Sharp R-9H10 User manual

R-9HlO
SHARP SERVICE MANUAL
S9808R9Hl OJ//
CONVECTION
MICROWAVE OVEN
In interests of user-safety the oven should be resto!ed to its original
condition and only parts identical to those specified should be used.
(RD161OlU)
TABLE OF CONTENTS Page
FOREWORD ..................................................................*....*............................................................................... 1
CAUTION, MICROWAVE RADIATION ............................................................~............................................. 1
PRODUCT DESCRIPTION .................................................................
.............................................................. 2
GENERAL INFORMATION ..............................................................
OPERATING INSUTRACTIONS ......................................................
OPERATION .......................................................................................
SERVICING ........................................................................................
TOUCH CONTROL PANEL ASSEMBLY ........................................
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDl J
MICROWAVE MEASUREMENT PROCEDURE .............................
............................................................... 3
............................................................... 3
............................................................... 4
............................................................ 11
............................................................ 22
RE ..................................................... 31
............................................................ 37
PICTORIAL DIAGRAM .................................................................................................................................. 38
CONTROL PANEL CIRCUIT ......................................................................................................................... 39
PRINTED WIRING BOARD .......................................................................................................................... 40
PARTS LIST .................................................................................................................................................... 41
PACKING AND ACCESSORIES ................................................................................................................... 46
SHARPCORPORATION

R-9HlO

R-9HlO
SERVICE MANUAL
SHARI=
CONVECTION MICROWAVE OVEN
R-9HlO
FOREWORD
This Manual has been prepared to provide Sharp Corp. Service
Personnel with complete Operation and Service Information for
the SHARP CONVECTION MICROWAVE oven, R-9HlO.
It is recommended that service personnel carefully study the
entire text of this manual so they -will be qualified to render
satisfactory customer service.
Check interlock switches and door seal carefully. Special at-
tention should be given to avoid electrical shock and microwave
radiation hazard. (RD361 OZU)
CAUTION
MICROWAVE RADIATION
Personnel should not be exposed to the microwave energy
which may radiate from the magnetron or other microwave
generating devices if it is improperly used or connected. All
input and output microwave connections, waveguides, flanges
and gaskets must be secured. Never operate the device without
a microwave energy absorbing load attached. Never look into
an open waveguide or antenna while the device is energized.
Note (Parts List) : The parts marked ‘I*” are used in voltage
more than 250V. (RD36202U)
SHARPCORPORATION
OSAKA, JAPAN
PRODUCT DESCRIPTION
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TOUCH CONTROL PANEL
: ASSEMBLY
1 COMPONET REPLACEMENT I
AND ADJt’“,TMENT
MICROWAVE ‘I
1” MEASUREMENT 3
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WIRING DIAGRAM J
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PARTS LIST
(RD37201 U)

R-9HlO
PRODUCT DESCRIPTION
SPECIFICATIONS
ITEM
Power Requirements 240 Volts
50 Hertz
DESCRIPTION
Power Consumption
Power Output
Convection Power Output
Case Dimensions
Single phase, 3 wire earthed
1500W (Microwave)
16OOW (Convection)
750 watts nominal of RF microwave energy (2 liter water load)
Operating frequency of 24501311Hz
1500 Watts
Width 627mm
Height 378mm
Depth 481 mm
Cooking Cavity Dimensions
Control Complement
Width 41 Omm
Height 245mm
Depth 41 Omm
Touch Control System
Clock( I:00 - 12:59 )
Set Weight
Timer (0 - 99 min. 99sec. )
Microwave Power for Variable Cooking
Repetition Rate;
HIGH ................................. Full power throughout the cooking time
MED HIGH ................I.....*....................*... approx. 70% of Full Power
MED .,.................,,.........,.,........I..............,. approx. 50% of Full Power
MED LOW (DEFROST) .......................... approx. 30% of Full Power
LOW .......................................................... approx. 10% of Full Power
Convection Temperature for Variable Cooking
CONVECTION ..................................... 40 to 250 “C Temp. control
LOW MIX, BAKE ..,................ 180 “C with 10% microwave power
HIGH MIX, ROAST ............... 200 “C with 30% microwave power
SLOW COOK ............................... 130 “C for 4 hours (no preheat)
GRILL ..................................................................... 250 “C (preheat)
Variable cooking control pads, AUTO START/CLOCK pad
EASY DEFROST pad, ONE TOUCH REHEAT pad, SENSOR COOK pad
COMPU COOK pad, STOP/CLEAR pad, MEMORY pad
INSTANT COOK/START pad
Approx. 30.0 kg 1
U)
QOTE: Numbers and letters shown after sentences such as “RD44101 U” are for factory use only.
2

