Sharp R-2277 User manual

SHARP CORPORATION
R-2277
R-2287
SERVICE MANUAL
TABLE OF CONTENTS Page
CAUTION, MICROWAVE RADIATION....................................................................................................... 1
WARNING....................................................................................................................................................1
PRODUCT SPECIFICATIONS ................................................................................................................... 2
GENERAL IMPORTANT INFORMATION ...................................................................................................2
APPEARANCE VIEW ................................................................................................................................. 3
OPERATION SEQUENCE.......................................................................................................................... 4
FUNCTION OF IMPORTANT COMPONENTS .......................................................................................... 5
SERVICING ................................................................................................................................................ 7
TEST PROCEDURE................................................................................................................................. 10
CONTROL PANEL ASSEMBLY ................................................................................................................18
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE..................................................... 23
MICROWAVE MEASUREMENT .............................................................................................................. 28
TEST DATA AT A GLANCE ..................................................................................................................... 29
WIRING DIAGRAM................................................................................................................................... 30
PICTORIAL DIAGRAM ............................................................................................................................. 31
CONTROL PANEL CIRCUIT .....................................................................................................................32
PRINTED WIRING BOARD .......................................................................................................................34
PARTS LIST ............................................................................................................................................. 35
S5504R2277H//
In interests of user-safety the oven should be restored to its original
condition and only parts identical to those specified should be used.
COMMERCIAL
MICROWAVE OVEN
MODEL R-2277
R-2287

R-2277
R-2287
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.
VARNING
MICKROVAGSSTRALING
Personal får inte utsättas för mikrovågsenergi som kan ustrala från magnetronen eller
andre mikrovågsalstrande anordningar om dessa är felanslutna eller används på fel sätt.
Alla in-och utgångsanslutningar för mikrovågor, vagledare, flänsar och packningar måste
vara fast anslutna.
Mikrovågsgeneratorn får inte arbeta utan att absorberande belastning är ansluten. Titta
aldrig in i ën öppen vågledare eller antenn när mikrovågsgeneratorn är påkopplad eller
laddad.
VAROITUS
MIKROAALTOSÄTELYÄ
Käyttäjä ei saa joutua alttiiksi mikroaaltoenergialle, jota voi säteillä magnetronista tai
muusta mikroaaltoja kehittävästä laitteesta, jos sitä käytetään tai jos se kytketään väärin.
Kaikkien mikroaaltoliitäntöjen sekä syöttö-että ulostulopuolella, aaltoputkien laippojen ja
tiivisteiden tulee olla varmistettuja.
Mikroaaltouunnia ei koskaan saa käyttää ilman kuormaa jossa mikroaaltoenergiaa kuluu.
Avoimeen aaltoputkeen tai antenniin ei koskaan saa katsoa virran ollessa kytkettynä.
ADVARSEL
MIKROBØLGESTRÅLING
Personell må ikke utsettes for mikrobølge-energi som kan utståles fra magnetronen eller
andre mikrobølge-generende deler dersom apparatet feilbetjenes eller blir feiltikoplet.
Alle inn-og ut-tilkoplinger i forbindelse med mikrobølge-strålingen, bølgeledere, flenser og
tetningsringer/pakninger må festes ordentlig.
Aldri bruk apparatet med mindre en mikrobålge-absorberende last er plassert i
ovnsrommet.
Aldri se direkte inn i en åpen bølgeleder eller antenne imens apparatet er strømførende.
ADVARSEL
MIKROBØLGEBESTRÄLING
Man bør ikke udsætte sig for mikrobølgebestråling fra magnetronen eller andre
mikrobølgefrembringende anordninger, hvilket kan ske hvis apparatet er forkert tilsluttet
eller bruges forkert. Alle mikrobølgeindgange og-udgange, bølgeledere, flanger og
tætningsstrimler må være forsvarligt udført.
Anvend aldrig ovnen uden en mikrobølgesabsorberende anordning. Se aldrig ind i en
åben bølgeleder eller antenne, mens ovnen er i brug.

1
R-2277
R-2287
SHARP CORPORATION
OSAKA, JAPAN
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door latches and hinges are not defective.
(C) The door is not deformed or warped.
(D) There is not any other visible damage with the oven.
Servicing and repair work must be carried out only by trained
service engineers.
Removal of the outer wrap gives occess to potentials above 250V.
All the parts marked "∆" on the parts list may cause undue
microwave exposure, by themselves, or when they are dam-
aged, loosened or removed.
WARNING
Note: Thepartsmarked"*"areusedinvoltagemore
than 250V. (Parts List)
Anm: Delar märket med "*" har en spänning
överstigande 250V.
Huom: Huolto-ohjeeseen merkitty "tähdella" osat
joissa jännite on yli 250 V.
Bemerk: Deler som er merket "asterisk" er utsatt for
spenninger over 250V til jord.
Bemærk: "Delemærketmedstjernebenyttesmedhøjere
spænding end 250 volt.
CAUTION
MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM THE
MICROWAVE GENERATOR OR OTHER PARTS
CONDUCTING MICROWAVE ENERGY.
SERVICE MANUAL
COMMERCIAL
MICROWAVE OVEN
R-2277 / R-2287
GENERAL IMPORTANT INFORMATION
This Manual has been prepared to provide Sharp Corp. 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.
PRODUCT SPECIFICATIONS
FUNCTION OF IMPORTANT
COMPONENTS
SERVICING AND
TROUBLESHOOTING CHART
TEST PROCEDURE
APPEARANCE VIEW
OPERATING SEQUENCE
GENERAL INFORMATION
MICROWAVE MEASUREMENT
TEST DATA AT A GLANCE
WIRING DIAGRAM
PARTS LIST
COMPONENT
REPLACEMENT AND
ADJUSTMENT PROCEDURE
CONTROL PANEL ASSEMBLY

