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R-890SLM

9 - 2

This unit uses CMOS LSI in the integral part of the circuits. 

When handling these parts, the following precautions should 

be strictly followed. CMOS LSI have extremely high impedance 

at its input and output terminals. For this reason, it is easily 

influenced by the surrounding high voltage power source, static 

electricity charge in clothes, etc., and sometimes it is not fully 

protected by the built-in protection circuit.
In order to protect CMOS LSI.
1)  When storing and transporting, thoroughly wrap them in 

aluminium foil. Also wrap PW boards containing them in 

aluminium foil.

2)  When soldering, ground the technician as shown in the 

figure and use grounded soldering iron and work table.

approx. 1M ohm

We describe the procedures to permit servicing of the control 

panel of the microwave oven and the precautions you must take 

when doing so. To perform the servicing, power to the control 

panel is available either from the power line of the oven or from 

an external power source.
1)  Servicing the control panel with power supply of the 

CAUTION: THE HIGH VOLTAGE TRANSFORMER OF THE 

MICROWAVE  OVEN  IS  STILL  LIVE  DURING 

SERVICING AND PRESENTS A HAZARD. 

 

Therefore, before checking the performance of the control 

panel, 
(1)  Disconnect the power supply cord, and then remove 

outer case.

(2)  Open the door and block it open.
(3)  Discharge high voltage capacitor.
(4)  Disconnect  the  leads  to  the  primary  of  the  power 

transformer.

(5)  Ensure that these leads remain isolated from other 

components and oven chassis by using insulation tape.

(6)  After that procedure, re-connect the power supply cord.
After checking the performance of the control panel,
(1)  Disconnect the power supply cord.
(2)  Open the door and block it open.
(3)  Reconnect  the  leads  to  the  primary  of  the  power 

transformer.

(4)  Reinstall the outer case (cabinet).
(5)  Reconnect the power supply cord after the outer case is 

installed.

(6)  Run the oven and check all functions.

a) On some models, the power supply cord between the 

control panel and the oven is so short that the two 

can’t be separated.

 

 

  For those models, check and repair all the controls 

(sensorrelated ones included) of the control panel 

while keeping it connected to the oven.

b)  On some models, the power supply cord between the 

control panel and the oven is long enough that they 

may be separated from each other. For those models, 

therefore, it is possible to check and repair the controls 

of the control panel while keeping it apart from the 

oven; in this case you must short both ends of the door 

sensing switch (on PWB) of the control panel with a 

jumper, which brings about an operational state that 

is equivalent to the oven door being closed. As for the 

sensor related controls of the control panel, checking 

them is possible if the dummy resistor(s) with resistance 

equal to that of the controls are used.

 

Disconnect the control panel completely from the oven, and 

short both ends of the door sensing switch (on PWB) of 

the control panel, which brings about an operational state 

that is equivalent to the oven door being closed. Connect 

an external power source to the power input terminal of the 

control panel, then it is possible to check and repair the 

controls of the control panel; it is also possible to check the 

sensor-related controls of the control panel by using the 

dummy resistor(s).

Tools required to service the control panel assembly.
1)  Soldering iron: 60W
 

(It is recommended to use a soldering iron with a grounding 

terminal.)

2)  Oscilloscope: Single beam, frequency range: DC - 10MHz 

type or more advanced model.

3)  Others: Hand tools

1)  Before turning on the power source of the control unit, 

remove the aluminium foil applied for preventing static 

electricity.

2)  Connect the connector of the switch unit to the control unit 

being sure that the lead wires are not twisted.

3)  After aluminium foil is removed, be careful that abnormal 

voltage due to static electricity etc. is not applied to the input 

or output terminals.

4)  Attach connectors, electrolytic capacitors, etc. to PWB, 

making sure that all connections are tight.

5)  Be sure to use specified components where high precision 

is required.

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10 - 1

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.

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.

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11 - 1

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: 

Disconnect the power supply cord.

1.

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;

Door does not close firmly.
Door hinge, support or latch hook is damaged.
The door gasket or seal is damaged.
The door is bent or warped.

2.

1.
2.
3.
4.

There are defective parts in the door interlock system.
There are defective parts in the microwave generating and 

transmission assembly.
There is visible damage to the oven.

Do not operate the oven:

Without the RF gasket (Magnetron).
If the wave guide or oven cavity are not intact.
If the door is not closed.
If the outer case (cabinet) is not fitted.

5.
6.

7.

1.
2.
3.
4.

Before wiring, 

Disconnect the power supply cord.
Open the door and block it open.
Discharge the high voltage capacitor and wait for 60 

seconds.

2.  Don't let the wire leads touch to the following parts;

High voltage parts:
Magnetron,  High  voltage  transformer,  High  voltage 

capacitor and High voltage rectifier assembly.
Hot parts:
Grill  heating  element,  Oven  lamp,  Magnetron,  High 

voltage transformer and Oven cavity.

1.

1)
2)
3)

1)

2)

Sharp edge:
Bottom plate, Oven cavity, Waveguide flange, Chassis 

support and other metallic plate.
Movable parts (to prevent a fault)
Fan blade, Fan motor, Switch, Turntable motor, Convection 

motor.

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,

  referring to the Pictorial Diagram. 

3)

4)

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

removal procedures:

To remove the outer case cabinet, proceed as follows.
1.   Disconnect oven from power supply.
2.   Open the oven door and wedge it open.
3.   Remove the two (2) screws holding the back plate to the 

oven cavity rear plate. Remove the back plate.

