Daewoo KOT-1G1A, Service Manual, Page: 40 / 58

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2. CIRCUIT DESCRIPTION
MICROWAVE COOKING
- TIME COOKING
1. When the food is placed inside the oven and door is closed.
1) The low voltage transdormer supplies the necessary voltage to the touch control circuit when the power cord is
plugged in.
2) The contacts of the interlock monitor switch open.
This switch creates short circuit to blow 20A fuse and stop magnetron oscillation when door is opened during oper
ation under abnormal condition (i.e. the contacts of primary interlock switch do not open the circuit).
3) The contacts of primary interlock switch close the primary circuit.
2. When contacts of the interlock monitor switch open.
1) The function indicating bars are located on the digitron light to indicate that function have been set.
2) The time you set appears in the display window.
3) The touch control circuit memorizes the cooking program you set.
3. When the start pad is touched.
The RELAY 1,2 and 4 are controlled by the touch control circuit.
1) 120VAC is applied to the high voltage transformer through the contacts of RELAY 1
2) Fan motor starts to cool the magnetron by blowing the air coming from the intake on the grille hole.
3) The oven lamp light the inside of the oven.
4) Indicator light turns on to indicate function operation. Cooking time starts count down.
5) 3.3 Volts AC is generated from filament winding of the voltage transformer. This filament voltage is applied to the
magnetron to heat the magnetron filament through two noise preventing choke coils.
6) A high voltage of 2000 Volts AC is generated in the secondary of high voltage transformer and this secondary
voltage is increased by the action of the diode and the charging of the high voltage capacitor. This resultant DC
voltage is then applied to the anode of the magnetron. As shown in Figure the first half cycle of the high voltage
produced in the voltage transformer secondary charges the high voltage capacitor. 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 voltage capacitor are combined and applied to the magnetron as shown by the solid line so that oscillations
begin. The disturbance wave generated by the magnetron is prevented by the choke coils of 3.2mH, filter capacitors
of 16pF and the magnetron’s shielded case so that TV and radio programs are not impaired by noise.