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R-959(SL)M-AA

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.

R-959(SL)M-AA

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

n

o

it

c

u

d

e

r

 

o

N

n

o

it

c

e

v

n

o

C

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

R-959(SL)M-AA

6 – 1

R959(SL)MA

The door can be opened by pushing the open button on the control
panel. When the open button is pushed, the open lever is pushes
lower latch head on the door upward. The upper latch head is linked
with the lower latch head, so now, the door can be opened.

Figure D-1. Door Open Mechanism

1. When the oven door is closed, the contacts (COM-NO) of the

switch must be closed. And the contacts (COMNC) must be
opened.

2. When the oven door is opened, the contacts (COM-NO) of the

switch must be opened. And the contacts (COM-NC) must be
closed.

1. When the oven door is closed, the contacts (COM-NO) of the

switch must be closed.

2. When the oven door is opened, the contacts (COM-NO) of switch

must be opened.

The monitor switch is activated (the contacts opened) by the upper
latch head on the door while the door is closed. The switch is intended
to render the oven inoperative by means of blowing the fuse F8A when
the contacts of the monitored latch switch fail to open when the door is
opened.

1. When the door is opened, the contacts (COM-NC) of monitor

switch close (to the ON condition) due to their being normally
closed and contacts (COM-NO) open. At this time the contacts
(COM-NO) of monitored latch switch is in the OFF condition (con-
tacts open) due to their being normally open contact switches.

2. As the door goes to a closed position, the monitor switch contacts

(COM-NC) are opened and contacts (COM-NO) closed and then
contacts (COM-NO) of monitored latch switch and stop switch are
closed. (On opening the door, each of these switches operate
inversely.)

3. If the door is opened and the monitored latch switch contacts

(COM-NO) fail to open, the fuse F8A blows immediately after clos-
ing of the monitor switch (COMNC) contacts.

CAUTION: BEFORE REPLACING A NOISE FILTER (BLOWN FUSE

F8A), TEST THE MONITORED LATCH SWITCH AND
MONITOR SWITCH FOR PROPER OPERATION. (REFER
TO CHAPTER “TEST PROCEDURE”).

If the wire harness or electrical components are shortcircuited, this
fuse 20A blows to prevent an electric shock of fire hazard.

1. If the wire harness or electrical components are shortcircuited, this

fuse blows to prevent an electric shock or fire hazard.

2. The fuse also blows when the monitored latch switch remains

closed with the oven door open and when the monitor switch con-
tact (COM-NC) closes.

3. The fuse also blows when the asymmetric rectifier, H.V. rectifier,.

H.V. wire harness, H.V. capacitor, magnetron or secondary winding
of high voltage transformer is shorted.

T/C transformer converts A.C. line voltage into low voltage to drive the
control unit.

°C

This thermal cut-out protects the magnetron against overheat. If the
temperature goes up higher than 125

°C because the fan motor is

interrupted or the ventilation openings are blocked, the thermal cut-out
will open and switch off all the electrical parts. The defective thermal
cut-out must be replaced with a new one.

°C

This thermal cut-out protects the oven against the overheat during grill
cooking, convection cooking or dual cooking. If the temperature rises
above 170

°C because the fan motor is interrupted, the air inlet duct is

blocked or the ventilation openings are obstructed, the thermal cut-out
opens and switches off all the electrical parts. When the cut-out cools
itself down to the operating temperature of 155

°C, the contacts of the

thermal cut-out will close again.

°C

This thermal cut-out protects the convection motor against overheat-
ing. If the temperature of the thermal cut-out rises above 170

°C

because the convection fan is interrupted, the ventilation openings are
obstructed or the other abnormal matter occurs, the thermal cut-out
opens and switches off the convection heating element and the other
electrical parts. When the cut-out cools itself down to the operating
temperature of 155

°C, the contacts of the thermal cut-out will close

again.

The asymmetric rectifier is solid state device that prevents current flow
in both directions. And it prevents the temperature rise of the high volt-
age transformer by blowing the fuse F8A when the high voltage recti-
fier is shorted.

