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R26STM

11 – 1

R26STM

Service Manual

 

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 fuse, High Voltage Harness etc..

WARNING:

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.

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,
High voltage rectifier assembly and High voltage fuse.

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:

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.

1. CARRY OUT 3D CHECKS.

2. Disconnect the wire leads (main wire harness and H.V. fuse) from

high voltage transformer.

 

                                                                                                

                                                      1) Disconnect the supply.                                                     3)Discharge high voltage capacitor.
                                                      2)Door opened, and wedged open.

R26STM

11 – 2

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. Remove the two (2) screws holding the transformer to bottom plate

from below.

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

from above. 

7. Remove the transformer. 

To remove the components, proceed as follows.

1. CARRY OUT 3D CHECKS.

2. Disconnect the H.V. fuse from the high voltage transformer.

3. Disconnect the H.V. wire of the H.V. rectifier assembly from the

magnetron.

4. Disconnect the filament lead of the high voltage transformer from

the H.V. capacitor.

5. Remove one (1) screw holding capacitor holder to the oven cavity

back plate.

6. Remove one (1) screw holding earth side terminal of high voltage

rectifier assembly, and remove capacitor holder.

7. Disconnect all the leads and terminals of high voltage rectifier

assembly from high voltage capacitor.

8. Disconnect the H.V. fuse from the high voltage capacitor.

9. Now H.V. rectifier assembly, H.V. fuse 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.

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.

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.

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

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

R26STM

11 – 3

7. Remove the TTM packing from the turntable motor.

8. Now, the turntable motor is free.

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

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.

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.

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. 

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.

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

R26STM

11 – 4

                    Figure C-3(a) Power Supply Cord Replacement                                      

        Figure C-3(a) Figure C-3(b) Power Supply Cord Replacement

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.

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.

1. Re-install each switch in its place. The 1st. latch switch and the

monitor switch are in the lower position and the 2nd. interlock relay
control 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.

1. CARRY OUT 3D CHECKS.

If the 1st. latch switch, 2nd. interlock relay control 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 1st. latch switch and 2nd. interlock relay control 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.

5. Check the operation of all switches. If each switch has not activated

with the door closed, loosen screw and adjust the latch hook posi-
tion.

1. In and out play of door remains less than 0.5mm when in the

latched position. First check upper position of latch hook, pushing
and pulling upper portion of door toward the oven face. 

Then check lower portion of the latch hook, pushing and pulling
lower portion of the door toward the oven face. Both results (play in
the door) should be less than 0.5mm.

2. When the door is open, the contacts of the 1st. latch switch and

2nd. interlock relay control switch open within 1.6mm gap between

 right side of cavity face and the door.

3. Monitor switch contacts close when door is opened.

4. Re-install outer case and check for microwave leakage around

door with an approved microwave survey meter. (Refer to Micro-
wave Measurement Procedure.)

                          Figure C-5. Latch Switch Adjustments

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

Latch Heads

Latch Hook

Door

2nd. Interlock Relay
Control Switch

1st. Latch Switch

Monitor Switch