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R-852 - 8

STARTkey is touched, the following 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 energized.

3. The relay RY3 is energized and the main supply

voltage is applied to the top grill heater.

4. Now, the food is cooked by the top grill heater.

BOTTOM GRILL (Figure O-3b)
In this condition the food is cooked by bottom grill heating
element energy. Programme the desired cooking time by
touching the TIME keys and touh the GRILL key twice.
When the STARTkey is touched, the following 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 energized.

3. The relay RY4 is energized and the main supply

voltage is applied to the bottom grill heatier.

4. Now, the food is cooked by the bottom grill heater.

TOP AND BOTTOM GRILL (Figure O-3c)
In this condition the food is cooked by top and bottom grill
heating elements energy. Programme the desired cook-
ing time by touching the TIME keys and touh the GRILL
key three times. When the STARTkey is touched, the
following 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 energized.

3. The relay RY4 is energized and the main supply

voltage is applied to the bottom grill heating element.

4. The relay RY3 is energized and the main supply

voltage is applied to the top grill heating element.

5. Now, the food is cooked by the top and bottom grill

heating elements.

PRE-HEATING (Figure O-4)
Programme the desired convection temperature by touch-
ing CONVECTION key. When the STARTkey is touched,
the following operations occur:
1. The coil shut-off relays RY1  and RY6 are energized,

the oven lamp, cooling fan motor and turntable motor
are turned on.

2. The coil shut-off relays RY3  and RY4 are energized by

control unit and the main supply voltage is added to the
top and bottom heating elements.

3. When the oven temperature reaches the selected pre-

heat temperature,  the following operations occur:

3-1. The coil shut-off relays RY3  and RY4 are energized

by control unit temperature circuit and thermistor,
opening the circuit to the top and bottom grill heating
elements.

3-2. The oven will continue to function for 30 minutes,

turning the top and bottom heating elements on and
off, as needed to maintain the selected pre-heat
temperature. The ovenwill shut-down completely af-
ter 30 minutes.

NOTE:The fan motor will be turned on and off at

preheating. And the convection motor will be turned
off at  preheating. See "Power setting" on page 9.

CONVECTION COOKING (Figure O-4)
When the pre-heat temperature is reached, a beep signal
will sound indicating that the holding the temperature has
been reached in the oven cavity. Open the door and place
the food to cooked in the oven. Program desired cooking
time by touching the TIME keys and program convection
temperature by touching the CONVECTION key . When
the START key is touched, the following operations occur:
1. The numbers on the digital readout start the count

down to zero.

2. The oven lamp, cooling fan motor, turntable motor and

convection motor are energized.

NOTE: When the convection temperature 40˚C is se-

lected, the convection motor is not energized.

3. The relays RY3  and RY4 are energized (if the cavity

temperature is lower than selected temperature) and
the main supply voltage is applied to the top and
bottom heating elements to return to the selected
cooking temperature.

4. Upon completion of the cooking time, the audible sig-

nal will sound, and the oven lamp, turntable motor,
cooling fan motor, convection motor, top and bottom
heating elements are de-energized. At the end of
convection cycle, if the cavity air temperature rise
above 120˚C, the circuit to the relay RY6 will be main-
tained (by the thermistor circuit) to continue operation
of the cooling fan motor until temperature drops below
105˚C, at that time the relay RY6 will be de-energized,
turning off the fan motor.

MICROWAVE AND CONVECTION  (Figure O-5a)
Programme the desired cooking time by touching the
TIME keys. Touch the DUAL key once. Select the micro-
wave power level by touching the MICROWAVE POWER
LEVEL key. And select the convection temperature by
touching the CONVECTION key.

NOTE: The microwave power level can be selected from

90W, 270W and 450W.

When the STARTkey is touched, the following operations
occur:

1. The numbers on the digital readout start the count

down to zero.

2. The oven lamp, cooling fan motor, turntable motor and

convection motor are energized.

3. The relay RY3 will be energized and the main supply

voltage is applied to the top grill heatier.

