Sharp R-THY11 User manual

_ .“” 1 *I ”
R-7Hll
R-7H21
SHARP SERVICE MANUAL
S8907R7Hll JZ/
CONVECTION
MICROWAVE OVEN
MODELS R-THY 1
R-7H21
In interests of user-safety the oven should be restored to its original
condition and only manufacturer original spare parts must be used.
(R016101U)
I TABLE OF CONTENTS Page
FOREWORD ....................................................................................................................................................... 1 -
CAUTION, MICROWAVE RADIATION ....*.............................................*..............*........................................
PRODUCT DESCRIPTION ...............*.............................*..............................................*.................................. :
GENERAL INFORMATION .............................................................................................................................. 3
OPERATION ..,........................~..........*.............,...............*.......................~............*.............................................
SERVICING ................................................................~.................................................................................... 1:
TOUCH CONTROL PANEL ASSEMBLY .........,....................*...................................................................... 24
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ..................................................... 33
MICROWAVE MEASUREMENT PROCEDURE ..,......,......................................................................,......... 39
PICTORIAL DIAGRAM .............~.................................................................................................................... 40
CONTROL PANEL CIRCUIT ..........................................................~.............~................................................ 42
PRINTED WIRING BOARD ............................................................................................................~..~.......... 43
PARTS LIST ...........~..~..............................................................~............*..............................*.......*..*.~.............
PACKING AND ACCESSORIES .......................*.*......................................................................................... 2
SHARPCORPORATtON

R-7Hll
R-7H21
SERVICE MANUAL
SHAFZP
CONVECTION MICROWAVE OVEN
R-7H11/ R-7H21
FOREWORD
This Manual has been prepared to provide Sharp Corp. Service
Personnel with Operation and Service Information for the
SHARP CONVECTION MICROWAVE OVENS, R-7Hl I/
R-7H21.
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 micro-
wave radiation hazard. (RD36102U)
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 N*fl are used in voltage
more than 250V. (RD36202U)
SHARPCORPORATtON
OSAKA, JAPAN
SPECIFICATIONS
AND ADJUSTMENT PROCEDURE
I>
+&ha*
‘:i;pq
_,^:’ PARTS LIST
(RD37201 u)

R-7H71
R-7H21

R-7Hll
R-7HZl
.-- _I.I--I-“““UI-I.U,“.“” ...-. ,,..“..l”“......,“..........“...,,,,...~~”..., ...1. ,.. ..I. .0.11. ./ ,/,,
PRODUCT DESCRIPTION
SPECIFICATION
ITEM
Power Requirements 240 Volts
50 Hertz
DESCRIPTION
Single phase, 3 wire earthed
Power Consumption Microwave cooking 1.3 kW
Convection cooking 1.6 kW
Power Output 700 watts nominal of RF microwave energy (2 liter water load)
Operating frequency of 2450MHz
Convection Heater Power Output 1.5kW
Case Dimensions Width 520 mm
Height 336 mm including foot
Depth 466 mm
Cooking Cavity Dimensions Width 340 mm
Height 215 mm
Turntable diameter
Control Complement
Set Weight
, Depth 350 mm
330mm
Touch Control System
Clock{ (I:00 - 12:59) )
Timer (0 - 99min.99 sec. )
Microwave Cooking Control
Repetition Rate;
HIGH ........................ Full power throughout the cooking time
MED HIGH ....................*..*............ approx. 70% of Full Power
MED ............................................... approx. 50% of Full Power
MED LOW, DEFROST ................. approx. 30% of Full Power
LOW .................I................. ....*....... approx. 10% of Full Power
Convection Temperature Control Range;
i 40 “C, 70 “C to 250 “C
SENSOR COOK pad
COMPU COOK pad
CONVECTION COOKING FUNCTION pads
NUMBER AND TEMPERATURE pads
VARIABLE COOKING CONTROL pads
STOP/CLEAR pad
ONE TOUCH REHEAT pad
EASY DEFROST pad
INSTANT COOK pad
MORE/LESS pads
AUTO START/CLOCK pad
TIMER/HOLD pad
START pad
Approx. 24 kg ,-- ___-_
(KU441Ul
NOTE: Numbers and letters shown after sentences such as “RD44101 U” are for factory use only.
2

