Sharp Microwave Drawer SMD3070ASY User manual

1
SMD2470ASYSMD3070ASY
S45M383SMD307Y
MICROWAVE DRAWER MODEL
SERVICE MANUAL
TABLE OF CONTENTS
Page
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO
AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY.....................INSIDE FRONT COVER
BEFORE SERVICING.......................................................................................................INSIDE FRONT COVER
WARNING TO SERVICE PERSONNEL.................................................................................................................3
MICROWAVE MEASUREMENT PROCEDURE.....................................................................................................4
FOREWORD AND WARNING ...............................................................................................................................5
PRODUCT SPECIFICATIONS...............................................................................................................................6
SCHEMATICS......................................................................................................................................................10
TROUBLE SHOOTING GUIDE.............................................................................................................................11
TEST PROCEDURES..........................................................................................................................................13
MICROWAVE DRAWER DISASSEMBLY.............................................................................................................25
WIRING DIAGRAMS............................................................................................................................................32
PARTS LIST .........................................................................................................................................................33
PACKING AND ACCESSORIES..........................................................................................................................39
This document has been published to be used for after sales service only.The contents are subject to change without notice.
SHARP ELECTRONICS CORPORATION
SMD2470ASY SMD3070ASY
In the interest of user-safety the unit should be restored to its original condition and only parts identical to those specified should
be used.
WARNINGTO SERVICE PERSONNEL:
This service manual is intended for use by persons having electrical and mechanical training and a level
of knowledge of these subjects generally considered acceptable in the appliance repair trade. BSH Home
Appliances Corporation cannot be responsible, nor assume any liability, for injury or damage of any kind
arising from the use of this manual.
THIS SERVICE MANUAL IS FOR MODELS USINGTHE STANDBY POWER CIRCUIT.
MODELS NOT USING STANDBY POWER, PLEASE REFERTO SERVICE MANUAL:
(SMD2470AS & SMD3070AS) - S45M383SMD307

2
SMD2470ASY SMD3070ASY
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURINGSERVICINGTOAVOIDPOSSIBLEEXPOSURE
TO EXCESSIVE MICROWAVE ENERGY
(a) Do not operate or allow the oven to be operated with the door open.
(b) Makethefollowingsafetychecks onallovens tobeservicedbeforeactivatingthemagnetronorothermicrowave
source, and make repairs as necessary: (1) interlock operation, (2) proper door closing, (3) seal and sealing
surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and latches, (5) evidence of
dropping or abuse.
(c) Before turning on microwave power for any service test or inspection within the microwave generating compart-
ments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and
connections.
(d) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation and
transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before
the oven is released to the owner.
(e) A microwave leakage check to verify compliance with the Federal Performance Standard should be performed
on each oven prior to release to the owner.
BEFORE SERVICING
Before servicing an operative unit, perform a microwave emission check as per the Microwave Measure-
ment Procedure outlined in this service manual.
If microwave emissions level is in excess of the specified limit, contact SHARP ELECTRONICS
CORPORATION immediately @1-800-237-4277.
If the unit operates with the door open, service person should 1) tell the user not to operate the oven
and 2) contact SHARP ELECTRONICS CORPORATION and Food and Drug Administration's Center for
Devices and Radiological Health immediately.
ServicepersonnelshouldinformSHARPELECTRONICSCORPORATIONofanycertifiedunitfoundwith
emissions in excess of 4mW/cm2.The owner of the unit should be instructed not to use the unit until the
oven has been brought into compliance.

3
SMD2470ASYSMD3070ASY
WARNINGTO SERVICE PERSONNEL
Microwave Oven units contain circuitry capable of producing very high voltage and current,
contact with following parts
may result in a severe, possibly fatal, electrical shock.
(Example)
High Voltage Capacitor, High Voltage PowerTransformer, Magnetron, High Voltage Rectifier
Assembly, High Voltage Harness, Heating Elements, etc..
Read the Service Manual carefully and follow all instructions.
Before Servicing
1. Disconnect the power supply cord , and then
remove cabinet.
2. Open the drawer and keep it open.
3. Discharge high voltage capacitor.
WARNING: RISK OF ELECTRIC SHOCK.
DISCHARGETHE HIGH-VOLTAGE
CAPACITOR BEFORE SERVICING.
The high-voltage capacitor remains charged about 60
seconds after the oven has been switched off. Wait for
60 seconds and then short-circuit the connection of the
high-voltage capacitor (that is the connecting lead of the
high-voltage rectifier) against the chassis with the use of
an insulated screwdriver.
Whenever troubleshooting is performed the power supply
must be disconnected.It may, in some cases, be necessary
to connect the power supply after the outer case has been
removed, in this event:
1. Disconnect the power supply cord, and then remove
neccessary covers.
2. Open the drawer and keep it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power
transformer.
5. Ensure that the leads remain isolated from other
components and oven chassis by using insulation tape.
6. After that procedure, reconnect the power supply cord.
When the testing is completed,
1. Disconnect the power supply cord, and then remove
covers.
2. Open the drawer and keep it open.
3. Discharge high voltage capacitor.
4. Reconnect the leads to the primary of the power
transformer.
5. Reinstall the covers.
6. Reconnect the power supply cord.
7. Run the unit and check all functions.
After repairing
1. Reconnect all leads removed from components during
testing.
2. Reinstall the covers.
3. Reconnect the power supply cord.
4. Run the oven and check all functions.
Microwave ovens should not be operated empty.To test for
the presence of microwave energy within a cavity, place a
cup of cold water on the oven tray, close the drawer and set
the power to HIGH and set the microwave timer for two (2)
minutes.When the two minutes has elapsed (timer at zero)
carefullycheckthatthewaterisnowhot.Ifthewaterremains
coldcarryoutBeforeServicingprocedureandre-examine
the connections to the component being tested.
When all service work is completed and the oven is fully
assembled,themicrowavepoweroutputshouldbechecked
and a microwave leakage test should be carried out.

