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R-765M - 14

If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat 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, press stop/clear
pad while checking continuity between pins 5 and 12 of connector CN-G.  If no continuity is measured,
the key unit is faulty and should be replaced.  If continuity is measured, the control unit is faulty and
should be replaced.  If a specific pad does not respond, the above method may be used.  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 connector). Use the Key unit matrix indicated on 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.

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc.
Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with
only a voltmeter and ohmmeter.
In this service manual, the touch 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 unit replacement is described according to the symptoms indicated.
1.  Key Unit

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 Unit

The following symptoms indicate a defective control unit. Replacing the control unit.

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.
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 problems 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.

G12

G11

G10

G 9

G 1

G 2

G 3

G 4

G 5

G 6

G 7

G 8

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.)

R-765M - 15

Problem: POWER ON, indicator does not light up.

CARRY OUT 3D CHECKS.

STEPS

OCCURANCE

CAUSE OR CORRECTION

The rated AC voltage is not present at

1

POWER terminal of CPU connector (CN-A).

Check supply voltage and oven power cord.

The rated AC voltage is present at primary

Low voltage transformer or secondary circuit defective.

2

side of low voltage transformer.

Check and repair.

*Insert jumper wire J1 and solder.

3

Only pattern at "a" is broken.

(CARRY OUT 3D CHECKS BEFORE REPAIR)

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

4

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

(CARRY OUT 3D CHECKS BEFORE REPAIR)

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

visual inspection of the varistor for burning
damage and examine the transformer with
tester for the presence of layer short-
circuit (check primary coil resistance). If
any abnormal condition is detected,
replace the defective parts.

CARRY OUT 4R CHECKS.

3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 1 and 3 of the 3 pin connector (A) on the control unit with

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

6. RY1, RY2 and RY3 TEST
   These are operated by D.C. voltage. Check voltage at the relay coil with a D.C. voltmeter during the

microwave cooking operation, grill cooking or dual grill 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. 18.0V D.C.

Oven lamp / Turntable motor / Cooling fan motor

RY2

APPROX. 24.0V D.C.

Grill heating element

RY3

APPROX. 18.0V D.C.

High voltage transformer

CN - A

AC

31

VRS1

(J1)

R-765M - 15

Problem: POWER ON, indicator does not light up.

CARRY OUT 3D CHECKS.

STEPS

OCCURANCE

CAUSE OR CORRECTION

The rated AC voltage is not present at

1

POWER terminal of CPU connector (CN-A).

Check supply voltage and oven power cord.

The rated AC voltage is present at primary

Low voltage transformer or secondary circuit defective.

2

side of low voltage transformer.

Check and repair.

*Insert jumper wire J1 and solder.

3

Only pattern at "a" is broken.

(CARRY OUT 3D CHECKS BEFORE REPAIR)

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

4

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

(CARRY OUT 3D CHECKS BEFORE REPAIR)

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

visual inspection of the varistor for burning
damage and examine the transformer with
tester for the presence of layer short-
circuit (check primary coil resistance). If
any abnormal condition is detected,
replace the defective parts.

CARRY OUT 4R CHECKS.

3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 1 and 3 of the 3 pin connector (A) on the control unit with

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

6. RY1, RY2 and RY3 TEST
   These are operated by D.C. voltage. Check voltage at the relay coil with a D.C. voltmeter during the

microwave cooking operation, grill cooking or dual grill 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. 18.0V D.C.

Oven lamp / Turntable motor / Cooling fan motor

RY2

APPROX. 24.0V D.C.

Grill heating element

RY3

APPROX. 18.0V D.C.

High voltage transformer

CN - A

AC

31

VRS1

(J1)

R-765M - 15

Problem: POWER ON, indicator does not light up.

CARRY OUT 3D CHECKS.

STEPS

OCCURANCE

CAUSE OR CORRECTION

The rated AC voltage is not present at

1

POWER terminal of CPU connector (CN-A).

Check supply voltage and oven power cord.

The rated AC voltage is present at primary

Low voltage transformer or secondary circuit defective.

2

side of low voltage transformer.

Check and repair.

*Insert jumper wire J1 and solder.

3

Only pattern at "a" is broken.

(CARRY OUT 3D CHECKS BEFORE REPAIR)

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

4

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

(CARRY OUT 3D CHECKS BEFORE REPAIR)

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

visual inspection of the varistor for burning
damage and examine the transformer with
tester for the presence of layer short-
circuit (check primary coil resistance). If
any abnormal condition is detected,
replace the defective parts.

CARRY OUT 4R CHECKS.

3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 1 and 3 of the 3 pin connector (A) on the control unit with

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

6. RY1, RY2 and RY3 TEST
   These are operated by D.C. voltage. Check voltage at the relay coil with a D.C. voltmeter during the

microwave cooking operation, grill cooking or dual grill 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. 18.0V D.C.

Oven lamp / Turntable motor / Cooling fan motor

RY2

APPROX. 24.0V D.C.

Grill heating element

RY3

APPROX. 18.0V D.C.

High voltage transformer

CN - A

AC

31

VRS1

(J1)