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R-7H21
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 + or coloured green or green-and-yellow.
The wire which is coloured blue must & 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.
OVEN DIAGRAM
1. Ventilation openings 6. Oven lamp 11. Waveguide cover
2. Access cover for oven lamp 7. Coupling 12. Roller Stay
replacement 8. Door open button 13. Turntable
3. Hinges 9. Touch control panel 14. Low rack
4. Safety door latches 10. Lighted Digital Display 15. High rack
5. See through door

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R-7H21
TOUCH CONTROL PANEL
R-7Hll
SENSOR COOK PAD
Touch to select sensor cook
mode
SENSOR COOK MENUS
-r
ONE TOUCH REHEAT PAD -
Touch to start automatic re-
heat cycle
NUMBER AND TEMPERATURE
pact
AUTO START/CLOCK PAD-----1
Touch to set clock or auto
start time I
MORE1A 1, LESS{ v 1 PADS
Touch to increase/decrease
the time in one minute incre-
ments during cooking or to in-
crease/decrease the time
whilst programming the One
Touch Reheat, Sensor Cook,
Compu Cook or Easy Defrost
modes.
STOP/CLEAR PAD
Touch to erase during
programming.
Touch once to stop operation
of oven during cooking; touch
twice to cancel cooking
programme.
CONVEC I GRILL I SLOW _
COOK
LOW MIX I HIGH MIX
BAKE ROAST-
STOP
. CLEAR lNsTANTcoDK - START.
-COMPU COOK PAD
Touch to select Compu Cook
mode
1
COMPU COOK MENUS
-EASY DEFROST PAD
Touch to defrost meat by en-
tering weight only
i-
CONVECTION COOKING
FUNCTION PADS
Touch to cook for each func-
tion
r
MEMORY PAD
Touch to enter one frequent-
ly used cooking programme.
Touch to recall the memorized
programme.
i-
VARIABLE COOKING CON-
TROL PADS
Touch to select microwave
power setting. If not touched,
HIGH is automatically selec-
ted.
- INSTANT COOK/START PAD
Touch once to cook for 1
minute at HIGH or increase by
1 minute multiples each time
this pad is touched during
microwave, convection, grill
or mix cooking.
R-7HZl
SENSOR COOK PAD -COMPU COOK PAD
llama-
is?- pmth”
SENSOR COOK MENUS
i
; !g$$$ ARogt- 1 COMPU COOK MENUS
9 tziifzz i3izstz
K2iriiz 7--m-@a
8ZG I-
0hotsn- 0- i
ONE TOUCH REHEAT PAD EASY DEFROST PAD
1CONVEC 1 GRILL 1 pg +,
NUMBER AND TEMPERATURE
PADS-, LOW ix
I
H;GH MIX CONVECTION COOKING
ROAST 1 FUNCTION PADS
AUTO START/CLOCK PAD -
MORE( A 1. LESS( v 1 PADS
r
I
ir
-
MEMORY PAD
VARIABLE COOKING CON-
TROL PADS
I+ STOP
CLEAR lN6TAfnuxx START
d-- INSTANT COOK/START PAD
STOP/CLEAR PAD - I R 4