4
SMD2470ASY SMD3070ASY
MICROWAVE MEASUREMENT PROCEDURE
A. Requirements:
1) Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave
oven should not exceed 1mW/cm2at any point 5cm or more from the external surface of the oven, measured prior to
acquisition by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm2at any point 5cm or more
from the external surface of the oven.
2) Safety interlock switches:
Primary interlock relay switch shall prevent microwave radiation emission in excess of the requirement as above
mentioned.Secondary interlock relay and door sensing switch shall prevent microwave radiation emission in excess of
5 mW/cm2 at any point 5cm or more from the external surface of the oven.
B. Preparation for testing:
Before beginning the actual measurement of leakage, proceed as follows:
1) Make sure that the actual instrument is operating normally as specified in its instruction booklet.
Important:
Survey instruments that comply with the requirement for instrumentation as prescribed by the performance standard for
microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.
2) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5O C (68OF) in the center of the oven cavity.
The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-1/2 in.)
and made of an electrically nonconductive material such as glass or plastic.
Theplacing of thisstandard load inthe oven isimportant not onlyto protectthe oven, butalsotoinsure thatany leakage
is measured accurately.
3) Set the cooking control on Full Power Cooking Mode.
4) Close the drawer and select a cook cycle of several minutes.If the water begins to boil before the survey is completed,
replace it with 275 ml of cool water.
C. Leakage test:
Closed-drawer leakage test (microwave measurement):
1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the drawer and the body of the
oven.
2) Move the probe slowly, not faster than 1 in./sec. (2.5 cm/sec.) along the gap, watching for the maximum indication on
the meter.
3) Check for leakage at the drawer screen, sheet metal seams and other accessible positions where the continuity of the
metal has been breached (eg., around the switches, indicator, and vents).
While testing for leakage around the drawer, pull the drawer away from the front of the oven as far as is permitted by
the closed latch assembly.
4) Measure carefully at the point of highest leakage and make sure that the highest leakage is no greater than 4mW/cm2,
and that the primary interlock switch/secondary interlock relay does turn the oven OFF before any door movement.
NOTE: After servicing, record data on service invoice and microwave leakage report.

5
SMD2470ASYSMD3070ASY
SHARP ELECTRONICS CORPORATION
SHARP PLAZA, MAHWAH,
NEW JERSEY 07430-2135
SERVICE MANUAL
MICROWAVE DRAWER
SMD2470ASY & SMD3070ASY
FOREWORD
This Manual has been prepared to provide Sharp Electronics Corp.
Service Personnel and Service Information for the MICROWAVE
DRAWER using the Standby Power Circuit.
It is recommended that service personnel carefully study the entire
text of this manual so that they will be qualified to render satisfactory
customer service.
Check the interlock switches and the door seal carefully. Special
attention should be given to avoid electrical shock and microwave
radiation hazard.
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
personnel. DANGER
Certaininitialpartsareintentionallynotgroundedandpresent
a risk of electrical shock only during servicing. Service
personnel - Do not contact the following parts while the ap-
pliance is energized;
HighVoltage Capacitor,PowerTransformer,Magnetron,High
Voltage Rectifier Assembly, HighVoltage Harness;
If provided,Vent Hood, Fan assembly, Cooling Fan Motor.
All the parts marked “*” on parts list are used at voltages more
than 250V.
Removal of the outer wrap gives access to voltage above 250V.
Allthepartsmarked“ ”onpartslistmaycauseunduemicrowave
exposure, by themselves, or when they are damaged, loosened
or removed.
PRODUCT DESCRIPTION
SCHEMATICS
TEST PROCEDURE
MICROWAVE DRAWER
DISSASSEMBLY AND
ADJUSTMENT PROCEDURE
WIRING DIAGRAM
PARTS LIST
∆