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R-2277
R-2287
PRODUCT DESCRIPTION
SPECIFICATION
ITEM DESCRIPTION
Power Requirements 230 Volts
50 Hertz
Single phase, 3 wire grounded
Power Consumption 2.7 kW Approx. 13A (R-2287) / 2.0kW 9A for R-2277
Power Output 1700 watts (R-2287) /1200 watts (R-2277) nominal of RF microwave energy
(Method of IEC 705)
Operating frequency of 2450MHz
Outside Dimensions Width 510mm
Height 335 mm
Depth 470 mm
Cooking Cavity Dimensions Width 330 mm
Height 180 mm
Depth 330 mm
Control Complement Electronic timer (0 - 30 min.)
Microwave Power level
100% 50% 20% 10%
MICROWAVE POWER SETTING button
START button
Set Weight Approx. 33kg (R-2287) / Approx. 31kg R-2277)
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

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R-2277
R-2287
APPEARANCE VIEW
OVEN
1. Control panel
2. Door lock openings
3. Tray
4. Splash cover
5. Oven lamp
6. Air intake filter
7. Air intake openings
8. Oven cavity
9. Door seals and sealing surfaces
10. Door hinges
11. Door
12. Safety door latches
13. Door open handle.
14. Outer cabinet
15. Oven lamp access cover
16. Ventilation openings
17. Power supply cord
18 Mounting plate
19 Screw for mounting plate
DISPLAY AND INDICATORS
Checkindicators afterthe ovenstarts to
confirm the oven is operating as de-
sired.
1. Cook indicator
This indicator shows cooking in progress.
2. Digital display
3. Microwave power level indicator
OPERATING KEYS
4. Power 100%
5. Power 50%
6. Power 20%
7. Power 10%
8. ELECTRIC TIMER
Rotate the knob to enter cooking time.
9. START button
CONTROL PANEL
1
2345
76
8
9
1011
12
13
15
16
14
18 19
17
MICROWAVE POWER
LEVEL button
POWER
%
ON
2
13

4
5
6
7
8
9
/100%
/ 50%
/ 20%
/ 10%

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R-2277
R-2287
OPERATION SEQUENCE
OFF CONDITION
Closing the door activates all door interlock switches
(1st latch switch, 2nd latch switch, 3rd 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
plunged in a wall outlet (230 volts, 50Hz), the line voltage is
supplied to the point A5+A7 in the control panel.
Figure O-1 on page 30
1. The digital display shows .
NOTE: When the door is opened or after cooking, oven
lamp, blower motor and stirrer motors work for 1
minute.
MICROWAVE COOKING CONDITION
Enter a desired cooking time with the turning ELECTRIC
TIMER knob. And then push START button.
Function sequence Figure O-2 on page 30
CONNECTED COMPONENTS RELAY
Oven lamp/ Blower motor/ Stirrer motors RY1
Power transformer T1 RY3
Power transformer T2 RY4
1. Thelinevoltageissupplied tothe primarywindingofthe
high voltage transformer. The voltage is converted to
about 3.3 volts A.C. output on the filament winding and
high voltage of approximately 2000 volts A.C. on the
secondary winding.
2. The filament winding voltage (3.3 volts) heats the mag-
netron filament and the high voltage (2000 volts) is sent
to the voltage doubling circuit, where it is doubled to
negative voltage of approximately 4000 volts D.C..
3. The 2450 MHz microwave energy produced in the
magnetron generates a wave length of 12.24 cm. This
energy is channelled through the waveguide (transport
channel) into the oven cavity, where the food is placed
to be cooked.
4. When the cooking time is up, a signal tone is heard and
therelaysRY3+RY4gobacktotheirhomeposition.The
circuits to the high voltage transformers T1+T2. The
relay RY1 remains and oven lamp, blower motor and
stirrer motors work for 1 minute.
5. When the door is opened during a cook cycle, the
switches come to the following condition.
CONDITION
DURING DOOR OPEN
SWITCH CONTACT COOKING (NO COOKING)
1st latch switch COM-NO Closed Open
Monitor switch COM-NC Open Closed
2nd latch switch COM-NO Closed Open
Stop switch COM-NO Closed Open
3rd latch switch COM-NO Closed Open
The circuits to the high voltage transformers T1+T2 are
cut off when the 1st latch, 2nd latch, 3rd latch and stop
switches SW1+SW2+SW3+SW5 are made open. The
blowermotorBM,stirrermotorsandovenlamp remains
on even if the oven door is opened after the cooking
cyclehasbeeninterrupted,becausetherelayRY1stays
closed. Shown in the display is the remaining time, but
the program is cancelled if the oven is not started within
3 minutes.
6. MONITOR SWITCH CIRCUIT
The monitor switch SW4 is mechanically controlled by
oven door, and monitors the operation of the 1st latch
switch SW1.
6-1. Whentheovendoorisopenedduringorafterthe cycle
of a cooking program, the 1st, 2nd, 3rd latch and stop
switchesSW1+SW2+SW3+SW5 mustopentheircon-
tacts first. After that the contacts (COM-NC) of the
monitor switch SW4 can be closed.
6-2. Whentheovendoorisclosed,thecontacts(COM-NC)
of the monitor switch SW4 must be opened first. After
that the contacts (COM-NO)of the 1st, 2nd, 3rd latch
and stop switches SW1+SW2+SW3+SW5 must be
closed.
6-3. When the oven door is opened and the contacts of the
1st latch switch SW1 remain closed, remains closed,
thefuseF2F6.3Awillblow,becausethemonitorswitch
is closed and a short circuit is caused.
MICROWAVE VARIABLE COOKING
When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the high voltage
transformers T1+T2 intermittently within a 48 second time
base through the contacts of the relays RY3+RY4.
The following levels of microwaves power are given.
48 sec. ON
100% 26sec. ON
50% 12 sec. ON
20% 8 sec. ON
10%
NOTE: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power, be-
causeapprox.3secondsareneededforheatingup
the magnetron filament.
TWO MAGNETRON OPERATION SYSTEM
Two magnetrons MG1+MG2 are equipped in order to get
highermicrowavepoweroutput.Theprimarywindingsofthe
highvoltagetransformersT1+T2areconnectedsothateach

