Sharp R-22AT User manual

R-22AT
R-23AM
R-24AT
SHARP CORPORATION
SERVICE MANUAL
SX910R24ATK//
COMMERCIAL
MICROWAVE OVEN
MODELS R-22AT
R-23AM
R-24AT
In interests of user-safety the oven should be restored to its
original condition and only parts identical to those specified
should be used.
TABLE OF CONTENTS Page
SERVICING ................................................................................................................. INSIDE FRONT COVER
CAUTION, MICROWAVE RADIATION............................................................................................................. 1
WARNING..........................................................................................................................................................1
PRODUCT SPECIFICATIONS ......................................................................................................................... 2
GENERAL INFORMATION................................................................................................................................2
APPEARANCE VIEW ....................................................................................................................................... 3
OPERATION SEQUENCE................................................................................................................................ 4
FUNCTION OF IMPORTANT COMPONENTS ................................................................................................ 6
TROUBLESHOOTING GUIDE ..........................................................................................................................7
TEST PROCEDURE ......................................................................................................................................... 9
TOUCH CONTROL PANEL ASSEMBLY ........................................................................................................18
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ........................................................... 28
MICROWAVE MEASUREMENT .................................................................................................................... 35
WIRING DIAGRAM ......................................................................................................................................... 36
PICTORIAL DIAGRAM ................................................................................................................................... 38
CONTROL PANEL CIRCUIT ...........................................................................................................................39
PRINTED WIRING BOARD .............................................................................................................................42
PARTS LIST ................................................................................................................................................... 44
1900W/R-24AT
1
2
3
4
5
6
7
8
9
0
11
12
13
14
15
16
17
18
19
20
EXPRESS
DEFROST
MANUAL/
REHEAT STOP / CLEAR
POWER LEVEL START
SET CHECK VOLUME
DOUBLE
QUANTITY
R-24AT

R-22AT
R-23AM
R-24AT
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high two voltage capacitors.
WARNING: AGAINST THE CHARGE OF THE TWO
HIGH-VOLTAGE CAPACITORS.
The two high-voltage capacitors remain charged
about 60 seconds after the oven has been switched
off. Wait for 60 seconds and then short-circuit the
connection of the two high-voltage capacitors (that
is, of the connecting lead of the high-voltage recti-
fier) against the chassis with 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
3D checks andthen disconnecttheleads to theprimary
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 iscompleted carryout 3D checksand reconnect
the leads to the primary of the power transformer.
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.
High voltage capacitors, High voltage transformers, Magnetrons, High voltage rectifier assembly, High voltage
fuses, High voltage harness.
REMEMBER TO CHECK 4R
1) Reconnectallleadsremovedfromcomponents dur-
ing 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
acup ofcold wateron theoventurntable,closethedoor
andset themicrowavetimerforone(1)minut.Whenthe
one minute has elapsed (timer at zero) carefully check
thatthewater is nowhot.If the waterremainscold carry
out 3D checks and re-examine the connections to the
component being tested.
Whenallservice workiscompleted andtheoven isfully
assembled, the microwave power output should be
checked and microwave leakage test should be carried
out.
1800W/R-23AM
START
HIGH
MEDIUM
MED LOW
DEFROST
TIME 
CONTROL
R-23AM

1
R-22AT
R-23AM
R-24AT
SERVICE MANUAL
COMMERCIAL
MICROWAVE OVEN
R-22AT/ R-23AM/ R-24AT
GENERAL IMPORTANT INFORMATION
This Manual has been prepared to provide Sharp Corp. Service
engineers with Operation and Service Information.
Itisrecommendedthatserviceengineerscarefullystudytheentiretext
ofthismanual,sotheywillbequalifiedtorendersatisfactorycustomer
service.
CAUTION
MICROWAVE RADIATION
Service engineers should not be exposed to the microwave
energy which may radiate from the magnetron or other micro-
wave generating devices if it is improperly used or connected.
Allinputandoutputmicrowaveconnections,waveguides,flanges
andgasketsmustbesecured.Neveroperatethedevicewithout
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.
Allthe partsmarked"*"onparts listareusedatvoltages morethan
250V.
Removal of the outer wrap gives access to potentials above 250V.
All the parts marked "∆" on parts list may cause undue microwave
exposure,bythemselves, orwhen they aredamaged, loosenedor
removed.
SHARP CORPORATION
OSAKA, JAPAN
PRODUCT SPECIFICATIONS
GENERAL INFORMATION
APPEARANCE VIEW
OPERATING SEQUENCE
FUNCTION OF IMPORTANT
COMPONENTS
SERVICING AND
TROUBLESHOOTING GUIDE
TEST PROCEDURE
TOUCH CONTROL PANEL
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
MICROWAVE MEASUREMENT
WIRING DIAGRAM
PARTS LIST

2
R-22AT
R-23AM
R-24AT
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
PRODUCT DESCRIPTION
SPECIFICATION
ITEM DESCRIPTION
Power Requirements 230 - 240 Volts
50 Hertz
Single phase, 3 wire earthed
Power Comsumption 2.4 kW Approx. 11 A [R-22AT] / 2.9 kW Approx. 13 A [R-23AM, R-24AT]
Power Output 1500 W [R-22AT]/ 1900 W [R-23AM/24AT] nominal of RF microwave energy
(measured by method of IEC 60705) Operating frequency 2450 MHz
Case Dimensions Width Height Depth
510mm 335 mm 470mm
Cooking Cavity Dimensions Width Height Depth
330 mm 180 mm 330mm
Control Complement for R-22AT/24AT Touch Control System
The combination of cooking time and microwave power
The oven can be programmed a series of up to 3 cookling stages.
The combination of microwave power and cooking time that can be input as
folllows.
Cooking Sequence Micrwave power levelthat can be iused. Cooking time that can be iused.
1 Stage only 0-100% Max. 30 minutes
0-40% all stages Max. 30 minutes any stages
Max. 60 minutes for 2 stages
2 or 3 Stage Max. 90 minutes for 3 stages
50-100% Max. 30 minutes for 3 stages
NOTE:If the oven used with the power level above 40% on any stage, the
maximum cooking time is 30 minutes in total.
Microwave Power level
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
MANUAL / REPEAT key, NUMBER keys
POWER LEVEL key, STOP / CLEAR key
START Key, DOUBLE QUANTITY key
EXPRESS DEFROST key, SET key
CHECK key, VOLUME key
Control Complement for R-23AM Electronic Timer (0 - 30 minutes)
Microwave Power level
100% 50% 20% 10%
MICROWAVE POWER SETTING buttons
START button
Set Weight Approx. 33 kg

