Sharp R-340A Service Manual page 15

PROCEDURE
LETTER
N RELAY TEST
Remove the outer case and check voltage between Pin No 3 of the 2-pin connector (A) and the
common terminal of the relay RY2 on the power unit with an A.C. voltmeter. The meter should indicate
220 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 or
convection 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.
O PROCEDURES 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 primary
on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS
1
2
3
4
NOTE: *At the time of making these repairs,
make a visual inspection of the varistor.
Check for burned
examine the transformer with a tester
for the presence of layer short-circuit
(check the primary coil resistance). If
any abnormal condition is detected,
replace the defective parts.
CARRY OUT 4R CHECKS.
TEST PROCEDURES
control unit is defective.
OPERATIONAL VOLTAGE
RY1 APPROX. 13.1V D.C.
RY2 APPROX. 11.7V D.C.
OCCURRENCE
The rated AC voltage is not present between
Pin No. 3 of the 2-pin connector (A) and the
common terminal of the relay RY2.
The rated AC voltage is present to primary
side of low voltage transformer.
Only pattern at "a" is broken.
Pattern at "a" and "b" are broken.
damage and
COMPONENT TEST
CONNECTED COMPONENTS
Oven lamp / Turntable motor / Cooling fan motor
Power transformer
CAUSE OR CORRECTION
Check supply voltage and oven power cord.
Low voltage transformer or secondary circuit defective.
Check and repair.
*Insert jumper wire J1 and solder.
*Insert the coil RCILF2003YAZZ between "c" and "d".
c
(J1)
13
R-340A
a
d
b