Latch hook

Door

Stop switch

Latch

Heads

Monitor switch

Monitored

latch switch

Tab

R-959(SL)M-AA

6 – 2

the asymmetric rectifier is 1.7 KV. D1 and D2 of the asymmetric recti-
fier or high voltage rectifier are shorted when the each peak reverse
voltage goes beyond the each rated peak reverse voltage. (The pro-
cess of the blowing the fuse F8A.) 

1. The high voltage rectifier is shorted by some fault when microwave

cooking or dual cooking.

2. The peak reverse voltage of D2 of the rectifier goes beyond the

rated peak reverse voltage 1.7 KV in the voltage doubler circuit.

3. D2 of the rectifier is shorted.

4. The large electric currents flow through the high voltage winding of

the high voltage transformer.

5. The large electric currents beyond 8A flow through the primary

winding of the high voltage transformer.

6. The fuse F8A blows by the large electric currents.

7. The power supplying to the high voltage transformer is cut off.

The noise filter assembly prevents radio frequency interference that
might flow back in the power circuit.

The turntable motor rotates the turntable.

The fan motor drives a blade which draws external cool air. This cool
air is directed through the air vanes surrounding the magnetron and
cools the magnetron. This air is channelled through the oven cavity to
remove steam and vapours given off from heating food. It is then
exhausted through the exhausting air vents of the oven cavity.

The convection motor drives the convection fan and provide the
heated air.

The grill heating elements are provided to brown the food and are
located on the top of the oven cavity.

The convection heating element situated at the rear of the oven cavity.
It is intended to heat air driven by the convection fan. The heated air is
kept in the oven and force-circulated and reheated by the convection
heating element.

This oven is designed with a hot air heating system where food is
heated by forced circulation of the hot air produced by the grill heaters.
The air heated by the grill heating elements is circulated through the
convection passage provided on the outer casing of the oven cavity by
means of the convection fan which is driven by the convection motor. It
is then enters the inside of the oven through the vent holes provided
on the back side of the oven. 

Next, the hot air heats the food on the turntable and leaves the oven
cavity through the vent in the oven cavity rear wall. In this way, the hot
air circulates inside the oven cavity to raise its temperature and, at the
same time, comes into contact with the food being cooked. When the
temperature inside the oven cavity reaches the selected temperature,
the heating elements are de-energized. When the temperature inside
the oven cavity drops below the selected temperature, the heating ele-
ments are energized again. In this way, the inside of the oven cavity is
maintained at approximately the selected temperature. When the con-
vection time reaches “0”, the heating elements are deenergized and
the convection fan stops operating and the oven shuts off. At that time
if the cavity air temperature has risen above 120

°C, the fan motor

remains rotating. Automatically the fan motor will be shut down at low
temperature (less than 105

°C).

Figure D-2. Convection Cooking System

The oven will stop its operation when there is a fire in the oven cavity
in microwave cooking condition. LSI measures the voltage across the
temperature measurement circuit intermittently within 32-seconds time
base since the oven is started in microwave cooking condition. The
oven will stop its operation when the difference of the voltage is more
than 0.39 volts in microwave cooking condition.

1. Within a 32-seconds base, the thermistor is energized for 2 sec-

onds. At that time, the voltage across the temperature measure-
ment circuit is measured.

2. The oven carries out the procedure above again. If the second volt-

age is 0.39V higher than first voltage, LSI judges it is a fire in the
oven cavity and stop the oven. 

3. When LSI judges it is a fire in the oven cavity, LSI will switch off the

relays to high voltage transformer and fan motor and LSI stops
counting down.

1. If the temperature of the thermistor does not rise to more than 40

°C

after 4 minutes and 15 seconds from when the oven is started in
convection, grill or dual cooking mode, the oven is turned off.

2. When the thermistor or the wire harness to the thermistor is

opened, the oven is turned off after 4 minutes and 15 seconds
because this condition is same as above.

D2

D1

ASYMMETRIC
RECTIFIER

HIGH VOLTAGE
RECTIFIER

Door

Oven Cavity

Grill Heating

Elements

Convection

Passage

Cooling

Fan

Convection

Motor

Convection

Fan

Turntable

Turntable Motor

Roller Stay

Convection

Heating Element

THERMISTOR

Sensing

Voltage

ON

OFF

ON

OFF

Sensing the voltage across temperature measurement circuit.