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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
RYl damper motor
RY2 fan motor
RY3 convection motor
KY4 oven lamp / turntable motor
MICRO RELAY power transformer
HEATER RELAY convection heater
OFF CONDITION
Closing the door activates all door interlock switches
: Upper latch switch, lower latch switch and stop
switch (in this condiction, the monitor switch con-
tacts are opened.)
When oven is plugged in, 240 volts A.C. is supplied
to control unit. (Figure O-l)
1. The display will show flashing ‘X8:88”.
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”,“,,l is input to the control unit, energizing the
coil of shut-off relay (RYI ).
RYI 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 RYI is de-energized, opening its
contacts, thereby turning off the damper motor.
COOKING CONDITION
HIGH COOKING
Program desired cooking time and Variable Cooking
Control by touching the NUMBER pads and 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
connected to the relays are turned on (RY2, RY4,
MICRO RELAY)
(For details, refer to Figure O-2)
2. 240 volts A.C. is supplied to the primary winding
of the power transformer and is converted to about
3.28 volts A.C. output on the filament winding, and
approximately 2125 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
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, upper
latch switch, lower latch switch and stop switch are
activated with the following results. The circuits to
the turntable motor, the cooling fan motor, and the
high voltage components are deenergized, the oven
lamp remains on, and the digital readout displays
the time still remaining in the cook cycle when the
door was opened.
The monitor switch is electrically monitoring the
operation of the upper latch switch and lower latch
switch and is mechanically associated with the door
so that it will function in the following sequence.
(1)
(2)
When the door opens from a closed position,
the lower latch switch opens its contacts, and
then the monitor switch and upper latch switch
contacts close.
When the door is closed from the open posi-
tion, the monitor switch and upper latch switch
contacts first open, and then the contacts of the
lower latch switch close.
if the upper latch switch and lower latch switch fail
with its contacts closed when the door is opened, the
closing of the monitor switch contacts will form a short
circuit through the’fuse, upper latch switch and lower
latch switch, causing the fuse to blow,
MED HIGH, MED, MED LOW, DEFROST, LOW
COOKING
When Variable Cooking Power is programed, the 240
volts A.C. is supplied to the power transformer
intermittently through the contacts of MICRO RELAY
which is operated by the control unit within a 32 sec-
ond time base. Microwave power operation is as fol-
lows:
VARI-MODE
HIGH ’
(100% power)
MED HIGH
(approx. 70% power)
MED
(approx. 50% power)
MED LOW, DEFROST
(approx. 30% power)
LOW
(approx. 10% power)
ON TIME OFF TIME
32 sec. 0 sec.
24 sec. 8 sec.
18 sec. 14 sec.
12 sec. 20 sec.
6 sec. 26 sec.
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.
5

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R-7H21
CONVECTION COOKING CONDITION
PREHEATING CONDITION (Figure O-3)
Program desired convection temperature by touching
the CONVECTION pad and the temp. pad.
When the START pad is touched, the following oper-
ations occur:
1. The coil of shut-off relays (RY2,RY3 and RY4) are
energized, the oven lamp, cooling fan motor,
turntable motor and convection motor are turned
2. y:e coil of relay (RYI) is energized by the control
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 control unit de-energizing
the relay (RYI ) and opening the circuit to the
damper motor.
3. The coil of heater relay is energized by the control
unit and the mains supply voltage is added to the
convection heater.
4. When the oven temperature reaches the selected
preheat temperature, the following operations oc-
cur:
4-1. The heater relay is de-energized by the con-
trol unit temperature circuit and thermistor,
opening the circuit to the convection heater.
4-2. the oven will continue to function for 15
minutes, turning the heater on and off, as
needed to maintain the selected preheat tem-
perature.
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 de-
sired cooking time and convection temperature by
touching the NUMBER pad, CONVECTION pad and
Temperature pad. When the START pad is touched,
the following operation occur:
1.
2.
3.
4.
5.
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 is energized (if the cavity temperature
is lower than the selected temperature) and the
mains supply voltage is applied to the convection
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 118 “C, the cir-
cuit to RY2 will be maintained (by the thermistor
circuit) to continue operation of the cooling fan
motor. The cavity air temperature drops below 118
“C, at which time the relay will be de-energized,
turning off the fan motor. Relay RY3 will however,
open as soon as the convection cycle has ended,
turning off the convection fan motor.
At the end of the convection cook cycle, shut-off
relay (RYl ) is energized turning on the damper
motor. The damper is returned to the open position,
closing the damper switch contacts which send a
signal to the control unit, de-energizing shut-off
relay (RYI ) .
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
The LOW MIX/BAKE pad is preprogrammed for 180
“C with 40% micro wave power, while the HIGH
MIX/ROAST pad is preprogrammed for 200 “C with
30% microwave power. When the START pad is
touched, the following operations occur:
I. The numbers of the digital readout start the count
down to zero.
2. The shut-off relay (RY2, RY3 and RY4) are ener-
gized, turning on the oven lamp, turntable motor,
cooling fan motor and convection motor.
3. The shut-off relay (RYI ) is energized.
The damper door is closed from the open position.
4. The heater relay is energized, adding the mains
supply voltage to the convection heater.
5. Now, the oven is in the convection cooking con-
dition.
6. When the oven temperature reaches the selected
temperature, the following operations occur:
6-1. The power supply voltages is alternated to
the convection heater and power transfor-
mer.
6-2. The convection heater operates through the
heater relay contacts and the power trans-
former operates through the micro relay
contacts.
6-3. These are operated by the control unit to
supply alternately within a 32 second time
base, convection heat and microwave en-
ergy.
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.
YkCROWAVE KIMR
-APPtO8.10%
f I
I I i
I ION I
I
lcmvEcJ OFF
I I
r -I
CONVECTION
TEMPERATURE
-ECU%
6

