Sharp R-300BW Service Manual page 17

PROCEDURE
LETTER
c) Only one LED does not light up.
d) All or some LEDs continue to light up.
e) A certain group of LEDs do not light up.
f) The LEDs flicker.
1-2 Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock is not possible.
c) Cooking time can not be set.
d) Power level can not be set.
When testing is completed,
1) Disconnect the power supply cord and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Reconnect all leads removed from components during testing.
5) Re-install the outer case (cabinet).
6) Reconnect the power supply cord after the outer case is installed.
7) Run the oven and check all functions.
J RELAY TEST
1. Disconnect the power supply cord and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure that these leads remain isolated from other components and oven chassis by using insulation
tape.
6. After that procedure, re-connect the power supply cord.
7. Remove the outer case and check voltage between Pins No. 3 and 5 of the 3 pin connector (A) on
the control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
RY1 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
RELAY SYMBOL
8. Disconnect the power supply cord and then remove outer case.
9. Open the door and block it open.
10.Discharge high voltage capacitor.
11.Reconnect all leads removed from components during testing.
12.Re-install the outer case (cabinet).
13.Reconnect the power supply cord after the outer case is installed.
14.Run the oven and check all functions.
K FOIL PATTERN ON THE PRINTED WIRING BOARD TEST
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.
1. Foil pattern check and repairs.
1) Disconnect the power supply cord and then remove outer case.
TEST PROCEDURES
unit is defective.
OPERATIONAL VOLTAGE
RY1 Approx. 12.5V D.C.
RY2 Approx. 12.5V D.C.
(*) The voltage under the condition when all LEDs light up.
COMPONENT TEST
CONNECTED COMPONENTS
(*)
Oven lamp / Turntable motor / Cooling fan motor
(*)
Power transformer
15
R-300BW