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SMD2470ASY SMD3070ASY
ITEM DESCRIPTION
Power Requirements 120 Volts
14.5 Amperes, 1000 watts
60 Hz
Single phase, 3 wire grounded
Standby power: 1 Watt
Power Output 1000 watts (IEC TEST PROCEDURE)
Operating frequency of 2450MHz
Cooking Cavity Dimensions Width 17-11/32
Height 7-7/8"
1.2 Cubic Feet Depth 16-1/2"
SMD2470AS SMD3070AS
Outside Dimensions Width 23-7/8" 30"
Height 15-3/4" 15-3/4"
Depth 23-1/16" 23-1/16"
SMD2470AS SMD3070AS
Packing Case Dimensions Width 27-11/16" 33-5/8"
Height 21-1/2" 21-1/2"
Depth 29-1/16" 29-1/16"
(Packed unit) 86 Lbs 91lbs
Control Complement Touch Control System
Clock ( 1:00 - 12:59 )
Timer (0 - 99 min. 99 seconds)
Microwave Power for Variable Cooking
Repetition Rate;
P-HI..................................................Full power throughout the cooking time
P-90.....................................................................approx. 90% of Full Power
P-80.....................................................................approx. 80% of Full Power
P-70.....................................................................approx. 70% of Full Power
P-60.....................................................................approx. 60% of Full Power
P-50.....................................................................approx. 50% of Full Power
P-40.....................................................................approx. 40% of Full Power
P-30 ....................................................................approx. 30% of Full Power
P-20.....................................................................approx. 20% of Full Power
P-10.....................................................................approx. 10% of Full Power
P-0..................................................... No power throughout the cooking time
SENSOR: Popcorn, Reheat, Potatoes, Vegetables, Cook
SETTINGS: Beverage, Defrost, Melt/Soften, Keep Warm, Help/Settings,
Open/Close, Start/+30 sec, Stop/Clear, Power Level, Timer/Clock,
Number Pad
Oven Cavity Light Yes
Safety Standard UL Listed FCC Authorized
MICROWAVE DRAWER SPECIFICATION

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SMD2470ASYSMD3070ASY
GROUNDING INSTRUCTIONS
This oven is equipped with a three prong grounding plug.It must be
pluggedintoawallreceptaclethatisproperlyinstalledandgrounded
inaccordance withtheNational Electrical Codeandlocal codesand
ordinances.
Intheeventofanelectricalshortcircuit,groundingreducestheriskof
electric shock by providing an escape wire for the electric current.
WARNING: Improper use of the grounding plug can result
in a risk of electric shock.
Electrical Requirements
The electrical requirements are a 120 volt 60 Hz, AC only, 15 or
20 amp. fused electrical supply. It is recommended that a separate
circuit serving only this appliance be provided.When installing this
appliance, observe all applicable codes and ordinances.
Where a two-pronged wall-receptacle is encountered, it is the
personal responsibility and obligation of the customer to contact a
qualified electrician and have it replaced with a properly grounded
three-pronged wall receptacle or have a grounding adapter prop-
erly grounded and polarized. If an extension cord must be used,
it should be a 3-wire, 15 amp. or higher rated cord. Do not drape
over a counter top or table where it can be pulled on by children or
tripped over accidentally.
NOTE:
Thedirected featuresare disabledafteroneminutewhentheoven isnot inuse.Thesefeaturesareautomatically enabled
when the door is opened and closed or the STOP/ CLEAR pad is pressed.
3-Pronged
Plug
Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
CAUTION: DO NOT UNDER ANY CIRCUMSTANCES
CUT OR REMOVETHE ROUND GROUND-
INGPRONGFROMTHISPLUG. ALSO,"DO
NOT USE AN EXTENSION CORD".
OVEN DIAGRAM
GENERAL INFORMATION
KEY SHEET
2
13
5
4
7
8
6
1Hidden control panel & keysheet
2Waveguide cover DO NOT REMOVE
3Nameplate:opentheMicrowaveDrawer
fully. The label is beyond the back wall
of the microwave cavity facing up from
4Drawer sealing surfaces
5Drawer light
6Microwave Drawer guides
7Vent
8Menu label
9Keysheet