4. The relay RY4 is energized (if the cavity temperature is

lower than selected temperature) and the main supply
voltage is applied to the bottom heating elementer.

5. The relay RY2 is energized and the microwave energy

is generated by magnetron.

6. Now, the food is cooked by microwave and convection

energy simultaneously.

MICROWAVE AND TOP GRILL  (Figure O-5b)
Programme the desired cooking time by touching the
TIME keys. Touch the DUAL key twice. Select the micro-
wave power level by touching the MICROWAVE POWER
LEVEL key. When the STARTkey is touched, the following
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 energized.

R-852 - 9

3. The relay RY3 is energized and the main supply

voltage is applied to the top grill 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 top grill

simultaneously.

Programme the desired cooking time by touching the
TIME keys. Touch the DUAL three times. Select the
microwave power level by touching the MICROWAVE
POWER LEVEL key. When the STARTkey is touched, the
following 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 energized.

3. The relay RY4 is energized and the main supply

voltage is applied to the bottom grill 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 bottom grill

simultaneously.

The power setting of the top heating element, bottom
heating element and  fan motor in the oven  cooking mode
and preheating mode is 100%.

POWER OUTPUT

ON TIME

OFF TIME

100%

48 sec.

0 sec.

90%

44 sec.

4 sec.

80%

40 sec.

8 sec.

70%

36 sec.

12 sec.

60%

32 sec.

16 sec.

50%

26 sec.

22 sec.

40%

22 sec.

26 sec.

30%

16 sec.

32 sec.

20%

12 sec.

36 sec.

10%

8 sec.

40 sec.

FRESH PIZZA/ FRESH QUICHE
FROZEN PIZZA/ FROZEN QUICHE
FRENCH FRIED POTATO
BOILED/ JACKET POTATOES
INSTANT ACTION
Above functions are automatic cooking. They automati-
cally work out the correct cooking mode and cooking time
and/or cooking temperature. They will cook according to
the special cooking sequence.

After the same cooking mode is carried out for more than
the specified cooking time, the power output is automati-
cally 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. In case of Automatic operations, the limitations of

power output are not carried out.

2. In case that the stop key is touched or the oven door is

opened during cooking, the limitations of power output
are not carried out after the total cooking time beyond
the specified cooking time.

3. In case of the two or more same cooking modes  are

carried out,  the limitations of power output are not
carried out after the total cooking time beyond the
specified cooking time.

4. In case of the two or more different cooking modes  are

carried out,  the specified cooking time is started to
count from the point when the cooking mode is changed.

5. If the cooking mode has the power level display, the

power level is also displayed when the limitations of
power output are carried out.

D

U

A

L

Specified cooking

Limited power

Time base

Cooking mode

time (minutes)

output (%)

(seconds)

Microwave (100%)

20

70

32

Top grill

30

50

48

Bottom grill

45

50

48

Top grill and

15 (Top)

50

48

Bottom grill

15(Bottom)

50

48

Micro. (100%)

20 (Micro.)

70

48

+ Top grill

15 (Grill)

50

48

Micro. (100%)

20 (Micro.)

70

48

+ Bottom grill

15 (Heater)

50

48

In grill cooking, convection cooking or dual cooking, the
top heater, bottom heater or magnetron operate whithin a
48 second time base. The following table is the ON / OFF
time ratio at each power output of the top heaters, bottom
heater or magnetron.

250˚C

100%

100%

60%

0%

230˚C

100%

100%

60%

0%

220˚C

100%

100%

60%

0%

200˚C

100%

100%

60%

0%

180˚C

100%

100%

60%

0%

160˚C

100%

100%

60%

0%

130˚C

100%

100%

60%

0%

100˚C

100%

100%

60%

0%

70˚C

100%

100%

60%

0%

40˚C

100%

100%

60%

0%

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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.

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

of the switch must be closed. And the contacts (COM-
NC) 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 F2  F8A when the contacts of the monitored
latch switch SW1 fail to open when the door is opened.
Function
1. When the door is opened, the contacts (COM-NC) of

monitor switch SW3 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 SW1 is in the OFF condition (contacts
open) due to their being normally open contact switches.