R-7H11
R-7H21
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:
I.. x.Potatoes at room temperature.
Vapor is emitted very slowly.
2. Heat potatoes. Moisture and humidity is emitted
rapidly. You can smell the aroma as it cooks.
3. Sensor detects moisture and humidity and calcu-
lates cooking time and variable power.
Cooking Sequence.
1. Touch SENSOR COOK or ONE TOUCH REHEAT
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.
2. Select desired Sensor setting.
3.
4.
5.
6.
7.
Touch START pad.
The coil of shut-off relays( RY2,RY4) 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 micro relay is ener-
gized. The power transformer is turned on, micro-
wave 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
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 relays and micro 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.
4.
5.
6.
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 (RY2, RY3, RY4 and HEATER
RELAY) are energized, turning on the oven lamp,
turntable motor, cooling fan motor and convection
motor. The power supply voltage is added to the
heating element.
Now, the oven is in the convection cooking mode.
When the oven temperature has reached the pro-
grammed convection temperature, the oven goes
into the programmed cooking mode.
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 other food faster and better.
EASY DEFROST automatically defrosts foods.
This key has 4 defrost stages.
When the food weight is entered by using the number
pads, the oven will cook according to the special
cooking sequence, refer to Easy Defrost Chart on Op-
eration Manual.
7

R-7Hll
R-7H21
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SCliEMATIC 1
NOTE: CONDlTlON OF
OVEN
1 DOOR CLOSED
2 CONVECTION PAD
TOUCIfEO
3 OESREO TEMPERATUnE
PAD TOUCttED
4 START PAD TOUCIIEO
Figure O-3. Oven Schematic
OVEN
THERM0
CUT-OM
104’C
UPPER
LATCH
SWITCH
II}
Q-Y/l? MBA
EARTH
OAWER MOTOR
1
MONITOR RESISTOR
0.0/2OW
I
A-l
--w--s
A-S CONTROL UN I T
CONVECTION MOTOR
TURNTABLE MOTOR
POWER TRANSFORMER
-l I
ASYMTRIC
RECTIFIER r -3
i-i
t!-
H.V. RECTIFIER
OVEN
THERM0
CUT-OUT
104-c
FAN
THERM0
CUT-OUT
104’C
TEMP.
FUSE
l6O’C
1OWER
1 ATCH
SWITCH
UPPER
LATCH
SWITCH
SCHEMATIC
- -. -.-_
NOTE CONDITION OF OVEN I
1 DOOR CLOSED
2MlX COOKING PAD TOUCHED
3 DESIRED TEMP TOUCHED
4 SrART PAD TOUCHED
_. -- - - --. .---- _ __--~_-_-_ J
d a
Q
MONITOR RESISTOR MONITOR SWITCH
o.edow 1
- A-l
-w---.-s -
A-3 CONTROL UN I T
!Q~;:; ( yY!!I!--~&~
...*.-bnDII1”
L *I,b”” “CLfii
-------
HEATER RELAY
m
) FAN
THERM0
CUT-OUT
lO4’C
I TEMP.
FUSE
16O’C
LOWER
LATCH
SW1TCH
ASYMME
AECTIF TRIG
IER
H.V. RECTIFIER
- Convection Cooking Conditon mlu Figure O-4 Oven Schematic-Automatic Mix Cooking Condition 3:
(For Australia) I

