Sharp R-3C57 User manual

R-3C57
SHARP CORPORATION
SERVICE MANUAL
In interests of user-safety the oven should be restored to its original
condition and only parts identical to those specified should be used.
MODEL R-3C57
S7501R3C57PJZ
MICROWAVE OVEN
TABLE OF CONTENTS Page
CAUTION, MICROWAVE RADIATION ................................................................................................................ 1
WARNING..............................................................................................................................................................1
PRODUCT SPECIFICATIONS............................................................................................................................. 2
GENERAL INFORMATION ................................................................................................................................... 2
APPEARANCE VIEW........................................................................................................................................... 3
OPERATION SEQUENCE ................................................................................................................................... 4
FUNCTION OF IMPORTANT COMPONENTS .................................................................................................... 5
SERVICING .......................................................................................................................................................... 7
TEST PROCEDURE ............................................................................................................................................ 9
TOUCH CONTROL PANEL ................................................................................................................................ 16
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE............................................................... 20
MICROWAVE MEASUREMENT ........................................................................................................................ 26
WIRING DIAGRAM ............................................................................................................................................. 27
PICTORIAL DIAGRAM....................................................................................................................................... 29
CONTROL PANEL CIRCUIT .............................................................................................................................. 31
PRINTED WIRING BOARD ................................................................................................................................ 32
PARTS LIST........................................................................................................................................................ 33

R-3C57

R-3C57
1
SERVICE MANUAL
PRODUCT SPECIFICATIONS
SHARP CORPORATION
OSAKA, JAPAN
TEST PROCEDURE
SERVICING AND
TROUBLESHOOTING CHART
FUNCTION OF IMPORTANT
COMPONENTS
OPERATING SEQUENCE
APPEARANCE VIEW
MICROWAVE MEASUREMENT
WIRING DIAGRAM
PARTS LIST
TOUCH CONTROL PANEL
ASSEMBLY
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
MICROWAVE OVEN
R3C57
GENERAL IMPORTANT INFORMATION
ThisManualhasbeenpreparedtoprovideSharpCorp.Service
engineers with Operation and Service Information.
It is recommended that service engineers carefully study the
entire text of this manual, so they will be qualified to render
satisfactory customer service.
CAUTION
MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM
THE MICROWAVE GENERATOR OR OTHER PARTS
CONDUCTING MICROWAVE ENERGY.
Serviceengineersshouldnotbeexposedtothemicrowave
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.
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is not any other visible damage with the oven.
Servicing and repair work must be carried out only by trained
service engineers.
All the parts marked "*" on parts list are used at voltages more
than 250V.
Removal of the outer wrap gives access to potentials above
250V.
All the parts marked "∆" on parts list may cause undue
microwave exposure, by themselves, or when they are dam-
aged, loosened or removed.

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PRODUCT SPECIFICATIONS
ITEM DESCRIPTION
Power Requirements 240 Volts (for Australia) / 230 - 240 Volts (for New Zealand)
50 Hertz
Single phase, 3 wire earthed
Power Consumption 1.37kW
Power Output 900 watts nominal of RF microwave energy (IEC 705)
750 watts (2 litre water load)
Operating fequency 2450 MHz
Case Dimensions Width 520 mm
Height 305 mm including foot
Depth 389 mm
Cooking Cavity Dimensions Width 348 mm
Height 197 mm
Depth 368 mm
Turntable diameter 325mm
Control Complement Touch Control System
Clock ( 1:00 - 12:59)
Timer (0 - 99 minutes 99 seconds)
Microwave Power for Variable Cooking
Repetition Rate;
HIGH............................................... Full power throughout the cooking time
MEDIUM HIGH .................................................. approx. 70% of Full Power
MEDIUM .............................................................approx. 50% of Full Power
MEDIUM LOW ....................................................approx. 30% of Full Power
LOW ................................................................... approx. 10% of Full Power
INFORMATION COOK pads
HELP pad
CONVENIENCE MEALS pads
NUMBER pads
POWER LEVEL pad
MORE, LESS pads
TIMER pad
MEMORY pads
CLOCK pad
AUTO START pad
STOP/CLEAR pad
INSTANT COOK/START pad
Set Weight Approx. 15 kg
GENERAL INFORMATION
WARNING
THIS APPLIANCE MUST BE EARTHED
IMPOTANT
THE WIRES IN THIS MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:
GREEN-AND-YELLOW : EARTH
BLUE : NEUTRAL
BROWN : LIVE

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APPEARANCE VIEW
8
9
10
4 27 13
5
3
6
11
14
4
1
12
1. Ventilation openings
2. Oven lamp
3. Door hinges
4. Door safety latches
5. See through door
6. Door seals and sealing
surfaces
7. Coupling
8. Door open button
9. Touch control panel
10.Digital readout
11.Wave guide cover
12.Power supply cord
13.Rating label
14.Menu label TOUCH CONTROL PANEL
HELP
REHEAT
CONVENIENCE MEALS
MEAT
Pasta Meal
POWER
LEVEL AUTO
START
STOP
CLEAR
TIMER
LESS MORE
CLOCK
MEMORY
1MEMORY 2
Frozen Dinner
DEFROST
RICE
PASTA
VEGETABLES
Info Display

1 2 3 4 5
6 7 8 9 O
INSTANT COOK
START
INFORMATION COOK PADS
Press to select Information
Cook
mode. 
POWER LEVEL PAD
Press to select microwave
power setting.
If not pressed, HIGH is
automatically selected.
TIMER PAD
Press to set Timer.