3
R-22AT
R-23AM
R-24AT
APPEARANCEVIEW
OVEN
1. Control panel
2. Hole for safety door latches
3. Ceramic floor
4. Splash cover
5. Oven light
6. Air intake filter
7. Air intake openings
8. Oven cavity
9. Door seals and sealing surfaces
10. Door hinges
11. Oven door with see-through window
12. Door safety latches
13. Door handle.
14. Outer cabinet
15. Removable cover over oven light bulb
16. Air vent openings
17. Power supply cord
18 Mounting plate
19 Screw for mounting plate
DISPLAY AND INDICATORS
for R-22AT and R-24AT
Check indicators after the oven
startstoconfirmtheovenisoper-
ating as desired.
1. Heating indicator
This indicator shows cooking in
progress.
2. Memory number indicator
3. Express defrost
4. Check mode indicator
5. Power level display
6. Time display
7. Filter indicator
8. Double quantity mode indicator
9. 3rd. stage indicator
10. 2nd. stage indicator
11. 1st. stage indicator
OPERATING KEYS
12. DOUBLE QUANTITY key
13. EXPRESS DEFROST key
14. NUMBER keys
15. MANUAL/ REPEAT key
16. STOP/CLEAR key
17. POWER SLEVEL key
18. START key
19. SET key
20. VOLUME key
21. CHECK key
AUTO TOUCH CONTROL PANEL
INSTALLATION INFORMATION
When this commercial microwave oven is installed near other commercial electrical appliances, connect a lead wire to
each equivalent potential terminal with equipotential marking between them (insert a lead wire between a washer and
an earth angle, and screw them), as shown in Fig. A-1, to make sure that they are at equivalent potential.
If any lead wire is not connected between them, when person touch them he/she will get a electric shock.
COMMERCIAL MICROWAVE OVEN OTHER COMMERCIAL 
ELECTRICAL APPLIANCE
Lead wire
Equipotential marking
Earth angle
(Equivalent potential terminal)
Equivalent 
potential terminal
Screw
Washer
Lead wire
Figure A-1
DISPLAY AND INDI-
CATORS for R-23AM
Check indicators after
the oven starts to con-
firm the oven is operat-
ing as desired.
1. Cook indicator
This indicator shows
cooking in progress.
2. Time display
3. Microwave power level
display
OPERATING KEYS
4. HIGH 100%
5. MEDIUM 50%
6. MED LOW 20%
7. DEFROST 10%
8. TIME CONTROL
Rotate the control to en-
ter cooking time.
9. START button
MICROWAVE
POWER LEVEL
buttons
4
1
52 10 3
679
8
11
12
13 17 16
14
15
19
18
START
HIGH
MEDIUM
MED LOW
DEFROST
TIME 
CONTROL
4
5
6
7
8
9
POWER
%
ON
2
13
DEF CHECK POWER
%
DOUBLE ON
NUMBER
123
16
18
20
13
5
2
1
12
15
17
19
21
11 10
FILTER
34 6
7
8
9
1
2
3
4
5
6
7
8
9
0
11
12
13
14
15
16
17
18
19
20
14
EXPRESS
DEFROST
MANUAL/
REHEAT STOP / CLEAR
POWER LEVEL START
SET CHECK VOLUME
DOUBLE
QUANTITY

4
R-22AT
R-23AM
R-24AT
OPERATION SEQUENCE
the two high voltage transformers. The voltage is
convertedtoabout3.3voltsA.C.outputonthefilament
winding and high voltage of approximately 2000 volts
A.C. on the secondary winding.
2. The filament winding voltage (3.3 volts) heats the
magnetronfilamentandthehighvoltage(2000volts)is
senttothevoltagedoubling circuit, where it isdoubled
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
energyischannelledthroughthewaveguide(transport
channel)intothe oven cavity,wherethe food isplaced
to be cooked.
4. Whenthecookingtimeisup,asignaltoneisheardand
the relays RY3+RY4 (for R-22AT/24AT)/ RY2+RY3
(for R-23AM) go back to their home position. 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
ThecircuitstothehighvoltagetransformersT1+T2 are
cutoffwhenthe 1st latch,2ndlatch,3rd latch andstop
switches SW1+SW2+SW3+SW5aremadeopen.The
blower motor BM, stirrer motors and oven lamp re-
mains on even if the oven door is opened after the
cookingcyclehasbeen interrupted, becausetherelay
RY1 stays closed. Shown in the display is the remain-
ingtime,butthe program is cancellediftheoven 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. When the oven door is opened during or after the
cycleofacookingprogram,the1st,2nd,3rdlatchand
stopswitchesSW1+SW2+SW3+SW5mustopentheir
contactsfirst.Afterthatthecontacts(COM-NC)ofthe
monitor switch SW4 can be closed.
6-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switchSW4 must be opened first.
Afterthatthecontacts(COM-NO)ofthe1st,2nd,3rd
latchandstopswitchesSW1+SW2+SW3+SW5must
be closed.
6-3. Whentheovendoorisopenedandthecontactsofthe
1st latch switch SW1remain closed, remains closed,
the fuse F2 F6.3A will blow, because the monitor
switch is closed and a short circuit is caused.
MICROWAVE VARIABLE COOKING (for R-22AT
and R-24AT)
When the microwave oven is preset for variable cooking
Closing the door activates all door interlock switches (1st
latch switch, 2nd latch switch, 3rd latch switch and stop
switch).
IMPORTANT
Whentheovendoorisclosed,themonitorswitchcontacts
COM-NC must be open. When the microwave oven is
plugged in a wall outlet (230 - 240 volts, 50Hz), the line
voltage issupplied to thepoint A5+A7 inthe control panel
through the noise filter.
Figure O-1 on page 36
1. The digital display shows .
IDLE CONDITION
When the door is opened, the contacts of the 1st. latch
switchSW1,2nd.latchswitchSW2,3rd.latchswitchSW3
and stop switch SW5 open, initiating the following:
Figure O-2 on page 36
1. Asignalisinputtothecontrolunitenergizingthecoilof
shut-off relay RY-1.
2. The shut-off relay RY-1 contacts close completing
circuits to turn on the oven lamp, blower motor and
stirrer motors.
3. If the door remains open, 60 seconds later the control
unit de-energizes shut-off relay RY-1 turning off the
oven lamp, blower motor and stirrer motors.
When the door is closed, the contacts of the 1st. latch
switchSW1,2nd.latchswitchSW2,3rd.latchswitchSW3
and stop switch SW5 close. With the closing of the stop
switch SW5 contacts, an additional circuit is provided
whichwillpermittheoperationoftheovenwhenoneofthe
touch pads is depressed. Since the control is enabled
through the stop switch SW5, the door must be closed
before the touch pads will be effective. When the door is
closed,afull60secondIDLEconditionisalwaysprovided
for selecting and pressing the desired touch pads. A 60
secondIDLEconditionwillalsofollowtheendofeachcook
cycle.
MICROWAVE COOKING CONDITION
for R-22AT and R-24AT
Touch MANUAL/ REPEAT key and enter a desired
cookingtimewiththetouchingNUMBERkey.Andthen
touch START key.
Function sequence Figure O-3 on page 37
CONNECTED COMPONENTS RELAY
Oven lamp/ Blower motor/ Stirrer motors RY1
High voltage transformer T1 RY3
High voltage transformer T2 RY4
for R-23AM
Enter a desired cooking time with the turning TIME
CONTROL knob. And then push STARTbutton.
Function sequence Figure O-3 on page 37
CONNECTED COMPONENTS RELAY
Oven lamp/ Blower motor/ Stirrer motors RY1
High voltage transformer T1 RY2
High voltage transformer T2 RY3
1. The line voltage is supplied to the primary winding of