8
SMD2470ASY SMD3070ASY
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions dur-
ing oven operation.
OFF CONDITION
Closing the drawer activates the door sensing switch and
secondary interlock switch. (In this condition, the monitor
switch contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
control unit. (Page 10).
1. Thedisplaywillshowflashing"EnjoyYourDrawerTouch
Clear and Touch Clock".
Tosetanyprogramorsettheclock,youmustfirsttouch
the STOP/CLEAR pad.The display will clear, and " : "
will appear.
COOKING CONDITION
Program desired cooking time by touching the NUMBER
pads. Program the power level by touching the POWER
LEVEL pad and then a Number pad.
When the START pad is touched, the following operations
occur:
1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Page 10)
RELAY CONNECTED COMPONENTS
RY-1 Oven lamp/stir fan motor/fan motor
RY-2 Power transformer
RY-3 Stirrer motor
RY-4 Fan motor
2. 120 volts A.C. is supplied to the primary winding of the
power transformer and is converted to about 3.3 volts
A.C. output on the filament winding, and approximately
2370 volts A.C.on the high voltage winding.
3. The filament winding voltage heats the magnetron
filamentandtheH.V.winding voltage issentto avoltage
doubler circuit.
4. The microwave energy produced by the magnetron is
channelled through the waveguide into the cavity feed-
box, and then into the cavity where the food is placed
to be cooked.
5. Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped. The oven
will revert to the OFF condition.
6. When the drawer is opened during a cook cycle, the
monitorswitch,doorsensingswitch,secondaryinterlock
switch, relay (RY1) and primary interlock relay are
activatedwiththefollowingresults.Thecircuitstothestir
fan motor, the cooling fan motor, and the high voltage
componentsarede-energized,theovenlampremainson,
and the digital read-out displays the time still remaining
in the cook cycle when the door was opened.
7. Themonitorswitchelectricallymonitorsthe operationof
the secondary interlock switch and secondary interlock
relay and is mechanically associated with the drawer so
that it will function in the following sequence.
8. When the drawer opens from the closed position, the
primary interlock relay (RY2) and secondary interlock
switch open their contacts. And contacts of the relay
(RY1) remainsclosed.Then themonitor switch contacts
close.
9. When the drawer is closed from the open position, the
monitor switch contacts open first.Then the contacts of
the secondary interlock switch and door sensing switch
close.And contacts of the relay (RY1) open.
If the secondary interlock switch and primary interlock
relay (RY2) fail with the contacts closed when the drawer
is opened, the closing of the monitor switch contacts will
form a short circuit through the fuse, secondary interlock
switch, relay (RY1) and secondary interlock relay (RY2),
causing the fuse to blow.
POWER LEVEL P-0TO P-90 COOKING
When Variable Cooking Power is programmed, the 120
voltsA.C.issuppliedtothepowertransformerintermittently
through the contacts of relay (RY-2) which is operated by
the control unit within a 32 second time base. Microwave
power operation is as follows:
VARI-MODE ON TIME OFF TIME
Power 10(P-HI) 32 sec. 0 sec.
(100% power)
Power 9(P-90) 30 sec. 2 sec.
(approx. 90% power)
Power 8(P-80) 26 sec. 6 sec.
(approx. 80% power)
Power 7(P-70) 24 sec. 8 sec.
(approx. 70% power)
Power 6(P-60) 22 sec. 10 sec.
(approx. 60% power)
Power 5(P-50) 18 sec. 14 sec.
(approx. 50% power)
Power 4(P-40) 16 sec. 16 sec.
(approx. 40% power)
Power 3(P-30) 12 sec. 20 sec.
(approx. 30% power)
Power 2(P-20) 8 sec. 24 sec.
(approx. 20% power)
Power 1(P-10) 6 sec. 26 sec.
(approx. 10% power)
Power 0(P-0) 0 sec. 32 sec.
(0% power)
Note: TheON/OFFtimeratiodoesnotcorrespondwiththe
percentageofmicrowavepower,becauseapprox.2
seconds are needed for heating of the magnetron
filament.

9
SMD2470ASYSMD3070ASY
SENSOR COOKING CONDITION
Using the SENSOR function, food is cooked without figur-
ing time, power level or quantity. When the oven senses
enough steam from the food, it relays the information to its
microprocessor which will calculate the remaining cooking
timeandpowerlevelneededforbestresults. Whenthefood
is cooked, water vapor is developed. the sensor "senses"
the vapor and its resistance increase gradually. When the
resistance reaches the value set according to the menu,
supplementary cooking is started.
Thetimeofsupplementarycookingisdeterminedbyexperi-
ment with each food category and inputted into the LSI. An
example of how sensor works: (Potatoes)
1. Potatoes at room temperature.Vapor is emitted very
slowly.
MICROWAVE
2.Heat Potatoes. Moisture and humidity is emitted very
rapidly. You can smell the aroma as it cooks.
MICROWAVE
AH SENSOR
3.Sensor detects moisture and humidity and calculates
cooking time and variable power.
Cooking Sequence.
1. Touch one of the SENSOR pads.
NOTE: The oven should not be operated on sensor
immediately after plugging in the unit. Wait two
minutes before cooking on SENSOR.
2. The coil of shut-off relay (RY-1) is energized, but the
power transformer is not turned on.
3. After about 16 seconds, the cook relay (RY-2) is
energized. The power transformer is turned on,
microwaveenergyisproducedandfirststageisstarted.
The 16 seconds is the cooling time required to remove
any vapor from the oven cavity and sensor.
NOTE: During this first stage, do not open the drawer or
touch STOP/CLEAR pad.
4. When the sensor detects the vapor emitted from the
food,thedisplayswitchesovertotheremainingcooking
time and the timer counts down to zero.
At this time, the drawer may be opened to stir, turn or
season food.
5. Whenthetimerreacheszero,anaudiblesignalsounds.
Theshut-offrelayandcookrelayarede-energizedand
the power transformer, oven lamp, etc.are turned off.
6. OpeningthedrawerortouchingtheSTOP/CLEARpad,
the time of the day will reappear on the display and the
oven will revert to an OFF condition. When the timer
reaches zero, an audible signal sounds.

