Read Sharp R-248D (serv.man2) Service Manual online
R248D(SL)
8 – 4
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.
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.
[12] Procedure L: SWITCH UNIT TEST
1. CARRY OUT 3D CHECKS.
2. Isolate the switch unit with the control panel frame to be tested.
3. Using an ohmmeter and referring to the switch unit matrix indicated on the switch unit circuit, check the circuit between the pins of the switch unit
that correspond to the STOP button. When the button is pressed, the ohmmeter should indicate short circuit. When the button is released, the
ohmmeter should indicate open circuit. If incorrect readings are obtained, the switch unitbutton is faulty and must be replaced. About the other but-
tons, the above method may be used.
ohmmeter should indicate open circuit. If incorrect readings are obtained, the switch unitbutton is faulty and must be replaced. About the other but-
tons, the above method may be used.
4. CARRY OUT 4R CHECKS.
[13] Procedure M: RELAY (RY1, RY2) TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between the normal open terminal of the relay RY1 and the normal open terminal of the relay RY2 on the
control unit with an A.C. voltmeter. The meter should indicate 230 - 240 volts, if not check oven circuit.
control unit with an A.C. voltmeter. The meter should indicate 230 - 240 volts, 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 unit is defective.
CARRY OUT 4R CHECKS.
RELAY SYMBOL
OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RY1
Approx. 12.6V D.C.
Oven lamp / Turntable motor / Cooling fan motor
RY2
Approx. 12.3V D.C.
High voltage transformer
< SWITCH UNIT >
1
B
A
2
3
4
5
6
WH-A
8-PIN
WIRE HARNESS
SW100
SW1
SW3
SW2
SW4
EXPRESS
COOK & DEFROST
7
8
C100
0.01uF/ 16V
R100
100K 1/4W
R101
100K 1/4W
C101
0.01uF/ 16V
STOP
POWER
AUTO
MINUTE
START
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