5
R-22AT
R-23AM
R-24AT
power, the line voltage is supplied to the high voltage
transformersT1+T2intermittentlywithina48secondtime
base through the contacts of the relays RY3+RY4.
The following levels of microwaves power are given.
NOTE: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 3 seconds are needed for heat-
ing up the magnetron filament.
MICROWAVEVARIABLECOOKING(forR-23AM)
When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the high voltage
transformers intermittently within a 48 second time base
through the contacts of the relays RY2+RY3.
The following levels of microwaves power are given.
NOTE: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 3 seconds are needed for heat-
ing up the magnetron filament.
 48 sec. ON
Number key 
 44sec. ON
Number key 9
 40 sec. ON
Number key 8
 36 sec. ON
Number key 7
 32 sec. ON
Number key 6
 26 sec. ON
Number key 5
 22 sec. ON
Number key 4
 16 sec. ON
Number key 3
 12 sec. ON
Number key 2
 8 sec. ON
Number key 1
 0 sec. ON
Number key 0
 48 sec. ON
 100% 
 26sec. ON
 50%
 12 sec. ON
 20%
 8 sec. ON
 10%
T1: HIGH VOLTAGE
TRANSFORMER
H. V. RECTIFIER
C1: H.V. CAPACITOR
MG1: MAGNETRON (UPPER)
(REAR)
H. V. RECTIFIER
H. V. FUSE H. V. FUSE
C2: H.V. CAPACITOR
MG2: MAGNETRON (LOWER)
T2: HIGH VOLTAGE
TRANSFORMER (FRONT)
COMMERCIAL
FREQUENCY
(50HZ)
POWER OUTPUT
BY MAGNETRON T1
POWER OUTPUT
BY MAGNETRON T2
OPERATION OF
MAGNETRON
TWO MAGNETRON OPERATION SYSTEM
Two magnetronsMG1+MG2 are equipped in order to get
higher microwave power output. The primary windings of
the high voltage transformers T1+T2 are connected so
that each magnetron can be oscillated alternatively ac-
cording to the frequency of the power supply. Refer to the
Figure B-1 and B-2.
Figure B-1. High Voltage Circuit
Figure B-2. Operation of Magnetron

6
R-22AT
R-23AM
R-24AT
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 head lever is lifted up by the door release lever.
4. The joint lever is lifted up by the head 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.
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 contacts COM-NO
must be closed.
2. When theoven door is opened,the contacts COM-NO
must be opened.
MONITOR SWITCH SW4
ThemonitorswitchSW4isactivated(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
contacts of the 1st latch switch SW1fail to open when the
door is opened.
Function
1. When the door is opened, the monitor switch SW4
contacts close (to the ON condition) due to their being
normally closed. At this time the 1st latch 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 SW4 contacts are opened and 1st latch switch
SW1 contacts are closed (On opening the door, each
of these switches operate inversely.)
3. If the door is opened and the 1st latch switch SW1
contacts failto open, thefuse F2 F6.3Ablows simulta-
neously with closing of the monitor switch SW4 con-
tacts.
FUNCTION OF IMPORTANT COMPONENTS
CAUTION:BEFORE REPLACING A BLOWN FUSE F2
F6.3A TEST THE 1ST LATCH SWITCH SW1,
MONITOR SWITCH SW4 AND MONITOR
RESISTOR R1 FOR PROPER OPERATION.
(REFER TO CHAPTER “TEST PROCE-
DURE”).
MONITOR RESISTOR R1
The monitorresistorR1 prevents thefuseF2 F6.3A250V
bursting when the fuse F 2 F6.3A 250V blows due to the
operation of the monitor switch SW4.
NOISE FILTER
The noise filter assembly prevents radio frequency inter-
ference that might flow back in the power circuit.
FUSE F1 F13A
Ifthewireharnessorelectricalcomponentsmakeashort-
circuit, this fuse F1 (F13A) blows to prevent an electric
shock or fire hazard.
FUSE F2 F6.3A 250V
1. If the wire harness or electrical components are short-
circuited,thisfuseblowstopreventanelectricshockor
fire hazard.
2. The fuse F2 also blows when 1st latch switch SW1
remains closed with the oven door open and when the
monitor switch closes.
FUSE(S) F3, F4 M8A
Ifthe wireharness orthehigh voltagetransformersT1, T2
are short-circuited, these fuses F3 and /or F4 blow to
prevent an electric shock or fire hazard.
HIGH VOLTAGE FUSE(S)
Thehighvoltagefuseblowswhenthehighvoltagerectifier
or the magnetron is shorted.
MAGNETRON TEMPERATURE FUSES TF1, TF2
The temperature fuses TF1, TF2 located on the top of the
upper and lower waveguide, are designed to prevent
damage to the magnetrons MG1, MG2. If an over heated
conditiondevelopsinthetubedueto blowermotorfailure,
obstructed air ducts, dirty or blocked air intake, etc., the
circuit to the magnetrons are interrupted. Under normal
operation, the temperature fuses remains closed. How-
ever, when abnormally high temperatures are generated
within the magnetrons, the temperature fuses will open at
150˚C causing the microwave energy to stop. The defec-
tive temperature fuses must be replaced with new rated
ones.
OVEN TEMPERATURE FUSE TF4
The temperature fuse TF4, located on the side of the
exhaustduct assembly,isdesignedtopreventdamageto
the oven by fire. If the food load is overcooked, by either
errorincooktimeordefectinthecontrolunit,thetempera-
ture fuse will open. Under normal operation, the oven
temperature fuse remains closed. However, when abnor-
mally high temperatures are generated within the oven
Latch head
SW4: Monitor switch
Latch hook
SW1: 1st. latch switch
SW2: 2nd. latch switch
SW5: Stop switch
SW3: 3rd. latch switch
Latch head
Joint lever
Door release
lever
Head lever