10
SMD2470ASY SMD3070ASY
SCHEMATIC (OFF CONDITION)
ＳＭ
ＯＬ
ＦＭ
ＲＹ１
ＲＹ２
ＲＹ３
HUMIDITY
SENSOR
NOISE SUPRESSION COIL
RESISTOR 470 kΩ 1/2W
LINE CROSS CAPACITOR 1.0μF 275V
LINE BYPASS CAPACITOR
0.0022μF 250V
LINE BYPASS CAPACITOR
0.0022μF 250V
FUSE
20A
FAN MOTOR
OVEN LAMP
MONITOR SWITCH
PRIMARY INTERLOCK RELAY
RECTIFIER MAGNETRON
POWER TRANSFORMAR
CAPACITOR
1.00μF
AC 2300V
STIRRER
MOTOR
Ｌ
Ｎ
Ａ７Ａ５
Ａ１ Ａ３
C
１
C
５
ＣＮ２０１ 1
ＣＮ１０１ 1
ＣＮ１０１ 3
ＣＮ２０１ 2
〜
CONTROL UNIT
Ｎ１
Ｎ２
Ｎ３
Ｎ４
Ｎ５
Ｎ６
Ｎ７
Ｎ８
SWITCHING REGULATOR
CIRCUITS SUBJECT TO CHANGE WITHOUT NOTICE.
OVEN THERMAL CUT-OUT
MG THERMAL CUT-OUT
〜 〜〜
SECONDARY INTELOCK SWITCH
ＤＭ
MICROWAVE DRAWER DOOR OPEN-CLOSE MOTOR
ＲＹ４
〜
DOOR SENSING SWITCH
C４
C２
Ｆ１
Ｆ２
Ｆ３
〜
〜
〜
〜
〜〜
VRS1
FUSE 1
RY2 (NO)
RY2 (COM)
RY1 (NO) RY1 (COM)

11
SMD2470ASYSMD3070ASY
TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
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
(A ~ P) which will be found in the "Test Procedure "section (starting on Page 13).
IMPORTANT: If the oven becomes inoperative because of a blown monitor fuse, check the primary switch, and monitor
switch, before replacing the monitor fuse. If the monitor fuse is replaced, the monitor switch must also be
replaced.
IMPORTANT: Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases,
be necessary to connect the power supply cord after the outer case has been removed, in this event,
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure that the leads remain isolated from other components and oven chassis by using insulation tape.
6. After that procedure, reconnect the power supply cord.
When the testing is completed
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.

12
SMD2470ASY SMD3070ASY
TROUBLESHOOTING CHART
CK = Check / RE = Replace
Display does not operate properly when
STOP/CLEAR key is touched.
(Buzzer should sound and ":" or time of
day should appear in display.)
Oven seems to be operating but little or
no heat is produced in oven load. (Food
incompletely cooked or not cooked at all
at end of cook cycle.)
AH sensor does not end during sensor
cooking condition. (Oven does not shut
o after a cup of water is boiling by
sensor cooking)
TEST PROCEDURE REFERENCE LETTER
SECONDARY/THIRD INTERLOCK SWITCH PRIMARY/THIRD OR STOP SWITCH
E & Q

13
SMD2470ASYSMD3070ASY TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST
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, Key-
boardUnitandSwitchingPowerSupply,andtroubleshootingbyunitreplacementisdescribedaccording
to the symptoms indicated.
Before testing,
1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER
DISASSEMBLY" page 25.
2) Open the drawer and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5) Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.
1. Keyboard Unit.
NOTE ;
1) Check Keyboard unit connection before replacement.
2) Reconnect all leads removed from components during testing.
3) Re-install the covers.
4) Reconnect the power supply cord after the covers are installed.
5) Run the oven and check all functions.
The following symptoms indicate a defective keyboard unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
If the Keyboard unit is defective.
1) Disconnect the power supply cord, and then remove covers.
2) Open the drawer and block it open.
3) Discharge high voltage capacitor.
4) Replace the Key Unit and/or Hidden Control Panel Hinge Assembly
5) Reconnect all leads removed from components during testing.
6) Re-install the covers.
7) Reconnect the power supply cord after the covers are installed.
8) Run the oven and check all functions.
2. Control Unit
The following symptoms indicate a defective control unit. Before replacing the control unit, perform
the Keyboard unit test (Procedure B) to determine if control unit is faulty.
2-1 In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-2 Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
3. Power Unit or Switching Power Supply
a) Fan motor, stirrer motor, oven lamp or electrical parts do not turn on or do not turn off.
b) Digital display on the control unit does not show anything.
When testing is completed,
1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER
DISASSEMBLY" page 25.
2) Open the drawer and block it open.
3) Discharge high voltage capacitor.
A TOUCH CONTROL PANEL ASSEMBLYTEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc.Therefore,

14
SMD2470ASY SMD3070ASY
C RELAYTEST
4) Reconnect all leads removed from components during testing.
5) Re-install the covers.
6) Reconnect the power supply cord after the covers are installed.
7) Run the oven and check all functions.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST
B KEY UNITTEST
1. Disconnect the power supply cord, and then remove outer case.
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensurethattheseleadsremainisolatedfromothercomponentsandovenchassisbyusinginsulation
tape.
6. After that procedure, re-connect the power supply cord.
7. RemovetheoutercaseandcheckvoltagebetweenpinsA1~A2whichshouldequal120Vacwithan
A.C.voltmeter , then pins C1-C5 which should be 24Vdc on the power unit with an D .C.voltmeter.
The meter should indicate both the 120 volts AC and 24 volts DC , if not check the switching power
supply voltages (and harness wires for break/ shorts). If it you have the voltages as stated above
and there is still no operation then check oven circuit RY1, RY2, RY3 and RY4 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, then
the control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx.26V D.C. Oven lamp / Common
RY2 Approx.25V D.C. Power transformer
RY3 Approx.26V D.C. Stirrer motor
RY4 Approx.26V D.C. Fan motor
8.Disconnect the power supply cord, and then remove outer case.
9.Open the door and block it open.
10.Discharge high voltage capacitor.
11.Reconnect all leads removed from components during testing.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4.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 drawer is closed and open when the
drawer is open. If the door sensing switch (stop switch) is good,
disconnect the flat ribbon cable that connects the key unit to the
control unit and make sure the drawer sensing switch is closed
(eitherclosethe drawerorshortthe doorsensingswitchconnecter).
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.
5. Reconnect all leads removed from components during testing.
6. Re-install the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
L-1
L-2
L-3
L-4
L-5
L-6
L-7
L-8
L-9
L-12
L-11
L-10
CN-L
OPEN
CLOSE
7
COOK
START
(+30 Sec)
TIMER
CLOCK
STOP
CLEAR
1
4
DEFROST
HELP/
SETTINGS
KEEP
WARM
8
5 2
3
POPCORN
BEVERAGE
MELT/
SOFTEN
9POTATOES
6POWER
LEVEL
0
REHEAT VEGATABLES

