Circuit Description - Samsung CE979GSE Service Manual

6. Circuit Description

6-1 When food is placed inside oven and door is closed
1. Low voltage transformer supplies the necessary voltage to the touch control circuit when power cord is
plugged in.
2. The primary interlock switch is closed.
3. The interlock monitor switch is opened. This interlock monitor switch blows the 10A fuse and stops
magnetron oscillation when the door is opened (abnormal condition).
4. The door key is caught by the door hook, this clodesthe door sensing switch is closed to send the door-
close signal to the touch control circuit.
6-2 When cooking, power and time are set by touching the function pads
1. The time appears in the display window.
2. The touch control circuit stores the cooking data at.
6-3 When the START pad is touched
1. The main relay and the power control relay are controlled by the touch control circuit.
2. An oven lamp lights the inside of the oven by (The lamp relay in the Touch Control Circuit).
3. The fan motor rotates and cools the magnetron by blowing the air 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.
Primary Switch
Lamp
L
DC12V
Lamp Relay
Monitor Fuse
Main Relay
4. 230V~50Hz AC is applied to the high voltage transformer through the contacts of primary windings (
shown by the solid line) just after the power control relay turns ON. (Fig. 1)
5. 3.4V AC is generated from the filament winding of the high voltage transformer. This 3.4V is applied to
the magnetron to heat the magnetron filament through two noise preventing choke coils.
6. High voltage (2,230 volts AC) is generated by the high voltage transformer secondary. This secondary
voltage is increased by the diode and high voltage capacitor. This resultant DC voltage is then applied
to the anode of the magnetron. As shown in Fig. 2, the first half cycle of the high voltage produced in
the secondary high voltage transformer charges the high voltage capacitor.The dotted lines indicate the
current flow. During operation of the second half cycle, the voltage produced by the transformer
secondary (plus the charge of the high voltage capacitor) is applied to the magnetron as shown in the
solid line, which cawses the magnetron to oscillate. The electrlcal interference generated by the
magnetron is prevented by the 1.6uH choke coils, 500pF filter capacitors and the magnetrons shielded
case (so that TV and radio signals are immune).
7. The power control relay is turned on intermittently by the touch control circuit (when the oven is set at
any power) except full power. The touch control circuit controls the ON/OFF time of the power control
relay in order to vary the output power of the microwave oven from Low to "Full" power. One
complete ON/OFF cycle of the power control is 30 seconds.
8. The cooking when the oven is set at any power setting is shown on the display (starts to count down.)
Samsung Electronics
H.V.Trans
Interlock
Monitor
Switch
Power Relay
H.V.
Capacitor
Diode
H.V.
TRANS
Magnetron
6-1