MORE ( ), LESS ( ) PADS 
Press to increase/decrease
the time in one minute
increments during cooking or
to alter the doneness for the
Convenience Meals or
Information Cook modes.
STOP/CLEAR PAD
Press to clear during
programming.
Press once to stop operation
of oven during cooking;
press twice to cancel cooking
programme.
HELP PAD
Press to select information
guide on/off, child lock or
demonstration modes.
Press to get cooking
information.

CONVENIENCE MEALS PADS
Press to select Convenience
Meals menu.
NUMBER PADS
Press to enter cooking times,
clock time, weight or quantity of
food.
MEMORY PADS
Press to enter two frequently
used cooking programmes.
Press to recall the memorized
programme.
AUTO START PAD
Press to set Auto Start time.
CLOCK PAD
Press to set Clock
INSTANT COOK/START PAD
Press once to cook for 1 minute
at HIGH or increase by 1 minute
multiples each time this pad is
pressed during cooking.
Press to start oven after setting
programmes.
COOK KG DEF HELP
Indicator

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OPERATION SEQUENCE
OFF CONDITION
Closing the door activates all door interlock switches
(1st. latch switch, 2nd. latch switch and stop switch)
IMPORTANT
When the oven door is closed, the monitor switch contacts
(COM-NC) must be open.
When the microwave oven is plugged in a wall outlet, rated
voltage is supplied to the point A3+A5 in the control unit.
Figure O-1 on page 27
1. The display shows SHARP , MICRO- , WAVE
and OVEN .
2. To set any programmes or set the clock, you must first
touch the STOP/CLEAR pad.
3. : appears in the display.
NOTE: When the oven door is opened, the oven lamp
comes on at this time.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter a desired cooking time with the touching NUMBER
pad and start the oven with touching START pad.
Function sequence
Figure O-2 on page 28
CONNECTED COMPONENTS RELAY
Oven lamp, Fan motor, Turntable motor RY1
Power transformer RY2
1. Rated voltage. is supplied to the primary winding of the
powertransformer.Thevoltageisconvertedtoabout3.3
volts A.C. output on the filament winding and high
voltageofapproximately2000voltsA.C.onthesecondary
winding.
2. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2000 volts) is
senttothevoltagedoublingcircuit,whereitisdoubledto
negative voltage of approximately 4000 volts D.C..
3. The 2450 MHz microwave energy produced in the
magnetron generates a wave length of 12.24 cm. This
energy is channeled through the waveguide (transport
channel)intotheovencavity,wherethefoodisplacedto
be cooked.
4. When the cooking time is up, a signal tone is heard and
therelaysRY1+RY2gobacktotheirhomeposition.The
circuits to the oven lamp, power transformer, fan motor
and turntable motor are cut off.
5. When the door is opened during a cook cycle, the
switches come to the following condition
CONDITION
DURING DOOR OPEN
SWITCH CONTACT COOKING (NOCOOKING)
1st. latch switches COM-NO Closed Open
2nd. latch switch COM-NO Closed Open
Monitor switch COM-NC Open Closed
Stop switch COM-NO Closed Open
The circuits to the power transformer, fan motor and
turntable motor are cut off when the 1st. latch switch,
2nd. latch switch, and stop switch are made open. The
oven lamp remains on even if the oven door is opened
after the cooking cycle has been interrupted, because
the relay RY1 stays closed. Shown in the display is the
remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by oven
door, and monitors the operation of the 1st and 2nd.
latch switches.
6-1 Whentheoven door isopenedduringor after thecycle
of a cooking program, the 1st. latch switch, 2nd. latch
switch and stop switch must open their contacts first.
Afterthatthecontacts(COM-NC)ofthemonitorswitch
can be closed.
6-2. Whentheoven door isclosed,thecontacts (COM-NC)
of the monitor switch must be opened. After that the
contacts of the 1st. latch switch, 2nd. latch switch and
stop switch are closed.
6-3. When the oven door is opened and the contacts of
the1st. latch switch, 2nd. latch switch remain closed.
The fuse M8A will blow, because the monitor switch is
closed and a short circuit is caused.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking
power, 230-240 volts A.C. power is supplied to the power
transformer intermittently within a 32-second time base
through the relay contact which is coupled with the current-
limiting relay. The following levels of microwave power are
given.
SETTING;
32 sec. ON
24 sec. ON
18 sec. ON
12 sec. ON
6 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
26 sec. OFF
HIGH
MEDIUM HIGH
MEDIUM
MEDIUM LOW
LOW
Approx. 70%
Approx. 50%
Approx. 30%
Approx. 10%
NOTE: TheON/OFFtimeratiodoesnotexactlycorrespond
to the percentage of microwave power, because
approx. 2 seconds are needed for heating up the
magnetron filament.