A-4
240V-50Hz
ill 240V550Hx
o-*/t7 b46A
EARTU
r -NOISE SUPPRESSION COIL - NOISE
I FILTER
I II
I FILTER
SCHEMATIC DIAGRAM
I
I I* 0.00228 ”
II 4
OVEN --
CIRCUIT SUBJECT TO
CHANQE WltMWf NOTICE
OOOR CLOSED OVEN 1
COOK OFF CONOlflON THERUO
CUT-OUT
104-c
I.AC CORO CONNECTION
CUT-WT
104-c FAN
lM!ERw
CUT-OUT
IM’C
TDQ.
FUSE
IW’C
BAN : BROWN
BLU : BLUE
9-Y : QREEN AN0
YELLOW STRIPE
/I7 : SECT 1ONAL AREA
OF 1.011’ MIN.
MONITOR RESISTOR
0. a/20*
I
TDP
FUSE
160-C
LOWER
LATCH
SWI TCH
OVEN LAW
m-m---+
CONTROL UN IT
I /
,r I
A-l
-p---p-
CONTROL UNIT
,
2.ORANQE WIRE UIVE)
wST DE CONNECTED
TO THE UPPER
TERMINAL OF POWER
TAAWSFORUER:
.I’
SCH~~.~ATIC
NOTE: CONOITION OF OVEN
I DOOR CLOSED
2. COOKINO TIME
PROGRAMME0
3. START PA0 TOUCHED
UPPER
LATCH
1 /
SWITCH _
1
COnVCCT ION MOTOR
n
u TWTAWF M)TOR
wrpER
LhTCti
SWITCH
SCHEMATIC
NOlE, CONOITION OF OVEN
1. DOOR CLOSED
2. CLOCK APPEARS ON
DISPLAY
--
TURNTALlLE MOTOR
9
f
L-0
-b
.-.-
‘-)
d
d
* MEATER POWFR TbJANSFMUER
LOWER
LATCH
SWITCH
ASYMTRIC
RECTlFlER
Figure O-l. Oven Schematic - Off Conditon Figure O-2. Oven Schematic - Microwave Cooking Conditon
(For New Zealand)

