Operation Sequence - Sharp R-15AM Service Manual

OFF CONDITION
Closing the door activates the 1st. interlock switch SW1
and 2nd. interlock relay control switch SW2.
IMPORTANT:
When the oven door is closed, the contacts COM-NC
of the monitor switch SW3 must be open. When the
microwave oven is plugged in a wall outlet (230V
50Hz), the line voltage is supplied to the control unit
through the noise filter.
Figure O-1 on page 26
1. The display will flash 88:88 .
2. Touch the stop button and the display will show
. .
MICROWAVE COOKING CONDITION
Program desired cooking time by rotating the TIMER knob
clockwise. When the START button is pressed, the follow-
ing operations occur:
Figure O-2 on page 26
RELAY CONNECTED COMPONENTS
RY-1 Oven lamp/Antenna motor/Fan motor
RY-2 ,RY3 High voltage transformer
1. The line voltage is supplied to the primary winding of
the high voltage transformer. The voltage is converted
to about 3.3 volts A.C. output on the filament winding
and high voltage of approximately 2300 volts A.C. on
the secondary winding.
2. 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..
3. The 2450 MHz microwave energy produced in the
magnetron 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.
4. When the cooking time is up, a signal tone is heard and
the relays RY1+RY2+RY3 go back to their home
position. The circuits to the oven lamp, high voltage
transformer, fan motor and antenna motor are cut off.
5. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch Contact
1st. interlock switch COM-NO
2nd. interlock relay
COM-NO
control switch
Monitor Switch COM-NC
The circuit to the high voltage transformer, fan motor, oven
lamp and antenna motor are cut off when the 1st. interlock
switch SW1 and 2nd. interlock relay control switch SW2
are made open. The oven lamp remains on even if the
oven door is opened after the cooking cycle has been
interrupted, because the relay RY-1 stays closed. Shown
in the display is remaining time.

OPERATION SEQUENCE

Condition
During Oven Door
Cooking Open(No cooking)
Closed Opened
Closed Opened
Opened Closed
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by the
oven door, and monitors the operation of the 1st.
interlock switch SW1 and the relay RY-2.
6-1. When the oven door is opened during or after the
cycle of a cooking program, the 1st. interlock switch
SW1, and 2nd. interlock relay control switch SW2
must open their contacts first. After that the contacts
(COM-NC) of the monitor switch SW3 can be closed.
6-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switch SW3 must be opened. After
that the contacts of the 1st. interlock switch SW1, and
2nd. interlock relay control switch SW2 are closed.
6-3. When the oven door is opened and the contacts of the
1st. latch switch SW1 and the relay RY-2 remain
closed, the fuse F10A will blow, because the monitor
switch SW3 is closed and a short circuit is caused.
POWER LEVEL 10P TO 90P COOKING
When Variable Cooking Power is programmed, the line
voltage is supplied to the power transformer intermittently
through the contacts of relay (RY-3) which is operated by
the control unit within a 32 second time base. Microwave
power operation is as follows:
VARI-MODE
100P (100% power)
70P (approx. 70% power) 24 sec.
50P (approx. 50% power) 18 sec.
30P (approx. 30% power) 12 sec.
10P (approx. 10% power)
Note: The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approx. 3 seconds are needed for heating of the
magnetron filament.
7
R-15AM
ON TIME OFF TIME
32 sec. 0 sec.
8 sec.
14 sec.
20 sec.
6 sec. 26 sec.