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FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door is opened by pushing the open button on the
control panel, refer to the Figure D-1.
Whentheopenbuttonispushed,theopenbuttonpushesup
theswitchlever,andthentheswitchleverpushesupthethe
latch head. The latch heads are moved upward and re-
leased from latch hook. Now the door will open.
LATCH
HEADS
LATCH HOOK
2ND. LATCH
SWITCH
MONITOR 
SWITCH
SWITCH
LEVER
STOP SWITCH
1ST. LATCH
SWITCH
Figure D-1. Door Open Mechanism
1ST. LATCH SWITCH, 2ND. LATCH SWITCH AND
STOP SWITCH
1. When the oven door is closed, the contacts COM-NO)
must be closed.
2. Whentheovendoorisopened,thecontacts.(COM-NO)
must be opened.
MONITOR SWITCH
1. When the oven door is closed, the contacts (COM-NC)
must be opened.
2. When the oven door is opened, the contacts (COM-NC)
must be closed.
3. If the oven door is opened and the contacts (COM-NO)
ofthe 1st.latch switch and2nd. latchswitch failto open,
the fuse M8A blows simultaneously with closing the
contacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE M8A
TESTTHE1ST.LATCHSWITCH, 2ND.LATCH
SWITCH MONITOR SWITCH AND MONITOR
RESISTOR FOR PROPER OPERATION.
MONITOR RESISTOR R 0.8Ω20W
The monitor resistor prevents the fuse M8A bursting when
the fuse M8A blows due to the operation of the monitor
switch.
ASYMMETRIC RECTIFIER
Theasymmetricrectifierisasolidstatedevicethatprevents
currentflow inboth directions. Andit preventsthe tempera-
ture rise of the power transformer by blowing the fuse M8A
when the high voltage rectifier is shorted.
D2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER
AB
C
The rated peak reverse voltage of D1 of the asymmetric
rectifier is 6 KV The rated peak reverse voltage of D2 of the
asymmetricrectifieris1.7KV.D1andD2oftheasymmetric
rectifier or high voltage rectifier are shorted when the each
peak reverse voltage goes beyond the each rated peak
reverse voltage. (The process of blowing the fuse M8A.)
1. Thehighvoltagerectifierisshortedbyanycauseswhen
microwave 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 voltage
winding of the power transformer.
5. ThelargeelectriccurrentsbeyondM8Aflowthroughthe
primary winding of the power transformer.
6. The fuse M8A blows by the large electric currents.
7. The power supply to the all electrical parts are cut off.
FUSE M8A
1. ThefuseM8Ablowswhenthecontacts(COM-NO)ofthe
1st.latchswitchand2nd.latchswitchremainclosedwith
theovendooropenandwhenthemonitorswitchcloses.
2. The fuse M8A also blows when asymmetric rectifier,
H.V. rectifier, H.V. wire harness, H.V.capacitor,
magnetronorsecondarywindingofpowertransformeris
shorted.
3. If the wire harness or electrical components are short-
circuited, this fuse M8A blows to prevent an electric
shock or fire hazard.
THERMAL CUT-OUT TC 145˚C (MG)
This thermal cut-out protects the magnetron against over-
heating. If the temperature goes up higher than 145˚C
because the fan motor is interrupted, the ventilation open-
ings are blocked, the thermal cut-out will open and the line
voltages to the power transformer will be cut off and the
operation of the magnetron will be stopped.
The defective thermal cut-out must be replaced with new
one.
THERMAL CUT-OUT TC 145˚C (OVEN)
The thermal cut-out located on the top of the oven cavity is
designed to prevent damage to the oven if the foods in the
oven catch fire due to over heating produced by improper
setting of cook time or failure of control unit. Under normal

R-3C57
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operation, the oven thermal cut-out remains closed. How-
ever, when abnormally high temperatures are reached
within the oven cavity, the oven thermal cut-out will open at
145˚C, causing the oven to shut down. The defective
thermal cut-out must be replace with new one.
THERMAL CUT-OUT 95˚C (FAN MOTOR)
Thethermalcut-outprotect the fanmotoragainstoverheat-
ing.Ifitstemperaturegoesuphigherthan95˚Cbecausethe
fanmotor islocked or theventilation operatingare blocked,
the contacts of the thermal cut-out will open and switch off
the oven. When the oven cools itself down to 75˚C, the
contacts of the thermal cut-out will close again.
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to
rotate the turntable.
FAN MOTOR
The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vanes surrounding
themagnetronandcoolsthemagnetron.Thisairischanneled
through the oven cavity to remove steam and vapors given
off from the heating foods. It is then exhausted through the
exhausting air vents at the oven cavity
NOISE FILTER (FOR NEW ZEALAND)
The noise filter prevents the radio frequency interference
that might flow back in the power circuit.