7
R-22AT
R-23AM
R-24AT
cavity, the oven temperature fuse will open at 120˚C,
causingtheoventoshutdown.Thedefectivetemperature
fuse must be replaced with new rated one.
BLOWER MOTOR TEMPERATURE FUSE TF3
This temperature fuse TF3 protects the blower motor
against overheating. If its temperature goes above 120˚C
because the blower motor is stalled or the ventilation
openings are blocked, the contacts of the temperature
fusewillopen.Thelinevoltagetothecontrolunitwillbecut
off and the operation of the oven will be stopped. The
defective temperature fuse must be replaced with a new
one.
OVEN THERMISTOR (1)
The thermistor is a negative temperature coefficient type.
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.
OVEN THERMISTOR (2)
This thermistor detects temperature of the oven cavity
bottom plate. The thermistor is a negative temperature
coefficient type. The temperature is detected through the
resistance of the thermistor.
If the temperature is high, the control will display “EE17”
and the oven will stop.
MAGNETRON THERMISTOR
The thermistor is a negative temperature coefficient type.
The air temperature around the upper magnetron is de-
tected 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.
Iftheoventhermistor(2)andthemagnetronthermistorare
open at the same time, the control panel will display
"EE16" and the oven will stop.
BLOWER MOTOR BM
TheblowermotorBMdrivesabladewhichdrawsexternal
cool air into the oven. This cool air is directed through the
air vanes surrounding the magnetrons and cools the
magnetrons.Thisairischannelledthroughtheovencavity
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 MOTORS SM
Theupperand lowerstirrermotors SMdrivestirrer anten-
nas to stir the microwave radiation from the upper and
lower waveguides.
OVEN LAMP OL
Theoven cavitylight illuminatesthe interiorof theovenso
that food being cooked can be examined visually through
the door window without having to open the door. The
oven lamp is on during the cooking cycle and idle condi-
tion.
TROUBLESHOOTING GUIDE
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.
IMPORTANT: If the oven becomes inoperative because of a blown fuse F2F6.3A in the 1st latch switch SW1 - monitor
switchSW4-monitorresisitorR1circuit,checkthe1stlatchswitchSW1,monitorswitchSW4and monitor
resistor R1 before replacing the fuse F2 F6.3A

8
R-22AT
R-23AM
R-24AT
“ . “ 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.  Home fuse blows when power cord is plugged into wall outlet.  Fuse F1 F13A blows when power cord is plugged into wall outlet. Oven lamp, fan motor and stirrer motors do not work for 1 minute when the door is opened or after cooking. Fuse F2 F6.3A blows 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” (Magnetron MG1 failure)  “EE 2” (Magnetron MG2 failure) “EE 3” (Magnetron MG1 and MG2 failure)  “EE 6” (Thermistor (1) failure)  “EE 7” (Exhaust air temperature is high)  “EE 9” (Exceeded max. heating time) for R-22AT/ R-24AT Oven lamp, blower motor and stirrer motors 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 motors stop.) Home fuse blows when starting the oven. Oven goes into cook cycle but shuts down before end of cooking cycle.  It passed more than 1 minute after cooking but oven lamp, blower motor and stirrer motors do not stop. “EE 16” (Thermistor of MG. and (2) are open.)  “EE 17” (Magnetron temperature is high.)  “EE 8” (Relay melt short) Stirrer motors do not work.
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
FUSE M8A F3
FUSE M8A F4
FUSE F13A F1
FUSE F6.3A F2
MAGNETRON TEMPERATURE FUSE TF1
MAGNETRON TEMPERATURE FUSE TF2
B. MOTOR TEMPERATURE FUSE TF3
OVEN TEMPERATURE FUSE TF4
MONITOR RESISTOR R1
MAGNETRON THERMISTOR
OVEN THERMISTOR (1)
OVEN THERMISTOR (2)
STIRRER MOTORS SM
BLOWER MOTOR BM
HIGH VOLTAGE FUSE(S)
OVEN LAMP OR SOCKET
NOISE FILTER
POWER SUPPLY CORD
FUSE HOLDERS
Shorted wire harness
Opened wire harness
TOUCH CONTROL PANEL
RELAY RY-1
RELAY RY-3 [for R-22AT/24AT], RY2 [for R-23AM]
RELAY RY-4 [for R-22AT/24AT], RY3 [for R-23AM]
FOIL PATTERN
Mis adjustment of switches
HOME FUSE or BREAKER
No power at wall outlet
Over the max. cooking time [for R-22AT/24AT]
Due to programme lock
Temperature of magnetron thermistor is high.
Temperature of oven thermistor (1) is high.
Temperature of oven thermistor (2) is high.
KEY UNIT [for R-22AT/24AT], or SWITCH UNIT [for R-23AM]

A ABBCC DDEEEEEFFGHI I I I JKKKL LN M OQQQR P
TESTPROCEDURE
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
CONDITION
OFF
CONDITION
ON
CONDITION
PROBLEM