A 240V-50Hz
-
SCHEMATIC
NOIE CONOITION OF
OVEN
I DOOR CLOSED
2 CONVECTION PAD
TOUCl1EO
3 DESIRED TEMPERAlWE
PAD TOUCtiEO
4 Slhnl PAD TOUCIIEO
--____
OVEN
THERM0
CUT-W1
ID4’C
UPPER
LATCti
SWITCH
240V-50Hz
qpLUf 17 BRNfI7 -7
IY I 2 FUSE
‘I} O-Y/l7 M&A
EARTH
NOISE SUPPRESSION COIL NOISE
I FILTER
1~“-oo22a ,I
1 ‘?F
-- --
MONITOR RESISTOR UINITOR SWITCH
A-I
--m--w
CONTROL UNIT
CONVECT I ON U)TOR I
n
w TURMTASLE LOTOR ”
HEATER POWER TRhNSFOR(ER
ASTUlETRfC
RECTIFIER
FAN
THERM
CUT-WT
IM’C
TEMP.
FUSE
ISO’C
LOWER
LATCH
SWI TCH
SCHEMATIC
--- ---_ ---
NOTE.CONDITION OF OVEN
1 DOOR CLOSED
2 MIX COOKING PAD TOUCHED
3 DESIRED TEMP TOUCHED
4 START PAD TOUCHED
OVEN
THERbiO
CUT-OUT
104-c
UPPER
LATCIi
SW1TCII
O-Y/ 17 WA
EARTii
NOI
8FIL
OVEN LAMP I
I
CONVECT 1ON MOTDR
n
L/ TURNTABLE KITOR
ASYMTRIC
RECTIFIER
SE
TER
FAN
Ttuswl
CUT-W1
IM’C
TW.
FUSE
I6O’C
I. OWER
LATCH
SWITCH
t4.V. MCTICIEll
Figure O-3 Oven Schematic -Convection Cooking Conditon Figure O-4 Oven Schematic-Automatic Mix Cooking Condition
(For New Zealand) ??
22
22
I

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i-7H21
DESCRIPTION AND FUNCTION OF COMPONENTS
DOOR OPEN MECHANISM
The door can be opened by pushing the open button
on the control panel. When the open button is pushed,
the open lever pushes the latch lever. The latch lever
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.
UPPER LATCH SWITCH
The upper latch switch is activated by the upper latch
head on the door.
When the door is opened, the switch interrupt the cir-
cuit to ail components, except oven lamp, fan motor,
damper motor and control unit. Then the cook cycle
is stopped.
A cook cycle cannot be take place until the door is
firmly closed and the start pad is depressed with the
cooking time set.
LOWER LATCH SWITCH
The lower latch switch is activated by the lower latch
head on the door.
When the door is opened, the switch interrupts the
circuit to the convection heater and the power trans-
former. Then the cook cycle is stopped.
STOP SWITCH
The stop switch is activated by the upper latch head.
When the door is opened whrle the oven is in cook
cycle, th stop switch contacts open to de-energize the
micro relay, heater relay and relays (except RYI) cir-
cuits in the control unit and causes cook time count
down to pause. MONITOR SWITCH
The monitor switch is mounted on the middle of latch
hook. It is activated (the contacts opened) by the
lower latch head when the door is closed, The switch
is intended to render the oven inoperative by means of
blowing the fuse when the contacts of the upper latch
switch and lower latch switch fail to open when the
door is opened.
Function
1.
2.
3.
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 upper latch
switch, lower latch switch and stop switch are in
the OFF condition (contacts open) due to their
being normally open contact switches.
As the door goes to a closed position, the monitor
switch contacts are first opened and upper latch
switch contacts are closed and then the stop
switch and the lower latch switch contacts close.
(On opening the door, each of these switches op-
erate inversely.)
If the door is opened during cooking, and the upper
latch switch and lower latch switch contacts fail to
open, the fuse blows simultaneously with closing
of the monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN FUSE,
TEST THE UPPER LATCH SWITCH AND
LOWER LATCH SWITCH FOR PROPER
OPERATION.
(REFER TO CHAPTER “TEST PROCE-
DURE”). -
, LATCH HOOK
LATCH LEVER
WEid WTTON
Figure D-l. Upper and lower Latch Switch,
Stop Switch and Monitor Switch
12

