Sharp R-939(BK), Руководство по обслуживанию

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R939(W)
5 – 1
R939(W)
Service Manual
CHAPTER 5.
OPERATION SEQUENCE
[1] OFF CONDITION
Closing the door activates the monitored latch switch and the stop
switch.
IMPORTANT
When the oven door is closed, the contacts COM-NC of the moni-
tor switch must be open. When the microwave oven is plugged in
a wall outlet (230V / 50Hz), the line voltage is supplied to the noise
filter.
Figure O-1 on page 14-1
1. The control unit is not energized. The display shows nothing (Fig.
O-1 (a)).
2. Open the door. The contacts (COM-NC) of the monitored latch
switch are closed and the control unit is energized. Then contacts
of relays RY1 and RY5 are closed, and the oven lamp will light and
the display will show “SELECT LANGUAGE” in 5 languages. (Fig.
O-1(b)).
NOTE: NOTE: Once the language is selected using the LANGUAGE
key, the display will show “ENERGY SAVE MODE TO GO
OUT OF ENERGY SAVE MODE SET CLOCK” when the oven
is plugged in.
3. Close the door. The contacts (COM-NC) of the monitored latch
switch are opened and the contacts of relay RY1 are opened and
the oven lamp will be turned off. The display will show “ . 0". (Fig.
O-1(c)).
NOTE: Energy save mode
1) If the oven has not been used for more than 3 minutes, the
contacts of the relay RY5 will be opened and the control
unit will be not energized. Open and close the door, the
control unit will resume.
2) If the clock is set, this energy save mode does not work.
3) If the display shows different messages from ENERGY
SAVE MODE, the oven may be set in demo mode. Close
the door, see operation manual to cancel demo mode.
[2] MICROWAVE COOKING CONDITION
1. HIGH COOKING
Rotate the COOKING MODE dial to the micro setting. And press the
POWER LEVEL button once. And enter the cooking time by rotating
the TIMER/WEIGHT dial. And start the oven by pressing START but-
ton.
Function sequence
Figure O-2 on page 14-2
1. The line voltage is supplied to the primary winding of the high volt-
age transformer. 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.
2. The filament winding voltage (3.3 volts) heats the magnetron fila-
ment and the high voltage (2000 volts) is sent to the voltage dou-
bling circuit, where it is doubled to negative voltage of
approximately 4000 volts D.C..
3. The 2450 MHz microwave energy produced in the magnetron gen-
erates a wavelength 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 + RY6 go back to their home position.
The circuits to the oven lamp, high voltage transformer, fan motor
and turntable motor are cut off.
5. When the oven door is opened during a cooking cycle, the switches
come to the following condition.
The circuit to the high voltage transformer is cut off when the contacts
of relay RY2, and the contacts (COM-NO) of the monitored latch
switch SW1 and monitor switch SW3 are made open. The circuit to the
fan motor is cut off when the relay RY6 is made open. The circuit to the
turntable motor is cut off when the contacts (COM-NO) of the moni-
tored latch switch SW1 are made open. The oven lamp remains on
even if the oven door is opened after the cooking cycle has been inter-
rupted, because the relay RY1 stays closed. Shown in the display is
remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch SW3 is mechanically controlled by the oven
door, and monitors the operation of the monitored latch switch
SW1.
1) When the oven door is opened during or after the cycle of a
cooking program, the monitored latch switch SW1 and stop
switch SW2 must open their contacts (COM-NO) first. And the
contacts (COMNC) of the monitored latch switch SW1 are made
closed. After that the contacts (COM-NC) of the monitor switch
SW3 can be closed and the contacts (COM-NO) of monitor
switch SW3 are made open.
2) When the oven door is closed, the contacts (COMNC) of the
monitor switch SW3 must be opened and the contacts (COM-
NO) of monitor switch SW3 must be closed. After that the con-
tacts (COM-NO) of the monitored latch switch SW1 and the stop
switch SW2 are made closed. And the contacts (COM-NC) of
the monitored latch switch SW1 are made open.
3) When the oven door is opened and the contacts (COM-NO) of
the monitored latch switch SW1 remain closed, the fuse F2 F8A
will blow. Because the relay RY1 and monitor switch SW3 are
closed and a short circuit is caused.
2. MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking power, the
line voltage is supplied to the high voltage transformer intermittently
within a 32-second time base through the relay contact which is cou-
pled with the current-limiting relay RY2. The following levels of micro-
wave power are given.
CONNECTED COMPONENTS RELAY
Oven lamp, Turntable motor RY1
High voltage transformer RY2
Fan motor, RY6
CONDITION
SWITCH CONTACT
DURING
COOKING
DOOR OPEN
(NO COOKING)
Monitored latch
switch COM-NO
COM-NC Closed
Opened
Opened
Closed
Stop switch COM-NO Closed Opened
Monitor switch
COM-NO
COM-NC Closed
Opened
Opened
Closed