LG / GOLDSTAR MH6807
Manual de Servicio

CIRCUIT DESCRIPTION
� When door is closed, the primary switch is ON, the secondary switch is ON and the monitor switch is connect the main line (contact COM and NO).

WHEN THE OVEN IS SET AT ANY LEVEL EXCEPT MAXIMUM.
� The power control switch controls the ON-OFF time of the power as you set.

WHEN MICROWAVE POWER LEVEL AND COOKING TIME SET
� The contacts of the timer switch changes to ON position when the timer knob is rotated. (While power control knob is set at �Full Power�) � The contacts of primary and secondary switch close the circuit. � Input is applied to H.V.Transformer through, I/R (Inrush resistor) and monitor switch. (Some reduce by I/R) � AC relay is close and full input voltage is applied to H.V Transformer as shown below.
MONITOR SWITCH H.V.T FUSE L N

WHEN THE DOOR IS OPENED DURING COOKING
� Both primary switch and secondary switch open to cut off the primary winding voltage to the high voltage transformer to stop microwave oscillation. � Timer, turntable and fan motor stop. � As the door is opened, if the contact of primary switch fail to open, the fuse opens due to the large current surge caused by the monitor circuit as shown below.
MONITOR SWITCH H.V.T FUSE L N

PRIMARY TIMER MICROWAVE SECONDARY SWITCH SWITCH SELECT SWITCH PRIMARY TIMER MICROWAVE SECONDARY SWITCH SWITCH SELECT SWITCH SWITCH

WHEN THE GRILL COOKING FUNCTION SELECTED
� The contacts of the timer switch change to ON position. � The contacts of the grill select switch close the circuit. � Input volts AC is applied to the grill heater through thermostat-grill as shown by the solid line. � The fan motor and turntable rotates.
FUSE THERMOSTAT GRILL

� The fan motor rotates and cools the magnetron by blowing the air (coming from the intake holes on the backplate). � The air is also directed into the oven to exhaust the vapor in the oven through the upper plate. � Timer starts rotating. � 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 the magnetron filament through two noise preventing choke coils. A high voltage of approximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the diode and charging of the high voltage capacitor. � The negative DC voltage is applied to the filament of the magnetron.

L

L N

G -Y

E

N

GRILL HEATER

PRIMARY SWITCH

TIMER SWITCH

GRILL SELECT SWITCH

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