SHARP R-874(W)M
Service Manual

OPERATION SEQUENCE
voltage is applied to the top grill heating element . 4. Now, the food is cooked by the top grill heating element. BOTTOM GRILL (Figure O-3b) In this condition the food is cooked by bottom grill heating element energy. Programme the desired cooking time by touching the TIME keys and touh the GRILL key twice. When the STARTkey is touched, the following operations occur: 1. The numbers on the digital readout start the count down to zero. 2. The oven lamp, cooling fan motor and turntable motor are energized. 3. The relay RY4 is energized and the main supply voltage is applied to the bottom grill heating element . 4. Now, the food is cooked by the bottom grill heating element . TOP AND BOTTOM GRILL (Figure O-3c) In this condition the food is cooked by top and bottom grill heating elements energy. Programme the desired cooking time by touching the TIME keys and touh the GRILL key three times. When the STARTkey is touched, the following operations occur: 1. The numbers on the digital readout start the count down to zero. 2. The oven lamp, cooling fan motor and turntable motor are energized. 3. The relay RY4 is energized and the main supply voltage is applied to the bottom grill heating element. 4. The relay RY3 is energized and the main supply voltage is applied to the top grill heating element. 5. Now, the food is cooked by the top and bottom grill heating elements. temperature by touching the CONVECTION TEMPERATURE key . When the START key is touched, the following operations occur: 1. The numbers on the digital readout start the count down to zero. 2. The oven lamp, cooling fan motor, turntable motor and convection motor are energized. NOTE: When the convection temperature 40�C is selected, the convection motor is not energized. 3. The relays RY3 and RY4 are energized (if the cavity temperature is lower than selected temperature) and the main supply voltage is applied to the top and bottom heating elements to return to the selected cooking temperature. 4. Upon completion of the cooking time, the audible signal will sound, and the oven lamp, turntable motor, cooling fan motor, convection motor, top and bottom heating elements are de-energized. At the end of convection cycle, if the cavity air temperature rise above 120�C, the circuit to the relay RY6 will be maintained (by the thermistor circuit) to continue operation of the cooling fan motor until temperature drops below 105�C, at that time the relay RY6 will be de-energized, turning off the fan motor.

DUAL COOKING CONDITION
MICROWAVE AND CONVECTION (Figure O-5a) Programme the desired cooking time by touching the TIME keys. Touch the DUAL CONVECTION/GRILL key once. Select the microwave power level by touching the MICROWAVE POWER LEVEL key. And select the convection temperature by touching the CONVECTION TEMPERATURE key. NOTE: The microwave power level can be selected from 90W, 270W and 450W. When the STARTkey is touched, the following operations occur: 1. The numbers on the digital readout start the count down to zero. 2. The oven lamp, cooling fan motor, turntable motor and convection motor are energized. 3. The relay RY3 will be energized and the main supply voltage is applied to the top grill heatier. 4. The relay RY4 is energized (if the cavity temperature is lower than selected temperature) and the main supply voltage is applied to the bottom heating elementer. 5. The relay RY2 is energized and the microwave energy is generated by magnetron. 6. Now, the food is cooked by microwave and convection energy simultaneously. MICROWAVE AND TOP GRILL (Figure O-5b) Programme the desired cooking time by touching the TIME keys. Touch the DUAL CONVECTION/GRILLL key twice. Select the microwave power level by touching the MICROWAVE POWER LEVEL key. When the STARTkey is touched, the following operations occur: 1. The numbers on the digital readout start the count down to zero. 2. The oven lamp, cooling fan motor and turntable motor are energized. 3. The relay RY3 is energized and the main supply voltage is applied to the top grill heating element. 4. The relay RY2 is energized and the microwave energy is generated by magnetron. 5. Now, the food is cooked by microwave and top grill

CONVECTION COOKING CONDITION
PRE-HEATING (Figure O-4) Programme the desired convection temperature by touching CONVECTION TEMPERATURE key. When the STARTkey is touched, the following operations occur: 1. The coil shut-off relays RY1 and RY6 are energized, the oven lamp, cooling fan motor and turntable motor are turned on. 2. The coil shut-off relays RY3 RY 7 and RY4 are energized by control unit and the main supply voltage is added to the top and bottom heating elements and covection motor. 3. When the oven temperature reaches the selected preheat temperature, the following operations occur: 3-1. The coil shut-off relays RY3 and RY4 are energized by control unit temperature circuit and thermistor, opening the circuit to the top and bottom grill heating elements and convection motor. 3-2. The oven will continue to function for 30 minutes, turning the top and bottom heating elements on and off, as needed to maintain the selected pre-heat temperature. The ovenwill shut-down completely after 30 minutes. NOTE: The fan motor will be turned on and off at preheating. And the convection motor will be turned off at preheating. See "Power setting" on page 9. CONVECTION COOKING (Figure O-4) When the pre-heat temperature is reached, a beep signal will sound indicating that the holding the temperature has been reached in the oven cavity. Open the door and place the food to cooked in the oven. Program desired cooking time by touching the TIME keys and program convection

R-874M - 7
R-874 S/MANUAL 7 11/7/01, 10:59 am