R-2498G (serv.man2). Part 1 Text(1-25) - Sharp Home Appliance Service Manual (repair manual). Page 18

16

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

OCCURANCE

CAUSE OR CORRECTION

1

The rated AC voltage is not present at

Check supply voltage and oven power cord.

POWER terminal of CPU connector (CN-A)

2

The rated AC voltage is present at 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 J9 and solder.

(CARRY OUT 3D CHECKS BEFORE REPAIR)

4

Pattern at "a" and "b" are broken.

*Insert the coil RCILF2003YAZZ between "c" and "d".

(CARRY OUT 3D CHECKS BEFORE REPAIR)

S1

S2

2

3

P

TI

C31

D23

+

–

VRS1

(J9)

(J8)

OL, BM

POWER

7

5

3

1

D21

CN–A

NOTE: *At the time of these repairs, make a

visual inspection of the varistor for burn-
ing damage and examine the trans-
former with tester for the presence of
layer short-circuit (check primary coil
resistance). If any abnormal condition
is detected, replace the defective parts.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Remove the outer case and  check voltage between Pin Nos. 5 and 7 of the  connector (A) on the control
unit with an A.C. voltmeter. The meter should indicate 230-240 volts, if not check control unit circuity.

RY1, RY2 and RY3 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 ................................ Defective relay.
DC.  voltage  not  indicated .......................... Check diode which is connected to the relay coil. If diode

is good, control unit is defective.

RY1

APPROX. 18.0V D.C.

Oven lamp,Blower motor and Stirrer motor

RY2

APPROX. 17.5V D.C.

Power transformer 1

RY3

APPROX. 17.5V D.C.

Power transformer 2

CARRY OUT 4R CHECKS.