R-1900M (serv.man5). Operation - Sharp Home Appliance Service Manual (repair manual). Page 3

R1900M

4 – 3

During cooking, they operate. After cooking, they will operate at least
for 1 minute and the maximum operating time is 4 minutes. When the
temperature of the magnetron thermistor becomes bellow 110

°C, the

fan motors will stop. These two (2) fan motors are D.C. motors.

The exhaust motor is located on the side of the exhaust duct assem-
bly. This motor drives a blade in the exhaust duct assembly. The
driven blade draws the external cool air into the oven from the intake
duct assembly. Then it sends the air out of the oven through the
exhaust duct assembly. During cooking, the exhaust motor operates.
After cooking, it will operate at least for 1 minute and the maximum
operating time is 4 minutes. When the temperature of the exhaust
thermistor becomes bellow 65

°C, the exhaust motor will stop. This

motor is D.C. motor. 

NOTE: Do not disconnect the power supply from the exhaust motor

when it is turned on. Or it may be out of order.

The upper and lower antenna motors drive antennas to radiate the
microwave.

The exhaust fan is located to the rear cover. It sends the air (which is
at the top of the oven cavity) out of the oven. This motor is D.C. motor.

The antenna sensors are located to the top and bottom of the oven
cavity. And they watch if the antennas are rotating or not.

The microwave sensor is located on the top of the oven cavity. And it
watch if the microwave is radiated into the oven cavity or not.

If the wire harness or electrical components make a short-circuited,
this weak point blows to prevent an electric shock or fire hazard.

The H.V.asymmetric rectifiers (1) (2) are solid state devices that pre-
vent current flow is both directions. And they prevent the temperature
rise of the power transformers (1) (2) by blowing the fuses 12A (1) (2)
when the high voltage rectifiers (1) (2) are shorted. 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 fuse 12A.)

NOTE: The H.V.asymmetric rectifier is assembled with the high volt-

age rectifier actually.

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 power transformer.

5. The large electric currents beyond 12A flow through the primary

winding of the power transformer.

6. The fuse 12A blows by the large electric currents.

7. The power supplying to the power transformer is cut off.

The oven cavity light illuminates the interior of the oven so that food
being cooked can be examined visually through the door window with-
out having to open the door. 

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

D2

D1

ASYMMETRIC
RECTIFIER

HIGH VOLTAGE
RECTIFIER