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R-2277
R-2287
MONITOR SWITCH SW4
Themonitorswitchisactivated(thecontactsopened)the
upper latch head and switch lever A while the door is
closed.Theswitchisintendedtorendertheoveninopera-
tive by means of blowing the fuse F2 F6.3A when the
contactsofthe1stlatchswitchSW1failtoopen whenthe
door is opened.
Function
1. When the door is opened, the monitor switch SW4
contactsclose (totheONcondition)due totheirbeing
normallyclosed. Atthis timethe 1stlatch switch SW1
is in the OFF condition (contacts open) due to their
being normally open contact switches.
2. As the door goes to a closed position, the monitor
switch contacts are opened and 1st latch switch con-
tacts are closed (On opening the door, each of these
switches operate inversely.)
3. Ifthedoor is openedandthe 1st latchswitch contacts
fail to open, the fuse F2 F6.3A blows simultaneously
with closing of the monitor switch contacts.
CAUTION:BEFORE REPLACING A BLOWN FUSE F2
F6.3A TEST THE 1ST LATCH SWITCH,
MONITOR SWITCH AND MONITOR RESIS-
TOR FOR PROPER OPERATION. (REFER
TO CHAPTER “TEST PROCEDURE”).
MONITOR RESISTOR R1
The monitor resistor prevents the fuse F2 F6.3A 250V
bursting when the fuse F2 F6.3A 250V blows due to the
operation of the monitor switch.
NOISE FILTER
The noise filter assembly prevents radio frequency inter-
ference that might flow back in the power circuit.
WEAK POINT (R-2287)/ FUSE (R-2277) F1
Ifthewireharnessorelectricalcomponentsmakeashort-
circuit, this weak point/ Fuse F1 blows to prevent an
electric shock or fire hazard.
DOOR OPEN MECHANISM
1. The door release lever is pulled.
2. The upper latch head is lifted up by the linked door
release lever.
3. The latch lever is lifted up by the door release lever.
4. The joint lever is lifted up by the latch lever.
5. The lower latch head is lifted up by the joint lever.
6. Now both latch heads are lifted up, so they can be
released from the latch hook.
7. Now the door can be opened.
Latch head
Monitor switch
Latch hook
1st. latch switch
2nd. latch switch
Stop switch
3rd. latch switch
Latch head
Joint lever
Door release
lever
Figure D-1. Door Open Mechanism
1ST LATCH SWITCH SW1, 2ND LATCH SWITCH
SW2, 3RD LATCH SWITCH SW3 AND STOP
SWITCH
SW5
1. When the oven door is closed, the contactsCOM-NO
must be closed.
2. Whentheovendoorisopened,thecontactsCOM-NO
must be opened.
COMMERCIAL
FREQUENCY
(50HZ)
POWER OUTPUT
BY MAGNETRON 1
POWER OUTPUT
BY MAGNETRON 2
OPERATION OF
MAGNETRON
magnetron can be oscillated alternatively according to the
frequency of the power supply. Refer to the Figure 1 and 2.
Figure B-1. High Voltage Circuit
Figure B-2. Operation of Magnetron
FUNCTION OF IMPORTANT COMPONENTS
T1: HIGH VOLTAGE
TRANSFORMER
ASYMMETRIC RECTIFIER
H. V. RECTIFIER
C1: H.V. CAPACITOR
MG1: MAGNETRON (UPPER)
(REAR)
ASYMMETRIC RECTIFIER
H. V. RECTIFIER
C2: H.V. CAPACITOR
MG2: MAGNETRON (LOWER)
T2: HIGH VOLTAGE
TRANSFORMER
(FRONT)

