Test Procedures - Sharp R-244(W)M Service Manual

PROCEDURE
LETTER
A TOUCH CONTROL PANEL ASSEMBLY TEST
CAUTION
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
Switch Unit, and troubleshooting by unit replacement is described according to the symptoms
indicated.
1. Switch Unit.
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. Before replacing the control unit
perform the Switch unit test (Procedure M) to determine if control unit is faulty.
2-1 In connection with keys.
a) When touching the keys, a certain group of keys do not produce a signal.
b) When touching the 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.
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.
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.
B TACT SWITCH TEST
1. Disconnect the oven from the power supply.
2. Discharge the high voltage capacitor.
3. Remove the control unit from the control panel.
4. By using an ohmmeter, check the tact switch operation.
5. When the tact switch is not depressed, an ohmmeter should indicate an open circuit. When the tact
switch is depressed, an ohmmeter should indicate a short circuit. If improper operation is indicated,
the tact switch is probably defective and should be checked.
C RELAY TEST
Remove the outer case and check voltage between Pin No 5 of the 3 pin connector (A) and common
terminal of the relay (RY2) on the control unit with an A.C. voltmeter.
The meter should indicate rated voltage, if not check oven circuit.
RY1 and RY2 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
RELAY SYMBOL

TEST PROCEDURES

COMPONENT TEST
Do not touch the electrical parts and the printed wiring board to prevent an electric
shock. Because the control unit is " TRANSLESS CIRCUIT " and all electrical parts
are used at A.C. line voltage.
Note : Check switch unit lead wire harness connection before replacement.
OPERATIONAL VOLTAGE
RY1 Approx. 18.0V D.C.
RY2 Approx. 7.0V D.C.
unit is defective.
Oven lamp / Turntable motor / Cooling fan motor
High voltage transformer
R-244M - 7
CONNECTED COMPONENTS