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SERVICING
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with any part of the
high voltage circuit will result in electrocution. High voltage capacitor, Power transformer, Magnetron, High voltage
rectifier assembly, High voltage harness.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING: AGAINST THE CHARGE OF THE
HIGH-VOLTAGE CAPACITOR
The high-voltage capacitor remains charged about
60 seconds after the oven has been switched off.
Wait for 60 seconds and then short-circuit the con-
nection of the high-voltage capacitor (that is, of the
connectingleadofthe high-voltage rectifier)against
thechassiswiththe use ofaninsulatedscrewdriver.
Sharp recommend that wherever possible fault-finding
is carried out with the supply disconnected. It may in,
some cases, be necessary to connect the supply after
theoutercasehasbeenremoved,inthiseventcarryout
3D checks and then disconnect the leads to the primary
of the power transformer. Ensure that these leads re-
main isolated from other components and the oven
chassis. (Use insulation tape if necessary.) When the
testing is completed carry out 3D checks and reconnect
the leads to the primary of the power transformer.
REMEMBER TO CHECK 4R
1) Reconnectallleadsremovedfromcomponentsduring
testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. Check all functions.
Microwave ovens should not be run empty. To test for
thepresenceof microwaveenergywithina cavity, place
acup ofcold water onthe oventurntable, close thedoor
andset themicrowavetimerfortwo(2)minutes.Setthe
powerlevel to HIGHandpush theSTARTbutton. When
the two minutes has elapsed (timer at zero) carefully
checkthatthewaterisnowhot.Ifthewaterremainscold
carry out 3D checks and re-examine the connections to
the component being tested.
Whenallserviceworkiscompleted,and the oven is fully assembled,themicrowavepoweroutputshouldbechecked
and microwave leakage test carried out
When troubleshooting the microwave oven, it is helpful to
follow 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.
TROUBLESHOOTING GUIDE
IMPORTANT: Iftheovenbecomesinoperativebecauseof
a blown fuse M8A in the 1st. latch switch -
2nd. latch switch - monitor switch - monitor
resistor circuit, check the 1st. latch switch,
2nd.latchswitch,monitorswitchand moni-
tor resistor before replacing the fuse M8A.
.

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MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR
1ST. LATCH SWITCH 2ND. LATCH SWITCH STOP SWITCH MONITOR SWITCH MONITOR RESISTOR TEMPERATURE FUSE 95˚C
THERMAL CUT-OUT 145˚C FAN MOTOR TURNTABLE MOTOR FUSE M8A TOUCH CONTROL PANEL
KEY UNIT RELAY (RY-1, RY-2) FOIL PATERN ON P.W.B. POWER SUPPLY CORD SHORTED WIRE HARNESS OPENED WIRE HARNESS
OVEN LAMP OR SOCKET WALL OUTLET MISADJUSTMENT SWITCH HOME FUSE OR BREAKER BLOCKED COOLING FAN
BLOCKED VENTILATION NOISE FILTER (FOR N.Z.)
Home fuse blows when power
supply cord is plugged into wall
outlet.
FUSE M8A blows when power
supply cord is plugged into wall
outlet.
Display does not show anything
whenpowersupplycordisplugged
into wall outlet.
Display does not operate prop-
erly when STOP/CLEAR pad is
touched.
Oven lamp does not light at door
opened. (Display appears.)
Oven does not start when the
START pad is touched. (Display
appears)
Ovenlampdoesnot light(Display
appears.)
Fanmotordoesnotoperate.(Dis-
play appears.)
Turntable motor assembly does
not operate. (Display appears.)
Oven or any electrical parts does
notstopwhen cookingtimeis0or
STOP/CLEAR pad is touched.
Oven seems to be operating but
little or no heat is produced in
ovenload.(Microwavepowerlevel
is set at HIGH)
Oven does not seems to be oper-
ating properly when MEDIUM
HIGH, MEDIUM, MEDIUM LOW
or LOW is set. (Oven operates
properly at HIGH and then the
STOP/CLEARpad is touched the
oven stops.)
Oven goes into cook cycle but
shutsdownbeforeendofcooking
cycle.
Oven stops as soon as when the
START pad is touched.
OFF
CONDITION
PROBLEM
CONDITION
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
TEST PROCEDURE
ON
CONDITION
CK = Check / RE = Replace
ABC D EEEEGFFHHIJKLMRECKCKRE CK CKCKCK CK N

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TEST PROCEDURES
PROCEDURE
LETTER
CARRY OUT 3D CHECK.
Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.
To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron
filament terminals, the meter should show a reading of less than 1 ohm.
To test for short filament to anode condition, connect ohmmeter between one of the filament terminals
and the case of the magnetron (ground). This test should be indicated an infinite resistance. If a low or
zero resistance reading is obtained then the magnetron should be replaced.
MICROWAVE OUTPUT POWER (1 Litre water load)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (outer case fitted). Microwave output power from the magnetron can be measured by way of
IEC 705, i.e. it can be measured by using water load how much it can be absorbed by the water load.
Tomeasurethemicrowaveoutputpower in themicrowave oven,therelationofcalorieandwattis used.
When P(W) heating works for t(second), approximately P x t/4.187 calorie is generated. On the other
hand, if the temperature of the water with V(ml) rises ∆T (°C) during this microwave heating period, the
calorie of the water is V x ∆T.
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
AMAGNETRON TEST
The formula is as follows;
P x t / 4.187 = V x ∆T P (W) = 4.187 x V x ∆T / t
Our condition for water load is as follows:
Room temperature..............around 20°C PowersupplyVoltage.........Ratedvoltage
Water load.........1000 g Initial temperature...........10±2°C Heating time.........47 sec.
P = 90 x ∆T
Measuring condition:
1. Container
The water container must be a cylindrical borosilicate glass vessel having a maximum material
thickness of 3 mm and an outside diameter of approximately 190 mm.
2. Temperature of the oven and vessel
The oven and the empty vessel are at ambient temperature prior to the start the test.
3. Temperature of the water
The initial temperature of the water is (10±2)°C.
4. Selectthe initial andfinal watertemperatureso thatthemaximum differencebetweenthe finalwater
temperature and the ambient temperature is 5˚C.
5. Select stirring devices and measuring instruments in order to minimize addition or removal of heat.
6. Thegraduationofthethermometermustbe scaled by 0.1°C at minimum andaccurate thermometer.
7. The water load must be (1000±5) g.
8. “t” is measured while the microwave generator is operating at full power. Magnetron filament heat-
up time is not included.
NOTE: The operation time of the microwave oven is “t + 2” sec. 2 sec. is magnetron filament heat-up time.
Measuring method:
1. Measure the initial temperature of the water before the water is added to the vessel.
(Example: The initial temperature T1 = 11°C)
2. Add the 1 litre water to the vessel.
3. Place the load on the centre of the shelf.
4. Operate the microwave oven at HIGH for the temperature of the water rises by a value ∆T of
(10 ±2)˚C.
5. Stir the water to equalize temperature throughout the vessel.
COMPONENT TEST