9
R-22AT
R-23AM
R-24AT
AMAGNETRON TEST
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
CARRY OUT 3D CHECKS.
Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.
Totestfor anopencircuitfilament useanohmmeter to makeacontinuity testbetweenthemagnetron
filament terminals, the meter should show a reading of less than 1 ohm.
To test for short circuit filament to anode condition, connect ohmmeter between one of the filament
terminalsandthe caseofthe magnetron(ground).This testshouldbe indicatedaninfiniteresistance.
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 60705, i.e. it is measured by how much power the water load can absorb. To measure the
microwave output power in the microwave oven, the relation of calorie and watt is used. When P(W)
heating works for t(second), approximately P x t/4.187 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.
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±1)°C.
4. Selecttheinitialandfinalwatertemperaturesothatthemaximumdifferencebetweenthefinalwater
temperature and the ambient temperature is 5°C.
5. Selectstirring devicesand measuringinstruments inordertominimizeadditionorremovalofheat.
6. The graduation of the thermometer must be scaled by 0.1°C at minimum and be an accurate
thermometer.
7. The water load must be (1000±5) g.
8. “t”ismeasured while themicrowavegeneratoris operatingatfullpower. Magnetron filamentheat-
up time is not included.
NOTE:The operationtimeofthe microwaveovenis “t+3”sec. (3sec.is magnetronfilamentheat-uptime.)
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 until the temperature of the water rises by a value ∆T of
(10 ±2) K.
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.
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
The formula is as follows;
P x t / 4.187 = V x ∆T+ 0.55 x mc (T2-T0) P (W) = 4.187 x V x ∆T / t + 0.55 x mc (T2-T0)/t
Our condition for water load is as follows:
Room temperature (T0) ...... around 20°C Power supply Voltage.............. Rated voltage
Water load.....................................1000 g Initial temperature (T1) ...................... 10±1°C
Heating time...... 28 sec. [R-22AT] / 22sec. [R-23AM/24AT] Mass of container (mc) ..... 330 g
T2.........Final Temperature P = 150 x ∆T [R-22AT] / P = 190 x ∆T [R-23AM, R-24AT]

10
R-22AT
R-23AM
R-24AT
Room temperature ................................................................................................. T0 = 21°C
Initial temperature .................................................................................................. T1 = 11°C
Temperature after (28 + 3) = 31 sec [for R-22AT].................................................. T2 = 21°C
Temperature after (22 + 3) = 25 sec [for R-23AM/24AT] ....................................... T2 = 21°C
Temperature difference Cold-Warm......................................................................∆T1 = 10˚C
Measured output power
The equation is “P = 150 x ∆T” [for R-22AT]........................... P = 150 x 10°C = 1500 Watts
The equation is “P = 190 x ∆T” [for R-23AM/24AT] ................ P = 190 x 10°C = 1900 Watts
JUDGMENT: The measured output power should be within the range of ±15 % of the rated output
power.
CAUTION: 1°C CORRESPONDS TO 150 WATTS [R-22AT]/ 190 WATTS [R-23AM, R-24AT]. REPEAT
MEASUREMENT IF THE POWER IS INSUFFICIENT.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
1000g
1000g
1000g
T1˚C T2˚C
Heat up for 31 sec. for R-22AT
Heat up for 25 sec. for R-23AM/ R-24AT
MICROWAVE OUTPUT POWER (2000 cc alternative method)
The power output of this oven is rated using the method specified by IEC 60705. Full details of how
to curry out this procedure can be found in the Sharp Technical Training notes which is available from
Sharp Parts Centre (part number SERV-LITMW01).
TheIEC-60705proceduremustbecarriedoutusinglaboratory-typeproceduresandequipment.
These requirements make the procedure unsuitable for routine performance checks.
NOTE: The following test method gives an indication of the output power only, it cannot be used to
establishtheactual/ratedoutputpower. Ifthetrueoutputpowerisrequired,thenthe IEC60705
test method must be used.
Alternative simplified method:
1. Place 2 litres of cold water (between 12°C and 20°C) in a suitable container.
2. Stir the water and measure the temperature in °C. Note temperature as T1.
3. Place the container in the microwave and heat the water for 56 sec. [R-22AT]/ 44 sec. [R-23AM,
R-24AT] on fill power.
4. When the 56 sec. [R-22AT]/ 44 sec. [R-23AM, R-24AT] is completed, remove the container and
stir the water. Note temperature as T2.
5. Calculate the output power using the following formula:
R.F. Power Output = (T2 - T1) x 150 for R-22AT.
R.F. Power Output = (T2 - T1) x 190 for R-23AM, R-24AT.
NOTE: The result from this test should be within the allowance of 2000cc alternative method.
(±10%).
MICROWAVE LEAKAGE TEST
Thisovenshouldbetestedformicrowaveleakageoncompletionofany repairoradjustment,following
the procedure described in the Sharp Technical Training notes (part number SERV-LITMW01). The
maximum leakage permitted in BS EN 60335-2-25 is 50W/m2 (equivalent to 5W/m2), however it is not
normal to detect any significant leakage, therefore, any leakage which is detected should be
investigated.
It is essential that only leakage detectors with current calibration traceable to National Physical
Laboratories are used.
Suitable leakage detectors: CELTEC A100
APOLLO X1

11
R-22AT
R-23AM
R-24AT
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
BHIGH VOLTAGE TRANSFORMER TEST
WARNING: High voltage and large currents are present at the secondary winding and
filamentwindingofthehighvoltagetransformer.Itisverydangeroustowork
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 high voltage transformer. Disconnect the filament
andsecondarywindingconnectionsfrom therestoftheHV circuitry.Using anohmmeter,set ona low
range, it is possible to check the continuity of all three windings. The following readings should be
obtained:-
If the readings obtained are not stated as above, then the high voltage transformer is probably faulty
and should be replaced.
CARRY OUT 4R CHECKS.
R-22AT R-23AM, R-24AT
a. Primary winding approximately 1.8 Ωapproximately 1.2 Ω
b. Secondary winding approximately 75 Ωapproximately 75 Ω
c. Filament winding less than 1 Ω
CARRY OUT 3D CHECKS.
Isolatethehighvoltage rectifier assemblyfromtheHV circuit. Thehighvoltagerectifier can be tested
usinganohmmetersettoitshighestrange.ConnecttheohmmeteracrosstheterminalB+Cofthehigh
voltagerectifierandnotethereadingobtained.Reversethemeterleadsandnotethissecondreading.
The normal resistance is infinite in one direction and more than 100 kΩin the other direction.
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, BE-
CAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIREC-
TIONS.
CHIGH VOLTAGE RECTIFIER ASSEMBLY TEST
D HIGH VOLTAGE CAPACITOR TEST
BC
HIGH VOLTAGE RECTIFIER
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. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10MΩ
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
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in
the following table.

