Sharp R-1500AT User manual

CHAPTER 1. BEFORE SERVICING
CHAPTER 2. WARNING TO SERVICE PERSONNEL
CHAPTER 3. PRODUCT DESCRIPTION
CHAPTER 4. OPERATION
CHAPTER 5. TROUBLESHOOTING GUIDE
CHAPTER 6. TEST PROCEDURES
CHAPTER 7. TOUCH CONTROL PANEL ASSEMBLY
CHAPTER 8. PRECAUTIONS FOR USING LEAD-
FREE SOLDER
CHAPTER 9. COMPONENT REPLACEMENT AND
ADJUSTMENT PROCEDURE
CHAPTER 10. MICROWAVE MEASUREMENT
CHAPTER 11. TEST DATA AT A GLANCE
CHAPTER 12. CIRCUIT DIAGRAMS
Parts List
S5902R210ATPH
SERVICE MANUAL
R1500AT
CONTENTS
This document has been published to be used for
after sales service only.
The contents are subject to change without notice.
TopPage
COMMERCIAL
MICROWAVE OVEN
R-1500AT
R-2100AT
MODELS
In the interests of user-safety the oven should be restored to its original condition and only parts identical to those
specified should be used.

CONTENTS
CHAPTER 1. BEFORE SERVICING
[1] GENERAL IMPORTANT INFORMA-
TION ........................................................... 1-1
[2] WARNING................................................... 1-1
[3] CAUTION MICROWAVE RADIATION ........ 1-2
CHAPTER 2. WARNING TO SERVICE PERSON-
NEL
CHAPTER 3. PRODUCT DESCRIPTION
[1] SPECIFICATIONS ...................................... 3-1
[2] APPEARANCE VIEW ................................. 3-1
[3] INSTALLATION INFORMATION ................. 3-2
CHAPTER 4. OPERATION
[1] DESCRIPTION OF OPERATING SE-
QUENCE .................................................... 4-1
[2] DESCRIPTION AND FUNCTION OF
COMPONENTS .......................................... 4-2
CHAPTER 5. TROUBLESHOOTING GUIDE
CHAPTER 6. TEST PROCEDURES
[1] A: MAGNETRON TEST .............................. 6-1
[2] B: POWER TRANSFORMER TEST ........... 6-2
[3] C: HIGH VOLTAGE RECTIFIER (1)
AND/OR (2) TEST ...................................... 6-2
[4] D: HIGH VOLTAGE CAPACITOR (C1)
AND/OR (C2) TEST.................................... 6-3
[5] E: SECONDARY INTERLOCK SWITCH
(SW1) AND/OR (SW2) TEST ..................... 6-3
[6] F: PRIMARY INTERLOCK SYSTEM
TEST........................................................... 6-3
[7] G: MONITOR SWITCH (SW3) AND/OR
(SW4) TEST................................................ 6-3
[8] H: FUSE F8 TEST ...................................... 6-4
[9] I: WEAK POINT (FOR FAN MOTOR OR
EXHAUST FAN) TEST................................ 6-4
[10] J: WEAK POINT (IN NOISE FILTER)
TEST........................................................... 6-4
[11] K: TEMPERATURE FUSE TEST ................ 6-4
[12] L: MAGNETRON THERMISTOR TEST...... 6-4
[13] M: EXHAUST THERMISTOR TEST ........... 6-4
[14] N: NOISE FILTER TEST............................. 6-5
[15] O: KEY UNIT TEST .................................... 6-5
[16] P: CONTROL UNIT TEST .......................... 6-5
[17] Q: POWER UNIT TEST .............................. 6-6
[18] R: RELAY UNIT TEST ................................ 6-6
[19] S: ANTENNA SENSOR TEST .................... 6-7
[20] T: MICROWAVE SENSOR TEST................ 6-7
CHAPTER 7. TOUCH CONTROL PANEL ASSEM-
BLY
[1] SPECIAL FUNCTION FOR SERVICING..... 7-1
[2] SERVICING FOR BRINTED WIRING
BOARDS..................................................... 7-7
CHAPTER 8. PRECAUTIONS FOR USING LEAD-
FREE SOLDER
CHAPTER 9. COMPONENT REPLACEMENT AND
ADJUSTMENT PROCEDURE
[1] WARNINGS ................................................ 9-1
[2] OUTER CASE AND REAR COVER RE-
MOVAL........................................................ 9-1
[3] POWER TRANSFORMERS (1) AND/
OR (2) REMOVAL....................................... 9-2
[4] MAGNETRONS (1) AND/OR (2) RE-
MOVAL........................................................ 9-2
[5] MAGNETRON THERMISTOR ASSEM-
BLY REPLACEMENT ................................. 9-2
[6] HIGH VOLTAGE CAPACITOR AND
HIGH VOLTAGE RECTIFIER ASSEM-
BLY REMOVAL ........................................... 9-2
[7] POWER SUPPLY CORD REPLACE-
MENT.......................................................... 9-3
[8] HOW TO RELEASE THE POSITIVE
LOCK CONNECTOR. ................................. 9-3
[9] EXHAUST FAN REMOVAL......................... 9-3
[10] FAN MOTORS REMOVAL .......................... 9-4
[11] ANTENNA MOTORS (UPPER AND
LOWER) REMOVAL ................................... 9-4
[12] POWER UNIT REMOVAL........................... 9-4
[13] CONTROL PANEL ASSEMBLY AND
CONTROL UNIT REMOVAL....................... 9-4
[14] RELAY UNIT REMOVAL............................. 9-4
[15] DOOR SENSING SWITCH (SW5)/SEC-
ONDARY INTERLOCK SWITCHES
(SW1, SW2) AND MONITOR SWITCH-
ES (SW3, SW4) REPLACEMENT .............. 9-5
[16] OOR SENSING SWITCH (SW5)/SEC-
ONDARY INTERLOCK SWITCHES
(SW1, SW2) AND MONITOR SWITCH-
ES (SW3, SW4) ADJUSTMENT ................. 9-5
[17] DOOR REPLACEMENT ............................. 9-5
[18] DOOR DISASSEMBLY ............................... 9-6
[19] OVEN LAMP AND LAMP SOCKET RE-
MOVAL........................................................ 9-8
CHAPTER 10. MICROWAVE MEASUREMENT
CHAPTER 11. TEST DATA AT A GLANCE
CHAPTER 12. CIRCUIT DIAGRAMS
[1] Oven Schematic........................................ 12-1
[2] Figure S-1. Pictorial Diagram.................... 12-3
[3] Figure S-2. Switching Power Supply Unit
Circuit........................................................ 12-6
[4] Figure S-3. Relay Unit Circuit ................... 12-7
[5] Figure S-4. Control Unit/ Antenna sen-
sor/ Microwave Sensor Circuit .................. 12-8
[6] Figure S-5. Printed Wiring Board .............. 12-9
Parts List