6
R-2277
R-2287
MAGNETRON THERMISTOR
The air temperature around the lower magnetron is
detected through the resistance of the thermistor.
If the temperature is high, the control panel will display
"EE17" and the oven will stop to protect the lower magn-
etron against overheat.
If the thermistor is open, the control panel will display
"EE16" and the oven will stop.
MAGNETRON THERMAL CUT-OUTS 145˚ TC1,
TC2
These thermal cut-outs protect the magnetrons against
overheat. If their temperature go up higher than 145˚C
because the blower motor is interrupted, the ventilation
openingsareblocked,thethermalcut-outsTC1+TC2will
open and the line voltage to the high voltage transformer
T1+T2willbecutoffandtheoperationsofthemagnetrons
MG1+MG2willbestopped.Thedefectivethermalcut-out
must be replaced with new rated one.
BLOWER MOTOR THERMAL CUT-OUT 115˚C
TC3
This thermal cut-out protect the blower motor against
overheat. If its temperature goes up higher than 115˚C
because the blower motor is locked or the ventilation
openingsare blocked,thecontacts ofthethermalcut-out
TC3 will open and the line voltage to the control unit will
be cut off and the operation of the oven will be stopped.
Thedefectivethermal cut-out mustbereplaced with new
rated one.
OVEN THERMAL CUT-OUT 115˚C TC4
This thermal cut-out protects the oven against overheat. If
the temperature goes up higher than 115˚C because the
food catches fire, the contacts of thermal cut-out will open
and the line voltage to the control unit will be cut off and the
operationoftheovenwillbestopped.Thedefectivethermal
cut-out must be replaced with a new rated one.
BLOWER MOTOR BM
The blower motor drives a blade which draws external
cool air. This cool air is directed through the air vanes
surrounding the magnetrons and cools the magnetrons.
This air is channelled through the oven cavity to remove
steam and vapours given off from the heating foods. It is
then exhausted through the exhausting air vents at the
oven cavity.
STIRRER MOTOR SM
The stirrer motor drives a stirrer antenna to stir the
microwave radiation from the waveguide.
FUSE F6.3A 250V F2
1. Ifthewireharnessorelectricalcomponentsareshort-
circuited, this fuse blows to prevent an electric shock
or fire hazard.
2. The fuse also blows when 1st latch switch SW1
remainsclosedwiththeovendooropenandwhenthe
monitor switch SW4 closes.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is solid state device that pre-
vents current flow is both directions. And it prevents the
temperature rise of the high voltage transformer by
blowingthe weakpoint /fuseWP1 orWP2whenthe high
voltage rectifier is shorted.
AB
C
D2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER
The rated peak reverse voltage of D1 of the asymmetric
rectifier is 6 KV The rated peak reverse voltage of D2 of
the asymmetric rectifier is 1.7 KV. D1 and D2 of the
asymmetric rectifier or high voltage rectifier are shorted
when the each peak reverse voltage goes beyond the
each rated peak reverse voltage. (The process of the
blowing the weak point / fuse WP1 or WP2)
1. The high voltage rectifier is shorted by some fault
when 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 high voltage transformer.
5. The large electric currents flow through the primary
winding of the high voltage transformer.
6. The weak point/ fuse WP1 or WP2 blows by the large
electric currents.
7. The power supplying to the high voltage transformer
is cut off.
EXHAUST THERMISTOR
Thethermistorisanegativetemperaturecoefficienttype.
The temperature in the exhaust duct is detected through
the resistance of the thermistor.
If the temperature is high, the control panel will display
“EE7” and the oven will stop to avoid overheating and
catching fire.
If the thermistor is open, the control panel will display
"EE6" and the oven will stop.
INTAKE THERMISTOR
This thermistor detects ambient air temperature.

7
R-2277
R-2287
SERVICING
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with following parts
will result in electrocution.
Highvoltage capacitor,Highvoltage transformer,Magnetron,High voltage rectifierassembly,High voltageharness.
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
switchedoff.Waitfor60secondsandthenshort-
circuittheconnectionofthehigh-voltagecapacitor
(thatis,oftheconnectingleadofthehigh-voltage
rectifier) against the chassis with the use of an
insulated screwdriver.
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
3Dchecksand then disconnecttheleadstothe primary
ofthehighvoltagetransformer.Ensurethattheseleads
remain isolated from other components and the oven
chassis. (Use insulation tape if necessary.) When the
testingiscompletedcarryout3D checksand reconnect
theleads totheprimary ofthehigh voltage transformer.
When all service work is completed, and the oven is fully assembled, the microwave power output should be checked
and microwave leakage test carried out.
REMEMBER TO CHECK 4R
1) Reconnect all leads removed from components
during 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
thepresenceofmicrowaveenergywithinacavity,place
a cup of cold water on the oven tray, close the door and
set the microwave cooking time for one (1) minute. Set
the power level to 100% and push the START button.
When the one minutes has elapsed (timer at zero)
carefully check that the water is now hot. If the water
remains cold carry out 3D checks and re-examine the
connections to the component being tested.
Whentroubleshootingthemicrowaveoven,itishelpfulto
followtheSequenceofOperationinperformingthechecks.
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: Iftheovenbecomesinoperativebecause
of a blown fuse F2 F6.3A in the 1st latch
switch - monitor switch - monitor resisitor
circuit,checkthe1stlatchswitch,monitor
switch and monitor resistor before re-
placing the fuse F2 F6.3A