12
R-22AT
R-23AM
R-24AT
FFUSE F3, F4 M8A TEST
CARRY OUT 3D CHECKS.
IfthefusesF3and/or F4M8Aareblown,therecouldbeshortsinthehighvoltagetransformersT1 and/
orT2 or thereis agroundin wireharness. Checkand/or replacethe highvoltagetransformersT1and/
or T2 or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace fuses F3, F4 M8A with the correct value replacement.
GFUSE F1 F13A TEST
CARRY OUT 3D CHECKS.
If the fuse F1 F13A 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 fuse F1 F13A with the correct value replacement.
Table: Terminal Connection of Switch
Plunger Operation COM to NO COM to NC
Released Open circuit Short circuit
Depressed Short circuit Open circuit
COM; Common terminal,
NO; Normally open terminal
NC; Normally close terminal
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
HFUSE F2 F6.3A TEST
CARRY OUT 3D CHECKS.
IfthefuseF2F6.3Aisblownwhenthedoorisopened,checkthe1st.latchswitchSW1,monitorswitch
SW4 and monitor resistor R1.
If the fuse F2 F6.3A 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 F2 F6.3A with the correct value replacement.
1. CARRY OUT 3D CHECKS.
2. Acontinuitycheckacrossthetemperaturefuseterminalsshouldindicateaclosedcircuitunlessthe
temperature of the temperature fuse reaches specfied temperature as shown below.
ITEMPERATURE FUSE TEST
3. CARRY OUT 4R CHECKS.
CAUTION: IF THE temperature fuse INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE,
REPLACE temperature fuse.
Open Close Display or
temperature temperature Condition Check point
Magnetron tem-
perature fuse TF1
Magnetron tem-
perature fuse TF2
Blower motor tem-
perature fuse TF3
Oven temperature
fuse TF4
150˚C
120˚C
120˚C
Non resetable
type
Non resetable
type
Non resetable
type
EE1
EE3
EE2
Oven shut
off
Oven shut
off
Magnetron
MG1 Failure:
Test magnetron MG1 and Blower fan motor.
Magnetron MG1, MG2 Failure: Test magnetron MG1,
MG2. Check blower fan motor and ventilation opening.
Magnetron MG2 Failure:
Test magnetron MG2 and Blower fan motor.
Check blower fan motor and ventilation opening or
rocked rotating of blower fan motor.
Food has been burned in oven.
Temperature of oven inside is very high.

13
R-22AT
R-23AM
R-24AT
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
JMONITOR RESISTOR R1 TEST
CARRY OUT 3D CHECKS.
Disconnecttheleads fromthemonitor resistorR1. Usinganohmmeter andseton alowrange. Check
between the terminals of the monitor resistor R1.
The resistance of monitor resistor R1 should be read approx. 4.3Ω.
If incorrect readings are obtained, replace the monitor resistor R1.
CARRY OUT 4R CHECKS.
1. CARRY OUT 3D CHECKS.
2. Follow the procedures below for each thermistor.
2-1. MAGNETRON THERMISTOR TEST
Disconnect the connector of the magnetron thermistor from the switch harness. Measure the
resistance of the magnetron thermistor with an ohmmeter. Connect the ohmmeter leads to the leads
of the thermistor.
Room Temp. 59˚F (15˚C) 68˚F (20˚C) 77˚F (25˚C)
Resistance Approx. 373 kΩApprox. 292 kΩApprox. 231 kΩ
If the meter does not indicate above resistance, replace the thermistor.
2-2. OVEN THERMISTOR (1) TEST
Disconnect the connector of the oven thermistor (1) from the switch harness. Measure the resistance
oftheoventhermistor(1)withanohmmeter.Connecttheohmmeterleadstotheleadsofthethermistor.
Room Temp. 59˚F (15˚C) 68˚F (20˚C) 77˚F (25˚C)
Resistance Approx. 373 kΩApprox. 292 kΩApprox. 231 kΩ
If the meter does not indicate above resistance, replace the thermistor.
2-3. OVEN THERMISTOR (2) TEST
Disconnect the two connectors of the magnetron thermistor and oven thermistor (2) from the switch
harness.Measure theresistanceoftheoventhermistor(2)withanohmmeter.Connecttheohmmeter
leads to the leads of the thermistor.
Room Temp. 59˚F (15˚C) 68˚F (20˚C) 77˚F (25˚C)
Resistance Approx. 16 kΩApprox. 13 kΩApprox. 11 kΩ
If the meter does not indicate above resistance, replace the thermistor.
3. CARRY OUT 4R CHECKS.
KTHERMISTOR TEST
LMOTOR WINDING TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals.
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.
M NOISE FILTER TEST
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.

