Sharp R-3H57 Service Manual page 17

PROCEDURE
LETTER
L 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 230~240 volts, if not check oven circuit.
RY1 and RY2 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.
M 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,
CARRY OUT 4R CHECKS.
TEST PROCEDURES (CONT'D)
OPERATIONAL VOLTAGE
RY1 APPROX. 24.5V D.C.
RY2 APPROX. 24.0V D.C.
OCCURANCE
The rated AC voltage is not present at
POWER terminal of CPU connector (CN-A)
The rated AC voltage is present at primary
side of low voltage transformer.
Only pattern at "a" is broken.
Pattern at "a" and "b" are broken.
make a visual inspection of the varistor.
check for burned damage and examine
the transformer with an ohmmeter for the
presence of layer short-circuit (check
primary coil resistance). If any abnormal
condition is detected, replace the
defective parts.
COMPONENT TEST
control unit is defective.
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.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
*Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
(J8)
c
15
a
d
b
XH
3
R-3H57