R-7Hll
R-7H21
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system
where food is not directly heated up by the convection
heater, but is instead 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 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.
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 the 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 deenergized and the convection fan stops
operating and the oven shuts off.
At the high temperature(more then 118 “C), the fan
motor remains roataing. Automatically the fan motor
will be shut down at low temperature(less than 1A8
“Cl
Own cavw
coNVECTION HEATER
TWlt:W* T-SU-
Motor
Figure D-2. Convection Cooking System
The convection heater is located at the rear of the oven
cavity. It is intended to heat air driven by the con-
vection fan. The heated air is kept in the oven and
force-circulated and reheated by the convection heater.
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
control unit causes the heater relay to operate, thus the
current to the heating element is turned ON/OFF.
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, damper cam and damper shaft.
These components are operated by a signal that judges
if microwave cooking or convection cooking operation
is selected by the control 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 Ooeration
1.
2.
3.
When ‘power supply cord is plugged in:
l-l
1-2
1-3
1-4.
1-5.
When power &pply cord is plugged in, a sig-
nal is sensed in the control unit, and operates
shut-off relay (RYI )a
Contacts of shut-off relay (RYI ) 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 (RYI ) is
turned off.
The 240 volts A.C. to the damper motor is
stopped and the motor turns off.
When oven is microwave cooking:
Damper is in the open position.
When oven is convection cooking:
3-l. Damper motor is energized by touching the
convection, temperature and START pads.
3-2. When damper is in the closed position
(damper switch is OFF), its signal is sensed
by the control unit, and shut-off relay (RYI )
is de-energized.
3-3. The damper is held in the closed position
during the convection cooking operation.
3-4. At the end of the convection cooking, shut-off
relay (RYI ) is energized, and the damper is
returned to the open position.
NOTE: If the damper is not in the proper position,
closed during convection or open during
microwave, the control unit will stop oven op-
eration after 1 minute.
Figure D-3. Damper Mechanism
13

R-7Hll
R-7H21
SERVICING
TROUBLESHOOTING GUIDE
When troubleshooting the oven, it is helpfull to follow IMPORTANT: If the oven becomes inoperative be-
the Sequence of Operation in performing 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.
cause of a blown fuse (M8A) in the
monitor switch , lower latch and upper
latch switches circuit, check the moni-
tor switch, upper latch switch and
lower latch switch before replacing the
fuse.
TEST.PROCEDURE a m 0 0 w I UJ z
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CONDITION
8
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Problem
1 Home fuse blows when power cord is plugged into
wall receptacle.
Fuse blows when power cord is plugged into wall
receptacle.
OFF / 88:88 do not appear in display when power cord is
CONDITION ’
I first plugged into wall outlet.
Display does not operate properly when STOPCLE
AR Key is touched. (Beep should sound and time
of day should appear in display.)
s
-\
b G G G
’ Oven lamp does not light with door opened.
Oven lamp does not light in cook cycle.
(Does light when door is opened)
:OOKING Oven lamp does not light at all.
CONDTION 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 rnoven load.(Food incompletely cooked
or not cooked at all at end of cook cycle.)
-I Oven goes into a cook cycle but extremely uneven
3 0 0
MICRO
WAVE I heating is produced in open loadlfood).
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
0
not heat.
Temperature in the oven cavity is lower or higher
CONVEC- )I than preset.
TION I
1 Convention cycle runs 1 minute then shuts down. 1
I I
1 Convection cycle runs 3 minutes then shuts down.
(SENSOR) Oven is in the sensor cooking condition but AH
sensor does not end stage 1 or does not stop
cookrna cvcle or the oven stops soon.
14

R-7H11
R-7H21
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15

R-7Hll
R-7H21
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST -
A 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 assembly, 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;
P x t / 4.2 = V x AT
P (W) = 4.2 x V x AT / t
Our condition for the water ioad is as follows:
Water load ... 2000 ml, Heating time ...I 20 seconds
P=7Ox 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 (I.) 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 120 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 f 15% of the nominal one.
Calculation of output power;
Microwave output power ...P(W)=7Ox AT(%)
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.
1. Initial temperature of salt water should be 10 +, 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. .=-+.
16 “_