8
R-2277
R-2287
CONDITION
“ . “ does not appear on display when power
cord is plugged into wall outlet.
Control panel can not accept key in.
Fuse F2 F6.3A blows when the door is opened.
Homefuse blowns whenpower cord isplugged
into wall outlet.
Weakpoint/fuseF1blownswhenpowercord is
plugged into wall outlet.
Oven lamp, fan motor and stirrer motor do not
work for 1 minute whenever the door is opened
or after cooking.
Fuse F2 F6.3A blowns when power cord is
plugged into wall outlet.
Oven lamp does not light when door is opened.
(Blower and stirrer motors work)
Blower motor does not work when door is
opened. (Oven lamp lights and stirrer motors
work)
“EE 1” appear in display
“EE 2” appear in display
“EE 3” appear in display
“EE 6” appear in display
“EE 7” appear in display
“EE 9” appear in display
Oven lamp, blower motor and stirrer motor do
not work.
Oven lamp does not work.
Blower motor does not work.
Oven does not stop after end of cooking cycle.
(Oven lamp, blower motor and stirrer motor
stop)
Home fuse blows when starting the oven.
Oven goes into cook cycle but shuts down
before end of cooking cycle.
Oven seems to be operating but no heat is
produced in oven load. (Microwave power level
is set at 10%.)
It passed more than 1 minute after cooking but oven
lamp, blower motor and stirrer motor do not stop.
“ EE 0” appear in display
“EE 16” appear in display
“EE 17” appear in display
“EE 8” appear in display
“EE 10” appear in display
Stirrer motor does not work
PPROBLEM
TEST PROCEDURE AA BB CCCDD EE EEE F F GH
ON
CONDITION
OFF
CONDITION
MAGNETRON MG1 MAGNETRON MG2 HIGH VOLTAGE TRANSFORMER T1 HIGH VOLTAGE TRANSFORMER T2 H.V. RECTIFIER ASSEMBLY FOR MG1 H.V. RECTIFIER ASSEMBLY FOR MG2 H.V. WIRE HARNESS H.V. CAPACITOR C1 H.V. CAPACITOR C2 1ST. LATCH SWITCH SW1 2ND. LATCH SWITCH SW2 3RD. LATCH SWITCH SW3 MONITOR SWITCH SW4 STOP SWITCH SW5 WEAK POINT A018 / FUSE M6.3A WP1 WEAK POINT A018 / FUSE M6.3A WP2 WEAK POINT A017 / FUSE 13A F1 FUSE F6.3A F2
POSSIBLE CAUSE
AND
DEFECTIVE PARTS

9
R-2277
R-2287
MAGNETRON THERMAL CUT-OUT 145˚C TC1 MAGNETRON THERMAL CUT-OUT 145˚C TC2 B. MOTOR THERMAL CUT-OUT 115˚C TC3 OVEN THERMAL CUT-OUTT 115˚C TC4 MONITOR RESISTOR R1 STIRRER MOTOR MAGNETRON THERMISTOR EXHAUST THERMISTOR INTAKE THERMISTOR OVEN LAMP OR SOCKET BLOWER MOTOR NOISE FILTER POWER SUPPLY CORD FUSE HOLDER SHORTED WIRE HARNESS OPENED WIRE HARNESS CONTROL PANEL RELAY RY-1, RY-3, RY-4 FOIL PATTERN BLOCKED VENTILATION OPENINGS BLOCKED BLOWER MOTOR MIS ADJUSTMENT OF SWITCHES HOME FUSE OR BREAKER NO POWER AT WALL OUTLET OVER THE MAX. COOKING TIME DUE TO PROGRAMME LOCK
TEMPERATURE OF EXHAUST THERMISTOR IS HIGH
TEMPERATURE OF INTAKE THERMISTOR IS HIGH TEMPERATURE OF MAGNETRON THERMISTOR IS HIGH BLOCKED STIRRER ANTENNA SWITCH UNIT
IIIIJLKKK LM NPQ O

