Sharp R-880B Service Manual page 21

PROCEDURE
LETTER
To determine if the sensor is defective, the simplest method is to replace it with a new replacement
sensor.
(1) Disconnect oven from power supply and then remove outer case.
(2) Discharge the high voltage capacitor.
(3) Remove the AH sensor.
(4) Install the new AH sensor.
(5) Re-install the outer case.
(6) Reconnect the oven to the power supply and check the sensor cook operation, proceed as follows:
6-1. Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter measuring cup.
6-2. Place the container on the center of tray in the oven cavity.
6-3. Close the door.
6-4. Touch Fresh Vegetables pad.
6-5. The control panel is in automatic Sensor operation.
6-6. The display will start to count down the remaining cooking time, and the oven will turn off
automatically after the water is boiling (babbling).
If new sensor dose not operate properly, the problem is with the control unit.
(1) Disconnect oven from power supply and then remove outer case.
(2) Discharge the high voltage capacitor.
(3) Disconnect the wire leads from the cook relay.
(4) Disconnect the sensor connector that is mounted to lower portion of control panel.
(5) Then connect the dummy resistor circuit (see fig.) to the sensor connector of control panel.
(6) Reconnect the oven to the power supply and check the sensor cook operation, proceed as follows:
6-1. Touch Fresh Vegetables pad.
6-2. The control panel is in the sensor cooking operation.
6-3. After approximately 1 minute and 15 seconds, push plunger of select switch. This condition
is same as judgement by AH sensor.
6-4. After approximately 3 seconds, the oven stops.
If the above is not the case, the control unit is probably defective.
If the above is proper, the AH sensor is probably defective.
TEST PROCEDURES
COMPONENT TEST
TESTING METHOD FOR AH SENSOR AND/OR CONTROL UNIT
CHECKING CONTROL UNIT
To connector (F)
on Control Unit.
1
F-1
2
F-2
3
F-3
CONNECTOR
R1,R2 : 22
Sensor Dummy Resistor Circuit
19
R1
R3 R4
R2
1% 1/2W
R3 : 4.3k 5% 1/4W
R4 : 1M 5% 1/4W
R-880B
Plunger
NC
NO
COM
NO
COM
NC