DOWNLOAD Sharp R-90GCK (serv.man17) Service Manual ↓ Size: 1.28 MB | Pages: 48 in PDF or view online for FREE

23

Sn-Ag-Cu

The "Main PWB" of this model employs lead-free solder. This is indicated by the "LF" symbol printed on the PWB
and in the service manual. The suffix letter indicates the alloy type of the solder.
Example:

Indicates lead-free solder of tin, silver and copper.

When repairing a PWB with the "LF" symbol, only lead-free solder should be used. (Using normal tin/lead alloy solder
may result in cold soldered joints and damage to printed patterns.)
As the melting point of lead-free solder is approximately 40˚C higher than tin/lead alloy solder, it is recommend that
a dedicated bit is used, and that the iron temperature is adjusted accordingly.

As the melting point of lead-free solder (Sn-Ag-Cu) is higher and has poorer wettability, (flow), to prevent damage
to the land of the PWB, extreme care should be taken not to leave the bit in contact with the PWB for an extended
period of time. Remove the bit as soon as a good flow is achieved. The high content of tin in lead free solder will cause
premature corrosion of the bit. To reduce wear on the bit, reduce the temperature or turn off the iron when it is not
required.
Leaving different types of solder on the bit will cause contamination of the different alloys, which will alter their
characteristics, making good soldering more difficult. It will be necessary to clean and replace bits more often when
using  lead-free solder. To reduce bit wear, care should be taken to clean the bit thoroughly after each use.

24

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..

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

1) Disconnect the oven from 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 voltage
capacitor and High voltage rectifier assembly.

2) Hot parts:

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

1. Disconnect the oven from power supply.
2. Make sure that a definite” click” can be heard when

the microwave oven door is unlatched. (Pull down the
door handle in a closed position with one hand, then
push the door 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
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 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.

3) Sharp edge:

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

4) Moveable parts (to prevent a fault)

Fan blade, Fan motor, Switch, Door cam,
Convection motor, Convection fan, Turntable
motor, Damper motor, Damper door assembly.

3. Do not catch the wire leads in the outer case cabinet.
4. Insert the positive lock connector 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, referring to the Pictorial Diagram.

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

1. Disconnect the oven from power supply.
2. Open the oven door and wedge the door open.
3. Remove the four (4) screws holding the exhaust cover

to the back plate and the outer case cabinet.

4. Remove the three (3) screws holding the outer case

cabinet to the back plate.

5. Remove the four (4) screws holding the right and left

sides of the outer case cabinet to the bottom plate.

6. Slide the entire outer case cabinet back out about 1

inch (3cm) to free it from retaining clips on the oven
cavity front plate.

7. Lift entire outer case cabinet from the unit.
8. Discharge the H.V. capacitor before carrying out any

further work.

9. Do not operate the oven with the outer case removed.
N.B.; Step 1, 2 and 8 form the basis of the 3D checks.
CAUTION
1. DISCONNECT THE OVEN FROM THE POWER

SUPPLY BEFORE REMOVING THE OUTER CASE
CABINET.

2. DISCHARGE THE HIGH VOLTAGE CAPACITOR

BEFORE TOUCHING ANY OVEN COMPONENTS
OR WIRING.

25

Flat type
screw driver

Terminal 
insulator

Receptacle

Covers

1. Open covers of the terminal insulator by using small

flat type screw driver.

2. Remove the receptacle from the terminal insulator.
3. Now, the terminal insulator is free.

Installation
1. Insert the receptacle into terminal insulator.
2. Close covers of the terminal insulator, as shown

illustrated below

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

wire of the power supply cord to the bottom plate.

3. Disconnect the blue and brown wire leads of the power

supply cord from the noise filter.

4. Nip the cord bushing with bushing pliers and release it

from the hole of the back plate.

5. Remove the cord bushing from the power supply cord,

and the power supply cord from the back plate.

6. Now, the power supply cord is free.

Reinstall
1. Reinstall the cord bushing to the power supply cord.
2. Insert the power supply cord with the cord bushing into

the hole of the back plate.

3. Hold the green/ yellow wire of the power supply cord to

the bottom plate with the one (1) screw.

4. Reconnect the blue and brown wire leads of the power

supply cord to noise filter, referring to the pictorial
diagram.

5. Not to be caught by the outer case cabinet, pass the

green/ yellow wire of the power supply cord under the
high voltage capacitor.

6. Reinstall the outer case cabinet and check that the

oven is operating properly.

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

wire of the power supply cord to the bottom plate.

3. Disconnect the blue and brown wire leads wire of the

power supply cord from the noise filter.

4. Remove the three (3) screws holding the back plate to

the bottom plate.

5. Remove the two (2) screws holding the right and left

chassis supports to the back plate.

6. Release the tabs of the chassis supports from the back

plate.

7. Now, the back plate with the back plate is free.

1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to

“BACK PLATE REMOVAL”.

3. Disconnect the main wire harness from the high voltage

transformer.

