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R-21FBSTM/R-22FBSTM - 13

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance can not be performed with only a voltmeter
and ohmmeter.
In this service manual, the touch control panel assembly is in three units,Control unit,Switch Unit,  and
LED Unit. Troubleshooting by unit replacement is described according to the symptoms indicated.
Control Panel.

The following symptoms indicate a defective control unit.

1.  Switch Unit.

NOTE: Check switch unit lead wire harness connection before replacement.

The following symptoms indicate a defective switch unit. Replace the switch unit.

a) When touching the keys, a certain key produces no signal at all.
b) When touching a key,two figures or more are displayed.
c) When touching the keys,sometimes a key produces no signal.

2. Control Unit

The following symptoms indicate a defective control unit. Replace the control unit, perform the switch
 unit test(Procedure L) to determine if control unit is faulty.

2-1In connection with keys.

a) When touching a keys, a certain group of keys do not produce a signal.
b) When touching a keys, no keys produce a signal.

2-2.In connection with indicators.

a) At a certain digit, all or some dots do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding dots of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
h)  When touching a tact switch, the control unit does not respond.

2-3.Other possible problems caused by defective control unit.

a) Buzzer does not sound or continues to sound.
b) Clock does not operate prperly.
c) Cooking is not possible.

3.

LED Unit
a) No backlight behind display.
b) Dull backlight behind display.

CARRY OUT 3D CHECKS.

Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals as described in the table below.

Table: Resistance of Motor

Motors

Resistance

Fan motor

Approximately 290 

Ω

Turntable motor

Approximately 12 - 15 k

Ω

If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.

1. CARRY OUT 3D CHECKS.
2. Disconnect the leads from the primary of the high voltage transformer. Make sure that the leads

remain isolated from other oven components and chassis (Use insulation tape if necessary.)

3. Connect the voltmeter, set to 250V AC, across the motor terminals. (Refer to the relevant motor test

procedure or pictorial diagram for the correct terminal numbers.)

4. Arrange the meter in a position where it can be read during the test.

(Do not touch the meter, meter leads or oven circuitry while the oven is active.)

5. Close the oven door.
6. Set  the power level to 800W and set the relevant timer for about three (3) minutes.
7. Note the reading on the meter and carefully observe the motor under test to see if it is turning.
8. CARRY OUT 3D CHECKS.
9. Remove the test meter leads.
10. Reconnect the leads to the primary of the high voltage transformer.

If a reading of the line voltage was obtained (step 7) but the motor was not turning then it is faulty and
should be replaced. If the meter indicated that the no supply was present then the winding to the motor
should be checked for continuity or other circuit checks should be made, i.e. relays,switches.

R-21FBSTM/R-22FBSTM - 14

Remove the outer case and check voltage between Pin No 1and Pin No 3 of the 3 pin connector (A) on
the control unit with an A.C. voltmeter.
The meter should indicate rated voltage, if not check oven circuit.

RY1,RY3 and RY4 Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.

DC. voltage indicated ............. Defective relay.
DC. voltage not indicated ....... Check diode which is connected to the relay coil. If diode is good,

control unit is defective.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

Approx.   12.0V D.C.

Oven lamp / Turntable motor

RY3

Approx.   12.0V D.C.

High voltage transformer

RY4

Approx.   12.0V D.C.

Fan motor

If the display fails to clear when the STOP key is depressed, first verify the lead wire harness is
marking good contact, verify that the stop switch operates properly; that is the contacts are
closed when the door is closed and open when the door is open. If the stop switch is good,
disconnect the lead wire harness that connects the switch unit to the control unit and make sure
the stop switch is closed (either close the door or short the stop switch connecter). Use the
switch unit matrix indicated on the switch unit circuit and place a jumper wire between the pins
that correspond to the STOP key making momentary contact. If the control unit responds by
clearing with a beep the switch unit is faulty and must be replaced. If the control unit does not
respond, it is a faulty and must be replaced. If a specific key does not respond, the above
method may be used (after clearing the control unit) to determine if the control unit or switch
unit is at fault.

(J1

1

)

(J10)

13

12

10

11

ENCODER

A

B

C

RSW1

6

7

8

+1MIN

SW4

(J13)

(J12)

(J15)

(J14)

(J17)

(J16)

STOP

SW3

9

2

5

4

3

1

Switch unit

14

AUTOMATIC

SW1

SW2

4.7KF

12KF

R-21FBSTM/R-22FBSTM - 15

To protect the electronic circuits, this model is provided with a fine foil pattern added to the input circuit
on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.

STEPS

OCCURRENCE

CAUSE OR CORRECTION

1

The rated AC voltage is not present between

Check supply voltage and oven power cord.

 Pin No. 5 of the 3 pin connector (A)

2

.The rated AC voltage is not present at primary Low voltage transformer or secondary circuit defective.
 side of low voltage transformer.

check and repair.

3

Pattern at "a" and "b" are broken.

*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)

4

Pattern at "a" and "b" are broken.