15
SMD2470ASYSMD3070ASY
WARNING : The oven should be fully assembled before following procedure.
(1) Place one cup of water in the center of the tray in the oven cavity.
(2) Close the drawer, touch the Defrost pad. Then select Steaks/Chops by touching the number pad
2. And touch the number pad 5.(Now, weight 0.5lb is set.) And then touch the start pad.
(3) The oven is in Defrost cooking condition.
(4) The oven will operate as follows
WEIGHT 1ST STAGE 2ND STAGE 3RD. STAGE
LEVEL TIME LEVEL TIME LEVEL TIME
0.5lb 60% 20sec. 40% 20sec. 30% 45sec.
(5)If improper operation is indicated, the control unit is probably defective and should be checked.
D DEFROSTTEST
E PROCEDURESTO BE TAKENWHENTHE FUSE IS OPEN
12.Re-install the outer case (cabinet).
13.Reconnect the power supply cord after the outer case is installed.
14.Run the oven and check all function.
To protect the electronic circuits, this model is provided with a fuse added to the primary on the
Noise Filter Unit. In addition, there is a non-replaceable fuse on the Switching Power Supply.
1. Fuse check and repairs.
1) Disconnect the power supply cord.
2) Remove the outer case cabinet.
3) Open the door and block it open.
4) Discharge high voltage capacitor.
5) If the Fuse is blown, replace fuse. Also do filter test per procedure N.
6) Make a visual inspection of the varistors on Noise Unit as well as Switching Power Supply.Check for
burned damage.If the varistor on Switching Power Supply has burned damage, replace Switching
Power Supply. If the varistors on Noise Unit has burned damage replace Noise Filter Unit .
8) Reconnect all leads removed from components during testing.
9) Re-install the outer case (cabinet).
10) Reconnect the power supply cord after the outer case is installed.
11) Run the oven and check all functions.
2. Follow the troubleshooting guide given below, if power is not restored after above check and
repairs are finished.
1) Disconnect the power supply cord.
2) Remove the outer case cabinet.
3) Open the door and block it open.
4) Discharge high voltage capacitor.
5) Disconnect the leads to the primary of the power transformer.
6) Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.
7) After that procedure, re-connect the power supply cord.
8) Follow the troubleshooting guide given below for repair.
STEPS OCCURANCE CAUSE OR CORRECTION
TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST
The rated AC voltage is NOT present
across Switching Power Supply CN101
(pins 1,3)
No power to Switching Power Supply. Check
for wire breaks, open thermal cutouts.
1
2
3
24Vdc is NOT present across
Switching Power Supply CN201
(pins 1,2)
24Vdc is present across
Power Unit CN-C (pins 1,5) /and/
The rated AC voltage is present across
Power Unit CN-A (pins 1,3)
Switching Power Supply not operating.Re-
place Switching Power Supply.
Normal power is being received by Power
Unit but Power Unit is not operating. Replace
Power Unit.

