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3

1. Place the roller stay on the coupling.
2. Then place the turntable on it.

7

 

13

Low rack

High rack

Roller stay

Coupling

Turntable

1.

Door

2.

Door hinges

3.

Lamp filter

4.

Waveguide cover

5.

Contol panel

6.

Coupling

7.

Door latches

8.

Oven cavity

9.

Safety door latches

10. Ventilation openings
11. Outer case
12. Power supply cord
13.  Rear back plate

DISPLAY AND INDICATORS
Check indicators after the oven starts to confirm
the oven is operating as desired.

1.

LESS/MORE indicator

2.

COOK indicator
This indicator shows cooking in progress.

3.

AUTO DEFROST indicator

4.

SENSOR indicator

5.

GRILL indicator

6.

AUTO indicator

7.

Microwave power level indicators

8.

Digital display

9.

Units of weight indicator

OPERATING KEYS
10. INSTANT COOK key
11. AUTO COOK key
12. AUTO DEFROST key
13. Weight entry keys
14. LESS (

)/MORE (

) keys

15. Time keys
16. MICROWAVE key
17. GRILL key
18. DUAL COOK key
19. TIMER/HOLD key
20. AUTO START/CLOCK key
21. Conversion key
22. STOP/CLEAR key
23. AUTO MINUTE/START key
24. Door open button (

)

AUTO
GRILL
SENSOR
DEFROST
COOK

LOW M-LOW

MED M-HIGH

HIGH

Lbs

Kg

Oz

SMART
& EASY

INSTANT

COOK

AUTO

COOK

AUTO

DEFROST

Kg . Lb  g . oz

LESS

MORE

1O

1

1O

MIN.

MIN.

SEC.

MICROWAVE
POWER LEVEL DUAL COOK

GRILL

TIMER

/ HOLD

Kg / Lb

AUTO

START

STOP / CLEAR

AUTO MINUTE

/ START

R-4G75M

1

2

3

4

5

6

7

8

9

10

11

12

14

13

15

16

19

17

18
20

21

22

23

24

4

Closing the door activates all door interlock switches (pri-
mary latch switch, 2nd latch switch and stop switch).

IMPORTANT
When the oven door is closed, the monitor switch contacts
COM - NC must be open.
When the microwave oven is pluged in a wall outlet (240V
50Hz), the line voltage is supplied to the point A3+A5 in the
control unit.

1. The display flashes "88:88”.
2. To set any programmes or set the clock, you must first

touch the STOP/CLEAR pad.

3. “88:88” appears in the display and the time counts up

every minute.

NOTE: When the oven door is opened, the oven lamp

comes on at this time.

Enter a desired cooking time with the touching Time pad and
start the oven with touching AUTO MINUTE/START pad.

CONNECTED COMPONENTS

RELAY

Oven lamp, Fan motor, Turntable motor

RY1

Power transformer

RY2

1. The line voltage is supplied to the primary winding of the

power 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 filament and the high voltage (2000 volts) is
sent to the voltagedoubling circuit, where it is doubled to
negative voltage of approximately 4000 volts D.C..

3. The 2450 MHz microwave energy produced in the

magnetron generates a wave length of 12.24 cm. This
energy is channeled 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 single tone is heard and

the relays RY1 + RY2 go back to their home position. The
circuits to the oven lamp, power 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.

opened after the cooking cycle has been interrupted,
because the relay RY1 stays closed. Shown in the
display is the remaining time.

6. MONITOR SWITCH CIRCUIT

The monitor switch is mechanically controlled by oven
door, and monitors the operation of the primary switch.

6-1

When the oven door is open during or after the cycle of

cooking a program, the primary latch and stop switches
must open their contacts first. After that the contacts
(COM - NC) of the monitor switch can be closed and
then contacts of the 2nd latch switch can be opened.

6-2

When the oven door is closed, the contacts

(COM - NC) of the monitor switch must be opened and
contacts (COM - NO) of the 2nd latch switch must be
closed first. After that contacts of the primary latch and
stop switches are closed.