R-9H10
GENERAL INFORMATION
WARNING-THIS APPLIANCE MUST BE EARTHED
IMPORTANT
The wires in this mains lead are coloured in accordance with the following code:
Green-and-yellow : Earth
Blue : Neutral
Brown : Live
As the colours of the wires in the main lead of this appliance may not correspond with the coloured marking
identifying the terminals in your plug, proceed as follows:
The wire which is coloured green-and-yellow must be connected to the terminal in the plug which is marked
with the letter E or by the earth symbol f or coloured green or green-and-yellow.
The wire which is coloured blue must be connected to the terminal which is marked with the letter N or
coloured black.
The wire which is coloured brown must be connected to the terminal which is marked with the letter L or
coloured red.
(RD51108u
OPERATING INSTRUCTIONS
ONE TOUCH REHEAT PAD
. Touch to set clock or auto start
VARIABLE COOKING CONTROL
PADS
Touch to select microwave
power setting.
HIGH is automatically selected
if a power pad is not touched.
twice to cancel cooking pro-
gramme.
-M-ORE(A), LESS(v) PADS
Touch to increase/decrease the
time in one minute increments
multiples each time this pad is
touched during cooking.
Touch to start oven after set-
ting programmes.

R-9HlO
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions
during oven operation. (RD71101 U)
Relay and Components Connection
RELAY CONNECTED COMPONENTS
--. RY-1 oven lamp/turntable motor
-- RY-2 power transformer
RY-3 convection heater
RY-4 damper motor
RY-5 convection motor
RY-6 fan motor
OFF CONDITION
Closing the door activates both door interlock
switches: upper latch switch, lower latch switch and
stop switch. (In this condition, the monitor switch
contacts are opened.)
When oven is plugged in, 240 volts A.C. is supplied
to the control unit. (Figure O-l ).
1. The display will show flashing “88:88”.
To set any program or set the clock, you must first
touch the STOP/CLEAR pad. The display will
clear, and I:00 will appear and count up every
minute.
Note: When the door is opened, the oven lamp comes
2. A si”,“,el is input to the control unit, energizing the
coil of shut-off relay (RY4).
RY4 contacts close, completing a circuit to the
damper motor.
The damper motor now operates moving the
damper to the open position, thereby closing the
contacts of the damper switch inputs a signal to
the control unit.
The coil of relay RY4 is de-energized, opening its
contacts, thereby turning off the damper motor.
(RD71207U)
COOKING CONDITION
HIGH COOKING
Program desired cooking time and Variable Cooking
Control by touching the number pads and the HIGH
pad of the Variable Cooking Control. When the START
pad is touched, the following operations occur:
1. The contacts of relays are closed and components
2
connected to the relays are turned on (RY?, RY2,
RY6).
(For details, refer to Figure O-2)
240 volts A.C. is supplied to the primary winding
of the power transformer and is converted to about
3.35 volts A.C. output on the filament winding, and
approximately 2120 volts A.C. on the high voltage
winding.
3. The filament winding voltage heats the magnetron
filament and the H.V. winding voltage is sent to a
voltage doubler circuit.
4. The microwave energy produced by the magnetron
is channeled through the waveguide into the cavity
6.
7.
feed-box, and then into the cavity where the food
is placed to be cooked.
Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped. The
oven will revert to the OFF condition.
When the door is opened during a cook cycle,
monitor switch, upper latch switch, lower latch
switch and stop switch. are activated with the fol-
lowing results. The circuits to the turntable motor,
the cooling fan motor, and the high voltage com-
ponents are deenergized, the oven lamp remains on,
and the digital readout displays the time still re-
maining in the cook cycle when the door was
opened.
The monitor switch is electrically monitoring the
operation of the upper latch switch and is mechan-
ically associated with the door so that it will func-
tion in the following sequence.
(1) When the door opens from a closed position,
the upper latch switch and lower latch switch
open their contacts, and then the monitor
switch contacts close.
(2) When the door is closed from the open posi-
tion, the monitor switch contacts first open,
and then the contacts of the upper latch switch
and lower latch switch close.
If the common and normal open contacts of upper
latch switch fail with their contacts closed when the
door is opened, the closing of the monitor switch
contacts will form a short circuit through the fuse and
upper latch switch, causing the monitor fuse to blow.
MED HIGH, MED, MED LOW (DEFROST), LOW
COOKING
When Variable Cooking Power is programmed, the 240
volts A.C. is supplied to the power transformer
intermittently through the contacts of relay( RY-2)
which is operated by the control unit within a 32 sec-
ond time base. Microwave power operation is as fol-
lows:
VARI-MODE - ON TIME OFF TIME
HIGH . 32 sec. 0 sec.
(100% power)
MED HIGH 24 sec. 8 sec.
(approx. 70% power)
MED 18 sec. 14 sec.
(approx. 50% power)
MED LOW (DEFROST) 12 sec. 20 sec.
(approx. 30% power)
LOW 6 sec. 26 sec.
(aoarox. 10% Dower1
Note: The ON/OFF time ratio does not correspond
with the percentage of microwave power, be-
cause approx. 2 seconds are needed for heating
of the magnetron filament. (RD71401 U)
4

