Sharp R-240B Service Manual page 15

PROCEDURE
LETTER
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
DC. voltage not indicated
RELAY SYMBOL
RY1
RY2
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.
STEPS
1
2
3
4
NOTE: At the time of making these repairs,
make a visual inspection of the varistor.
Check for burned damage and exam-
ine the transformer with tester for the
presence of layer short-circuit (check
primary coil resistance). If any abnor-
mal condition is detected, replace the
defective parts.
TEST PROCEDURES
Defective relay.
Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
OPERATIONAL VOLTAGE
Approx. 15.0V D.C.
Approx. 14.0V D.C.
OCCURANCE
The rated voltage is not applied between Pin
No. 3 of the 2 pin connector (A) and the.
common terminal of the relay RY2.
The rated voltage is applied to primary side
of low voltage transformer.
Only pattern at "a" is broken.
Pattern at "a" and "b" are broken.
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".
P
1
d
T1
3
AC (N)
13
R-240B
2
a
RY2
c
(J1)
b
1
RY1
FM TTM OL