Operation Sequence - Sharp R-209FW Service Manual

OFF CONDITION
1. When the timer knob is at "
condition.
2. Closing the oven door activates the monitored latch
switch and the latch switch.
IMPORTANT
When the oven door is closed, the contacts (COM-NC) of
the monitor switch SW2 must be open.
When the microwave oven is plugged in a wall outlet, rated
voltage is supplied to the noise filter and the control unit.
Figure O-1 on page 25
MICROWAVE COOKING CONDITION
HIGH COOKING
Set the Microwave power control knob to
then set the timer.
Function sequence
Figure O-2 on page 25
1. Following components are energized.
High voltage rectifier
High voltage capacitor
Turntable motor
Magnetron
CONNECTED COMPONENTS
High voltage transformer
2. Rated voltage is supplied to the primary winding of the
high voltage transformer T. The voltage is converted to
about 3.3 volts A.C. output on the filament winding and
high voltage of approximately 2000 volts A.C. on the
secondary winding.
3. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2000 volts) is
sent to the voltage doubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..
4. The 2450 MHz microwave energy produced in the
magnetron MG generates a wave length of 12.24 cm.
This energy is channelled through the waveguide
(transport channel) into the oven cavity, where the food
is placed to be cooked.
5. When the cooking time is up, the timer returns to "
the bell rings and the contacts of the timer switch are
opened. The following components are turned off.
High voltage rectifier
High voltage capacitor
Turntable motor
Magnetron
6. When the oven door is opened during a cook cycle, the
switches come to the following position and they are
common to the other cooking conditions too.
SWITCH CONTACT
Monitored latch switch COM-NO
Latch switch COM-NO
Monitor switch COM-NC
The circuits to the high voltage transformer T, turntable

OPERATION SEQUENCE

", the oven is OFF
800W and
High voltage transformer
High voltage fuse
Timer motor Fan motor
Oven lamp Control unit
RELAY
RY1
High voltage transformer
High voltage fuse
Timer motor Fan motor
Oven lamp Control unit
CONDITION
DURING DOOR OPEN
COOKING (NO COOKING)
Closed Open
Closed Open
Open Closed
motor TTM, timer motor TM, fan motor FM, oven lamp
OL and control unit are cut off when the contacts
(COM-NO) of the monitored latch switch SW1 and
latch switch SW3 are made open.
The timer stops to indicate how much cooking time
remains.
7. MONITOR SWITCH CIRCUIT
The monitor switch SW2 is mechanically controlled by
oven door, and monitors the operation of the monitored
latch switch SW1.
7-1 When the oven door is opened during or after the
cycle of a cooking program, the monitored latch
switch SW1 and latch switch SW3 must open their
contacts (COM-NO) first. After that the contacts (COM-
NC) of the monitor switch SW2 can be closed.
7-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switch SW2 must be opened first.
And then the contacts (COM-NO) of the monitored
latch switch SW1 and the latch switch SW3 are
closed.
7-3. When the oven door is opened and the contacts
(COM-NO) of the monitored latch switch SW1 and
contacts of the timer switch remain closed. The fuse
F1 T6.3A will blow, because the monitor switch is
closed and a short circuit is caused.
POWER LEVEL COOKING
When the microwave oven is preset for variable cooking
power, rated voltage is supplied to the high voltage trans-
former intermittently within a 32-second time base through
the relay contact which is coupled with the current-limiting
relay. The following levels of microwave power are given.
SETTING;
32 sec. ON
800W
24 sec. ON
560W
18 sec. ON
400W
12 sec. ON
240W
",
6 sec. ON
80W
NOTE: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 3 seconds are needed for heat-
ing up the magnetron filament.
POWER OUTPUT REDUCTION
1. If the oven is set for more than 20 minutes at
after the first 20 minutes the power level will automati-
cally adjust itself to 70% power to avoid overcooking.
2. If the oven is operated for more than 90 minutes
continuously (at any power levels), the relay RY1
opens. And the circuit to the high voltage transformer
will be cut off.
7
R-209(IN)
R-209(W)
R-209(Y)
100%
8 sec. OFF
Approx. 70%
14 sec. OFF
Approx. 50%
10 sec. OFF
Approx. 30%
26 sec. OFF
Approx. 10%
800W,