R-9HlO
CONVECTION COOKING CONDITION 5. At the end of the convection cook cycle, shut-off
PREHEATING CONDITION relay (RY4) is energized turning on the damper
Program desired convection temperature by touching meotor. The damper is returned to the open position,
the CONVECTION pad and the temp. pad. closing the damper switch contacts which send a
When the START pad is touched, the following oper- signal to the control unit, de-energizing shut-off
ations occur: relay (RY4).
1.
2.
3.
4.
The coil of shut-off relays (RYI, RY5 and RY6) are
energized, the oven lamp, cooling fan motor,
turntable motor and convection motor are turned
y:e coil of relay (RY4) is energized by the CPU
unit. The damper is moved to the closed position,
opening the damper switch contacts.
The opening of the damper switch contacts sends
a signal to the LSI on the CPU unit de-energizing
‘the relay (RY4) and opening the circuit to the
damper motor. -.
The coil of heater relay (RY3) is energized by the
CPU unit and the main supply voltage is added to
the convection heater.
When the oven temperature reaches the selected
preheat temperature, the following operations oc-
cur:
4-1. The heater relay (RY3) is de-energized by
the CPU unit temperature circuit and
thermistor, opening the circuit to the con-
vection heater.
4-2. The oven will continue to function for 15
minutes, turning the convection heater on
and off, as needed to maintain the selected
preheat temperature.
The oven will shut-down completely after
15 minutes.
CONVECTION COOKING CONDITION
When the preheat temperature is reached, a beep signal
will sound indicating that the holding temperature has
been reached in the oven cavity. Open the door and
place the food to be cooked in the oven.
Program desired cooking time and convection temper-
ature by touching the number pad, CONVECTION pad
and Temperature pad.
When the START pad is touched, the following oper-
ations occur:
1.
2.
3.
4.
The numbers of the digital readout start the count
down to zero.
The oven lamp, turntable motor, cooling fan motor
and convection motor are energized.
Heater relay (RY3) is energized (if the cavity tem-
perature is lower than the selected temperature)
and the main supply voltage is applied to the con-
vection heater to return to the selected cooking
temperature.
Upon completion of the cooking time, the audible
signal will sound, and oven lamp, turntable motor,
cooling fan motor and convection motor are
de-energized. At the end of the convection cycle,
if the cavity air temperature is above 90 ‘C., the
circuit to RY6 will be maintained (by the thermistor
circuit) to continue operation of the cooling fan
motor until the temperature drops below 90 “C., at
which time the relay will be de-energized, turning
off the fan motor. Relay RY5 will however, open
as soon as the convection cycle has ended, turning
off the convection fan motor.This will now cool
and aNow the damper door to open.
AUTOMATIC MIX COOKING CONDITION
Program desired cooking time and temperature by
touching the number pads and the LOW MIX/BAKE
or HIGH MIX/ROAST pad
When the START pad is touched, the following oper-
ations occur:
1.
2.
3.
4.
5.
6.
The numbers of the digital readout start the count
down to zero.
The shut-off relay (RYI, RY5 and RY6) are ener-
gized, turning on the oven lamp, turntable motor,
cooling fan motor and convection motor.
The shut-off relay (RY4) is energized.
The damper door is closed from the open position.
The heater relay (RY3) is energized, adding the
mains supply voltage to the convection heater.
Now, the oven is in the convection cooking con-
dition.
When the oven temperature reaches the selected
temperature, the following operations occur:
6-l. The power supply voltages is added to the
convection heater and power transformer al-
ternately.
6-2. The convection heater operates through the
heater relay (RY3) contacts and the power
transformer operates through the cook relay
(RY2) contacts.
6-3. These are operated by the CPU unit to sup-
ply alternately within a 32 second time base,
convection heat and microwave energy.
The relationship between the convection and micro-
wave power operations are as follows.
Note: The ON and OFF time ratio does not correspond
with the percentage of microwave power, be-
cause approx. 2 seconds are needed for heating
of the magnetron filament.
(MICRO.1 OFF
I
I I I
! ‘ON I
I
OFF
LOWMIX’
BAKE
MICROWAVE POWER
- Approx. 10%
CONVECTION
TEMPERATURE
- lao°C
- Approx. 30%
CONVECTlOU
TEMPERATURE
ICONVECJ - 2oo”c
I 32 sac.
t=
HIGH MIX
-- ROAST
5