16
SMD2470ASY SMD3070ASY
WARNING : The oven should be fully assembled before following procedure.
(1) The oven should be plugged in at least two minutes before sensor cooking.
(2) Room temperature should not exceed 95οF (35οC).
(3) The unit should not be installed in any area where heat and steam are generated.The unit should not be
installed,forexample, nexttoaconventionalsurfaceunit.Refertothe“INSTALLATIONINSTRUCTIONS”
of the operation manual.
(4) Exhaust vents are provided on the back of the unit for proper cooling and air flow in the cavity.To permit
adequate ventilation, be sure to install so as not to block these vents.There should be some space for
air circulation.
(5) Be sure the exterior of the cooking container and the interior of the oven are dry.Wipe off any moisture
with a dry cloth or paper towel.
(6) The Sensor works with food at normal storage temperature. For example, chicken pieces would be at
refrigerator temperature and canned soup at room temperature.
(7) Avoid using aerosol sprays or cleaning solvents near the oven while using Sensor settings.The sensor
will detect the vapor given of by the spray and turn off before food is properly cooked.
(8) If the sensor has not detected the vapor of the food, ERROR will appear and the oven will shut off.
Water load cooking test
WARNING : The oven should be fully assembled before following procedure.
Make sure the oven has been plugged in at least two minutes before checking sensor cook operation.The
cabinet should be installed and screws tightened.
(1) Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter measuring cup.
(2) Place the container on the center of tray in the oven cavity.
(3) Close the drawer.
(4) Touch theTIMER/CLOCK pad once, the POWER LEVEL pad twice and the START pad once.And touch
the number pad 1 once and the number pad 4 once. Now, the oven is in the sensor cooking condition,
and "AH20" and "ON" will appear in the display.
(5) The oven will operate for the first 16 seconds, without generating microwave energy.
NOTE:ERROR will appear if the door is opened or STOP/CLEAR pad is touched during first stage of sensor
cooking.
(6) After approximately 16 seconds, microwave energy is produced.
If ERROR is displayed or the oven does not turn off, replace the AH sensor or check the control unit, refer to
explanation below. If the oven stops after 5 minutes and no ERROR code is displayed, then the AH sensor
is normal. Check other parts except the AH sensor.
TESTING METHOD FOR AH SENSOR AND/OR CONTROL UNIT
To determine if the sensor is defective, the simplest method is to replace it with a new replacement
sensor.
(1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER
DISASSEMBLY" page 25.
(2) Open the drawer and block it open.
(3) Discharge high voltage capacitor.
(4) Remove the AH sensor.
(5) Install the new AH sensor.
(6) Reconnect all leads removed from components during testing.
(7) Re-install the covers.
(8) Reconnect the power supply cord after the covers are installed.
(9) Reconnect the oven to the power supply and check the sensor cook operation as follows:
9-1. Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter measuring cup.
F AH SENSORTEST
Checking the initial sensor cooking condition
9) Disconnect the power supply cord, and then remove outer case.
10) Open the door and block it open.
11) Discharge high voltage capacitor.
12) Reconnect all leads removed from components during testing.
13) Re-install the outer case (cabinet).
14) Reconnect the power supply cord after the outer case is installed.
15) Run the oven and check all functions.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST

17
SMD2470ASYSMD3070ASY
TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST
9-2. Place the container on the center of tray in the oven cavity.
9-3. Close the drawer.
9-4. Touch theTIMER/CLOCK pad once, the POWER LEVEL pad twice and the START pad once.And
touch the number pad 1 once and the number pad 4 once.
9-5. The control panel is in automatic Sensor operation.
9-6. The oven turns off automatically, and the time for detecting moisture will be displayed.
If new sensor does not operate properly, the problem is with the control unit, and refer to explanation be-
low. CHECKING CONTROL UNIT
(1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER
DISASSEMBLY" page 25.
(2) Open the drawer and block it open.
(3) Discharge high voltage capacitor.
(4) Disconnect the sensor connector that is mounted to control panel.
(5) Then connect the dummy resistor circuit (see fig.) to the sensor connector of control panel.
(6) Disconnect the leads to the primary of the power transformer.
(7) Ensure that these leads remain isolated from other components and oven chassis by using insulation
tape.
(8) After that procedure, re-connect the power supply cord.
(9) Check the sensor cook operation proceed as follows:
9-1. Close the door.Touch theTIMER/CLOCK pad once, the POWER LEVEL pad twice and the START
pad once.And touch the number pads 1 once and the number pad 4 once.
9-2.The control panel is in the sensor cooking operation.
9-3. Afterapproximately25seconds,pushplungerofselectswitchformorethan3seconds.Thiscondition
is same as judgement by AH sensor.
9-4. After approximately 3 seconds, the display shows “ X X . X X “ which is the time for detecting
moisture.
If the above is not the case, the control unit is probably defective.
If the above is proper, the AH sensor is probably defective.
(10) Disconnect the power supply cord, and then remove covers.
(11) Open the drawer and block it open.
(12) Discharge high voltage capacitor.
(13) Disconnect the dummy resistor circuit from the sensor connector of control panel.
(14) Carry out necessary repair.
(15) Reconnect all leads removed from components during testing and repairing.
(16) Re-install the covers.
(17) Reconnect the power supply cord after the outer case is installed. Run the oven and check all
functions.
(18) Carry out "Water load cooking test" again and ensure that the oven works properly.
R1, R2 : 22Ω± 1% 1/2W
R3 : 4.3kΩ± 5% 1/4W
R4 : 1MΩ± 5% 1/4W
Plunger
NC
NO
COM
COM NO
NC
R3 R4
R1
R2
1
2
3
F-1
F-2
F-3
To connector (F)
on Control Unit.
CONNECTOR