10
R-2277
R-2287
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
AMAGNETRON TEST
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 (IEC-705-1988)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition(outercasefitted).Microwaveoutputpowerfromthemagnetroncanbemeasuredbyway
of IEC 705, i.e. It is measured by how much power the water load can absorb. To measure the
microwaveoutputpowerinthemicrowaveoven,therelationofcalorieandwattisused.WhenP(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.
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 Power supply Voltage............... Rated voltage
Water load........... 1000 g Initial temperature10±2°C
Heating time (R-2287)........25 sec. P=170x∆T ((R-2287)
Heating time (R-2277)........35 sec. P=120x∆T (R-2277)
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. Select the initial and final water temperature so that the maximum difference between the final
water temperature and the ambient temperature is 5K.
5. Select stirring devices and measuring instruments in order to minimize addition or removal of
heat.
6. The graduation of the thermometer must be scaled by 0.1°C at minimum and can be accurate
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: Theoperationtime of themicrowave oven is“t+ 3” sec.(3 sec. ismagnetronfilament heat-
up time.) Therefore total reheating time = 28 seconds (for R-2287) and 38 seconds (for R-
2277).
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) K.
NEVERTOUCH ANYPARTINTHECIRCUIT WITHYOURHANDORAN INSULATEDTOOL
WHILE THE OVEN IS IN OPERATION.
CARRY OUT 3D CHECK.
Isolatethemagnetronfromhighvoltagecircuitbyremovingallleadsconnectedtofilamentterminal.

11
R-2277
R-2287
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
5. Stir the water to equalize temperature throughout the vessel.
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 (25 + 3) = 28 sec (for R-2287) ............................................. T2 = 21°C
Temperature after (35 + 3) = 38 sec (for R-2277) ............................................. T2 = 21°C
Temperature difference Cold-Warm ................................................................... ∆T = 10°C
Measured output power
The equation is “P = 170 x ∆T” for R-2287 .......................... P = 170 x 10°C = 1700 Watts
The equation is “P = 120 x ∆T” for R-2277 .......................... P = 120 x 10°C = 1200 Watts
JUDGMENT: The measured output power should be at least ±15 % of the rated output power.
CAUTION: 1°C CORRESPONDS TO 170 WATTS ( FOR R-2287) / 120 WATTS (FOR R-2277).
REPEAT MEASUREMENT IF THE POWER IS INSUFFICIENT.
WARNING: High voltages and large currents are present at the secondary winding and
filament winding of high voltage 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.
Disconnecttheleadstotheprimarywindingofthehighvoltagetransformer.Disconnectthefilament
and secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set on a
lowrange, itis possible tocheckthe continuity ofall three windings.Thefollowing readings should
be obtained:
a. Primary winding approx. 1.06 Ω(R-2287)/ approx. 2 Ω(R-2277)
b. Secondary winding approx. 57.3 Ω(R-2287)/ approx. 83 Ω(R-2277)
c. Filament winding less than 1 Ω
Ifthereading obtainedare not statedas above,thenthe highvoltagetransformer isprobably faulty
and should be replaced.
CARRY OUT 4R CHECKS.
B HIGH VOLTAGE TRANSFORMER TEST
1000g
1000g
1000g
T1˚C T2˚C
Heat up for 28 sec. (for R-2287)
Heat up for 38 sec. (for R-2277)
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
testedusingan ohmmetersetto itshighestrange. Connecttheohmmeter acrosstheterminal B+C
of the high voltage rectifier and note the reading obtained. Reverse the meter leads and note this
second reading.

12
R-2277
R-2287
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
The normal resistance is infinity in one direction and more than 100 kΩin the other direction.
CARRY OUT 4R CHECKS.
ASYMMETRIC RECTIFIER TEST
CARRY OUT 3D CHECKS.
IsolatethehighvoltagerectifierassemblyfromtheHVcircuit.Theasymmetricrectifiercanbetested
using an ohmmeter set to its highest range. Contact the ohmmeter 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 directions then the asymmetric rectifier is good. If an
asymmetricrectifierisshortedineitherdirection,thentheasymmetricrectifierisprobablyfaultyand
must be replaced with high voltage rectifier. When the asymmetric rectifier is defective, check
whether magnetron, high voltage rectifier, high voltage wire or filament winding of the high voltage
transformer is shorted.
CARRY OUT 4R CHECKS.
NOTE: FORMEASUREMENTOFTHERESISTANCEOFTHERECTIFIER,THEBATTERIESOF
THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS,
BECAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH
DIRECTIONS.
CARRY OUT 3D CHECK.
SIsolate the switch to be tested and using an ohmmeter check between the terminals as described
in the following table.
Table: Terminal Connection of Switch COM; Common terminal
Plunger Operation COM to NO COM to NC NO; Normally open terminal
Released O.C. S.C. NC; Normally close terminal
Depressed S.C. O.C. S.C.; Short circuit
O.C.; Open circuit
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
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)andthenaresistanceofabout10MΩ
after it has 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 10MΩ
resistance.
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.
E SWITCH TEST
AB
C
D2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER

13
R-2277
R-2287
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
FWEAK POINT A018 / FUSE M6.3A (WP1 OR WP2) TEST
G WEAK POINT A017/ FUSE 13A (F1) TEST
CARRY OUT 3D CHECKS.
If the weak point/ fuse F1 is blown, there could be a shorts or grounds in electrical parts or wire
harness.
Check them and replace the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS
CAUTION: Only replace weak point/ fuse with the correct value replacement. Type A017 is
for R-2287. Type13A is for R-2277.
H FUSE F6.3A (F2) TEST
CARRY OUT 3D CHECKS.
If the fuse F2 F6.3A is blown when the door is opened, check the latch switch, monitor switch and
monitor resistor.
If the fuseF2 F6.3 is blown by incorrect door switching replace the defective switch(s) and the fuse
F2 F6.3A.
CARRY OUT 4R CHECKS.
CAUTION: Only replace fuse with the correct value replacement.
I TTHERMAL 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 each two terminals as described in the table below.
CARRY OUT 4R CHECKS.
Table: Thermal Cut-out Test
Temperature of “ON” Temperature of “OFF” Indication of ohmmeter
Parts Name condition (closed circuit). condition (open circuit). (When room temperature
(˚C) (˚C) is approx. 20˚C.)
Thermal cut-out 145˚C This is not resetable type. Above 145˚C Closed circuit.
Thermal cut-out 115˚C This is not resetable type. Above 115˚C Closed circuit
If incorrect readings are obtained, replace the thermal cut-out.
Anopen circuitoven thermalcut-out 115˚Cindicates thatthe ovencavityhasoverheated,thismay
be due to no load operation.
Anopencircuitmagnetronthermalcut-out145˚Cindicatesthatthemagnetronhasoverheated,this
may be due to resistricted ventilation, cooling fan failure or a fault condition within the magnetron
or HV circuit.
An open circuit blower motor thermal cut-out 115˚C indicates the blower motor winding has
overheated, this may be due to resisted ventilation or locked cooling fan.
CARRY OUT 3D CHECKS.
Iftheweakpoint/fuseWP1orWP2isblown,therecouldbeashortintheasymmetricrectifierorthere
is a ground in wire harness. A short in the asymmetric rectifier may have occured due to short or
ground in H.V. rectifier, magnetron, high voltage transformer or H.V. wire. Check them and replace
the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace weak point/ fuse with the correct value replacement. Type A018 is
for R-2287. Type M6.3A is for R-2277.

14
R-2277
R-2287
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals.
CARRY OUT 3D CHECKS.
Disconnect the leads from the monitor resistor. Using an ohmmeter and set on a low range. Check
between the terminals of the monitor resistor.
The resistance of monitor resistor should be read approx. 4.3Ω.
If incorrect readings are obtained, replace the monitor resistor.
CARRY OUT 4R CHECKS.
JMONITOR RESISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect connector-H from the CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.
Room Temp. Resistance
15˚C........................ Approx. 15.91 kΩ
20˚C........................ Approx. 13.04 kΩ
25˚C........................ Approx. 10.74 kΩ
If the meter does not indicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
EXHAUST THERMISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect connector-B from the CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.
Room Temp. Resistance
15˚C........................ Approx. 77.45 kΩ
20˚C........................ Approx. 61.47 kΩ
25˚C........................ Approx. 49.12 kΩ
If the meter does not indicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
INTAKE THERMISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect connector-D from the CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.
Room Temp. Resistance
15˚C........................ Approx. 15.88 kΩ
20˚C........................ Approx. 13.03 kΩ
25˚C........................ Approx. 10.74 kΩ
If the meter does not indicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
K MAGNETRON THERMISTOR TEST
L MOTOR WINDING TEST

15
R-2277
R-2287
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
Resistance of Blower motor should be approximately 52Ω.
Resistance of Stirrer motor should be approximately 8.8 kΩ.
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
L (min) Cx ±20% Cy ±20%
0.5mH 0.22 µF 4700 pF
MEASURING POINT INDICATION OF OHMMETER
Between N and L Open circuit
Between terminal N and WHITW Short circuit
Between terminal L and BLK Short circuit
If incorrect readings are absorbed, replace the noise filter.
CARRY OUT 4R CHECKS
L
NL
L
F1
Cy BLK
WHT
Cx
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of noise filter. Using an ohmmeter, check between the
terminals as described in the following table.
M NOISE FILTER TEST
N CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI etc. Therefore,
unlike conventional microwave ovens, proper maintenance cannot be performed with only a
voltmeterandohmmeter.Inthisservicemanual,thetouchcontrolpanelassemblyisdividedintotwo
units, Control Unit and Switch Unit, troubleshooting by unit replacement is described according to
the symptoms indicated.
1. Switch Unit
The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the select buttons, a certain button produces no signal at all.
b) When touching the select buttons, sometimes a button produces no signal.
2. Control Unit
The following symptoms may indicate a defective control unit. Replacing the control unit.
2-1 Programming problems.
a) When touching the select buttons, a certain group of buttons do not produce a signal.
2-2 Display problems.
a) For a certain digit, all or some segments do not light up.
b) For 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 problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.
Note: Whendefectivecomponents,(theControlUnitorSwitchUnit)arereplaed,thedefectivepart
or parts must be properly packed for return in the shipping carton. with its cushion material,
in which the new replacement part was shipped to you.