14
R-22AT
R-23AM
R-24AT
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
The touch control panel consists of circuits including semiconductors such as LSI, IC, etc. Therefore,
unlikeconventionalmicrowave ovens, propermaintenancecannot be performedwithonly a voltmeter
and ohmmeter. In this service manual, the touch control panel assembly is divided into two units,
ControlUnitandKeyUnit,troubleshootingbyunitreplacementisdescribedaccordingtothesymptoms
indicated.
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 the pads, sometimes a pad produces no signal.
2. Control Unit
The following symptoms may indicate a defective control unit. Replacing the control unit. Before
replacingthecontrolunit,performthekeyunittest(ProcedureP)todetermineifcontrolunitisfaulty.
2-1 Programming problems.
a) When touching the pads, a certain group of pads 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.
CONTROL PANEL ASSEMBLY TEST FOR R-23AM
The control panel consists of circuits including semiconductors such as LSI 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 three units, Control Unit,
Switch Unit and Encoder Unit troubleshooting by unit replacement is described according to the symptoms
indicated.
1. Switch Unit Note : Check the lead wire harness connections among big and small switch units and
control unit before replacement.
The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the buttons, a certain button produces no signal at all.
b) When touching the buttons, sometimes a button produces no signal.
2. Encoder Note:Checktheleadwireconnectionbetweenencoderandcontrolunitbeforereplacement.
The following symptoms indicate a defective encoder. Replace the encoder.
OTOUCH CONTROL PANEL ASSEMBLY TEST FOR R-24AT / R-22AT
MEASURING POINT INDICATIONOFOHMMETER
Between N and L Approx. 680 kΩ
Between terminal N and WHIT Short circuit
Between terminal L and BLK Short circuit
If incorrect readings are absorbed, replace the noise filter.
CARRY OUT 4R CHECKS.
N HIGH VOLTAGE FUSE TEST
CARRY OUT 3D CHECKS.
If the high voltage fuse is blown, there could be a short in the high voltage rectifier or the magnetron.
Check them and replace the defective parts and the high voltage fuse.
CARRY OUT 4R CHECKS.
CAUTION: Only replace high voltage fuse with the correct value replacement.
F1 : FUSE F13A
NOISE FILTER
NOISE SUPPRESSION COIL
DISCHARGE RESISTOR 680 kΩ1/2W
DISCHARGE RESISTOR 10 MΩ1/2W
LINE CROSS CAPACITOR 0.22µF/ AC250V
LINE CROSS CAPACITOR 
10000 pF/ AC250V LINE CROSS CAPACITOR  10000 pF/ AC250V
L
BLK
WHT
N

15
R-22AT
R-23AM
R-24AT
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.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
CARRY OUT 3D CHECKS.
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable is
making good contact, verify that the door sensing switch (stop switch ) operates properly; that is the
contacts are closed when the door is closed and open when the door is open. If the door sensing switch
(stopswitch)isgood,disconnecttheflatribboncablethatconnectsthekeyunittothecontrolunitandmake
sure the door sensing switch is closed (either close the door or short the stop switch connector ). 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 making 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 replaced.
If a specific pad does not respond, the
above method may be used (after clearing
the control unit ) to determine if the control
unit or key pad is at fault.
CARRY OUT 4R CHECKS.
SWITCH UNIT TEST FOR R-23AM
1. CARRY OUT 3D CHECKS.
2. Remove the switch unit from the control panel, referring to control panel removal.
3. To test the switches (SW1-SW5) on the switch unit, check between the terminals of the connector
CN-F as described in the following table by using ohmmeter when the switches are released and
depressed.
4. If incorrect readings are obtained, replace the
defective switch.
5. CARRY OUT 4R CHECKS.
P KEY UNIT TEST FOR R-24AT / R-22AT
a) When rotating the encoder, the cooking time can not be entered.
3. Control Unit
The following symptoms may indicate a defective control unit. Replacing the control unit. Before
replacingthecontrolunit,performtheswitchunittest(ProcedureP)todetermineifcontrolunitisfaulty.
3-1 Programming problems.
a) When touching the buttons, a certain group of buttons do not produce a signal.
3-2 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.
3-3 Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.
O.C. : Open Circuit / S.C. : Short Circuit
SET
3
4
5
6
7
8
9
0
2
CHECK
VOLUME
START
STOP /
CLEAR
1
11
12
13
14
15
16
19
20
17
18
DOUBLE
QUANTITY
EXPRESS
DEFROST MANUAL / REPEAT
POWER
LEVEL
G12
G11
G10
G 9
G 8 G 7 G 6 G 5 G 4 G 3 G 2
CARRY OUT 3D CHECKS.
Removetheoutercaseand checkvoltagebetweenPinNos.5and7ofthe connector(A)onthecontrol
unit with an A.C. voltmeter. The meter should indicate 230~240 volts, if not check control unit circuity.
RY1, RY3 and RY4 Relay Test For R-24AT / R-22AT
These relays are operated by D.C. voltage.
Q RELAY TEST

16
R-22AT
R-23AM
R-24AT
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on the
PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide given below
for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS OCCURRENCE 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 J24 and solder for R-24AT / R-22AT.
*Insert jumper wire J9 and solder for R-23AM.
(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: *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.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
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. 19.0V D.C. Oven lamp, Blower motor and Stirrer motors
RY3 APPROX. 16.0V D.C. High voltage transformer 1
RY4 APPROX. 18.0V D.C. High voltage transformer 2
RY1, RY2 and RY3 Relay Test For R-23AM
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 motors
RY2 APPROX. 17.5V D.C. High voltage transformer 1
RY3 APPROX. 17.5V D.C. High voltage transformer 2
CARRY OUT 4R CHECKS.
RPROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD(PWB) IS OPEN
(J29)
(VRS2)
VRS1
(J24)
(J23)
(9)9(7)5(3)3(1)
RY1
D81
c
ab
d
S1
S2
23
P
TI
C31
D23
+
–
VRS1
(J9)
(J8)
OL, BM POWER 7531
D21
CN–A
a
cb
d
R-24AT / R-22AT R-23AM