18
SMD2470ASY SMD3070ASY
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. To test for an open filament, isolate the magnetron from the high voltage circuit.A continuity check across
the magnetron filament leads should indicate less than 1 ohm.
5. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads
and chassis ground.This test should indicate an infinite resistance. If there is little or no resistance the
magnetron is grounded and must be replaced.
6. Reconnect all leads removed from components during testing.
7. Reassemble the unit.
8. Reconnect the power supply cord.
9. Run the oven and check all functions.
MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled condition.
HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD BE
OBSERVED.
Power output of the magnetron can be measured by performing a water temperature rise test. This test
should only be used if above tests do not indicate a faulty magnetron and there is no defect in the following
components or wiring: This test will require a 16 ounce (453cc) measuring cup and an accurate mercury
thermometer or thermocouple type temperature tester. For accurate results, the following procedure must
be followed carefully:
1. Fill the measuring cup with 16 oz. (453cc) of tap water and measure the temperature of the water with
a thermometer or thermocouple temperature tester. Stir the thermometer or thermocouple through the
water until the temperature stabilizes. Record the temperature of the water.
2. Place the cup of water in the oven.Operate oven at POWER 10(HIGH) selecting more than 60 seconds
cook time.Allow the water to heat for 60 seconds, measuring with a stop watch, second hand of a watch
or the digital read-out countdown.
3. Remove the cup from the oven and again measure the temperature, making sure to stir the thermometer
or thermocouple through the water until the maximum temperature is recorded.
4. Subtract the cold water temperature from the hot water temperature.The normal result should be 28οto
54οF (16οto 30οC) rise in temperature. If the water temperatures are accurately measured and tested
for the required time period the test results will indicate if the magnetron tube has low power output (low
rise in water temperature) which would extend cooking time or high power output (high rise in water
temperature) which would reduce cooking time. Because cooking time can be adjusted to compensate
for power output, the magnetron tube assembly should be replaced only if the water temperature rise
test indicates a power output well beyond the normal limits.The test is only accurate if the power supply
line voltage is 120 volts and the oven cavity is clean.
G MAGNETRON ASSEMBLYTEST
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. A continuity check across the DM Fuse terminals should indicate a closed circuit unless the
temperature of the DM Fuse reaches approximately 293οF(145οC).
An open thermal cut-out indicates overheating of the oven, exchange the oven DM Fuse and check
inside of oven cavity and for improper setting of cooking time or operation of control unit.Check for
restricted air flow through the vent holes of the oven cavity, especially the cooling fan and air guide.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the unit and check all functions.
CAUTION: IFTHEDM FUSE INDICATES ANOPEN CIRCUIT AT ROOMTEMPERATURE, REPLACE
DM FUSE
H DM FUSETEST
1. Disconnect the power supply cord.
Refer to the disassembly instructions found on Page 22.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST

19
SMD2470ASYSMD3070ASY
I SECONDARY INTERLOCK SWITCHTEST
STOP SWITCH
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO)
terminal of the switch.The meter should indicate an open circuit with the drawer open and a closed
circuit with the drawer closed. If improper operation is indicated, replace the stop switch.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
NOTE: If the stop switch contacts fail in the open position and the door is closed, the cooling fan motor,
stirrer motor and oven light will be activated by RY1.
J STOP SWITCHTEST
K MONITOR SWITCH TEST
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Before performing this test, make sure that the secondary interlock switch is operating, according to
the above SwitchTest Procedure.Disconnect the wire lead from the monitor switch (COM) terminal.
Check the monitor switch operation by using the ohmmeter as follows.When the drawer is open,
the meter should indicate a closed circuit.When the monitor switch actuator is pushed by a screw
driver through the lower latch hole on the front plate of the oven cavity with the drawer opened (in
this condition the plunger of the monitor switch is pushed in), the meter should indicate an open
circuit. If improper operation is indicated, the switch may be defective and both the monitor switch,
plus fuse will need to be replaced. After testing the monitor switch, reconnect the wire lead to the
monitor switch (COM) terminal and check the continuity of the monitor circuit.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Isolatetheswitchandconnecttheohmmetertothecommon(COM.)andnormally
open (NO) terminal of the switch.The meter should indicate an open circuit with
thedraweropen anda closed circuitwith thedrawerclosed.If improperoperation
is indicated, replace the secondary interlock switch.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
Screw Driver
Ohmmeter

20
SMD2470ASY SMD3070ASY
TEST PROCEDURES
PROCEDURE
LETTER COMPONENTTEST
M POWERTRANSFORMERTEST
1. Disconnect the power supply cord.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the primary input terminals and measure the resistance of the transformer with an
ohmmeter. Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance
of the primary coil should be less than 1 ohm and the resistance of the high voltage coil should
be approximately 82 ohms (+ or - 10%); the resistance of the filament coil should be less than 1
ohm.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
CAUTION:
(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO
MEASURE THE FILAMENT AND HIGH VOLTAGE.)
2. Open the drawer and block it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Ifthemonitorfuseisblownwhenthedrawerisopened,checktheprimaryinterlockswitch,secondary
interlockswitchand monitorswitchaccordingtothe"TESTPROCEDURE"forthoseswitchesbefore
replacing the blown monitor fuse.
CAUTION: BEFOREREPLACINGABLOWNMONITORFUSE,TESTTHESECONDARYINTERLOCK
SWITCH, STOP SWITCH AND MONITOR SWITCH FOR PROPER OPERATION.
If the monitor fuse is blown by improper switch operation, the monitor fuse and monitor switch must
be replaced with "monitor fuse and monitor switch assembly" part number FFS-BA018/KIT, even if
the monitor switch operates normally.The monitor fuse and monitor switch assembly is comprised
of a 20 ampere fuse and switch.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
L BLOWN MONITOR FUSE TEST
1. Disconnect the power supply cord.