook to the oven cavity
front flange.
3. With door closed, adjust latch hook by moving it back and forth,
and up and down. In and out play of the door allowed by the upper
and lower position of the latch hook should be less than 0.5mm.
The vertical position of the latch hook should be adjusted so that
the secondary interlock switch and door sensing switch are acti-
vated with the door closed. The horizontal position of the latch hook
should be adjusted so that the plunger of the monitor switch is
pressed with the door closed.
4. Secure the screws with washers firmly.
N
L
Power Supply
Cord
Oven Cavity
Back Plate
Screw
Green/Yellow
Wire
Brown Wire
Blue
Wire
Noise Filter
WHT
RED
P ower S upply
C ord
O ven C avity
B ack P late
S quare
Hole
Moulding
C ord S topper
Page of 6

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