6-3

When the oven door is opened and the contacts of the

primary latch switch remain closed, the fuse M8A will
blow, because the monitor switch is closed and a short
circuit is caused.

When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the power transformer
intermittently within a 32-second time base through the relay
contact which is coupled with the current-limiting relay RY2.
The following levels of microwave power are given.

SETTING

CONDITION

DURING

DOOR OPEN

SWITCH

CONTACT

COOKING

(NO COOKING)

Primary latch switch

COM-NO

Closed

Open

Monitor switch

COM-NC

Open

Closed

2nd latch switch

COM-NO

Closed

Open

Stop switch

COM-NO

Closed

Open

The circuits to the power transformer, fan motor and
turntable motor are cut off when the primary latch switch,
2nd latch switch and stop switch are made open.
The oven lamp remains on even if the oven door is

32 sec. ON

24 sec. ON

HIGH

LOW

Approx. 100%

Approx. 70%

Approx. 50%

Approx. 30%

Approx. 10%

24 sec. ON

8 sec. OFF

18 sec. ON

12 sec. ON

6 sec. ON

14 sec. OFF

20 sec. OFF

26 sec. OFF

MEDIUM

MEDIUM HIGH

MEDIUM LOW

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.

In this condition the food is cooked by grill heater energy.
Program desired cooking time and grill mode by touching
TIME pads and GRILL pad. When the START pad is touched,
the following operations occur:
1. The relay RY1 and RY3 are energized.
2. The numbers of the digital readout start the count down

to zero.

3. Then the grill heating elements, turntable motor, oven

lamp and fan motor are energized.

4. Now , the food is grilled by the grill heater.
5. Upon completion of the selected cooking time, audible

signal sounds, and contacts of relays are opened, then
the activated components as item 3 are de-energized.

5

In this condition the food is cooked by both microwave
energy and grill heating elements energy simultaneously.
1. The relay RY1, RY2 and RY3 are energized.
2. The numbers of the digital readout start the count down

to zero.

3. Then following components are energized.

Power transformer

Grill heating elements

Magnetron

Turntable motor

H.V. capacitor

Fan motor

H.V. rectifier

Oven lamp

4. Now, the food is cooked by microwave and grill heating

elements energy simultaneously.

5. Upon completion of selected cooking time, audible signal

sounds and contacts of relays are opened, then the
activated components as item 3 are de-energized.

AUTO DEFROST automatically works out the correct micro-
wave power and time for defrosting. What should be done is
to chose menu and to enter the weight of food with the weight
entry touch pad. Once the oven starts, it will cook according
to the special cooking sequence.

Keep on touching the AUTO COOK pad until the desired
cooking programme appears in the display. Then using the
WEIGHT ENTRY pad, enter the weight and touch the
START pad. The cooking modes and cooking time are
automatically computed and selected based on the pro-
grammes.

Using the INSTANT COOK function, the foods are cooked or
defrosted without figuring time, power level or quantity.
When the oven senses enough steam from the food, it relays
the information to its microprocessor which will calculate the
remaining cooking time and power level needed for best
results.
When the food is cooked, water vapor is developed. The
sensor "senses" the vapor and its resistance increases
gradually. When the resistance reaches the value set ac-
cording to the menu, supplementary cooking is started.
The time of supplementary cooking is determined by experi-
ment with each food category and inputted into the LSI.
An example of how sensor works: (BOILED POTATOES)

3. Sensor detects moisture and humidity and calculates

cooking time and variable power.

Cooking Sequence.
1. Touch INSTANT COOK pad.
NOTE:

The oven should not be operated on INSTANT

COOK immediately after plugging in the unit. Wait five
minutes before cooking on INSTANT COOK.

2. The coil of shut-off relay (RY-1) is energized, the turntable

motor, oven lamp and cooling fan motor are turned on,
but the power transformer is not turned on.

3. After about 16 seconds, the cook relay (RY-2) is energized.

The power transformer is turned on, microwave energy is
produced and first stage is started.
The 16 seconds is the cooling time required to remove
any vapor from the oven cavity and sensor.

