Sharp R-480J Service Manual page 17

PROCEDURE
LETTER
To determine if the sensor is defective, the simplest method is to replace it with a new replacement
sensor.
(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) Remove the AH sensor.
(5) Install the new AH sensor.
(6) Reconnect all leads removed from components during testing.
(7) Re-install the outer case (cabinet).
(8) Reconnect the power supply cord after the outer case is installed.
(9) Reconnect the oven to the power supply and check the sensor cook operation as follows:
9-1. Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter measuring cup.
9-2. Place the container on the center of tray in the oven cavity.
9-3. Close the door.
9-4. Touch the CLOCK pad once, the POWER LEVEL pad twice, the START pad once, the
number pad 1 once and the number pad 4 once.
9-5. The control panel is in automatic Sensor operation.
9-6. The oven turns off automatically, and the time for detecting moisture will be displayed.
If new sensor dose not operate properly, the problem is with the control unit, and refer to explanation
below.
(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 sensor connector that is mounted to control panel.
(5) Then connect the dummy resistor circuit (see fig.) to the sensor connector of control panel.
(6) Disconnect the leads to the primary of the power transformer.
(7) Ensure that these leads remain isolated from other components and oven chassis by using insulation tape.
(8) After that procedure, re-connect the power supply cord.
(9) Check the sensor cook operation proceed as follows:
9-1. Touch the CLOCK pad once, the POWER LEVEL pad twice, the START pad once and the
9-2. The control panel is in the sensor cooking operation.
9-3. After approximately 25 seconds, push plunger of select switch for more than 3 seconds.
9-4. After approximately 3 seconds, the display shows " X X . X X " which is the time for detecting
If the above is not the case, the control unit is probably defective.
If the above is proper, the AH sensor is probably defective.
(10) Disconnect the power supply cord, and then remove outer case.
(11) Open the door and block it open.
(12) Discharge high voltage capacitor.
(13) Disconnect the dummy resistor circuit from the sensor connector of control panel.
(14) Carry out necessary repair.
(15) Reconnect all leads removed from components during testing and repairing.
(16) Re-install the outer case (cabinet).
(17) Reconnect the power supply cord after the outer case is installed. Run the oven and check all
functions.
(18) Carry out "Water load cooking test" again and ensure that the oven works properly.
R1,R2 :
R3 : 4.3kΩ ± 5% 1/4W
R4 : 1MΩ ± 5% 1/4W
TEST PROCEDURES
TESTING METHOD FOR AH SENSOR AND/OR CONTROL UNIT
CHECKING CONTROL UNIT
number pad 1 once and the number pad 4 once.
This condition is same as judgement by AH sensor.
moisture.
22Ω ± 1% 1/2W
To connector (F)
on Control Unit.
F-1
F-2
F-3
CONNECTOR
Sensor Dummy Resistor Circuit
COMPONENT TEST
1
2
R1
3
R3 R4
R2
15
R-480J
Plunger
NC
NO
COM
NO
COM
NC