R-3C57
10
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
6. Measure the final water temperature. (Example: The final temperature T2 = 21°C)
7. Calculate the microwave power output P in watts from above formula.
Initial temperature.................................................................................................. T1 = 11°C
Temperature after (47 + 2) = 49 sec...................................................................... T2 = 21°C
Temperature difference Cold-Warm .................................................................... ∆T1 = 10°C
Measured output power
The equation is “P = 90 x ∆T”....................................................... P = 90 x 10°C = 900 Watts
JUDGMENT: The measured output power should be at least ±15 % of the rated output power.
CAUTION: 1°C CORRESPONDS TO 90 WATTS REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
1000g
1000g
1000g
T1˚C T2˚C
Heat up for49 sec.
MICROWAVE OUTPUT POWER (2 Litre water load)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (with outer case fitted).
Microwave output power from the magnetron can be measured by way of substitution, i.e. it can be
measured by using a 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.
Ontheotherhand,ifthetemperature of the waterwith V(ml)rises∆T(˚C)duringthis microwave heating
period, the calorie of the water is V x ∆T.
The formula is as follows;
P = 8330 x ∆T/t
Our condition for water load is as follows:
Room temperature ................. 23±2˚C Power supply Voltage............. Rated voltage
Water load...... 2000 ml Initial temperature ......23±1˚C Heating time...... 1 min. 51sec.
P = 75 x ∆T
Measuring method:
A) The two water containers must be prepared.
Thewatercontainermustbeone(1)litrebeakermadeofPyrex glassanditsdiameterapproximately
12cm.
B) Putthe one (1)litre water intoeachbeaker (Eachbeakerhas onelitrewater). Theinitialtemperature
of the water should be 23±1˚C.
C) Mark T1 on the one beaker and mark T2 on the other one. And stir the water and measure the
temperature of water the thermometer and note them. The graduation of the thermometer must be
scaled by 0.1˚C at minimum and an accurate mercury thermometer is recommended.
D) Place the two (2) beakers as touching each other in the centre of the oven cavity.
E) Set the timer to 1 minutes and 51 seconds, start the oven at 100% power.
F) The time must be measured with stopwatch or wristwatch.
G) After 1 minutes and 51 seconds, stop the oven by opening the door.
H) Put the two (2) beakers out of the oven cavity and measure the temperature of the water by stirring
the water with thermometer and note them.

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11
TEST PROCEDURES (CONT'D)
BPOWER TRANSFORMER TEST
WARNING: Highvoltagesandlargecurrentsarepresentatthesecondarywindingandfilament
winding of the power transformer. It is very dangerous to work near this part when
the oven is on. NEVER make any voltage measurements of the high-voltage
circuits, including the magnetron filament.
CARRY OUT 3D CHECKS.
Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and
secondarywindingconnectionsfromtherestoftheHVcircuitry.Usinganohmmeter,setonalowrange,
it is possible to check the continuity of all three windings. The following readings should be obtained:
a. Primary winding ................... approx. 1.4 Ω
b. Secondary winding............... approx. 98 Ω
c. Filament winding .................. less than 1Ω
Ifthereadingobtainedarenotstatedasabove,thenthepowertransformerisprobablyfaultyandshould
be replaced.
CARRY OUT 4R CHECKS.
C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST
HIGH VOLTAGE RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more than 100 kΩin the other direction.
Example
Initial temperature .............................................................................T1 = 23˚C T2 = 24˚C
Temperature after 1 min. 51 sec. ..................................................... T1 = 33˚C T2 = 34˚C
Temperature difference Cold-Warm.............................................. ∆T1 = 10˚C ∆T2 = 10˚C
Mean temperature rise ∆T......................... ∆T = (∆T1 ±∆T2) / 2 = (10˚C+10˚C) / 2 = 10˚C
Measured output power
The equation is P= 75 x ∆T ........................................................ P= 75 x 10˚C = 750 Watts
NOTE: The measured output power should be at least ±15 % of the rated output power.
CAUTION: 1˚C CORRESPONDS TO 75 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
COMPONENT TEST
PROCEDURE
LETTER
1 l 1 l
(T1 C) (T2 C)
1 l 1 l
(T1 C) (T2 C)
Heat up for 1min. 51 sec.