16
R-2277
R-2287
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER COMPONENT TEST
OSWITCH UNIT TEST
1. CARRY OUT 3D CHECKS.
2. Remove the switch unit from the control panel, referring to control panel removal.
3.Totesttheswitches(SW1-SW5)ontheswitchunit,checkbetweentheterminalsoftheconnector
CN-Fasdescribedinthefollowingtablebyusingohmmeterwhentheswitchesarereleasedand
depressed.
Switches Terminals Released Depressed
SW1 F1 - F4 O.C. S.C.
SW2 F1 - F5 O.C. S.C.
SW3 F2 - F4 O.C. S.C.
SW4 F2 - F5 O.C. S.C.
SW5 F3 - F4 O.C. S.C.
QPROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD(PWB) IS OPEN
Toprotect theelectronic circuits,thismodelisprovidedwitha finefoil patternadded totheprimary
onthePWB,thisfoilpatternactsasafuse.Ifthefoilpatternisopen,followthetroubleshootingguide
given 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-A)
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 J9 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)
O.C. : Open Circuit
S.C. : Short Circuit
PRELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 5 and 7 of the connector (A) on the
control unit with an A.C. voltmeter. The meter should indicate 230 volts, if not check control unit
circuity.
RY1, RY2 and RY3 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. voltage not indicated .......................Check diode which is connected to the relay coil.
If diode is good, control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 APPROX. 18.0V D.C. Oven lamp,Blower motor and Stirrer motor
RY2 APPROX. 17.5V D.C. Power transformer 1
RY3 APPROX. 17.5V D.C. Power transformer 2
CARRY OUT 4R CHECKS.

17
R-2277
R-2287
S1
S2
23
P
TI
C31
D23
+
–
VRS1
(J9)
(J8)
OL, BM POWER 7531
D21
CN–A
a
cb
d
NOTE: *At the time of these repairs, make a
visual inspection of the varistor for
burning damage and examine the
transformer with tester for the
presence of layer short-circuit (check
primary coil resistance). If any
abnormal condition is detected,
replace the defective parts.
CARRY OUT 4R CHECKS.

18
R-2277
R-2287
The control section consists of the following units as
shown in the touch control panel circuit.
(1) Control Unit
(2) Key Unit
The principal functions of these units and the signals
communicated among them are explained below.
1. Control Unit
Signal of key touch and oven function control are all
processed by one microcomputer.
1) Power Supply Circuit
This circuit changes output voltage at the secondary
side of the low voltage (T1) transformer to volatges
required at each part by full wave rectifying circuit,
constant voltage circuit, etc..
2) ACL Circuit
Thisisan Auto-clear Circuit,i.e.,a reset circuit,which
enables IC1 to be activated from initial state.
3) Power SYNC Signal Generating Circuit
This is a circuit for generating power SYNC signal by
virtue of the secondary side output of transformer T1.
This signal is used for a basic frequency to time
processing and so on.
4) Clock Circuit
Thisisacircuitforcontrollingclockfrequencyrequired
for operating IC1.
5) IC1 (Main Processor)
This is a one-chip microcomputer, responsible for
controlling the entire control unit.
6) Display Circuit
Thisis acircuit fordriving displaytubes byIC1 output.
7) Switch Input Circuit
This is a circuit for transmitting switch input informa-
tion to IC1.
8) Sound-body Driving Circuit
This is a circuit for driving sound body by IC1 output.
9) Relay Driving Circuit
This is a circuit for driving output relay by IC1 output.
10) Stop Switch Circuit
This is a circuit for driving IC1 to detect door opening/
closing.
11) Exhaust Air Temperature Detecting Circuit
This is a circuit for transmitting output change of
CONTROL PANEL ASSEMBLY
OUTLINE OF CONTROL PANEL
thermistor (Exhaust Air Temperature Sensor) to IC1.
12) High Voltage Monitoring Circuit.
This circuit detects problems in the magnetron / high
voltage circuit by sensing a variation in the current
flowingthroughtheprimarywindingofthehighvoltage
transformer.
Duringheating,theprimarycurrentofthehighvoltage
transformersalsoflowsthroughtheprimarywindingof
thecurrenttransformers CT1andCT2. Thiscausesa
current to be induced in the secondary windings of
CT1/CT2 and results in an AC voltage which is
determined by R30/R31.
ThisACvoltageisthenhalfwaverectifiedbyD30/D31
and smoothed (filtered) by C30/C31.
This AC voltage is the input to the AN3 and AN4 ports
ofIC1,whichdeterminesif thereisa magnetron/high
voltage problem. HIGH VOLTAGE TRANSFORMER
HIGH VOLTAGE CIRCUIT
MAIN BODY SIDE
T/C SIDE
CT1 or CT2 RY2 or RY3
R30 or
R31 R65 or
R66
D30 or
D31 R32 or R33 Vc
C30 or C31
IC1
AN3 or
AN4 PORT
D32 or
D33
Figure T-1. High Voltage Monitoring Circuit
13) Magnetron Temperature Detecting Circuit.
This is a circuit for transmitting output change of
thermistor (Magnetron Temperature Sensor) to IC1.
14) Intake Air Temperature Detecting Circuit.
This is a circuit for transmitting output change of
thermistor (Intake Air Sensor) to IC1.
2. Switch Unit
Theswitchunitiscomposedofamatrixcircuitinwhich
when a switch it touched, one of signals P43 - P45
generated by the LSI, is passed through the switch
and returned to the LSI as one of signals P50 - P51.
3. Encoder
TheencoderconvertsthesignalgeneratedbyLSIinto
thepulsesignal,andthepulsesignalisreturnedtothe
LSI.