R-891M - Sharp Home Appliance Service Manual (repair manual). Page 7

8

891M -

1. CARRY OUT 3D CHECKS.
2. Disconnect the leads from the primary of the high voltage transformer. Make sure that the leads remain isolated

from other oven components and chassis. (Use insulation tape if necessary.)

3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 1 and 3 of the 4 pin connector (A) on the control unit with an A.C.

voltmeter. The meter should indicate 240 volts, if not check oven circuit.

6. Relay Test

These 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, power unit is defective.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

Approx. 19.5V D.C.

Oven lamp / Turntable motor

RY2

Approx. 18.0V D.C.

High voltage transformer

RY3

Approx. 18.6V D.C.

Top heater

RY4

Approx. 18.6V D.C.

Bottom heater

RY5

Approx. 24.2V D.C.

Cooling fan motor

RY6

Approx. 23.2V D.C.

Convection fan motor

7. CARRY OUT 4R CHECKS.

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-cir-
cuit (check primary coil resistance). If any
abnormal condition is detected, replace
the defective parts.

CARRY OUT 4R CHECKS.

1 2

( J 1 )

R Y 6

C N   -   B

C N   -   A

7

1

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

OCCURRENCE

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 J1 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)