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PS HIGH-VOLTAGE
VARIABLE POWER
SWITCH
HIGH-VOLTAGE
TRANSFORME R
Fig. 7
CIRCUIT
Refer to the schematic diagram on page 11.
1. When the food is placed inside the oven and door is
closed.
(A) The low voltage transformer supplies the necessary
voltage
to the
digital
programmer
circuit when
power cord is plugged in.
The contacts of the short switch open. This switch
creates short circuit to blow 15 A fuse and stop
magnetron oscillation when door is opened during
operation under abnormal
condition (i.e. both the
contacts of latch switch A and B do not open the
circuit to stop oscillation.)
The door keyes are caught by the door hooks, the
contacts of latch switch A and B close the primary
circuit.
(D) The oven light. switch is activated to turn off the
oven light. The oven light turns on while the door is
opened or the magnetron oscillates.
(B)
(C
2. When
cooking
power
and
cooking
time
are set.
(ONE-STAGE COOKING)
(A) Power
indicator
light above
the power
selected
turns
on
and
stage
1 indicator
light for model
NE-8020 turns on.
(B) The time you set appears in the display window.
(C) The
digital
programmer
circuit
memorizes
the
function you set.
3. When the start pad is touched.
(A) 115 V A.C. is applied to the high voltage trans-
former through the power relay contacts which are
closed by the digital programmer circuit.
Fan motor starts rotating and cools the magnetron
by blowing the air coming from the intake on the
back panel over the magnetron fins.
Also the fan
motor
drives
the
turntable
by
means
of gears,
belts and pulleys for uniform cooking.
(See fig.9)
The oven light turns on.
Power
indicator
light (NE-7920
and
NE-7920C)
or stage 1 indicator light (NE-8020) starts blinking
to indicate magnetron oscillation.
Cooking time starts counting down.
(B)
(C)
(D)
VARIABLE
POWER
HIGH-VOLTAGE
= SWITCH
CAPACITOR
CHASSIS HIGH-VOLTAGE
TRANSFORMER
Fig. 8
DESCRIPTION
—At2
Fan motor
Pulley D
MAGNET
POLARITY
Turntable
5
Pulley D
Oven cavity bottom
Fig. 9
(E) 20V
A.C.
is supplied
to the digitd
programmer
circuit from the high voitage transform er.
3.2 volts AC is generated from the filament winding
of the high voltage transformer.
This 3.2 volts is
applied
to the magnetron
to heat tne magnetron
filament through two noise preventing choke coils.
A high voltage of 2,800 volts AC is generated in the
secondary of the high voltage transformer and this
secondary voltage is increased by the action of the
diode and the charging of the high volage capacitor.
This resultant DC voltage is then applied to the
anode of the magnetron.
As shown
in fig.10, the
first half cycle of the high voltage proaduced in the
high voltage transformer secondry chyrges the high
(F)
(G)
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