R-9HlO
Note: During alternate Microwave/Convection opera-
tion, the convection heater is energized only if
the cavity temperature drops below the set tem-
perature.
SENSOR COOKING CONDITION
Using the SENSOR COOK function, the foods are
cooked 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 in-
creases gradually. When the resistance reaches the
value set according to the menu, supplementary cook-
ing is started.
The time of supplementary cooking is determined by
experiment with each food category and inputted into
the LSI.
An example of how sensor works:
1.
2.
Potatoes at room temperature.
Vapor is emitted very slowly.
Heat potatoes. Moisture and humidi ty is emitted
rapidly You can .sr?ll the aroma as it cooks.
2. Select desired Sensor setting.
3. Touch START pad.
4.
The coil of shut-off relays( RYI ,RY6) are energized,
the oven lamp and cooling fan motor are turned
on, but the power transformer is not turned on.
After about 16 seconds, the cook relay (RY2) 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 re-
move any vapor from the oven cavity and sensor.
NOTE: During this first stage, do not open the door
5.
6.
7.
or touch STOP/CLEAR pad.
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.
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.
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.
COMPU COOK
COMPU COOK will automatically compute the oven
temperature, microwave power and cooking time for
baking, roasting and broiling.
Set the desired program by touching the COMPU
COOK pad, and number pad.
Enter the weight by touching the Number pads
When the START pad is touched, the following oper-
ations occur:
1.
2.
3.
The COOK indicator will light and the Convection
Fan Symbol will rotate.
The cooking time will appear on the display and
start counting down to zero.
The cooking time is adjusted automatically ac-
cording to the weight of the food.
The shut-off relays (RYI, RY3, RY5 and RY6) are
energized, turning on the oven lamp, turntable
motor, cooling fan motor and convection motor.
The power supply voltage is added to the con-
vection heater.
4. Now, the oven is in the convection cooking mode.
5. When the oven temperature has reached the pro-
grammed convection temperature, the oven goes
into the programmed cooking mode.
3. Sensor detects moisture and humidity and calcu-
lates cooking time and variable power.
Cooking Sequence.
1. Touch SENSOR COOK pad.
NOTE:The oven should not be operated on SEN-
SOR COOK immediately after plugging in
the unit. Wait five minutes before cooking
on SENSOR COOK.
6. At the end of the COMPU COOK cycle, the damper
is returned to the open position and the oven will
go to the off condition.
The cooling fan will remain on until the oven has
cooled.
EASY DEFROST COOKING
The EASY DEFROST key is a special function key to
defrost meats and poultry faster and better.
EASY DEFROST key has 4 defrost stages.
EASY DEFROST automatically defrosts roast beef, etc.
When EASY DEFROST is selected and the food weight
is entered by using the number pads, the oven will
cook according to the special cooking sequence.

A 240V-50Hz 240V-50Hz
TEMP.
FUSE
l45’C
7EMP.
FUSE
145’C OVEN
THERM0
CUT-OUT
150-c
OVEN
THERM0
CUT-OU’
15O’C
UPPER
LATCH
SWITCH
MONITOR RESISTOR MONITOR SWITCH
O.S/2OW “Y”
MONITOR RESISTOR MONITOR SWITCH
FM
THERM0
CUT- OUl
90’ c
LOWER
LATCH
SWITCH
I.AC CORD CONNECTION
BRN : BROWN
BLU : BLUE
G-Y : GREEN AND
YELLOW STRIPE
/I7 : SECT I ONAL AREA
OF I .Omm’ MIN.
2.ORANGE WIRE (LIVE)
MUST BE CONNECTED
TO THE CABINET-SIDE
TERMINAL OF POWER
TRANSFORMER.
/
FM
1HERMC
CUT- cJu1
90’ c
LOWER
L ATCH
SWITCH
“L
I A FAN MOTOR 7
_-_--
A-3
-----
A-3
UPPER
LATCH
SWITCH
CONTROL UN IT
SENSOR COOKING
SCHEMATIC
NOTE: CONDITION
OF OVEN
1. DOOR CLOSED
2. “SENSOR COOK”
PAD TOUCHED
3. “START” PAD
TOUCHED
SCHEMATIC
NOTE: CONDITION
OF OVEN
1. DOOR CLOSED
2. CLOCK APPEARS
HIGH COOKING
DAMPER MOTOR II
SCHEMATIC
NOTE: CONDITION
OF OVEN
1. DOOR CLOSED
2. COOKING TIME
PROGRAMMED
3. VARIABLE COOKING
CONTROL “HIGH”
4. START PAD TOUCHED
1
-CONVECTION MOTOR w CONVECTION MOTOR
TURNTABLE MOTOR
TURNTABLE MOTOR I
CONVECTION HEATER CONVECTION HEATER
POWER
TRANSFORMER
L.
H.V. RECTIFIER MAGNETRON
H.V. RECTIFIER MAGNETRON
Figure O-2. Oven Schematic-High and Sensor Cooking Condition
Figure O-l. Oven Schematic-OFF Condition

SCHEMATIC
NOTE: CONDITION
OF OVEN
1. DOOR CLOSED
2. CONVECTION PAD
TOUCHED
3. DESIRED TEMP. PAD
TOUCHED
4. START PAD TOUCHED
OVEN
THERM0
CUT-OUl
150-c
UPPER
LATCH
SWITCH
Figure O-3. Oven Schematic-Convection Cooking Condit #ion Figure O-4 Oven Schematic-Automatic Mix Cooking Cordition
AL
240V-50Hz
MONITOR RESISTOR MONITOR SWITCH
o.l3/2ow
OVEN LAMP
DAMPER MOTOR
-CONVECTION MOTOR
TURNTABLE MOTOR
FM
lHERM0
CUT-OUl
90’ c
LOWER
LATCH
SWITCH
$3, ~~:~~FORMEA
1
OVEN
THERM0
CUT-OUT
I50 c
4-h
240V-5OHz
UPPER
LATCH
SWITCH
SCHEMATIC
NOTE:CONDITION OF OVEN
1.DOOR CLOSED
2.MIX COOKING PAD TOUCHED
3,DESIRED TEMP. TOUCHED
4.START PAD TOUCHED
MONITOR RESISTOR MONITOR SWITCH
o.a/2ow
[..,
c E-4 I RY5 ;
DAMPER
SWITCH i E-5
CONTROL UN IT
-DAMPER MOTOR
~-CONVECTION MOTOR
1EhkP.
FUSE
145’C
/
FM
ltiERM0
CUT-OUT
90’ c
LOWER
LATCH
SW I TCH
CONVECTION HEATER
H.V. RECTIFIER MAGNETRON

