Sharp R-872M Service Manual page 16

TEST PROCEDURES
PROCEDURE
LETTER
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 - 240 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,
RELAY SYMBOL
RY1
RY2
RY3
RY4
RY5
RY6
RY7
CARRY OUT 4R CHECKS.
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.
STEPS
1
2
3
4
NOTE: *At the time of these repairs, make a visual
inspection of the varistor for burning dam-
age and examine the transformer with tester
for the presence of layer short circuit (check
primary coil resistance).
If any abnormal condition is detected, re-
place the defective parts.
CARRY OUT 4R CHECKS.
control unit is defective.
OPERATIONAL VOLTAGE
Approx. 18.0V D.C.
Approx. 18.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
OCCURRENCE
The rated AC voltage is not present between
Pin Nos. 1 and 3 of the 4-pin connector (E).
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.
R-872M - 16
COMPONENT TEST
CONNECTED COMPONENTS
Oven lamp / Turntable motor
High voltage transformer
Grill (Top) heating element
Bottom heating element
Touch control transformer
Fan motor
Convection motor
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.)
VRS1
RY6
d
b
a
c
POWER
F