R-7Hll
R-7H27
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
3. Water container should be one (1) litre beaker made of Pyrex gtass and its diameter approxi-
mately 12 cm.
4. Room temperature should be around 20 “C.
5. Power supply voltage should be specification voltage.
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 should be approx. 1.3 ohm and the resistance of the high voltage coil should
be approximately 78 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
MEASURE THE FILAMENT AND HIGH VOLTAGE.)
C HIGH VOLTAGE RECTIFIER AND ASYMMETRIC RECTIFIER TEST
DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPO-
NENTS OR WIRING.
HIGH VOLTAGE RECTIFIER TEST
Isolate the high voltage rectifier assembly from the circuit. Using the highest ohm scale of the
meter, read the resistance across the high voltage rectifier 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 prob-
ably defective and should be replaced with rectifier.
ASYMMETRIC RECTIFIER TEST
D
Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance
across the short protector terminals, reverse the leads to the short protector 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 .
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 1OM G once the capacitor is
charged. If the above is not the case, check the capacitor with an ohmmeter to see
between either of the terminals and case. If it is shorted, replace the caoacitor. if it is shorted
- (RD82603LJ)
E 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
(COW (NOI Common Terminal-Normally Close Terminal
Operation (COW (NC)
Plunger released Open circuit Close circuit 1
Plunger pushed Closed circuit Open circuit
17

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-7H21
TEST PROCEDURES (CONT’D)
PROCEDURE
LEl-f’ER COMPONENT TEST
F MONITOR SWITCH TEST
Disconnect oven from power supply. Disconnect the lead wire to the monitor switch. Connect
one ohmmeter lead to NC terminal of monitor switch, and the other lead to COM terminal of
monitor switch, as shown figure. When the door is opened, the meter should indicate a close
circuit. When the plunger of monitor switch is pushed by a screw-driver through the latch hook
hole on the front plate of the oven cavity with the door opened, the meter should indicate an
open circuit. In case improper operation is indicated, replace the defective monitor switch.
After testing moniter switch, re-connect the wire leads to the monitor switch.
\uu aq=;-Q@-
LATCH
SWITCH
G FUSE M8A
if the fuse in the monitor switch circuit is blown when the door is opened, check the upper latch
switch, lower latch switch and monitor switch according to the Test Procedure for those
switches, before replacing the blown fuse.
If the fuse is blown by improper switch operation, replace the defective switch and fuse at the
same time.
Replace just the fuse if the switches operate normally.
CAUTION; REPLACEMENT FUSE MUST BE THE LISTED FUSE IN PARTS LIST.
OVEN THERMAL CUT-OUT TEST
I
Oven thermal cut-out is thermal cut-out. A continuity check across the thermal cut-out terminals
should indicate an closed circuit unless the temperature of the oven thermal cut-out reaches
approximately 104 “C. The thermal cut-out closes automatically at approximately 80 “C. If im-
proper operation is indicated replace thermal cut-out.
When the oven thermal cut-out opens, it indicates overheating of the heater duct. Check the
convection motor and convection fan or check if the ventilation openings are not blocked.
MAGNETRON TEMP. FUSE TEST
J
A continuity check across the temp. fuse terminals should indicate a closed circuit.
if the temperature of the magnetron reaches 150 “C, the temp. fuse opens. If the temp. fuse has
opened, replace the fuse. An open temp. fuse indicates overheating of the magnetron assembly
Check for restricted air flow to the magnetron through the opening in the chassis especially the
fan duct. Or an open temp. fuse indicates stop of fan motor. Check for fan motor.’
FAN THERMAL CUT-OUT TEST
Fan thermal cut-out is thermal cut-out. A continuity check across the thermal cut-out terminals
should indicate an closed circuit unless the temperature of the thermal cut-out reaches approxi-
mately 104 “C. The thermal cut-out closes automatically at approximately 80 “C. If improper
operation is indicated replace thermal cut-out.
When the fan thermal cut-out opens, it indicates overheating of the cooling fan motor. Check the
cooling fan motor or check if the ventilation openings are not blocked.
18