R-9HlO
DESCRIPTION AND FUNCTION OF COMPONENTS
THERMISTOR
The thermistor is a negative temperature coefficient
type. The temperature in the oven cavity is detected
through the resistance of the thermistor, and then the
CPU unit causes the heater relay to operate, thus the
current to the convection heater is turned ON/OFF.
OVEN THERMAL CUT-OUT
The oven thermal cut-out located on the right side of
the thermal protection plate is designed to prevent
damage to the convection heater unit if an overheated
condition develops in the tube due to cooling fan fail-
ure, obstructed air ducts, dirty or blocked air intake, etc.
Under normal operation, the oven thermal cut-out re-
mains closed. However, when abnormally high tem-
peratures are reached within the heater unit, the oven
thermal cut-out will open, causing the oven to shut
down.
When the oven has cooled temperature, the oven
thermal cut-out closes. (RD72407U’)
MO’NITOR SWITCH
The monitor switch is mounted on the latch hook. It
is activated (the contacts opened) by the upper latch
head when the door is closed. The switch is intended
to render the oven inoperative by means of blowning
the fuse when the contacts of the common and normal
open contacts of upper latch switch fail to open when
the door is opened.
Functions:
I. When the door is opened, the monitor switch con-
tacts close (to the ON condition) due to their being
normally closed. At this time the the common and
normal open contacts of upper latch switch are in
the OFF condition (contacts open) due to their
being normally open contacts switch.
2. As the door goes to a closed position, the monitor
switch contacts are first opened and then the
common and normal open contacts of upper latch
switch close. (On opening the door, each of these
switches operate inversely.)
3. If the door is opened during cooking, and the
common and normal open contacts of upper latch
switch fail to open, the monitor fuse blows simul-
taneously with closing of the monitor switch con-
tacts
CAUTION:BEFORE REPLACING A BLOWN FUSE
TEST THE UPPER LATCH SWITCH AND
MONITOR SWITCH FOR PROPER
OPERATION.( REFER TO CHAPTER “TEST
PROCEDURE”).
AFTER REPLACING FUSE ALSO REPLACE
MONITOR SWITCH.
STOP -SWITCH
The stop switch is activated by the latch head.
When the door is opened while the oven is in cook
cycle, the stop switch contacts open to de-energize the
relay( RY-1 ,RY-2,RY-3,RY-5,RY-6).
Then the cook cycle is stopped. (RD72EOl U’)
UPPER AND LOWER LATCH SWITCHES
Those latch switches are mounted in the latch hooks
as shown in figure. They are activated by the latch
heads on the door.
When .the door is opened, the switches interrupt the
circuit to all components except CPU unit and relay
unit and oven lamp. A cook cycle cannot take place
until the door is firmly closed thereby activating both
interlock switches.
.A LATCH HOOK
LATCH
HEAD
/
UPPER LATCH SWITCH
STOP SWITCH
MONITOR FUSE
MONITOR SWITCH
LOWER LATCH SWITCH
SWITCH LEVER
OPEN LEVER
DOOR OPEN BUTTON
Figure D-l. Upper Latch Switch, Lower Latch
Switch, Monitor Switch and Stop Switch
CONVECTION HEATER
The convection heater is located at the left side 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 heater.

