R-238ASL (serv.man5). Operation Sequence - Sharp Home Appliance Service Manual (repair manual)

r-238asl (serv.man5) service manual
Model
R-238ASL (serv.man5)
Pages
1 Few pages! See other manuals at the bottom of the first or last page.
Size
117.16 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Operation Sequence
File
r-238asl-sm5.pdf
Date

Read Sharp R-238ASL (serv.man5) Service Manual online

R238A(SL)
5 – 1
R238A(SL)
Service Manual
 
CHAPTER 5. 
OPERATION SEQUENCE
[1] OFF CONDITION
Closing the door activates all door interlock switches (1st. latch switch,
2nd. interlock relay control switch).
IMPORTANT
When the oven door is closed, the monitor switch contacts (COM-NC)
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 12-1 
1. The display will show flashing “88:88”.
2. To set any programmes or set the clock, you must first touch the
STOP/CLEAR key.
3. “  :  “ appears in the display.
[2] MICROWAVE COOKING CONDITION
1. HIGH COOKING
Enter a desired cooking time with the touching TIME keys and start the
oven with touching START key.
Function sequence 
                           Figure O-2 on page 12-1
1. Rated 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 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 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) 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 door is opened during a cook cycle, the switches come to
the following condition
The circuits to the high voltage transformer, fan motor, turntable motor
and oven lamp are cut off when the 1st. latch switch and 2nd. interlock
relay control switch are made open. 
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by oven door, and
monitors the operation of the 1st. latch switch, the relay (RY1) and
the 2nd. interlock relay (RY2).
1) When the oven door is opened during or after the cycle of a
cooking program, the 1st. latch switch and 2nd. interlock relay
control switch must open their contacts first. After that the con-
tacts (COM-NC) of the monitor switch can be closed.
2) When the oven door is closed, the contacts (COM-NC) of the
monitor switch must be opened. After that the contacts of the
1st. latch switch and 2nd. interlock relay control switch are
closed.
3) When the oven door is opened and the contacts of the 1st. latch
switch, the relay (RY1) and the 2nd. interlock relay (RY2)
remain closed. The fuse (T6.3A) will blow, because the monitor
switch is 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, rated
voltage is supplied to the high voltage transformer 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;
NOTE: The ON/OFF time ratio does not exactly correspond to the
percentage of microwave power, because approx. 3 seconds
are needed for heating up the magnetron filament.
[3] POWER OUTPUT REDUCTION
After 100% power cooking mode is carried out for more than 20 min-
utes, the power out-put is automatically reduced to 70%. Even if the
cooking time is shorter than for 20 minutes, the power output is
reduced to 70% after total cooking time over 20 minutes when the
oven is started in 100% power cooking mode again within 1 minute
and 35 seconds.
CONNECTED COMPONENTS
RELAY
Oven lamp, Fan motor, Turntable motor 
RY1
High voltage transformer 
RY2
          CONDITION
SWITCH CONTACT 
DURING 
COOKING
DOOR OPEN 
(NO COOKING)
1st. latch switch 
COM-NO 
Closed 
Open
2nd. interlock relay   
control switch   
COM-NO Closed 
Open
Monitor switch       
COM-NC 
Open   
Closed
100P (HIGH)
32 sec. ON
70P (MEDIUM
HIGH)
Approx. 70%
100%
24 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
26 sec. OFF
50P (MEDIUM)
Approx. 50%
18 sec. ON
30P (MEDIUM
LOW)
Approx. 30%
12 sec. ON
10P (LOW)
Approx. 10%
6 sec. ON
Display

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Here you can read online and download Sharp R-238ASL (serv.man5) Service Manual in PDF. R-238ASL (serv.man5) service manual will guide through the process and help you recover, restore, fix, disassemble and repair Sharp R-238ASL (serv.man5) Microwave Oven. Information contained in service manuals typically includes schematics / circuit diagrams, wiring diagrams, block diagrams, printed wiring boards, exploded views, parts list, disassembly / assembly, pcb.