Sharp R-340A, Service Manual

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R-340A
13
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 OCCURRENCE CAUSE OR CORRECTION
1 The rated AC voltage is not present between Check supply voltage and oven power cord.
Pin No. 3 of the 2-pin connector (A) and the
common terminal of the relay RY2.
2 The rated AC voltage is present to primary Low voltage transformer or secondary circuit defective.
side of low voltage transformer. Check and repair.
3 Only pattern at "a" is broken. *Insert jumper wire J1 and solder.
4 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".
NOTE: *At the time of making these repairs,
make a visual inspection of the varistor.
Check for burned damage and
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
PROCEDURE
LETTER
COMPONENT TEST
O PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD
(PWB) IS OPEN
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,
control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 APPROX. 13.1V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 APPROX. 11.7V D.C. Power transformer
CARRY OUT 4R CHECKS.
N RELAY TEST
RY2
a
b
c
d
HVT
AC
(COM)
VH
XH
3
3
CN - A
(J1)