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R-895M - 9

PREHEAT

Cooling

60%

CONV.

Cooling fan

60% 60 min. then 100%

Others

Cooling fan

100%

After cooking

Cooling fan

Indication

PREHEATING

TEMP

250˚C, 230˚C, 220˚C, 200˚C, 180˚C, 160˚C, 130˚C, 100˚C, 70˚C, 40˚C

HEATING   TOP

100%

ELEMENT  BOTTOM

100%

COOLING FAN

60%

CONV. FAN

0%

CONVECTION

TEMP

250˚C

230˚C

220˚C

200˚C

180˚C

160˚C

130˚C

100˚C

70˚C

40˚C

WITHOUT

HEATING

TOP

50%

40%

40%

30%

20%

10%

10%

10%

10%

10%

PREHEATING ELEMENT  BOTTOM

100%

90%

80%

70%

70%

60%

50%

40%

30%

20%

WITH

HEATING

TOP

50%

40%

40%

30%

20%

10%

10%

10%

10%

10%

PREHEATING ELEMENT  BOTTOM

90%

70%

60%

50%

50%

50%

50%

40%

30%

20%

COOLING FAN

60% 60min, then 100%

CONV. FAN

100%

0%

DUAL CONVECTION

TEMP

250˚C

230˚C

220˚C

200˚C

180˚C

160˚C

130˚C

100˚C

70˚C

40˚C

WITHOUT

HEATING

TOP

50%

40%

40%

30%

20%

10%

10%

10%

10%

10%

PREHEATING ELEMENT  BOTTOM

100%

90%

80%

70%

70%

60%

50%

40%

30%

20%

WITH

HEATING

TOP

50%

40%

40%

30%

20%

10%

10%

10%

10%

10%

PREHEATING ELEMENT  BOTTOM

90%

70%

60%

50%

50%

50%

50%

40%

30%

20%

MICRO

10%,30%,50%

COOLING FAN

100%

CONV. FAN

100%

0%

The  cooling fan continues to rotate when Oven temperature is more than 120˚C. Then,
it stops when it is less than 105˚C
NOW COOLING is indicated during the cooling fan movement after operation is finished.
(It isn't indicated during a fan movement to stop on the way.)

Latch hook

Door

SW2: Stop switch

Latch
Heads

SW3: Monitor switch

SW1: Monitored

latch switch

Tab

The door can be opened by pulling the door handle. When
the handle is pulled, the latch head is pulled, the latch head
is moved upward, and released from the latch hook 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.

R-895M - 10

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.
Function
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 (contacts 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 closing of the monitor switch (COM-
NC) contacts.

CAUTION: BEFORE REPLACING A 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 short-
circuited, this fuse blows to prevent an electric shock or
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

remains closed with the oven door open and when the
monitor switch 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 transformer 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 will open and line
voltage to the high voltage transformer will cut off and
operation of the magnetron will be stopped. The defec-
tive thermal cut-out must be replaced with a new one.

This thermal cut-out protects against overheat ing /fire inside
the oven. The cut-out contacts will open when temperatures
exceed 145˚C.When the cut-out cools itself down to the
operating temperature of 115˚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 fuseF8A when the high voltage rectifier is shorted.

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 fuseF8A.)

D2

D1

ASYMMETRIC
RECTIFIER

HIGH VOLTAGE 
RECTIFIER

A

B

C

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 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 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.

R-895M - 11

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 be forced circulation of the hot air produced
by the grill heaters.  The air heated be the grill heating
elements is circulated through the convectin passage
provided on the outer casing of the oven cavity be means
of the convection fan which is driven by the convection
motor.  It then enters the inside of the oven through the
vent holes provided on the back 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 ciculates inside the oven cavity to raise its
temperature and at the same time, comes into contact
with the food cooked.  When the temperature inside the
oven cavity reaches the selected temperature, the heat-
ing elements are de-energized.  When the temperature
inside the oven cavity drops below the selected tempera-
ture, the elements are energized again.  In thia way, the
inside of the oven is maintained at approximately the
selected temperature.  When the convection time reaches
"0", the heating elements are de-energzed and the con-
vection fan stops operating and the oven shuts off.  At that
time if the cavity air temperature has rised above 120

o

C,

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

o

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 oven cooking mode, dual
cooking mode or grill (top and bottom) 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

R-895M - 12

Fuse F8A blows when the door is opened.

