R-959SLMA (serv.man5). Operation Sequence - Sharp Home Appliance Service Manual (repair manual)

R959(SL)MA

5 – 1

R959(SL)MA

Service Manual

 

Closing the door activates the monitored latch switch and the stop
switch.

                                            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.

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.

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

R959(SL)MA

5 – 2

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.

°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.:

°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.

°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.

°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.

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.

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.

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.

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.

R959(SL)MA

5 – 3

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.

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.

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