R-9HlO
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system
where food is not directly heated by the convection
heater, but is heated by forced circulation of the hot
air produced by the convection heater.
The air heated by the convection heater 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 then
enters the inside of the oven through the vent holes
provided on the left 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 left side wall.
Without leaving the oven, this hot air is reheated by the
convection heater, passes through the convection
passage and enters the inside of the oven cavity again,
in a continuing cycle.
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 convection heater is
de-energized. When the temperature inside ihe oven
cavity drops below the selected temperature, the con-
vection heater is energized again. In this way, the in-
side of the oven cavity is maintained at approximately
the selected temperature.
When the convection time reaches 0, the convection
heater is deenergzed and the convection fan stops op-
erating and the oven shutts off.
Upon completion of the cooking time, the audible sig-
nal will sound, and oven lamp, turntable motor, cooling
fan motor and convection motor are de-energized. At
the end of the convection cycle, if the cavity air tem-
perature is above 90 “C., the circuit to RY6 will be
maintained (by the thermistor circuit) to continue op-
eration of the cooling fan motor until the temperature
drops below 90 OC., at which time the relay will be
de-en !rgized, turning off the fan motor. Relay RY5 will
howe? er, open as soon as the convection cycle has
ended, turning off the convection fan motor.This will
now cool and allow t!, damper door to open. (RD72NOl U’)
DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except
during convection cooking.
Damper position is set automatically by damper motor,
damper switch, motor cam and damper shaft..
These components are operated by a signal that judges
if microwave cooking or convection cooking operation
is selected by the CPU unit,
Microwave Cooking:
Damper is in the open position, because a portion of
cooling air is channeled through the cavity to remove
steam and vapors given off from the heating foods.
It is then exhausted at the top of the oven cavity into
a condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will
be allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in:
1-I. When power supply cord is plugged in, a sig-
1-2
1-3
1-4
1-5.
nal is sensed in the control unit, and operates
shut’-off relay (RY4).
Contacts of shut-off relay (RY4) close, the
damper motor is energized, opening the
damper door.
When the damper is moved to the open posi-
tion by the damper cam, damper switch is
closed (ON position).
The signal of damper switch is re-sensed in
the control unit and shut-off relay (RY4) is
turned off.
The 240 volts A.C. to the damper motor is
stopped and the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position.
3. When oven is convection cooking:
3-l.
3-2.
3-3.
3-4
NOTE:
Damper motor is energized by touching the
convection, temperature and START pads.
When damper is in the closed position
(damper switch is OFF), its signal is sensed
by the control unit, and shut-off relay (RY4)
is de-energized.
The damper is held in the closed position
during the convection cooking operation.
At the end of the convection cooking, shut-off
relay (RY4) is energized, and the damper is
returned to the open position.
If the damper door is not in the proper position,
closed durin convection or open durning
microwave, the control unit will stop oven op-
eration after 1 minute.
Cooking Mode Operation of Damper
Microwave cooking OPEN
Convection cooking CLOSE
Sensor cooking OPEN
Automatic mix cooking CLOSE
Grill cooking CLOSE
Slow cookina CLOSE
(RD72002U)
DAMPER SHAFT
DAMPER DUCT
DAMPER CAM
DAMPER SWITCH
DAMPER MOTOR
Figure D-l. Damper Mechanism
10

R-9HlO
SERVICING
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is
helpfull to follow the Sequence of Operation in per-
forming the checks. Many of the possible causes of
trouble will require that a specific test be performed.
These tests are given a procedure letter which will be
found in the “Test Procedure”section.
IMPORTANT: If the oven becomes inoperative be-
cause of a blown fuse in the monitor
switch and upper latch switch circuit,
check the monitor switch and upper
latch switch before replacing the fuse.
If the fuse is replaced, the monitor
switch should be replaced at same
time. (RD81102U’)
11

R-9HlO
OFF
CONDTION
COOKING
CONDTION
IYE-)
I
CONVEC-
TION
(SENSOR)
Problem
Home fuse blows when power cord is plugged into
wall receptacle.
Fuse blows when power cord is plugged into wall
receptacle.
88:88 do not appear in display when power cord is
first plugged into wall outlet.
Display does not operate properly when STOP/CLE
AR Key is touched. (Beep should sound and trme
of day should appear in display.)
Oven lamp does not light with door opened.
Oven lamp does not light in cook cycle.
(Does light when door is opened)
Oven lamp does not light at all.
Oven lamp lights, but turntable motor does not
operate.
Cooling fan motor does not operate
Oven does not go into a cook cycle when START
pad is touched.
Oven seems to be operating but little or no heat is
produced in oven load.(Food incompletely cooked
or not cooked at all at end of cook cycle.)
Oven goes into a cook cycle but extremely uneven
heating is produced in open load(food).
Oven does not cook properly when programed for
MEDIUM etc. cooking powers.(Operates properly
on HIGH)
Oven does not cook properly when programed in
EASY DEFROST cooking mode.
CONV indicator light but oven does not go into a
cook cycle when START pad is touched.
CONV indicator lights, but heating element does
not heat.
Temperature in the oven cavity is lower or higher
Convention cycle runs 1 minute then shuts down.
Convection cycle runs 3 minutes then shuts down.
Oven is in the sensor cooking condition but AH
sensor dbes not end stage 1 or does not stop
cooking cvcle or the oven stops soon.
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13

