Sharp R-939(BK), Service Manual

Page: 23 / 52

R939(W)
8 – 6
[15] Procedure O: RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 1 and 3 of the 4 pin connector (E) on the control unit with an A.C. voltmeter. The meter
should indicate 230 volts, if not check oven circuit.
Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation, grill operation, convection operation or dual 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.
CARRY OUT 4R CHECKS.
[16] Procedure P: 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 input circuit 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.
NOTE: *At the time of these repairs, make a visual inspection of the varistor for burn-
ing damage and examine the transformer with tester for the presence of layer
short circuit (check primary coil resistance).
If any abnormal condition is detected, replace the power unit.
CARRY OUT 4R CHECKS.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 APPROX. 18.0V D.C. Oven lamp / Turntable motor
RY2 APPROX. 18.0V D.C. High voltage transformer
RY3 APPROX. 24.0V D.C. Grill (Top) heating element
RY4 APPROX. 24.0V D.C. Convection heating element
RY5 APPROX. 24.0V D.C. Fan motor
RY6 APPROX. 24.0V D.C. Touch control transformer
RY7 APPROX. 24.0V D.C. Convection motor
RY8 APPROX. 24.0V D.C. Damper motor
STEPS OCCURRENCE CAUSE OR CORRECTION
1
The rated AC voltage is not present between Pin No. 1 and 3 of the 4-pin
connector (E).
Check supply voltage and oven power cord.
2 The rated AC voltage is present at primary side of low voltage transformer.
Low voltage transformer or secondary circuit defective.
Check and replace power unit.
3 Only pattern at “a” is broken. *Insert jumper wire J1 and solder.
4 Pattern at “a” and “b” are broken.
Replace power unit. (CARRY OUT 3D CHECKS BEFORE
REPAIR)
(J1)
(J2)
9
1
7
C
N-E
CN
-
A
VRS1
a
c
d
b