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Circuit Descriptions
Refer to the wiring diagram on page 16.
1. When the food is placed inside the oven and the
door is closed
(A) The low voltage transformer supplies necessary volt-
age to the touch control circuit when the power
cord is plugged in.
(B) The primary interlock switch and the secondary in-
terlock switch are closed.
(C) The interlock monitor switch is opened. This interlock
monitor switch acts to blow 15A fuse and stop mag-
netron oscillation when the door is opened during
operation under an abnormal condition.
(i.e. the
contacts of primary interlock switch do not open
and the contacts of secondary interlock switch do
not close the circuit to stop oscillation)
(D) The door key is caught by the door hook, the door
sensing switch is opened to give touch control circuit
the information that the door is closed.
2, When cooking cycle, power and time are set by touch-
ing the function pads and the desired numerical pads
(A) Cooking function word shown on the display window
blinks to indicate the selected function.
(B) The time set appears in the display window.
(C) The touch control circuit stores the cooking data
set.
3. When the START pad is touched
The main relay and the power control relay are controlled
by the touch control circuit.
(A) An ovenlamp lights the inside of the oven by operation
of the main relay in the Touch Control Circuit.
(B) Fan motor rotates and cools the magnetron by blow-
ing the air coming from the intake on the back panel
over the magnetron fins. After cooling the fins, this
air is directed into the oven to blow out the vapor.
(C) 220VAC is applied to the high voltage transformer
through the contacts of primary and secondary
switches shown by the solid line just after the power
control relay turns ON. (Fig. 3)
SECONDARY INTERLOCK
SWITCH
1A FUSE
MAIN
INTERLOCK
RELAY
| MONITOR
SWITCH
————
PRIMARY INTERLOCK
SWITCH
(D) 3.3V AC is generated from the filament winding of the
high voltage transformer.
This 3.3V is applied to the
magnetron to heat the magnetron filament through two
noise preventing choke coils.
(E) High voltage of 2,120 volts AC is generated from the
high voltage transformer secondary and this secondary
voltage is increased by the action of the diode and
the charging of the high voltage capacitor. This resul-
tant D.C. voltage is then applied to the anode of the
magnetron.
As shown in the Fig. 4, the first half cycle
of the high voltage produced in the secondary high
voltage transformer charges the high voltage capacitor.
| AC S.3ViEUF
FT RES
FFs |
|MAGNETRON
(Fig. 4)
Current flow is in the direction of the dotted line. During
the second half cycle, the voltage produced by the
transformer secondary and the charge of the high volt-
age capacitor are combined and applied to the mag-
netron as shown by the solid line so that oscillations
begin. The disturbance wave generated from the mag-
netron is prevented by the chock coils of 1.6uH, filter
capacitors of 500pF and the magnetron shielded case
so that TV and radio programs are not impaired by
noise.
(F) The power contro! relay is turned on intermittently by
the touch control circuit, when the oven is set at any
power selection except for full power. The touch con-
trol circuit controls the ON/OFF time of the power con-
trol relay in order to vary the output power of the
microwave oven from "Low" to "Full" power. One com-
plete ON/OFF cycle of the power control is 30 seconds.
The relation between indications on the control panel
and the output power level of the microwave oven is
on the page 35.
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