R1500AT
1 – 1
R1500AT ServiceManual

CHAPTER 1. BEFORE SERVICING
[1] GENERAL IMPORTANT INFORMATION
This Manual has been prepared to provide Sharp Corp. Service engineers with Operation and Service Information.
It is recommended that service engineers carefully study the entire text of this manual, so they will be qualified to render satisfactory customer ser-
vice.
[2] 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.
Removal of the outer wrap gives access to potentials above 250V.
All the parts marked “*” on parts list may cause undue microwave exposure, by themselves, or when they are damaged,
loosened or removed.
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

R1500AT
1 – 2
[3] CAUTION MICROWAVE RADIATION
Personnel should not be exposed to the microwave energy which may radiate from the
magnetron or other microwave generating devices if it is improperly used or connected.
All input and output microwave connections, waveguides, flanges and gaskets must be
secured.
Never operate the device without a microwave energy absorbing load attached.
Never look into an open waveguide or antenna while the device is energized.

R1500AT
2 – 1
R1500AT ServiceManual

CHAPTER 2. WARNING TO SERVICE PERSONNEL
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING: AGAINST THE CHARGE OF THE
HIGH-VOLTAGE CAPACITOR
GB Microwave ovens contain circuitry capable of producing very high voltage and current, contact with following
parts will result in electrocution.
High voltage capacitor, High voltage transformer, Magnetron, High voltage rectifier assembly, High voltage
harness.
REMEMBER TO CHECK 4R
1) Reconnect all leads removed from components dur-
ing testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. Check all functions.
NL Magnetronovens bevatten circuits die een zeer hoge spanning en stroom kunnen voortbrengen. Contact met de
volgende onderdelen kan elektrocutie tot gevolg hebben.
Hoogspanningscondensator, hoogspanningstransformator, magnetron, hoogspanningsgelijkrichter, hoogspannings
kabelboom.
VERGEET DE VOLGENDE 3 STAPPEN NIET
1) Haal de stekker uit het stopcontact.
2) Open de deur en zorg ervoor dat hij niet dicht kan vallen.
3) Ontlaad de hoogspanningscondensator.
PAS OP VOOR DE ELECTRISCHE LADING VAN DE
HOOGSPANNINGSCONDENSATOR
VERGEET DE VOLGENDE 4 STAPPEN NIET
1) Sluit de draden weer aan diezijn losgehaald voor de test.
2) Plaats de buitenmantel weer om het toestel heen (kabinet).
3) Stop de stekker weer in het stopcontact.
4) Zet de oven aan. Controleer alle functies.
Wanneer alle reparaties zijn uitgevoerd en de oven weer in
elkaar is gezet, moet de het magnetronvermogen worden
gecontroleerd en moet worden gecontroleerd of er geen
microgolflekkage is.
The high-voltage capacitor remains charged about
60 econds after the oven has been switched off. Wait
for 60 seconds and then short-circuit the connection
ofthe high-voltage capacitor (that is, of the connectin-
glead of the high-voltage rectifier) against the chas-
siswith the use of an insulated screwdriver.
Sharp recommend that wherever possible fault-findingis
carried out with the supply disconnected. It may in,some
cases, be necessary to connect the supply after the out-
er case has been removed, in this event carry out 3D
checks and then disconnect the leads to the primary of
the high voltage transformer. Ensure that these leadsre-
main isolated from other components and the oven chas-
sis. (Use insulation tape if necessary.) When the testing
