DOWNLOAD Sharp R-22AMM (serv.man7) Service Manual ↓ Size: 203.48 KB | Pages: 6 in PDF or view online for FREE

R22AMM

7 – 5

The touch control panel consists of circuits including semiconductors such as LSI etc. Therefore, unlike conventional microwave ovens, proper main-
tenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control panel assembly is divided into three units,
Control Unit, Switch Unit and Encoder Unit troubleshooting by unit replacement is described according to the symptoms indicated.

1. Switch Unit 

NOTE: Check the lead wire harness connections among big and small switch units and control unit before replacement.

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

a) When touching the buttons, a certain button produces no signal at all.

b) When touching the buttons, sometimes a button produces no signal.

2. Encoder

NOTE: Check the lead wire connection between encoder and control unit before replacement.

The following symptoms indicate a defective encoder. Replace the encoder.

a) When rotating the encoder, the cooking time can not be entered.

3. Control Unit

The following symptoms may indicate a defective control unit. Replacing the control unit. Before replacing the control unit, perform the switch unit
test (Procedure O) to determine if control unit is faulty.

1) Programming problems.

a) When touching the buttons, a certain group of buttons do not produce a signal.

2) Display problems.

a) For a certain digit, all or some segments do not light up.

b) For 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.

3) Other possible problems caused by defective control unit.

a) Buzzer does not sound or continues to sound.

b) Cooking is not possible.

1. CARRY OUT 3D CHECKS.

2. Remove the switch unit from the control panel, referring to control panel removal.

3. To test the switches (SW1-SW5) on the switch unit, check between the terminals of the connector CN-F as described in the following table by

using ohmmeter when the switches are released and depressed.

4. If incorrect readings are obtained, replace the defective switch.

5. CARRY OUT 4R CHECKS.

SW1

F1 - F4

Open Circuit

Short Circuit

SW2

F1 - F5

Open Circuit

Short Circuit

SW3

F2 - F4

Open Circuit

Short Circuit

SW4

F2 - F5

Open Circuit

Short Circuit

SW5

F3 - F4

Open Circuit

Short Circuit

R22AMM

7 – 6

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin Nos. 3 and 5 of the connector (A) on the control unit with an A.C. voltmeter. The meter should
indicate 230 - 240 volts, if not check control unit circuity.

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.

CARRY OUT 4R CHECKS.

When the indicator does not light up, follow the troubleshooting guide given below for repair.

CARRY OUT 3D CHECKS.

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 pres-

ence of layer short-circuit (check primary coil resistance). If any abnormal condition is detected, replace the defective parts.

CARRY OUT 4R CHECKS.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

APPROX. 25.9V D.C.

Oven lamp, Blower motor and Antenna motors

RY3

APPROX. 25.9V D.C.

High voltage transformer (T1)

RY4

APPROX. 25.9V D.C.

High voltage transformer (T2)

 1 

The rated AC voltage is not present at POWER terminal of 
CPU connector (CN-A). 

Check supply voltage and oven power cord. 

 2 

The rated AC voltage is present at primary side of touch con-
trol transformer. 

Touch control transformer or secondary circuit defective. Check and 
repair. 

R22AMM

7 – 6

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin Nos. 3 and 5 of the connector (A) on the control unit with an A.C. voltmeter. The meter should
indicate 230 - 240 volts, if not check control unit circuity.

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.

CARRY OUT 4R CHECKS.

When the indicator does not light up, follow the troubleshooting guide given below for repair.

CARRY OUT 3D CHECKS.

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 pres-

ence of layer short-circuit (check primary coil resistance). If any abnormal condition is detected, replace the defective parts.

CARRY OUT 4R CHECKS.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

APPROX. 25.9V D.C.

Oven lamp, Blower motor and Antenna motors

RY3

APPROX. 25.9V D.C.

High voltage transformer (T1)

RY4

APPROX. 25.9V D.C.

High voltage transformer (T2)

 1 

The rated AC voltage is not present at POWER terminal of 
CPU connector (CN-A). 

Check supply voltage and oven power cord. 

 2 

The rated AC voltage is present at primary side of touch con-
trol transformer. 

Touch control transformer or secondary circuit defective. Check and 
repair. 

R22AMM

7 – 6

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin Nos. 3 and 5 of the connector (A) on the control unit with an A.C. voltmeter. The meter should
indicate 230 - 240 volts, if not check control unit circuity.

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.

CARRY OUT 4R CHECKS.

When the indicator does not light up, follow the troubleshooting guide given below for repair.

CARRY OUT 3D CHECKS.

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 pres-

ence of layer short-circuit (check primary coil resistance). If any abnormal condition is detected, replace the defective parts.

CARRY OUT 4R CHECKS.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

APPROX. 25.9V D.C.

Oven lamp, Blower motor and Antenna motors

RY3

APPROX. 25.9V D.C.

High voltage transformer (T1)

RY4

APPROX. 25.9V D.C.

High voltage transformer (T2)

 1 

The rated AC voltage is not present at POWER terminal of 
CPU connector (CN-A). 

Check supply voltage and oven power cord. 

 2 

The rated AC voltage is present at primary side of touch con-
trol transformer. 

Touch control transformer or secondary circuit defective. Check and 
repair.