17
R-22AT
R-23AM
R-24AT
This AC voltage is the input to the IN3 and IN5 ports of
IC1, which determines if there is a magnetron / high
voltage problem.
Figure T-1. High Voltage Monitoring Circuit For R-24AT / R22AT
14) Magnetron Temperature Circuit.
(Detect Noload or Fan Lock)
Thisisa circuitfortransmittingoutputchange ofthermis-
tor (Magnetron thermistor) to IC1.
15) Oven Cavity Temperature Detecting Circuit.
Thisisa circuitfortransmittingoutputchange ofthermis-
tor (Oven thermistor (2)) to IC1.
2. Key Unit
Thekeyunitiscomposedofamatrixcircuitinwhichwhen
a key it touched, one of signals P11, P12, P15, P16 and
P17generatedbythe LSI,ispassedthroughthe keyand
returned to the LSI as one of signals R0--R3. This model
has20Memorypads.Whentheovenisshipped,Memory
pad 1 to 10 are set as follows: fig.1.
Memory No. Cook Time Output Power
1 5 sec. 100%
2 10 sec. 100%
3 20 sec. 100%
4 30 sec. 100%
5 40 sec. 100%
6 50 sec. 100%
7 1 min. 100%
8 1 min.15 sec. 100%
9 1 min.30 sec. 100%
10 2 mins. 100%
(fig. 1)
This model has a double quantity pad. When the oven
is shipped, Magnification "1.8" is preset in the double
quantity pad. This model has an defrost pad. When the
oven is shipped, defrost is set as follows: fig.2.
1STAGE 2STAGE 3STAGE
POWER 50% 30% 20%
DEFROSTING TIME 0.2T+20sec. 0.13T+30sec. 0.67T-50sec.
(fig. 2)
NOTE :
"CHECK" indicator will flash at half of defrosting time.
TOUCH CONTROL PANEL ASSEMBLY FOR R-24AT / R-22AT
OUTLINE OF TOUCH CONTROL PANEL
The touch control section consists of the following units as
shown in the touch control panel circuit.
(1) Control Unit
(2) Key Unit
Theprincipalfunctionsoftheseunitsandthesignalscommu-
nicated 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
Thiscircuitchangesoutputvoltageatthesecondaryside
of the low voltage (T1) transformer to voltages required
at each part by full wave rectifying circuit, constant
voltage circuit, etc..
2) ACL Circuit
This is an Auto-clear Circuit, i.e., a reset circuit, which
enables IC1 to be activated from initial state.
3) Power Synchronizing Signal Generating Circuit
Thisisacircuitforgeneratingpowersynchronizingsignal
by virtue of the secondary side output of transformer T1.
Thissignal isusedfor abasicfrequency totimeprocess-
ing and so on.
4) Clock Circuit
Thisisacircuitforcontrollingclockfrequencyrequiredfor
operating IC1.
5) IC1 (Main Processor)
This is a one-chip microcomputer, responsible for con-
trolling the entire control unit.
6) IC2 (Memory Processor)
This is a memory IC, responsible for memory function.
7) Display Circuit
This is a circuit for driving display tubes by IC1 output.
8) Key Input Circuit
This is a circuit for transmitting key input information to
IC1.
9) Sound-body Driving Circuit
This is a circuit for driving sound body by IC1 output.
10) Relay Driving Circuit
This is a circuit for driving output relay by IC1 output.
11) Stop Switch Circuit
This is a circuit for driving IC1 to detect door opening/
closing.
12) Exhaust Air Temperature Detecting Circuit
Thisisa circuitfortransmittingoutputchange ofthermis-
tor (Oven thermistor (1)) to IC1.
13) High Voltage Monitoring Circuit.
This circuit detects problems in the magnetron / high
voltage circuit by sensing a variation in the current
flowing through the primary winding of the high voltage
transformer.
During heating, the primary current of the high voltage
transformers also flows through the primary winding of
the current transformers CT1 and CT2. This causes a
current to be induced in the secondary windings of CT1/
CT2andresultsinanACvoltage whichisdeterminedby
R61/R62.
This AC voltage is then half wave rectified by D61/D62
and smoothed (filtered) by C61/C62.
HIGH VOLTAGE TRANSFORMER
HIGH VOLTAGE CIRCUIT
MAIN BODY SIDE
T/C SIDE
CT1 or CT2 RY3 or RY4
R61 or
R62 R65 or
R66
D61 or
D62 R63 or R64 Vc
C61 or C62
IC1
IN3 or
IN5 PORT
D63 or
D64

18
R-22AT
R-23AM
R-24AT
CONTROL PANEL ASSEMBLY FOR R-23AM
OUTLINE OF CONTROL PANEL
The control section consists of the following units as
shown in the control panel circuit.
(1) Control Unit
(2) Switch Unit
(3) Encoder Unit
Theprincipalfunctionsoftheseunitsandthesignalscommu-
nicated among them are explained below.
1. Control Unit
Signalofswitchtouchand ovenfunctioncontrol areall
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
This is an Auto-clear Circuit, i.e., a reset circuit, which
enables IC1 to be activated from initial state.
3) Power Synchronizing Signal Generating Circuit
This is a circuit for generating power synchronizing
signal by virtue of the secondary side output of trans-
former T1.
This signal is used for a basic frequency to time
processing and so on.
4) Clock Circuit
Thisis acircuitforcontrollingclockfrequencyrequired
for operating IC1.
5) IC1 (Main Processor)
This is a one-chip microcomputer, responsible for
controlling the entire control unit.
6) Display Circuit
This is a circuit for driving display tubes by IC1 output.
7) Switch Input Circuit
Thisisacircuitfortransmittingswitchinputinformation
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
thermistor (Oven thermistor (1)) 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,theprimarycurrentofthe
high voltage transformers also flows through the pri-
mary winding of the current transformers CT1 and
CT2. This causes a current to be induced in the
secondary windings of CT1/CT2 and results in an AC
voltage which is determined by R30/R31. This AC
voltage is then half wave rectified by D30/D31 and
smoothed(filtered)byC30/C31.ThisACvoltageisthe
input to the AN3 and AN4 ports of IC1, which deter-
mines if there is a magnetron / high voltage problem.
Figure T-1. High Voltage Monitoring Circuit For R-23AM
13) Magnetron Temperature Detecting Circuit.
This is a circuit for transmitting output change of
thermistor (Magnetron thermistor) to IC1.
14) Oven Cavity Temperature Detecting Circuit.
This is a circuit for transmitting output change of
thermistor (Oven thermistor (2)) to IC1.
2. Switch Unit
Theswitch unitiscomposedofamatrixcircuitinwhich
when a switch it touched, one of signals P43 - P45
generatedbytheLSI,ispassedthroughtheswitchand
returned to the LSI as one of signals P50 - P51.
3. Encoder
Theencoderconverts thesignalgenerated by LSIinto
thepulsesignal, andthepulse signalisreturned tothe
LSI.
HIGH VOLTAGE TRANSFORMER
HIGH VOLTAGE CIRCUIT
MAIN BODY SIDE
T/C SIDE
CT1 or CT2 RY2 or RY3
R30 or
R31 R34 or
R35
D30 or
D31 R32 or R33 Vc
C30 or C31
IC1
AN3 or
AN4 PORT
D32 or
D33
DESCRIPTION OF LSI FOR R-24AT / R-22AT
LSI(IZA646DR)
The I/O signal of the LSI(IZA646DR) is detailed in the following table.
Pin No. Signal I/O Description
1 VREF IN Reference voltage input terminal.
Areferencevoltage appliedtotheA/D converterinthe LSI. ConnectedtoGND.(0V)