R-3C57
12
TEST PROCEDURES (CONT'D)
CARRY OUT 4R CHECKS.
ASYMMETRIC RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric can be tested using an
ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and note the
reading obtained. Reverse the meter leads and note this second reading. If an open circuit is indicated
in both direction then the asymmetric rectifier is good. If an asymmetric rectifier is shorted in either
direction,thentheasymmetricrectifierisprobablyfaultyandmustbereplacedwithhighvoltagerectifier.
Whentheasymmetricrectifierisdefective,checkwhethermagnetron,highvoltagerectifier,highvoltage
wire or filament winding of the power transformer is shorted.
CARRY OUT 4R CHECKS.
NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF THE
MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BECAUSE
OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.
PROCEDURE
LETTER COMPONENT TEST
AB
C
D2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER
D HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest resistance
range.
C. Anormalcapacitorshowscontinuityforashorttime(kick)andthenaresistanceofabout10MΩafterithas
been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 MΩbecause of its internal 10MΩresistance.
F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 4R CHECKS.
ESWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the
following table. Table: Terminal Connection of Switch
Plunger Operation COM to NO COM to NC
Released O.C. S.C.
Depressed S.C. O.C.
COM; Common terminal,
NO; Normally open terminal
NC; Normally close terminal
S.C.; Short,
O.C.; Open circuit
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
ETHERMAL CUT-OUT TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a
continuity test across the two terminals as described in the table below.
CARRY OUT 4R CHECKS .Table: Thermal cut-out Test
Temperature of "ON" condition Temperature of "OFF" condition Indication ofohmmeter
Parts Name (closed circuit) (˚C) (open circuit) (˚C) (When room temperature
is approx. 20˚C)
Thermal cut-out 145˚C This is not resetable type Above 145˚C Closed circuit.
Thermal cut-out 95˚C Below 75˚C Above 95˚C Closed circuit.

R-3C57
13
PROCEDURE
LETTER COMPONENT TEST
TEST PROCEDURES (CONT'D)
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out 145˚C (MG) indicates that the magnetron has overheated, this may be
due to resistricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.
An open circuit thermal cut-out 145˚C (OVEN) indicates that the foods in the oven may catch fire, this
may be due to over heating produced by improper setting of the cooking time or failure of the control
panel.
An open circuit thermal cut-out 95˚C (FAN) indicates that the fan motor winding has overheated, this
may be due to blocked ventilation or locked cooling fan.
CARRY OUT 3D CHECKS.
Disconnecttheleadsfromthemonitorresist.Usinganohmmeterandsetonalowrange.Checkbetween
the terminals of the monitor resistor.
The resistance of monitor resistor is approx. 0.8 ohms.
If incorrect readings are obtained, replace the monitor resistor.
CARRY OUT 4R CHECKS.
G MONITOR RESISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor.
Using an ohmmeter, check the resistance between the two terminals as described in the table below.
HMOTOR WINDING TEST
Table: Resistance of Motor
Motors Resistance
Fan motor Approximately 370 Ω
Turntable motor Approximately 16.08 kΩ
If incorrect readings are obtained, replace the motor. CARRY OUT 4R CHECKS
IBLOWN FUSE F M8A
CARRY OUT 3D CHECKS.
1. If the fuse M8A is blown, there could be shorts or ground in electrical parts or wire harness.
Check them and replace the defective parts or repair the wire harness.
2. If the fuse M8A is blown when the door is opened, check the 2nd. latch switch, monitor switch and
monitor resistor.
IfthefuseM8Aisblownbyincorrectdoorswitchingreplacethedefectiveswitch(s)andthefuseM8A.
3. Ifthe fuseM8A isblown, therecould bea shortin the asymmetric rectifier or there couldbe aground
in wire harness. A short in the asymmetric rectifier may have occured due to short or ground in H.V.
rectifier, magnetron, power transformer or H.V. wire. Check them and replace the defective parts or
repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE FUSE M8A WITH THE CORRECT VALUE REPLACEMENT
J 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 divided into two units, Control Unit and Key
Unit, and troubleshooting by replacement is described according to the symptoms indicated.