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

switch SW3 contacts (COM-NC) are opened and con-
tacts (COM-NO) closed and then contacts (

COM-NO)

of monitored latch switch SW1  and stop switch SW2
are closed.(On opening the door, each of these switches
operate inversely.)

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

SW1 contacts  (COM-NO) fail to open, the fuse F2
(F8A) blows immediately after closing of the monitor
switch (COM-NC) contacts.

CAUTION: BEFORE REPLACING A BLOWN FUSE  F2

F8A, TEST THE MONITORED LATCH
SWITCH  SW1 AND  MONITOR SWITCH
SW3  FOR PROPER OPERATION.  (REFER
TO CHAPTER “TEST PROCEDURE”).

If the wire harness or electrical components are short-
circuited, this fuse F1 blows to prevent an electric shock of
fire hazard.

1. If the wire harness or electrical components are short-

circuited, this fuse blows to prevent an electric shock or
fire hazard.

2. The fuse also blows when the monitored latch switch

SW1 remains closed with the oven door open and
when the monitor switch SW3 contact (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 trans-
former is shorted.

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

This thermal cut-out protects the magnetron against over-
heat. If the temperature goes up higher than 125˚C be-
cause the fan motor is interrupted or the ventilation open-
ings are blocked, the thermal cut-out TC1 will open and
line voltage to the high voltage transformer T will cut off
and operation of the magnetron MG will be stopped. The
defective thermal cut-out must be replaced with a new
one.

This thermal cut-out protects the oven against the over-
heat during grill cooking, convection cooking or dual
(combination) cooking. If the temperature rises above
150˚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 cools itself down to the operating tem-
perature of 130˚C, the contacts of the thermal cut-out will
close again.

The asymmetric rectifier is solid state device that prevents
current flow is both directions. And it prevents the tem-
perature rise of the high voltage transformer by blowing
the fuse F2 F8A when the high voltage rectifier is shorted.

DOOR

LATCH HOOK

SW3: MONITOR SWITCH

SW1: MONITORED

LATCH SWITCH

SW2: STOP SWITCH

OPEN LEVER

LATCH
HEADS

The rated peak reverse voltage of D1 of the asymmetric
rectifier is 6 KV. The rated peak reverse voltage of D2 of
the asymmetric rectifier is 1.7 KV. D1 and D2 of the
asymmetric rectifier or high voltage rectifier are shorted
when the each peak reverse voltage goes beyond the
each rated peak reverse voltage. (The process of the
blowing the fuse F2 F8A.)
1. The high voltage rectifier is shorted by some fault when

R-852 - 11

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 volt-

age 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 F2 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 inter-
ference 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 chan-
nelled 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 element is provided to brown the food and
is located on the top of the oven cavity.

The grill heating element is provided to brown the food and
is located at the base of the oven cavity.

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-ener-
gized. When the temperature inside the oven cavity drops
below the selected temperature, the heating elements are
energized again. In this way, the inside of the oven cavity
is maintained at approximately the selected temperature.
When the convection time reaches “0”, the heating ele-

ments are de-energized and the convection fan stops
operating and the oven shuts off. At that time if the cavity
air temperature has rised above120˚C, the fan motor
remains rotating. Automatically the fan motor will be shut
down at low temperature (less than 105˚C).

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 meas-
urement 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 0.781 volts in microwave cooking
condition.

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

for 2 seconds.  At that time, the voltage across the
temperature measurement circuit is measured.

2. The oven carries out the procedure above again. If the

second voltage is 0.781V 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 countring 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 (top and
bottom grills) or dual cooking mode, the oven is turned
off.

2. When the thermistor or the wire harness to the thermis-

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

THERMISTOR

Sensing 

Voltage

ON

OFF

ON

OFF

30

32 (sec.)

Sensing the voltage across temperature measurement circuit.

Door

Oven Cavity

Grill Heating
Element

Bottom Grill 
Heating Element

Convection
Passage

Cooling
Fan

Convection
Motor

Convection
Fan

Turntable

Insulation

Turntable
Motor