4.   Remove the air duct assembly from the oven cavity rear 

plate.

5.   Remove the air duct assembly.
6.   Remove the nine (9) screws from rear and along the side 

edge of outer case cabinet.

7. Slide the entire case back about 3 cm to free it from retaining 

clips on the cavity face plate.

8.   Lift the entire outer case cabinet from the oven.
9.   Discharge the H.V. capacitor before carrying out any further work.
10. Do not operate the oven with the outer case cabinet removed.
NOTE: Step 1, 2 and 9 form the basis of the 3D checks.
CAUTION: DISCHARGE  HIGH  VOLTAGE  CAPACITOR 

BEFORE TOUCHING ANY OVEN COMPONENT 

OR WIRING.

CAUTION: W H E N   T H E   O U T E R   C A S E   C A B I N E T   I S 

REINSTALLED, INSTALL IT BEFORE THE BACK 

PLATE  IS  INSTALLED,  OR THE  OUTER  CASE 

CABINET WILL BE DEFORMED.

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R-890SLM

Carefully remove four (4) screws holding the magnetron to 

the waveguide. When removing the screws hold the magn-

etron to prevent it from falling.
Remove the magnetron from the waveguide with care so the 

magnetron antenna is not hit by any metal object around the 

antenna.

CAUTION: WHEN  REPLACING  THE  MAGNETRON,  BE 

SURE  THE  R.F.  GASKET  IS  IN  PLACE AND 

THE  MAGNETRON  MOUNTING  SCREWS ARE 

TIGHTENED SECURELY.

5.

6.

CARRY OUT 3D CHECKS.
Disconnect the H.V. wire and filament lead of the transformer 

from the magnetron.
Remove the one (1) screw holding the chassis support to 

the magnetron.
Move the air intake duct to left.

1.
2.

3.

4.

CARRY OUT 3D CHECKS.
Remove the one (1) screw holding the noise filter to the 

chassis support.
Release the noise filter from the tabs of the fan duct.
Remove the one (1) screw holding the chassis support to 

the oven cavity front flange.
Remove one (1) screw holding the chassis support to the 

magnetron.
Remove the chassis support from the oven cavity.
Disconnect the wire leads from the fan duct.
Remove the one (1) screw holding the capacitor holder to 

the oven cavity back plate.
Release the tabs of the capacitor holder from the fan duct.
Remove the one (1) screw holding the fan duct to the oven 

cavity back plate.
Remove the fan duct from the oven.
Remove the fan duct from the fan motor shaft according to 

the following procedure.

  i)  Hold the edge of the rotor of the fan motor by using a pair 

    of groove joint pliers.

1.
2.

3.
4.

5.

6.
7.
8.

9.
10.

11.
12.

CARRY OUT 3D CHECKS.
Disconnect the filament leads of high voltage transformer 

from high voltage capacitor and the magnetron.
Disconnect the high voltage transformer secondary wire 

from the high voltage transformer.
Disconnect the main wire harness from the high voltage 

transformer.

1.
2.

3.

4.

Remove the two (2) screws holding the transformer to the 

base plate.
Remove the transformer.
Now the high voltage transformer is free.

5.

6.
7.

(HIGH VOLTAGE CAPACITOR AND HIGH VOLTAGE RECTIFIER ASSEMBLY)
To remove the components, proceed as follows.

CARRY OUT 3D CHECKS.
Disconnect the filament lead of the high voltage transformer 

and the high voltage wire A from the high voltage capacitor.
Remove one (1) screw holding earth side terminal of the 

high voltage rectifier assembly.
Remove one (1) screw holding fan duct to the oven cavity 

rear plate.
Remove one (1) screw holding capacitor holder to the oven 

cavity rear plate.
Release the capacitor holder from the fan duct.
Remove the high voltage capacitor from the capacitor holder.

1.
2.

3.

4.

5.

6.
7.

Disconnect the high voltage rectifier assembly from the high 

voltage capacitor.
Disconnect the high voltage rectifier assembly from the high 

voltage capacitor.
Now, the high voltage rectifier assembly and the high volt-

age capacitor should be free. 

CAUTION: WHEN  REPLACING  HIGH  VOLTAGE  RECTI-

FIER ASSEMBLY, ENSURE THAT THE CATHODE 

(EARTH) CONNECTION IS SECURELY FIXED TO 

THE CAPACITOR HOLDER WITH AN EARTHING 

SCREW.

8.

9.

10.

CAUTION:  •  Make sure that no swarf from the rotor enters the 

gap between the rotor & stator of the fan motor.

 

•  Avoid touch 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.

    ii) Remove the fan blade assembly from the shaft of the fan

      motor by pulling and rotating the fan blade with your hand.

    iii) Now, the fan blade is free.
CAUTION: Do not reuse the removed fan blade as the fixing 

hole may be oversize.

13. Remove the two (2) screws holding the fan motor to the fan 

duct.

14. Now, the fan motor is free.

Install the fan motor to the fan duct with the two (2) screws.
Install the fan blade to the fan motor shaft according to the 

following procedure.

  i)   Hold the centre of the bracket which supports the shaft of 

    the fan motor on a flat table.

  ii)  Apply the screw lock tight into the hole (for shaft) of the

    fan blade.

  ii)  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.

1.
2.

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