Circuit Description - Sunbeam MA-6400W2 Service Manual

CIRCUIT DESCRIPTION

GENERAL DETAILS
• When the door is closed, the primary switch is ON, the
secondary switch is ON, and the monitor switch opens
(contact COM and NO).
• The latches are secured by the latch board, the oven
light turns on while the oven is operation.
WHEN THE TIMER KNOB IS ROTATED
• When the timer knob is rotated, the contacts of timer
switch close.
• The contact of the secondary switch close the circuit.
• Power input is supplied to the high voltage transformer
through the fuse to the primary timer and secondary
switches.
• Turntable rotates
• The fan motor rotates and cools the magnetron by
blowing the air (coming from the intake on the
baseplate).
• The air is also directed into the oven to exhaust the
vapor in the oven through the upper plate.
• Cooking time starts counting down.
FUSE
P/S
• 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.
T/S S/S
H.V.
TRANS-
FORMER
P/S : Primary Switch
T/S : Timer Switch
S/S : Secondary Switch
• 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 high
voltage diode and charging of the high voltage
capacitor.
• The negative 4,000 Volts DC is applied to the filament
of the magnetron.
WHEN THE DOOR IS OPENED DURING
COOKING
• Both the primary and timer switches are cut off primary
winding voltage of the high voltage transformer.
• When the door is opened, the secondary switch is
opened and when the door is closed, the secondary
switch is closed.
• The 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 switch activation, which in
turn stops magnetron oscillation.
FUSE
P/S
4-3
T/S S/S
H.V.
TRANS-
M/S
FORMER
P/S : Primary Switch
T/S : Timer Switch
M/S : Monitor Switch
S/S : Secondary Switch