R-98STMA (serv.man5). Operation Sequence - Sharp Home Appliance Service Manual (repair manual)

r-98stma (serv.man5) service manual
Model
R-98STMA (serv.man5)
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Service Manual
Brand
Device
Home Appliance / Microwave Oven / Operation Sequence
File
r-98stma-sm5.pdf
Date

Read Sharp R-98STMA (serv.man5) Service Manual online

R98STMAA
5 – 1
R98STMAA
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 (230 - 240V / 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 “  . 0” . (Fig. O-1(b)).
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] MICROWAVE COOKING CONDITION
1. HIGH COOKING
Enter a desired cooking time by touching the TIME keys and start the
oven by touching START key.
Function sequence 
                           Figure O-2 on page 14-1
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 and monitor switch 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 monitored latch
switch 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 RY1 stays closed. Shown in the display is remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by the oven door,
and monitors the operation of the monitored latch switch.
1) When the oven door is opened during or after the cycle of a
cooking program, the monitored latch switch and stop switch
must open their contacts (COM-NO) first. And the contacts
(COM-NC) of the monitored latch switch are made closed. After
that the contacts (COM-NC) of the monitor switch can be closed
and the contacts (COM-NO) of monitor switch are made open.
2) When the oven door is closed, the contacts (COMNC) of the
monitor switch must be opened and the contacts (COM-NO) of
monitor switch must be closed. After that the contacts (COM-
NO) of the monitored latch switch and the stop switch are made
closed. And the contacts (COM-NC) of the monitored latch
switch are made open.
3) 6-3. When the oven door is opened and the contacts (COM-NO)
of the monitored latch switch remain closed, the fuse F8A will
blow. Because the relay RY1 and monitor switch 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.
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.
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
100% (HIGH)
32 sec. ON
70% (MEDIUM
HIGH)
Approx. 70%
100%
24 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
26 sec. OFF
50% (MEDIUM)
Approx. 50%
18 sec. ON
30% (MEDIUM
LOW)
Approx. 30%
12 sec. ON
10% (LOW)
Approx. 10%
6 sec. ON
R98STMAA
5 – 2
[3] GRILL COOKING CONDITION
1. TOP GRILL (Figure O-3)
In this condition the food is cooked by the grill heating element . Pro-
gramme the desired cooking time by touching the TIME keys and
touch the GRILL key once. When the START key is touched, the fol-
lowing operations occur:
1. The numbers on the digital readout start the count down to zero.
2. The oven lamp, cooling fan motor and turntable motor are ener-
gized. 
3. The relay RY3 is energized and the main supply voltage is applied
to the top grill heating elements.
4. Now, the food is cooked by the top grill heating elements.
NOTE: The convection cooking condition will be carried out simulta-
neously until the temperature of the oven cavity rise to 220
°C.
[4] CONVECTION COOKING CONDITION
1. PRE-HEATING (by 40
°C - 130°C)
Programme the desired convection temperature of 40
°C - 130°C by
touching CONVECTION key. When the START key is touched, the fol-
lowing operations occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turn-
table motor, fan motor and convection motor are turned on.
2. The relay RY4 is energized and the main supply voltage is applied
to the convection heating element.
3. After the temperature of oven cavity rises to the selected one, the
oven will continue to turned the convection heating element on and
off to maintain the temperature for 30 minutes.:
2. PRE-HEATING (by 160
°C - 250°C)
Programme the desired convection temperature of 160
°C - 250°C by
touching CONVECTION key. When the START key is touched, the fol-
lowing operations occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turn-
table motor, fan motor and convection motor are turned on.
2. The relay RY4 and RY3 are is energized and the main supply volt-
age is applied to the convection heating element and the grill heat-
ing elements.
3. After the temperature of oven cavity rises to the selected one, the
oven will continue to turned the convection heating element on and
off to maintain the temperature for 30 minutes. And simultaneously
the grill heating element will be operated at 10% power output.
3. CONVECTION COOKING (by 250
°C)
Programme the cooking time by touching TIME keys. And then pro-
gramme the convection temperature of 250
°C by touching CONVEC-
TION key. When the START key is touched, the following operations
occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turn-
table motor, fan motor and convection motor are turned on.
