9
R-733 -
FUSE F1 F8A 250V
This fuse blows when monitored latch switch SW1 remains
closed with the oven door open and when the contacts
(COM + NC) of monitor switch SW2 closes.
1. If the wire harness or electrical components are short-
circuited, this fuse blows to prevent an electric shock or
fire hazard.
2. The fuse blows when the asymmetric rectifier, H.V.
rectifier, H.V. wire harness, H.V. capacitor, magnetron or
secondary winding of power transformer is shorted.
SPECIAL FUSE F2 15A
If the wire harness or electrical components are short-
circuited, this fuse blows to prevent an electric shock or fire
hazard.
THERMAL CUT-OUT 125
°
C TC1 (MG)
The thermal cut-out protects the magnetron against
overheating. If this temperature goes up higher than 125
°
C
because the fan motor is interrupted, or the ventilation
openings are blocked, the thermal cut-out TC1 will open
and line voltages to the power transformer T1 will be cut off
and the operation of the magnetron MG will be stopped. The
defective thermal cut-out TC1 must be replaced with a new
one.
THERMAL CUT-OUT 160
°
C TC2 (OVEN)
The thermal cut-out located on the top the oven cavity is
designed to prevent damage to the oven if the foods in the
oven catch fire due to over heating produced by improper
setting of cook time or failure of control unit. Under normal
operation, the oven thermal cut-out remains closed.
However, when abnormally high temperatures are reached
within the oven cavity, the oven thermal cut-out will open at
160
°
C, causing the oven to shut down. The defective
thermal cut-out TC2 must be replaced with new one.
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to
rotate the turntable.
FAN MOTOR
The fan motor drives a blade which draws in external cool
air. This cool air is directed through the air vanes surrounding
the magnetron and cools the magnetron. This air is then
channeled through the oven cavity to remove steam and
vapours given off from heating the food. It is then exhausted
through the exhaust air vents at the rear of the oven cavity.
NOISE FILTER
The noise filter prevents any radio frequency interference
that might flow back in the power circuit.
GRILL HEATING ELEMENT (GH)
The grill heating element GH is located on the top of the
oven cavity assembly. The grill heating element emits heat
to grill foods.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that prevents
current flow in both directions. And it prevents the tempera-
ture rise of the power transformer by blowing the fuse F1
when the high voltage rectifier is shorted.
A
B
C
D2
D1
ASYMMETRIC
RECTIFIER
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 each peak
reverse voltage goes beyond the rated peak reverse voltage.
The process of blowing the fuse F1 will blow during a
fault condition.
1. The high voltage rectifier is shorted circuited during
microwave cooking.
2. The peak reverse voltage of D2 of the rectifier goes
beyond the rated peak reverse voltage of 1.7 KV in the
voltage doubler circuit.
3. D2 of the rectifier then breaks down and short-circuits.
4. A large electric current then flows through the high
voltage winding of the power transformer.
5. A large electric current >10A flows through the primary
winding of the power transformer.
6. The fuse F1 blows due to its 8A current rating.
7. The power supply to the power transformer is cut off.
FUNCTION OF IMPORTANT COMPONENTS