Read Sharp R-238ASL (serv.man8) Service Manual online
R238A(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: KEY UNIT (MEMBRANE SWITCH) TEST
1. CARRY OUT 3D CHECKS.
2. Isolate the key unit with the control panel frame to be tested.
3. Using an ohmmeter and referring to the key unit matrix indicated on the control unit circuit, check the circuit between the pins of the key unit that
correspond to the STOP/CLEAR key. When the pad is pressed, the ohmmeter should indicate short circuit. When the pad is released, the ohmme-
ter should indicate open circuit. If incorrect readings are obtained, the key unit is faulty and must be replaced. About the other pads, the above
method may be used.
ter should indicate open circuit. If incorrect readings are obtained, the key unit is faulty and must be replaced. About the other pads, the above
method may be used.
4. CARRY OUT 4R CHECKS.
[13] Procedure M: RELAY 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
Pin NO. G1
Pin NO. G10
Key unit ribbon
cable
Key unit (Membrane Switch) front view
POWER
LEVEL
10min.
CHICKEN
QUARTERS
WHOLE
POULTRY
MEAT
JOINT
(TIME)
(TIME)
(WEIGHT)
(WEIGHT)
STOP
CLEAR
10sec.
1min.
ROAST
POULTRY
ROAST
PORK
ROAST
BEEF / LAMB
AUTO
COOK
START
AUTO MINUTE
KITCHEN TIMER
CLOCK SET
G1
G2
G3
G4
G5
G6
G7
G8
G9
G10
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