2. The relay RY4 and RY3 are energized and the main supply voltage
is applied to the convection heating element and the grill heating
elements.
3. The oven will continue to turn the convection heating element on
and off to maintain the temperature for the programmed cooking
time. And simultaneously the grill heating elements will be operated
at 10% power output.
4. CONVECTION COOKING (by 40
°C - 230°C)
Programme the cooking time by touching TIME keys. And then pro-
gramme the desired convection temperature of 40
°C 230°C by touch-
ing CONVECTION key. When the START key is touched, the following
operations occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turn-
table motor, fan motor and convection motor are turned on.
2. The relay RY4 is energized and the main supply voltage is applied
to the convection heating element. 
3. The oven will continue to turn the convection heating element on
and off to maintain the temperature for the programmed cooking
time.
[5] COMBI COOKING CONDITION
1. MICROWAVE AND CONVECTION (Figure O-5a)
Programme the desired cooking time by touching the TIME keys.
Touch the COMBI. key once. Select the microwave power level by
touching the MICRO. POWER key. And select the convection temper-
ature by touching the CONVECTION key.
NOTE: The 100% microwave power level can not be selected.
When the START key is touched, the following operations occur:
1. The numbers on the digital read-out start the count down to zero.
2. The oven lamp, fan motor, turntable motor and convection motor
are energized.
3. The relay RY4 will be energized and the main supply voltage is
applied to the convection heating element.
4. The relay RY2 is energized and the microwave energy is generated
by magnetron.
5. Now, the food is cooked by microwave and convection energy
simultaneously.
2. MICROWAVE AND TOP GRILL (Figure O-5b)
Programme the desired cooking time by touching the TIME keys.
Touch the COMBI. key twice. Select the microwave power level by
touching the MICRO. POWER key. When the START key is touched,
the following operations occur:
1. The numbers on the digital read-out start the count down to zero.
2. The oven lamp, fan motor and turntable motor are energized.
3. The relay RY3 is energized and the main supply voltage is applied
to the grill heating elements.
4. The relay RY2 is energized and the microwave energy is generated
by magnetron.
5. Now, the food is cooked by microwave and grill simultaneously.
[6] ON/OFF TIME RATIO
In grill cooking, convection cooking or dual cooking, the grill heating
elements or magnetron operate within a 54 second time base. The fol-
lowing table is the ON / OFF time ratio at each power output of the grill
heating element or magnetron.
[7] AUTOMATIC COOKING
Auto Cook functions automatically work out the correct cooking mode
and cooking time and/or cooking temperature. They will cook accord-
ing to the special cooking sequence.
POWER OUTPUT
ON TIME
OFF TIME
100%
54 sec.
0 sec.
70%
40 sec.
14 sec.
50%
29 sec.
25 sec.
30%
18 sec.
36 sec.
10%
9 sec.
45 sec.
R98STMAA
5 – 3
[8] POWER OUTPUT REDUCTION
After the same cooking mode is carried out for more than the basis
cooking time, the power output is automatically reduced by turning the
control relays on and off intermittently, as shown in the table below.
This is to protect the oven door against temperature rising.
NOTE: 1) If the multiple sequence cooking is carried out in the same
mode, the basis cooking time is calculated from the first.
2) Even if the cooking is stopped by the STOP key or opening
the door, the basis cooking time is calculated from the first.
3) If the same cooking mode is repeated within 1 minute and
15 seconds, the basis cooking time is calculated from the
first.
4) If the same menu of Automatic Cooking is repeated within
1 minute and 15 seconds, the power output of the micro-
wave or the grill will be reduced to 70% after 20 minutes
when the oven is started at first.
[9] FAN MOTOR OPERATION
(in Grill, Convection and COMBI. mode)
When oven is stopped during cooking, or after the cooking is com-
pleted, the fan motor will operate if the oven cavity temperature is
above 120
°C, and the fan motor will stop if the oven cavity tempera-
ture is below 105
°C.
[10] CONVECTION MOTOR OPERATION
If the temperature of oven cavity is higher than 120
°C after and when
operated by 250
°C convection cooking, 250°C combi. convection
cooking or 250
°C preheating, the convection motor will operate for
maximum 1 minute until the oven cavity temperature drops below
105
°C.
Cooking mode
Basis cooking 
time (minutes) 
Reduced power 
output (%)
Time base 
(seconds)
Microwave (100%) 20
70
32
Grill
15
70
54
Convection
No reduction
D
U
A
L
Micro. (70%)
+ Grill
40 (Micro.)
50
54
15 (Grill)
50
54
Micro. (100%) 
+ Grill
15 (Micro.)
50
54
15 (Grill) 
50
54
Micro. (70%)
+ Conv.
40 (Micro.) 
50
54
No reduction
Page of 3

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