Home fuse blows when power cord is plugged into wall outlet.

Fuse 15A blows when power cord is plugged into wall outlet.

Nothing appears in display when power cord is plugged into wall outlet 

and the door is opened and closed.

Display does not operate properly when STOP/CLEAR key is touched.

Oven lamp does not light when door is opened. (Display operates.)

Oven does not start when the START key is touched. (Display operates.)

Oven lamp does not light  and turntable motor does not operate.

Fan motor does not operate. (Oven lamp lights.)

Convection fan motor does not operate. (Oven lamp lights.)

Turntable motor does not operate. (Oven lamp lights.)

Oven or any electrical parts (except fan motor) does not stop when 

cooking time is 0 or STOP/CLEAR key is touched.

Oven stops after 4 minutes and 15 seconds since START key is 

touched. (Except Microwave mode)

Display operates properly but all electrical parts do not operate.

Oven goes into cook cycle but shuts down before end of cooking cycle.

After cooking, the temperature of oven cavity is higher than 105

˚C but 

fan motor does not operate.

Oven seems to be operating but little or no heat is produced in oven 

load. (Microwave power control is set at HIGH)

Oven does not seem to be operating properly during variable cooking 

condition except HIGH cooking condition.

Oven goes into cook cycle but shuts down before end of cooking cycle.

Convection cooking mode does not heat.

Oven seems to be operating but the temperature in the oven cavity is 

lower or higher than preset one. 

Grill heating element does operate.

Oven goes into cook cycle but shuts down before end of cooking cycle.

Oven seems to be operating but little or no heat is produced in oven 

load. (Microwave power does not seem to be generated properly)

Oven seems to be operating but the temperature in the oven cavity is 

lower or higher than preset one. 

Top and Bottom Grill heating elements do not heat.

Top or Bottom Grill heating element does not heat.

OFF

CONDITION

COOKING

CONDITION

(COMMON MODE)

MICROWAVE

COOKING

CONDITION

GRILL COOKING

CONDITION

CONVECTION

COOKING

CONDITION

DUAL COOKING

CONDITION

(COMMON MODE)

DUAL COOKING

CONDITION

(MICRO./CONV.)

DUAL COOKING

CONDITION

(MICRO./GRILL)

CONDITION 

PROBLEM

BLOCKED COOLING FAN
BLOCKED CONVECTION FAN
NO POWER AT WALL OUTLET
HOME FUSE OR BREAKER
MIS-ADJUSTMENT OF SWITCHES
BLOCKED VENTILATION OPENINGS
OPENED WIRE HARNESS
SHORTED WIRE HARNESS
OVEN LAMP OR SOCKET
POWER SUPPLY CORD
FOIL PATTERN ON P.W.B.
RELAY RY7
RELAY RY6
RELAY RY5
RELAY RY4
RELAY RY3
RELAY RY2
RELAY RY1
KEY UNIT
TOUCH CONTROL PANEL
TC TRANSFORMER
BTTOM GRILL HEATING ELEMENT
TOP GRILL HEATING ELEMENT
FUSE F8A
FUSE 20A
NOISE FILTER
CONVECTION FAN MOTOR
FAN MOTOR
TURNTABLE MOTOR
THERMAL CUT-OUT 145˚C (OVEN)
THERMAL CUT-OUT 125˚C (MG) 
THERMISTOR
MONITOR SWITCH
STOP SWITCH
MONITORED LATCH SWITCH
HIGH VOLTAGE CAPACITOR
H.V. HARNESS
H.V. RECTIFIER ASSEMBLY
HIGH VOLTAGE  TRANSFORMER
MAGNETRON

A 

B 

C 

 

D 

E E E 

F 

G 

G 

H 

H 

H

TEST PROCEDURE

POSSIBLE CAUSE

AND

DEFECTIVE PARTS

I 

J 

K 

L 

L 

 

M N 

O O O O O 

O O 

P

Q