NOTE:

During this first stage, do not open the door or

touch STOP/CLEAR pad.

4. When the sensor detects the vapor emitted from the food,

the display switches over to the remaining cooking time
and the timer counts down to zero.

At this time, the door may be opened to stir food, turn it or

season, etc.

!5. When the timer reaches zero, an audible signal sounds.

The shut-off relay and cook relay are de-energized and
the power transformer, oven lamp, etc. are turned off.

6. Opening the door or touching the STOP/CLEAR pad, the

time of day will reappear on the display and the oven will
revert to an OFF condition.

1. Potatoes at room temperature. Vapor is emitted very

slowly.

MICROWAVE

MICROWAVE

AH SENSOR

2. Heat potatoes. Moisture and humidity is emitted rapidly.

You can smell the aroma as it cooks.

6

DOOR OPEN MECHANISM
The door can be opened by pushing the door open button
on the control panel. When the door open button is pushed,
the cook lever is moved upward, operating the latch head.
The latch head is moved upward, and released from the
latch hook. Now, the door can be opened.

PRIMARY LATCH SWITCH AND
2ND LATCH SWITCH SW2
STOP SWITCH.
1. When the oven door is closed, the contacts (COM - NO)

must be closed.

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

must be opened.

MONITOR SWITCH.
1. When the oven door is closed, the contacts (COM - NC)

must be opened and the contacts (COM - NO) must be
closed.

2. When the oven door is opened,  the contacts (COM - NC)

must be closed

3. If the oven door is opened and the contacts (COM - NO)

of the primary latch switch  fail to open, the fuse  M8A
blows simultaneously with closing the contacts (COM -
NC) of the monitor switch.

CAUTION: BEFORE REPLACING A BLOWN FUSE  M8A

TEST THE PRIMARY LATCH SWITCH,
MONITOR SWITCH AND MONITOR
RESISTOR  FOR PROPER OPERATION.
(REFER TO CHAPTER ”TEST PROCEDURE”.)

FUSE  M8A 250V
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 primary latch switch remains

closed with the oven door open and when the contacts
of monitor switch closes.

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

rectifier,  H.V. wire harness,  H.V. capacitor, magnetron
or secondary winding of power transformer is shorted.

FUSE 13A
If the wire harness or electrical components are short-circuited,
this fuse blows to prevent an electric shock or fire hazard.

°

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

°

C because the

fan motor is interrupted, the ventilation openings are blocked,
the thermal cut-out will open and line voltages to the power
transformer  will be cut off and the operation of the magnetron
will be stopped.  The defective  thermal cut-out  must be
replaced with new one.

°

The thermal cut-out located on the top the oven cavity is
designed to prevent damage to the oven if the foods in the
oven catch fire due to over heating produced by unproper
setting of cook time or failure of control unit. Under normal
operation, the oven thermal cut-out remains closed. How-
ever, when abnormally high temperatures are reached within
the oven cavity, the oven thermal cut-out will open at 160

°

C,

causing the oven to shut down. The defective thermal cut-out
must be replaced with new one.

°

The thermal cut-out located at the bottom of the oven cavity
is designed to prevent damage to the door film and the door
screen when the oven operates in Grill or Dual cooking mode
without any foods. Under normal operation, the oven thermal
cut-out remains closed. If the temperature of the thermal cut-
out goes up higher than 150

°

C, the thermal cut-out will open

and grill heating elements will be turned off. When the
temperature of the thermal cut-out goes down lower than
130

°

C, thermal cut-out will close again.

TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to
rotate the turntable.

FAN MOTOR
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 channeled
through the oven cavity to remove steam and vapors given off
from the heating foods. It is then exhausted through the
exhausting air vents at the oven cavity.

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

Ω

The monitor resistor prevents the fuse  M8A 250V bursting
when the fuse  M8A 250V blows due to the operation of the
monitor switch.

GRILL HEATER
The grill heater element is located on the top of the oven cavity
assembly. The heater sends out heat to grill foods.