4. Disconnect the filament leads of the high voltage

transformer from the high voltage capacitor and the
magnetron.

5. Disconnect the high voltage fuse from the high voltage

transformer.

6. Remove the four (4) screws holding the transformer

mounting angle to the bottom plate from under the
bottom plate.

7. Remove the four (4) screws holding the high voltage

transformer to the transformer mounting angle.

8. Now, the high voltage transformer is free.

N

L

Back plate

Bottom plate

Power supply cord

Blue wire

Cord bushing

High voltage
capacitor

Brown wire

Green/ Yellow
wire

Noise filter

Screw

1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to

“BACK PLATE REMOVAL”.

3. Disconnect the high voltage wire of the high voltage

rectifier assembly from the magnetron.

4. Disconnect the filament wire of the high voltage

transformer from the magnetron.

5. Remove the two (2) screws holding the magnetron

guide to the magnetron and remove it.

6. Disconnect the wire leads and the connector from the

solid-state relay.

7. Release the main wire harness from the hole of the

magnetron separator and the hook of the fan motor.

8. Remove the three (3) screws holding the magnetron

separator to the bottom plate and the thermal cover back.

9. Remove the magnetron separator from the oven.

26

10.Carefully remove the four (4) screws holding the

magnetron to the waveguide. When removing the
screws, hold the magnetron to prevent it from falling.

11.Remove the magnetron from the unit with care so the

magnetron tube should not  be hit by any metal object
around the tube.

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. Remove the back plate from the oven, referring to

“BACK PLATE REMOVAL”.

3. Disconnect the high voltage wire of the high voltage

rectifier assembly from the magnetron.

4. Disconnect the filament lead of the high voltage

transformer from the high voltage capacitor.

5. Disconnect the high voltage fuse from the high voltage

transformer.

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

to the fan motor mounting angle.

1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to

“BACK PLATE REMOVAL”.

3. Remove the one (1) screw holding the capacitor holder

to the fan motor mounting angle. And remove the
capacitor holder from the fan motor mounting angle.

4. Disconnect the wire leads from the fan motor.
5. Remove the four (4) screws holding the fan motor

mounting angle to the bottom plate and the thermal
cover back.

6. Remove the three (3) screws holding the fan motor to

the fan motor mounting angle.

7. Now, the fan motor is free.

7. Remove the one (1) screw holding the high voltage

rectifier assembly to the capacitor holder.

8. Disconnect the high voltage rectifier assembly and

high voltage fuse from the high voltage capacitor.

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

fuse, and also the high voltage capacitor are free.

CAUTION: WHEN REPLACING HIGH VOLTAGE REC-

TIFIER ASSEMBLY, ENSURE THAT THE
CATHODE (EARTH) CONNECTION IS SE-
CURELY FIXED TO THE CAPACITOR
HOLDER WITH AN EARTHING SCREW.

1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to

“BACK PLATE REMOVAL”.

3. Disconnect the wire leads from the fan motor.
4. Disconnect the connector of the main wire harness

from the connector of the thermistor.

5. Release the main wire harness from the hole of the

magnetron separator and the hook of the fan motor.

6. Remove the three (3) screws holding the magnetron

separator to the bottom plate and the thermal cover back.

7. Remove the magnetron separator from the oven.
8. Remove the one (1) screw holding the fan motor to the

bottom plate.

9. Now, the fan motor is free.

1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to

“BACK PLATE REMOVAL”.

3. Disconnect the wire leads and the connector from the

solid-state relay.

4. Release the main wire harness from the hole of the

magnetron separator.

5. Remove the three (3) screws holding the magnetron

separator to the bottom plate and the thermal cover
back.

6. Remove the magnetron separator form the oven.

7. Remove the two (2) screws holding the solid-sate relay

to the magnetron separator.

8. Now, the solid-sate relay is free.
CAUTION : WHEN THE SOLID-STATE RELAY (MAGN-

ETRON SIDE ONE OR HEATER DUCT LEFT
SIDE ONE) IS REINSTALLED, APPLY THE
SILICON GREASE ( SHINETSU SILICON
GREASE G746 OF SHINETSU CHEMICAL
CO.,LTD.) TO THE BACK SIDE OF THE
SOLID-STATE RELAY IN A THICKNESS OF
0.3 MM. THIS IS TO PREVENT THE OVER
HEATING OF THE SOLID-STATE RELAY.

1. CARRY OUT 3D CHECKS.
2. Remove the back plate from the oven, referring to

“BACK PLATE REMOVAL”.

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

support to the oven cavity front plate.

4. Disconnect the wire leads from the damper motor.
5. Remove the two (2) screws holding the damper motor

to the motor mounting angle.

6. Now, the damper motor is free.
7. Disconnect the wire leads from the damper switch.
8. Remove the two (2) screws holding the motor mounting

angle to the damper duct assembly.

9. Remove the one (1) screw holding the damper switch

to the motor mounting angle.

10.Now, the damper switch is free.