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R-895M - 17

The 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 control panel assembly is divided into two units, Control Unit and Key Unit,
and also the Control unit is divided into two units, CPU unit and Power unit, and troubleshooting by
replacement is described according to the symptoms indicated.
1. Key Unit  Note : Check Key unit ribbon connection before replacement.

The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.

2. Control Panel

The following symptoms indicate a defective control unit. Before replacing the control unit perform
the key unit test (Procedure N) to determine if control unit is faulty.

2-1  In connection with pads

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

2-2  In connection with indicators

a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding segments 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.

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

a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.

If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the ribbon cable is
making 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 flat ribbon
cable that connects the key 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 Key unit matrix indicated on the control panel
schematic and place a jumper wire between the pins that correspond to the STOP/CLEAR pad making
momentary contact. If the control unit responds by clearing with a beep the key  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 pad
does not respond, the above method may be used (after clearing the control unit) to determine if the
control unit or key pad is at fault.
CARRY OUT 4R CHECKS.

G 9

G10

G11

G12

Pie/

Quiche

Ready

Meals

Rice/

Pasta

Italian

Dish

Indian

Dish

Roast

Pork

Chinese

Dish

Crispy

Potatoes

Roast

Beef/

Lamp

Crispy

Crumb

Foods

DUAL

CONV. /

GRILL

Roast

Poultry

POWER

LEVEL

STOP

CLEAR

PIZZA

Desserts

10sec.

1min.

10min.

GRILL BREAKFAST

MORE

Chicken

Quarters

Whole

Poultry

CONV

(˚C)

Meat

Joint

G 8

G 7

G 6

G 5

G 4

G 3

G 2

G 1

UP

LESS

DOWN

info

START

AUTO MINUTE

KITCHEN TIMER

CLOCK SET

R-895M - 18

control unit with an A.C. voltmeter.
The meter should indicate 230-240 volts, if not check oven circuit.

Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation, grill
operation, convection operation or dual 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. 18.0V D.C.

Oven lamp / Turntable motor

RY2

Approx. 18.0V D.C.

High voltage transformer

RY3

Approx. 24.0V D.C.

Grill (Top) heating element

RY4

Approx. 24.0V D.C.

Bottom heating element

RY5

Approx. 24.0V D.C.

Touch control transformer

RY6

Approx. 24.0V D.C.

Fan motor

RY7

Approx. 24.0V D.C.

Convection motor

CARRY OUT 4R CHECKS..

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.

CARRY OUT 3D CHECKS.

STEPS

OCCURRENCE

CAUSE OR CORRECTION

1

The rated AC voltage is not present between

Check supply voltage and oven power cord.

Pin Nos. 1 and 3 of the 4-pin connector (E).

2

The rated AC voltage is present at primary

Low voltage transformer or secondary circuit defective.

side of low voltage transformer.

Check and repair.

3

Only pattern at “a” is 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)

NOTE: *At the time of these repairs, make a visual

inspection of the varistor for burning dam-
age and examine the transformer with tester
for the presence of layer short circuit (check
primary coil resistance).

If any abnormal condition is detected, re-
place the defective parts.

CARRY OUT 4R CHECKS.

CN-A

CN-E

D12

7

(J1)

D13

VRS1

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin Nos. 1 and 3 of the 4 pin connector (E) on the

R-895M - 19

The touch control section consists of the following units as
shown in the touch control panel circuit.

(1) Key Unit
(2) Control Unit (The Control unit consists of Power unit

and CPU unit.)

The principal functions of these units and signals commu-
nicated among them are explained below.

Key Unit
The key unit is composed of a matrix, signals generated in
the LSI are sent to the key unit from P40, P41, P72, P73,
P74, P75, P76 and P77.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through P50 - P53
to perform the function that was requested.

Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, reset circuit, buzzer circuit, relay
circuit, temperature measurement circuit, indicator circuit
and back light circuit.

This LSI controls the temperature measurement  sig-
nal, key strobe signal, relay driving signal for oven
function and indicator signal.

This circuit generates voltage necessary in the control
unit.

Symbol

Voltage

Application

VC

-5.2V

LSI(IC1)

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.

OUTLINE OF TOUCH CONTROL PANEL

A circuit to generate a signal 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 (key touch sound and completion
sound).

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

To drive the magnetron, grill heating element, bottom
heating element, convection motor,  fan motor, turnta-
ble motor, touch control transformer and light the oven
lamp.

A circuit to drive the back light (Light emitting diodes
LD1 - LD10).

This circuit consists 7-digits, 39-segments and 3-com-
mon electrodes using a Liquid Crystal Display.

MISTOR)
The temperature in the oven cavity is sensed by the
thermistor. The variation of resistance according to
sensed temperature is detected by the temperature
measurement circuit and the result applied to LSI. The
LSI uses this information to control the relay and
display units.

R-895M - 20

8

AN2

IN

Input signal which communicates the door open/close information to LSI.
Door closed; “H” level signal.
Door opened; “L” level signal.

9

AN1

IN

10

AN0

IN

Terminal to change functions to the Models.

11

P57

OUT

Timing signal output terminal for temperature measurement(OVEN
THERMISTOR).
“H” level (GND) : Thermistor OPEN timing.
“L” level (-5V) : Temperature measuring timing. (Oven cooking)

12

P56

OUT

Terminal not used.

13

P55

OUT

Timing signal output terminal for temperature measurement(OVEN
THERMISTOR).
“H” level (GND) : Thermistor OPEN timing.
“L” level (-5V) : Temperature measuring timing. (Oven cooking)

14

P54

OUT

Terminal not used.

15

P53

IN

Signal coming from touch key.
When any one of G12 line keys on key matrix is touched, a corresponding signal
from P40, P41, P72, P73, P74, P75, P76 and P77 will be input into P53. When no
key is touched, the signal is held at “L” level.

16

P52

IN

Signal similar to P53.
When any one of G11 line keys on key matrix is touched, a corresponding signal
will be input into P52.

17

P51

IN

Signal similar to P53.
When any one of G10 line keys on key matrix is touched, a corresponding signal
will be input into P51.

18

P50

IN

Signal similar to P53.
When any one of G9 line keys on key matrix is touched, a corresponding signal will
be input into P50.

19-22

P47-P44

IN/OUT

Terminal not used.

23

TOUT

OUT

Signal to sound buzzer.
A: Tact switch touch sound.
B: Completion sound.
C: When the temperature of the oven cavity

reaches the preset temperature in the
preheating mode, or when the
preheating hold time (30 minutes) is
elapsed.

24

INT2

IN

Signal to synchronized LSI with commercial power source frequency(50Hz).
This is basic timing for time processing of LSI.

25

P41

OUT

Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P50-P53 terminal
while one of G8 line key on matrix is touched.

A

B

C

H : GND

L

0.1 sec.

2.0 sec.

1.0 sec.

1.0 sec.

20 msec.

H : GND

L (-5V)

The I/O signal of the LSI are detailed in the following table.

1

C1

IN

Terminal not used.

2

VL1

IN

Power source voltage input terminal.
Standard voltage for LCD.

3

AN7

IN

Terminal to change the on timing of the cook relay (RY2).

4-5

AN6-AN5

IN

6

AN4

OUT

Terminal not used.

7

AN3

IN

Temperature measurement input: OVEN THERMISTOR.
By inputting DC voltage corresponding to the temperature detected by the
thermistor, this input is converted into the temperature by the A/D converter built
into the LSI.