R-9HlO
TEST PROCEDURES
PROCEDURE
LETTER
A
COMPONENT TEST
MAGNETRON ASSEMBLY TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-
NENTS OR WIRING.
To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity
check across the magnetron filament leads should indicate less than 1 ohm.
To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament
leads and chassis ground. This test should indicate an infinite resistance. If there is little or no
resistance, the magnetron is grounded and must be replaced.
Power output of the magnetron can be measured by performing a water temperature rise test.
This test should only be used if above rests do not indicate a faulty magnetron and there is no
defect in the following components or wiring: high voltage rectifier, rectifier, high voltage
capacitor, and power transformer.
MICROWAVE OUTPUT POWER
Microwave output power from the magnetron can be measured by way of substitution, i.e. it can
be measured by using water load how much it can be absorbed by the water load. To measure
the microwave output power in the microwave oven, the relation of calorie and watt is used.
When P(W) heating works for t(second), approximately P x t/4.2 calorie is generated. On the
other hand, if the temperature of the water with V(ml) rises AT ( “C) during this microwave
heating period, the calorie of the water is V x AT.
The formular is as follows;
Pxt/4.2=Vx AT
P (W) = 4.2 x V x AT/t
Our condition for the water load is as follows:
Water load ... 2000 ml, Heating time ...I 12 seconds
P = 75 x AT
Measuring method;
1. Put the water load of two (2) litres on the center of the oven shelf. The water load should
be arranged in two (2) Pyrex beakers, the size of which is one (1) litre, and be placed at right
and left, side by side, on the oven shelf.
2. Measure the temperature of water before heating and also after heating during 112 seconds
by microwave, and calculate the temperature rise. The temperature rise should be the average
of temperature differences measured in each beaker.
3. The output power should be calculated as follows. In case the measuring result is not satis-
factory, execute the measurement several times and judge the result from the synthetic point
of view. Microwave output power should be within + 15% of the nominal one.
Calculation of output power;
Microwave output power ...P(W)=75x AT(C)
AT = ( ATL + ATR) / 2 : average temperature rise
ATL = (TL2 - TLI), ATR = (TR2 - TRI)
TL2 : water temperature after heating in left beaker
TLI : water temperature before heating in left beaker
TR2 : water temperature after heating in right beaker
TRI : water temperature before heating in right beaker
Measuring condition;
As the microwave output is affected by several conditions, the measurement should be made
carefully with following attentions.
I. Initial temperature of salt water should be IO f 1 “C. Well and quickly stir the water and the
temperature measurement should be done immediately after heating.
2. The graduation of thermometer should be scaled by 0.1 “C at minimum and an accurate mer-
cury thermometer is recommended.
3. Water container should be one (1) litre beaker made of Pyrex glass and its diameter approxi-
mately 12 cm.
14

R-9HlO
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
4. Room temperature should be around 20 “C.
5. Power supply voltage should be specification voltage. (RD82304U’)
B POWER TRANSFORMER TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-
NENTS OR WIRING.
Disconnect the primary input terminals and measure the resistance of the transformer with an
ohmmeter. Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance
of the primary coil sho.uId be approx. 1.3 ohm and the resistance of the high voltage coil should
be approximately 72 ohms; the resistance of the filament coil should be less than 1 ohm.
(HIGH VOLTAGES ARE PRESENT TO HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO
MEASlJRE THE FILAMENT AND HIGH VOLTAGE.) (RD82401 U’)
C HIGH VOLTAGE RECTIFIER AND RECTIFIER TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-
NENTS OR WIRING.
HIGH VOLTAGE RECTIFIER TEST
Isolate the high voltage rectifier from the circuit. Using the highest ohm scale of the meter, read
the resistance across the terminals and observe, reverse the leads to the high voltage rectifier
terminals and observe meter reading. If a short is indicated in both directions, or if an infinite
resistance is read in both directions, the high voltage rectifier is probably defective and should
be replaced.
ASYMMETRIC RECTIFIER TEST
Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance
across the terminals, reverse the leads to the rectifier terminals and observe meter reading. If an
infinite resistance is read in both directions, the rectifier is good.
If a short is indicated in either direction, the one is probably defective and should be replaced.
D HIGH VOLTAGE CAPACITOR TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-
NENTS OR WIRING.
If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input
leads and check for short or open between the terminals using an ohmmeter.
Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate
continuity for a short time and should indicate approximately IOM 0 once the capacitor is
charged. If the above is not the case, check the capacitor with an ohmmeter to see if it is shorted
between the terminals. If it is shorted, replace the capacitor. tRD82603U)
SWITCH TEST
Isolate the switch and check the contacts by using an ohmmeter using the following table.
If improper operation is indicated, make the necessary switch adjustment or replacement.
Table: Switch Connection
Connection Common Terminal-Normally Open Terminal
(COM) Common Terminal-Normally Close Terminal (NO)
Operation (COM) (NC) i
Plunger released
Plunger pushed Open circuit Closed circuit Close circuit
Open circuit
CRD82701 U)
15

q-9HlO
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
F MONITOR SWITCH TEST
Before performing this test, disconnect oven from power supply and make sure that the upper
latch switch is operating properly referring to the above Switch Test Procedure.
Disconnect the wire lead from the monitor switch (NC) terminal.
Check the monitor switch operation by using the ohmmeter as follows.
When the door is open, the meter should indicate a closed circuit.
When the monitor switch actuater is pushed by a screw driver through the latch hole on the front
plate of the oven cavity with the door opened (in this condition the plunger of the monitor switch
is pushed in), the meter should indicate an open circuit.
If improper operation is indicated, replace the defective switch.
After testing the monitor switch, re-connect the wire lead to the monitor switch (NC) terminal.
SWITCH
G BLOWN FUSE
If the fuse in the upper latch-monitor switch circuit is blown when the door is opened, check the
upper latch switch and monitor switch according to the Test Procedure for those switches, before
replacing the blown fuse.
If the fuse is replaced, the monitor switch should be replaced at the same time.
If the fuse is blown by improper switch operation, adjust or replace the defective switch, fuse at
the same time.
Replace the fuse and monitor switch, even if the switches operate normally
CAUTION; REPLACEMENT FUSE MUST BE THE LISTED FUSE IN PARTS LIST. (RD82C03U’)
H MAGNETRON TEMP. FiiSE TEST
A continuity check across the temp. fuse terminals should indicate a closed circuit unless the
temperature of the temp. fuse reaches approximately 145 “C.
An open magnetron temp. fuse indicates overheating of the oven cavity. If the temp. fuse indi-
cates an open circuit, replace the temp. fuse and check for restricted air flow to the magnetron
through the vent holes of the oven cavity, especially the air duct and cooling fan ass’y.
Or an open oven temp. fuse indicate overheating of oven cavity.
Replace the oven temp. fuse and check inside of the oven cavity and unproper setting of cooking
time or accident of the timer. (RD82G05U’)
16

