Sharp R-390B Service Manual page 17

PROCEDURE
LETTER
Water load cooking test
Make sure the oven has been plugged in at least two minutes before checking sensor cook operation.
The cabinet should be installed and screws tightened.
(1) Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter measuring cup.
(2) Place the container on the center of tray in the oven cavity.
(3) Close the door.
(4) Operate the oven in "SOUP" of sensor cooking condition, in accordance with the following
procedure.
4-1. Touch "REHEAT" key.
4-2. Touch "PAGE FORWARD" key until "SOUP" appears.
4-3. Touch "SOUP" key.
4-4. Touch "START" key.
4-5. Now, the oven is in the sensor cooking condition and "REHEATING" and "SENSING" will
appear in the display.
(5) The oven will operate for the first 16 seconds, without generating microwave energy.
NOTE: ERROR will appear if the door is opened or STOP/CLEAR key is touched during first stage
of sensor cooking.
(6) After approximately 16 seconds, microwave energy is produced, and the display should start to
count down the remaining cooking time and oven should turn off after water is boiling (bubbling).
If the oven does not turn off, replace the AH sensor or check the control unit, refer to explanation
below.
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 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. Operate the oven in "SOUP" of sensor cooking condition in accordance with the procedure
4-1 to 4-5 of Water load cooking test.
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 (bubbling).
If new sensor dose not operate properly, the problem is with the control unit.
(1) Disconnect oven from power supply and 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 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. Operate the oven in "SOUP" of sensor cooking condition in accordance with the procedure
4-1 to 4-5 of Water load cooking test.
6-2. The control panel is in the sensor cooking operation.
6-3. After approximately 2 minutes, push plunger of select switch for more than 3 seconds. This
condition is same as judgement by AH sensor.
6-4. After approximately 3 seconds, the display shows " X X . X X " which is the remaining cooking
time, and the display count down.
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
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R-390B