SHARP R-2277
Service Manual

R-2277 R-2287

FUSE F6.3A 250V F2
1. If the wire harness or electrical components are shortcircuited, this fuse blows to prevent an electric shock or fire hazard. 2. The fuse also blows when 1st latch switch SW1 remains closed with the oven door open and when the monitor switch SW4 closes.

MAGNETRON THERMISTOR
The air temperature around the lower magnetron is detected through the resistance of the thermistor. If the temperature is high, the control panel will display "EE17" and the oven will stop to protect the lower magnetron against overheat. If the thermistor is open, the control panel will display "EE16" and the oven will stop.

ASYMMETRIC RECTIFIER
The asymmetric rectifier is solid state device that prevents current flow is both directions. And it prevents the temperature rise of the high voltage transformer by blowing the weak point / fuse WP1 or WP2 when the high voltage rectifier is shorted.
A
D2 D1

MAGNETRON THERMAL CUT-OUTS 145� TC1, TC2
These thermal cut-outs protect the magnetrons against overheat. If their temperature go up higher than 145�C because the blower motor is interrupted, the ventilation openings are blocked, the thermal cut-outs TC1+TC2 will open and the line voltage to the high voltage transformer T1+T2 will be cut off and the operations of the magnetrons MG1+MG2 will be stopped. The defective thermal cut-out must be replaced with new rated one.

B

ASYMMETRIC RECTIFIER

C

HIGH VOLTAGE RECTIFIER

The rated peak reverse voltage of D1 of the asymmetric rectifier is 6 KV The rated peak reverse voltage of D2 of 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 weak point / fuse WP1 or WP2) 1. The high voltage rectifier is shorted by some fault when microwave 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 flow through the primary winding of the high voltage transformer. 6. The weak point/ fuse WP1 or WP2 blows by the large electric currents. 7. The power supplying to the high voltage transformer is cut off.

BLOWER MOTOR THERMAL CUT-OUT 115�C TC3
This thermal cut-out protect the blower motor against overheat. If its temperature goes up higher than 115�C because the blower motor is locked or the ventilation openings are blocked, the contacts of the thermal cut-out TC3 will open and the line voltage to the control unit will be cut off and the operation of the oven will be stopped. The defective thermal cut-out must be replaced with new rated one.

OVEN THERMAL CUT-OUT 115�C TC4
This thermal cut-out protects the oven against overheat. If the temperature goes up higher than 115�C because the food catches fire, the contacts of thermal cut-out will open and the line voltage to the control unit will be cut off and the operation of the oven will be stopped. The defective thermal cut-out must be replaced with a new rated one.

BLOWER MOTOR BM
The blower motor drives a blade which draws external cool air. This cool air is directed through the air vanes surrounding the magnetrons and cools the magnetrons. This air is channelled through the oven cavity to remove steam and vapours given off from the heating foods. It is then exhausted through the exhausting air vents at the oven cavity.

EXHAUST THERMISTOR
The thermistor is a negative temperature coefficient type. The temperature in the exhaust duct is detected through the resistance of the thermistor. If the temperature is high, the control panel will display �EE7� and the oven will stop to avoid overheating and catching fire. If the thermistor is open, the control panel will display "EE6" and the oven will stop.

STIRRER MOTOR SM
The stirrer motor drives a stirrer antenna to stir the microwave radiation from the waveguide.

INTAKE THERMISTOR
This thermistor detects ambient air temperature.

6