is completed carry out 3D checks and reconnectthe
leads to the primary of the high voltage transformer.
Microwave ovens should not be run empty. To test for
the presence of microwave energy within a cavity, place
a cup of cold water on the oven turntable, close the door
and set the power to HIGH and set the microwave timer
for two (2) minutes. When the two minutes has elapsed
(timer at zero) carefully check that the water is now hot.If
the water remains cold carry out 3D checks and re-
examine the connections to the component being tested.
When all service work is completed, and the oven is
fully assembled, the microwave power output should
be checked and a microwave leakage test should be
carriedout.
De hoogspanningscondensator blijft nog ongeveer 60
seconden lang opgeladen, nadat de oven is uitgeschakeld.
Wacht 60 seconden voordat u de verbinding van de
hoogspannings-condensator (m.a.w. de verbindingsdraad
van de hoogspanningsgelijkrichter) met een ge soleerde
schroevedraaier kortsluit tegen het chassis.
Sharp beveelt ten sterkste aan dat, voor zover mogelijk,
defecten worden opgespoord wanneer de stekker uit het
stopcontact is gehaald. Soms is het nodig om de stroomtoevoer
weer tot stand te brengen nadat de buitenmantel verwijderd is.
Herhaal dan de bovengenoemde 3 stappen en haal
deelectrische draden uit de primaire zijde van de
vermogenstransformator. Zorg ervoor dat deze draden
ge•soleerd blijven van andere elementen en van het chassis
van de oven. (Gebruik zo nodig isolatieband.) Wanneer de
test is uitgevoerd, herhaalt u de bovenstaande 3 stappen en
verbindt u de electrische draden weer aan de primaire zijde
van de vermogenstransformator.
Magnetronovens mogen niet leeg aangezet worden. Om te
controleren of er microgolf-energie binnen de oven wordt
geproduceerd, plaatst u een mok met koud water op de
draaitafel van de oven, sluit de deur, zet de oven op HIGH en
stelt de klok van de magnetron in op twee (2) minuten. Wanneer
de twee minuten voorbij zijn (klok staat op nul), controleert u
voorzichtig of het water heet is. Indien het water nog steeds
koud is, herhaalt u de allereerste drie stappen en controleer
nogmaals de aansluitingen naar de geteste onderdelen.

R1500AT
2 – 2

R1500AT
2 – 3

R1500AT
3 – 1
R1500AT ServiceManual

CHAPTER 3. PRODUCT DESCRIPTION
[1] SPECIFICATIONS
[2] APPEARANCE VIEW
1. OVEN
1. Touch control panels
2. Door latch openings
3. Ceramic shelf
4. Oven lamp
5. Air intake openings
6. Air intake flter
7. Door seals and sealing surfaces
8. Door hinges
9. Oven door with see-through window
10. Door latches
11. Door handle
12. Service window for replacing the oven light bulb
13. Ventilation openings
14. Power supply cord
15. Mounting plate
16. Screw for mounting plate
17. Splash cover
ITEM DESCRIPTION
Power Requirements Single phase 230V, 50Hz, 3 wire earthed
Power Consumption R-1500AT 2.3kW
R-2100AT 3.0kW
Power Output R-1500AT 1500W Operating frequency 2450 MHz (IEC60705)
R-2100AT 2100W Operating frequency 2450 MHz (IEC60705)
Outside Dimensions 445mm (W) x 573mm (D) x 346mm (H) (including feet)
Cooking Cavity Dimensions 356mm (W) x 326mm (D) x 177mm (H)
Control Complement
Touch Control System
Digital Display
Ten number Pads
STOP/CLEAR pad
CUSTOM SETTING pad
START pad
POWER LEVEL pad (Power level: 0 to 100%)
MANUAL/ REPEAT pad
DOUBLE/ TRIPLE QUANTITY pad
EXPRESS DEFROST pad
SET MEMORY pad
Weight Approx. 33.5 kg
13
16
12
14
15
76
1
1
2
8
9
10 43
17
11
5

