Sharp R-204EWA Service Manual page 18

R - 2 0 4 E W A
PROCEDURE
LETTER
K RELAY TEST
1. Disconnect the power supply cord and then remove outer case.
2. Open the door and blocked 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 Pin No. 3 of the 2 pin connector (A) and the
common terminal of the relay RY2 on the control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
RY1 and RY2 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.
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.
L EXPRESS DEFROST TEST
(1) Place one cup of water in the center of the turntable tray in the oven cavity.
(2) Close the door, touch the " EXPRESS DEFROST " pad once for 0.5lbs in weight.
(3) The oven is in Express Defrost cooking condition.
(4) The oven will operate as follows.
MENU
EXPRESS DEFROST
0.5lb
(5) If improper operation is indicated, the control unit is probably defective and should be checked.
M 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.
TEST PROCEDURES
G 7
G 8
G 9
G10
DC. voltage indicated ............... Defective relay.
DC. voltage not indicated ......... Check diode which is connected to the relay coil. If diode is good,
OPERATIONAL VOLTAGE
RY1 Approx. -13.5V D.C.
RY2 Approx. -12.5V D.C.
1ST STAGE
LEVEL TIME
70% 57sec.
COMPONENT TEST
G 6 G 5 G 4
DINNER
6 2
BEVERAGE
PLATE
FRESH
3
5
VEGETABLES
TIMER
ROLLS &
0
MUFFINS
CLOCK
9 8
control unit is defective.
Oven lamp / Turntable motor / Cooling fan motor
Power transformer
2ND STAGE
LEVEL TIME LEVEL
0% 57sec. 50%
16
G 3 G 2 G 1
MINUTE
PLUS
EXPRESS POWER
4
DEFROST
LEVEL
STOP
BAKED
1
POTATOES
CLEAR
7
START
POPCORN
CONNECTED COMPONENTS
3RD STAGE 4TH STAGE
TIME LEVEL
32sec. 30%
TIME
45sec.