R-3C57
14
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
1. Key Unit Note : Check key unit ribbon connection before replacement.
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 Panel
The following symptoms indicate a defective control unit. Before replacing the control unit, perform
the Key unit test (Procedure L) to determine if control unit is faulty.
2-1 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.
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 flicker.
2-3 Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
K KEY UNIT TEST
IfthedisplayfailstoclearwhentheSTOP/CLEARpadis depressed, first verify theflat ribbon ismarking
goodcontact,verifythatthedoorsensingswitch(stopswitch)operates properly; that is thecontacts are
closedwhen the dooris closed andopenwhen thedooris open.Ifthe doorsensingswitch (stop switch)
is good, disconnecct the flat ribbon cable that connects the key unit to the control unit and make sure
thedoorsensingswitchisclosed(eitherclosethedoororshortthedoorsensingswitchconnecter).Use
the Key unit matrix indicated on the control panel schematic and place a jumper wire between the pins
that correspond to the STOP/CLEAR
pad marking momentary contact. If the
control unit responds by clearing with a
beep the key unit is faulty and must be
replaced. If the control unit does not
respond, it is faulty and must be re-
placed. If a specific pad does not re-
spond, the above method may be used
(after clearing the control unit) to deter-
mine if the control unit or key pad is at
fault.
CARRY OUT 3D CHECKS.
Remove the outer case and check the voltage between Pin Nos. 3 and 5 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.
RY1 and RY2 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 operation.
DC. voltage indicated .............. Defective relay.
DC.voltagenot indicated ........Checkdiodewhichis connected to therelaycoil.Ifdiode is good,control
unit is defective.
L RELAY TEST
G12
G11
G10
G9
G8 G7 G6 G5 G4 G3 G2 G1
KEY UNIT
54321
09876
AUTO
START
POWER
LEVEL
RICE
PASTA
INSTANT
COOK

START
DEFROST
Frozen
Dinner
CLOCK
TIMER
MEMORY
1
MEMORY
2
REHEAT
MEAT
VEGE-
TABLES
Pasta
Meal
STOP
CLEAR
HELP
LESS
MORE

R-3C57
15
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
N NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the noise
filter.Usinganohmmeter,check between theterminals
as described in the following table. L (min) Cx ±20% Cy ±20%
1.0 mH 0.068µF 0.0022µF
N
LC
L
L
C
WHT
RED
XY
MEASURING POINT INDICATION OF OHMMETER
Between N and L Open circuit
Between terminal N and WHITE Short circuit
Between terminal L and RED Short circuit
If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
36
VRS1
(J1)
(J2)
5
CN-A
1
a
b
cd
LOT NO.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
thePWB, this foilpattern actsasa fuse.Ifthe foilpatternis open,followthe troubleshootingguidegiven
below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS OCCURANCE CAUSE OR CORRECTION
1 The rated AC voltage is not present at Check supply voltage and oven power cord.
POWER terminal of CPU connector (CN-H)
2 The rated AC voltage is present at primary Low voltage transformer or secondary circuit defective.
side of low voltage transformer. Check and repair.
3 Only pattern at "a" is broken. *Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
4 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
NOTE: *Atthetimeofmakingtheserepairs,make
a visual inspection of the varistor. check
for burned damage and examine the
transformerwith atester forthe presence
of layer short-circuit (check primary coil
resistance). If any abnormal condition is
detected, replace the defective parts.
CARRY OUT 4R CHECKS.
M PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD
(PWB) IS OPEN
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 APPROX. 25.0V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 APPROX. 29.0V D.C. Power transformer
CARRY OUT 4R CHECKS.

16
R-3C57
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
The touch control section consists of the following units
as shown in the touch control panel circuit.
(1) Key Unit
(2) Control Unit
The principal functions of these units and the signals com-
municated among them are explained below.
Key Unit
The key unit is composed of a matrix, signals generated in
theLSIaresenttothekeyunitthroughR11,R12,R13,R20,
R21 and R23.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through R00, R01,
R02 and R03 to perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizingsignalcircuit,ACLcircuit,buzzercircuitandindicator
circuit.
1) LSI
This LSI controls the key strobe signal, relay driving
signal for oven function and indicator signal.
2) Power Source Circuit
This circuit generates voltages necessary in the control
unit.
Symbol Voltage Application
VC -5V LSI(IC1)
VP -34V Fluorescent display tube : Grid
and anode voltage
VF1 2.2Vac Filament of fluorescent display
tube
VF2 (VF1 to VF2 voltage)
3) Synchronizing Signal Circuit
The power source synchronizing signal is available in
order to compose a basic standard time in the clock
circuit. It accompanies a very small error because it
works on commercial frequency.
4) ACL Circuit
AcircuittogenerateasignalswhichresetstheLSItothe
initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit
audiblesounds(keytouchsoundandcompletionsound).
6) Door Sensing Switch
A switch to “tell” the LSI if the door is open or closed.
7) Relay Circuit
To drive the magnetron, fan motor, turntable motor and
light the oven lamp.
8) Indicator Circuit
Indicator element is a Fluorescent Display.
Basically, a Fluorescent Display is triode having a
cathode, a grid and an anode. Usually, the cathode of a
Fluorescent Display is directly heated and the filament
serves as cathode.
The Fluorescent Display has 7-digits, 15-segments are
used for displaying figures.