R-9HlO
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
I OVEN THERMAL CUT-OUT
A continuity check across the thermal cut-out terminals should indicate a closed circuit unless
the temperature of the thermal cut-out reaches approximately 150 “C. The termal cut-out resets
automatically at approximately 130 “C.
If the thermal cut-out has opened under the normal condition, replace the same one is parts list.
An open thermal cut-out indicates overheating of the heater unit. Check for restricted air flow
to the heater unit through the vent holes of the oven cavity, especially the heater duct and con-
vection fan. FAN THERMAL CUT-OUT TEST
A continuity check across the thermal cut-out terminals should indicate a closed circuit unless
the temperature of the thermal cut-out reaches approximately 90 “C. The termal cut-out resets
automatically at approximately 70 “C.
An open thermal cut-out indicates locking the fan motor running and brocking the vent hole on
the unit. Check for restricted air flow to the magnetron through the opening in the chassis, es-
pecially the cooling duct and cooling fan motor.
CONVECTION HEATER TEST
Make sure the convection heater is fully cooled and test as follows;
a. Disconnect wire leads and measure the resistance with an ohmmeter. On the R x 1 scale, the
resistance between the convection heater terminals should be approximately 37.5 ohms.
b. Disconnect wire leads and measure the insulation resistance with 500V - 1OOM n insulation
resistance meter.
The insulation resistance between convection heater terminal and cavity should be more than
1OOM n.( However when convection heater is hot more than 0.5M n)
THERMISTOR TEST
Disconnect connector-E from the control unit, Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to Pin No’s E-3 and E-4.
Room Temp. Resistance
20 “C - 30 “C Approx. 300 fI - 192 n
If the meter does not indicate above resistance, replace the thermistor.
L DAMPER MOTOR TEST
When the power cord is plugged into the wall receptacle, and 240 volts A.C. is supplied to the
damper motor the motor operates until the damper is opened and the damper switch closes. Then
the damper motor stops operation.
If the damper motor does not operate, check for AC voltage with a voltmeter at the motor.
1. Disconnect the power cord from the wall receptacle.
2. Disconnect the wire leads of motor and connect the meter leads to the wire leads of main wire
harness.
3. Reconnect the power cord into the wall receptacle.
If 240 volts A.C. is indicated at the wire leads, replace the motor.
Not indicated, check the wire harness and the control unit.
M DAMPER SWITCH TEST
Disconnect the wire leads from the switch terminals and connect ohmmeter leads to the common
(COM) and normally open (NO) terminals of the switch.
1. When switch actuator is pushed by the damper motor cam, the meter should indicate a closed
circuit.
2. When the power cord is plugged into the wall receptacle, the damper motor operates and
damper cam starts to rotate.
The switch actuator is released the meter should indicate an open circuit.
If improper operation is indicated, replace the damper switch.
17

R-9HlO
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc.
Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with
only a voltmeter and ohmmeter. In this service manual, the touch control panel assembly is di-
vided into two units, Control Unit and Key Unit and troubleshooting by unit replacement is de-
scribed according to the symptoms indicated.
1. Key Unit.
The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
2. Control Unit
The following symptoms indicate a defective control unit. Replace the control unit.
2-l In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2 In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits ficker.
2-3 Other possible troubies caused by delx. je control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.
Note: When defective components, the Control Unit or Key Unit are replaced, the defective part
or parts must be properly packed for return in the shipping carton, with its cushion mate-
rial, in which the new replacement part was shipped to you. (RD82SOl U)
RELAY TEST
Remove the outer case and check voltage between Pin Nos. 1 and 3 of the 3-pin connector (A)
on the control unit with an A.C. voltmeter.
The meter should indicate 240 volts, if not check oven circuit.
Shut-off,Cook and Heater Relay Test
These relays are operated by D.C. voltage.
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking or convection
cooking operation.
DC. voltage indicated ..........Defective relay.
DC. voltage not indicated ........Check diode which is connected to the relay coil. If diode is
good, control unit is defective.
RELAY SYMBOL OPERATIONAL CONNECTED COMPONENTS
VOLTAGE
RYl Approx. 13 V.D.C Oven lamp and Turntable motor
RY2 (COOK) Approx. 13 V.D.C Power transformer
RY3 (HEATER) Approx. 13 V.D.C Heating element
RY4 Approx. 14 V. D.C. Damper motor
RY5 Approx. 14 V.D.C. Convection motor
RY6 Approx. 13 V.D.C Cooling fan motor
(RD82ROW)
18
-.