M: Procedures To The Control Unit - Sharp R-26ST-A Service Manual

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.
RELAY SYMBOL OPERATIONAL VOLTAGE
RY5
RY2
RY6
CARRY OUT 4R CHECKS.

[13] M: PROCEDURES TO THE CONTROL UNIT

Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS
The rated AC voltage is not present between the Pin No. 3 and Pin No. 5
1
of connector CN-A.
The oven door is opened and closed.
2 But the rated AC voltage is not present to primary side of low voltage
transformer.
The rated AC voltage is present to primary side of low voltage trans-
3
former.
NOTE: At the time of these steps, make a visual inspection of the varistor for burned damage. And examine the transformer with a tester for the pres-
ence of layer short-circuit (check the primary coil resistance). If any abnormal condition is detected, replace the control unit.
CARRY OUT 4R CHECKS.
Approx. 12.7V D.C. Oven lamp / Turntable motor / Cooling fan motor
Approx. 11.7V D.C. High voltage transformer
Approx. 12.7V D.C. Touch control transformer
OCCURRENCE
CONNECTED COMPONENTS
Check supply voltage and oven power cord.
Check the secondary interlock switch.
If the secondary interlock switch is normal, the fuse or the
relay RY-6 is defective.
Check and replace the control unit.
Low voltage transformer or secondary circuit defective.
Check and replace the control unit.
8 – 5
CAUSE OR CORRECTION
R26STA