17
R-3C57
DESCRIPTION OF LSI
LSI(IZA655DR)
The I/O signal of the LSI(IZA655DR) is detailed in the following table.
Pin No. Signal I/O Description
1 Vdisp IN Anode (segment) of Fluorescent Display light-up voltage: -34V
Vp voltage of power source circuit input.
2 R00 IN Signal coming from touch key.
WheneitheroneofG12linekeysonkeymatrixistouched,acorrespondingsignalout
of R11 - R13, R20, R21, R23 and D6 will be input into R00. When no key is touched,
the signal is held at "L" level.
3 R01 IN Signal coming from touch key.
WheneitheroneofG11linekeysonkeymatrixistouched,acorrespondingsignalout
of R11 - R13, R20, R21, R23 and D6 will be input into R01. When no key is touched,
the signal is held at "L" level.
4 R02 IN Signal coming from touch key.
WheneitheroneofG10linekeysonkeymatrixistouched,acorrespondingsignalout
of R11 - R13, R20, R21, R23 and D6 will be input into R02. When no key is touched,
the signal is held at "L" level.
5 R03 IN Signal coming from touch key.
When either one of G9 line keys on key matrix is touched, a corresponding signal out
of R11 - R13, R20, R21, R23 and D6 will be input into R03. When no key is touched,
the signal is held at "L" level.
6 TEST IN Connected to VC.
7 RESET IN Auto clear terminal.
Signal is input to reset the LSI to the initial state when power is applied. Temporarily
set to “L” level the moment power is applied, at this time the LSI is reset. Thereafter
set at “H” level.
8 OSC1 IN Internal clock oscillation frequency input setting.
Theinternalclockfrequencyissetby inserting the ceramic filter oscillationcircuitwith
respect to OSC1 terminal.
9 OSC2 OUT Internal clock oscillation frequency control output.
Output to control oscillation input of OSC2.
10/11 GND/AVSS IN/IN Connected to VC.
2 AN0 IN Input signal which communicates the door open/close information to LSI.
Door closed; "H" level signal.
Door opend; "L" level signal.
13-14 AN1-AN2 IN Terminal to change cooking constant.
15 R33 OUT Oven lamp, turntable motor and cooling fan motor driving signal. (Square
Waveform : 45Hz)
To turn on and off shut-off relay. The square (45Hz) is delivered to the relay driving
circuit and cook relay control circuit.
16 P40 OUT Magnetron high-voltage circuit driving signal.
To turn on and off the cook relay. In Low operation, the signals holds “L” level during
microwave cooking and “H” level while not cooking. In other cooking modes
(P10~P90) the signal turns to “H” level and “L” level in repetition according to the
power level.
17-19 R41-R43 OUT Segment data signal.
Refer to the touch control panel circuit for the relationship between signals and
indicators. Normally, one pulse is output in every synchronized signal period, and
input to the anode of the fluorescent display.
20/21 AVCC/VCC IN/IN Connected to GND.
22 INT IN Signal to synchronized with commercial source frequency(50Hz).
This is basic timing for time processing of LSI.
23-24 D1-D2 OUT Segment data signal.
Refer to the touch control panel circuit for the relationship between signals and
indicators. Normally, one pulse is output in every synchronized signal period, and
input to the anode of the fluorescent display.

18
R-3C57
Pin No. Signal I/O Description
25 BUZZ OUT Signal to sound buzzer.
A: key touch sound (0.12 sec.).
B: Completion sound (2.4 sec.).
26-27 D4-D5 OUT Segment data signal.
Refer to the touch control panel circuit for the relationship between signals and
indicators. Normally, one pulse is output in every synchronized signal period, and
input to the anode of the fluorescent display.
28 D6 OUT Segment data signal.
Signal similar to P41.
Key strobe signal.
Signalapplied to touch-key section. A pulse signal is inputto R00-R03terminal while
one of G8 line keys on key matrix is touched.
29-30 D7-D8 OUT Digit selection signal.
Refer to the touch control panel circuit about the relation between signals and digits.
Normally,onepulseisoutputineverysynchronizedsignalperiod,andinputtothegrid
of the fluorescent display.
31-34 R80-R83 OUT Digit selection signal.
Refer to the touch control panel circuit about the relation between signals and digits.
Normally,onepulseisoutputineverysynchronizedsignalperiod,andinputtothegrid
of the fluorescent display.
35 R10 OUT Digit selection signal.
Refer to the touch control panel circuit about the relation between signals and digits.
Normally,onepulseisoutputineverysynchronizedsignalperiod,andinputtothegrid
of the fluorescent display.
36 R11 OUT Segment data signal.
Signal similar to P41.
Key strobe signal.
Signalapplied to touch-key section. A pulse signal is inputto R00-R03terminal while
one of G7 line keys on key matrix is touched.
37 R12 OUT Segment data signal.
Signal similar to P41.
Key strobe signal.
Signalapplied to touch-key section. A pulse signal is inputto R00-R03terminal while
one of G6 line keys on key matrix is touched.
38 R13 OUT Segment data signal.
Signal similar to P41.
Key strobe signal.
Signalapplied to touch-key section. A pulse signal is inputto R00-R03terminal while
one of G5 line keys on key matrix is touched.
39 R20 OUT Segment data signal.
Signal similar to P41.
Key strobe signal.
Signalapplied to touch-key section. A pulse signal is inputto R00-R03terminal while
one of G4 line keys on key matrix is touched.
40 R21 OUT Segment data signal.
Signal similar to P41.
Key strobe signal.
Signalapplied to touch-key section. A pulse signal is inputto R00-R03terminal while
one of G3 line keys on key matrix is touched.
41 R22 OUT Segment data signal.
Signal similar to P41.
42 R23 OUT Segment data signal.
Signal similar to P41.
Key strobe signal.
Signalapplied to touch-key section. A pulse signal is inputto R00-R03terminal while
one of G1 line keys on key matrix is touched.