SHARP R-963(IN)
Service Manual

FUNCTION OF IMPORTANT COMPONENTS
the asymmetric rectifier is 1.7 KV. D1 and D2 of the asymmetric rectifier or high voltage rectifier are shorted when the each peak reverse voltage goes beyond the each rated peak reverse voltage. (The process of the blowing the fuse F2 F8A.) 1. The high voltage rectifier is shorted by some fault when microwave cooking or dual cooking. 2. The peak reverse voltage of D2 of the rectifier goes beyond the rated peak reverse voltage 1.7 KV in the voltage doubler circuit. 3. D2 of the rectifier is shorted. 4. The large electric currents flow through the high voltage winding of the high voltage transformer. 5. The large electric currents beyond 8A flow through the primary winding of the high voltage transformer. 6. The fuse F2 F8A blows by the large electric currents. 7. The power supplying to the high voltage transformer is cut off. with the food being cooked. When the temperature inside the oven cavity reaches the selected temperature, the heating elements are de-energized. When the temperature inside the oven cavity drops below the selected temperature, the heating elements are energized again. In this way, the inside of the oven cavity is maintained at approximately the selected temperature. When the convection time reaches �0�, the heating elements are deenergized and the convection fan stops operating and the oven shuts off. At that time if the cavity air temperature has risen above 120�C, the fan motor remains rotating. Automatically the fan motor will be shut down at low temperature (less than 105�C).
Grill Heating Elements

Door

Oven Cavity

Convection Passage Convection Heating Element Cooling Fan Convection Motor Convection Fan

NOISE FILTER
The noise filter assembly prevents radio frequency interference that might flow back in the power circuit.

TURNTABLE MOTOR TTM
The turntable motor rotates the turntable.
Turntable

FAN MOTOR FM
Roller Stay Turntable Motor

The fan motor drives a blade which draws external cool air. This cool air is directed through the air vanes surrounding the magnetron and cools the magnetron. This air is channelled through the oven cavity to remove steam and vapours given off from heating food. It is then exhausted through the exhausting air vents of the oven cavity.

Figure D-2. Convection Cooking System

FIRE SENSING FEATURE
The oven will stop its operation when there is a fire in the oven cavity in microwave cooking condition. LSI measures the voltage across the temperature measurement circuit intermittently within 32-seconds time base since the oven is started in microwave cooking condition. The oven will stop its operation when the difference of the voltage is more than 0.39 volts in microwave cooking condition. 1. Within a 32-seconds base, the thermistor is energized for 2 seconds. At that time, the voltage across the temperature measurement circuit is measured. 2. The oven carries out the procedure above again. If the second voltage is 0.39V higher than first voltage, LSI judges it is a fire in the oven cavity and stop the oven. 3. When LSI judges it is a fire in the oven cavity, LSI will switch off the relays to high voltage transformer and fan motor and LSI stops counting down. IMPORTANT: During sensor cooking operation, the fire sensing operation sequence will not begin until the AH sensor has detected vapours and initiated a sensor cooking cycle.
30 32 (sec.)

CONVECTION MOTOR CM
The convection motor drives the convection fan and provide the heated air.

GRILL HEATING ELEMENT GH
The grill heating elements are provided to brown the food and are located on the top of the oven cavity.

CONVECTION HEATING ELEMENT CH
The convection heating element situated at the rear of the oven cavity. It is intended to heat air driven by the convection fan. The heated air is kept in the oven and force-circulated and reheated by the convection heating element.

CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where food is heated by forced circulation of the hot air produced by the grill heaters. The air heated by the grill heating elements is circulated through the convection passage provided on the outer casing of the oven cavity by means of the convection fan which is driven by the convection motor. It is then enters the inside of the oven through the vent holes provided on the back side of the oven. Next, the hot air heats the food on the turntable and leaves the oven cavity through the vent in the oven cavity rear wall. In this way, the hot air circulates inside the oven cavity to raise its temperature and, at the same time, comes into contact
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THERMISTOR

ON OFF ON

Sensing Voltage

OFF

Sensing the voltage across temperature measurement circuit.