Sharp R-212B Service Manual page 48

R-212B
PROCEDURE
LETTER
L CONTROL PANEL ASSEMBLY TEST
The control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance can not be performed with only a
voltmeter and ohmmeter.
In this service manual, troubleshooting by replacement is described according to the symptoms
indicated.
1. Control Panel
The following symptoms indicate a defective control unit.
1-1 In connection with LEDs
a) At a certain LED, all or some LEDs do not light up.
b) At a certain LED, brightness is low.
c) Only one LED does not light up.
d) All or some LEDs continue to light up.
e) A certain group of LEDs do not light up.
f) The LEDs flicker.
1-2 Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.
c) Cooking time can not be set.
d) Power level can not be set.
M RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 3 and 5 of the 3 pin connector (A) on
the control unit with an A.C. voltmeter.
The meter should indicate 220 volts, if not check oven circuit.
Relay Test
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,
RELAY SYMBOL
CARRY OUT 4R CHECKS.
N PROCERES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD(PWB) IS OPEN
To protect the electronic circuits, this model is provided with a fine foil pattern added to the input
circuit on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the trouble-
shooting guide given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
TEST PROCEDURES
control unit is defective.
OPERATIONAL VOLTAGE
RY1 Approx. 11.5V D.C.
RY2 Approx. 11.5V D.C.
: The voltage under the condition when all LEDs light up.
COMPONENT TEST
CONNECTED COMPONENTS
Oven lamp / Turntable motor / Fan motor
Power transformer
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