*Insert the coil RCILF2003YAZZ between "c" and "d

(CARRY OUT 3D CHECKS BEFORE REPAIR)

                CARRY OUT 4D CHECKS

NOTE: *At the time of making these repairs,

make a visual inspection of the varistor.
Check for burned damage. If any ab-
normal condition is detected, replace
the defective parts.

The touch control section consists of the following

units as shown in the touch control panel circuit.

(1) Switch Unit

(3) LED Unit

(2) Control Unit

The principal functions of these units and the signals

communicated among them are explained below.

The switch unit is composed of a matrix, signals

generated in the LSI are sent to the switch unit

through P22,P23 and P24.

When a switch button is touched, a signal is com-

pleted through the switch unit  and passed back to the

LSI through P50 and P51 to perform the function that

was requested.

Control unit consists of LSI, power source circuit,

relay circuit, back light circuit, synchronizing signal

circuit, reset circuit, buzzer circuit, and indicator cir-

cuit.

This LSI controls the tact switch strobe signal,

relay driving signal, for oven function and indicator

signal.

This circuit generates voltage necessary in the

control unit.

Symbol

Voltage

Application

VC

-5.0V

LSI(IC1)

OUTLINE OF CONTROL PANEL

The power source synchronizing signal is available in

order to compose a basic standard time in the clock circuit.

It accompanies a very small error because it works on

commercial frequency.

A circuit to generate a signals which resets the LSI to the

initial state when power is supplied.

The buzzer is responsive to signals from the LSI to emit

audible sounds (tact switch touch sound and completion

sound).

A switch to "tell" the LSI if the door is open or closed.

To drive the magnetron, fan motor, turntable motor, light

the oven lamp.

This circuit consists of 4-digits, 12-segments and 3-com-

mon electrodes using a Liquid Crystal Display.

The encoder converts the signal generated by LSI into the

pulse signal, and the pulse signal is returned to the LSI

A circuit to drive the back light (Light emitting diodes LD1-

LD3).

A circuit consisting of three light emitting diodes (LD1-

LD3)which are drivenby  the control unit and provide the

backlight for the display.

R-21FBSTM/R-22FBSTM - 16

1

P50

IN

Signal coming from tact switch.
When tact switch SW4 is touched a signal out of P24 will be input into P50. When
no tact switch is touched, the signal is held at "H" level.

2

P51

IN

Signal coming from tact switch.
When either tact switch SW1,SW2 and SW3 is touched a corresponding signal out
of P22,P23 and P24 will be input into P51. When no tact switch is touched, the
signal is held at "H" level.

3

P52

IN

Terminal not used.

4

P53

OUT

Terminal not used.

5

VPP

-

Connected to VSS through the resistor.

6

XT1

IN

Connected to VSS.

7

XT2

-

Terminal not used.

8

VDD

IN

Power source voltage input terminal.
The power souce voltage to drive the LSI. Connected to GND.

9

VSS

IN

Power source voltage input terminal.
The power souce voltage to drive the LSI.

10

X1

IN

Internal clock oscillation frequency input setting.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit
with respect to X2 terminal.

11

X2

OUT

Internal clock oscillation frequency input setting.
Output to control oscillation input of X1.

12

RESET

IN

Auto clear terminal.
Signal is input to rest the LSI to the initial state when power is applied.

13-15

P00-P02

OUT

Terminal not used

16

R03

OUT

Back light circuit (Light emitting diodes) driving signal

17

CAPH

-

Terminal not used.

18

CAPL

-

Terminal not used.

19-21

VLCO-VLC2

IN

Power source voltage input terminal.
Standard voltage for LCD.

22

COMO

OUT

Connection to LCD signal C1.

23

COMO1

OUT

Connection to LCD signal C2.

24

COMO2

OUT

Connection to LCD signal C3.

25

COMO3

IN

Terminal not used.

26-37

SEG0 

-

SEG11

OUT

Segment data signal.
Connected to LCD.
The relation between signals are as follows:

LSI signal (Pin No.)

LCD segment

LSI signal (Pin No.) LCD segment

SEG 0 (26) .............................. S1

SEG 6 (32) ........................... S7

SEG 1 (27) .............................. S2

SEG 7 (33) ........................... S8

SEG 2 (28) .............................. S3

SEG 8 (34) ........................... S9

SEG 3 (29) .............................. S4

SEG 9 (35) ............................ 10

SEG 4 (30) .............................. S5

SEG 10 (36) ....................... S11

SEG 5 (31) .............................. S6

SEG 11 (37) ....................... S12

    38-40     

SEG0-SEG14

OUT

Terminal not used.

       41

    P17

OUT       Oven lamp and turntable motor driving signal.

To turn on and off shut off relay(RY1).
The square waveform voltage is
delivered to the RY1 driving curcuit.

LSI(IXA216DRZZ)
The I/O signal 

of the LS

I(IXA216DRZZ) are detailed in the following table.

20 msec.

During cooking

H : GND

L : -5V