R1500AT
3 – 2
2. TOUCH CONTROL PANEL
[3] INSTALLATION INFORMATION
When this commercial microwave oven is installed near other commercial electrical appliances, connect a lead wire to each equivalent potential ter-
minal 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.
Figure A-1
12 3456
89
56
7
1. MANUAL/REPEAT pad
2. POWER LEVEL pad
3. DOUBLE/TRIPLE QUANTITY pad
7. Ten number pads
8. EXPRESS DEFROST pad
9. SET MEMORY pad
DOOR SIDE
4. CUSTOM SETTING pad
5. STOP/CLEAR pad
6. START pad
COMMERCIAL MICROWAVE OVEN OTHER COMMERCIAL
ELECTRICAL APPLIANCE
Lead wire
Equipotential marking
Earth angle
(Equivalent potential terminal)
Equivalent
potential terminal
Screw
Washer
Lead wire

R1500AT
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R1500AT ServiceManual

CHAPTER 4. OPERATION
[1] DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during oven operation.
1. OFF CONDITION
1. When the oven is plugged in with the door closed, the line voltage
is supplied to the noise filter. And the display shows nothing.
(Refer to Figure O-1(a))
2. When the door is opened with plugged in, the contacts (COM-NC)
of the secondary interlock switch (1) SW1 are closed. And the line
voltage is supplied to the switching power supply unit (power unit),
the oven lamp and antenna motors. Then the switching power sup-
ply unit supplies D.C. voltage (approx.24V) to the relay unit. And
the contacts of the relay RY-4 on the relay unit are closed. The dis-
play shows “0”.
(Refer to Figure O-1(b))
3. When the door is closed, the contacts (COM-NC) of the secondary
interlock switch SW1 are opened. Because the contacts of the relay
RY-4 has been closed, the line voltage is kept supplying to the
switching power supply unit, oven lamp and antenna motors. And
the switching power supply unit keeps supplying D.C. voltage to the
relay unit. The display shows ”0”.
(Refer to Figure o-1(c))
NOTE: The contacts of the relay RY-4 will open if the oven is not oper-
ated for 3 minutes or more. And the oven condition will go
back to one of Figure O-1(a).
2. COOKING CONDITION
(For details, refer to Figure O-2)
Press MANUAL/ REPEAT pad. Enter cooking time by pressing the
number pads. Press the POWER LEVEL pad. Enter power level by
pressing the number pad. When the START pad is pressed, the follow-
ing operations occur:
1. The contacts of relays are closed. And the oven lamp and the
antenna motors connected to the relays are turned on (For details,
refer to Figure O-2).
2. D.C. voltage is supplied to the fan motors, exhaust fan and exhaust
motor from the control unit.
3. Rated voltage is supplied to the primary winding of the power trans-
former and is converted to about 3.00 volts output on the filament
winding, and approximately 2320 volts on the high voltage winding.
4. The filament winding voltage heats the magnetron filament and the
H.V. winding voltage is sent to a voltage doubler circuit.
5. 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.
6. Upon completion of the cooking time, the oven will revert to the
OFF condition. The fan motors, exhaust fan and the exhaust motor
will operate at least for 1 minute. Because the contacts of RY4
have been closed. And also the oven lamp and antenna motors will
operated at the same time.
7. When the door is opened during a cook cycle, monitor switches
SW3 & SW4, door sensing switch SW5, secondary interlock
switches SW1, SW2 and primary interlock relay RY1 are activated
with the following results. The circuits to the high voltage compo-
nents are de-energized.
8. The monitor switch SW3 is electrically monitoring the operation of
the secondary interlock switch SW1 and primary interlock relay
RY1, and monitor switch SW4 is electrically monitoring the opera-
tion of the secondary interlock switch SW2 and primary interlock
relay RY1, and monitor switches SW3, SW4 are mechanically
associated with the door so that it will function in the following
sequence.
1) When the door opens from a closed position, the contacts of the
primary interlock relay RY1 and the contacts (COM-NO) of sec-
ondary interlock switches SW1, SW2 open. Then the monitor
switches SW3, SW4 contacts close.
2) (When the door is closed from the open position, the monitor
switches SW3, SW4 contacts first open, and then the contacts
(COM-NO) of the secondary interlock switches SW1, SW2
close.
If the secondary interlock switches SW1, SW2 and primary interlock
relay RY1 fail with their contacts closed when the door is opened, the
closing of the monitor switches SW3, SW4 contacts will form a short
circuit through the secondary interlock switches SW1, SW2 and pri-
mary interlock relay RY1, causing the fuse F8 to blow.
3. VARIABLE POWER COOKING
When Variable Cooking Power is programmed, the rated voltage A.C.
is supplied to the power transformer intermittently through the contacts
of relay (RY-2, RY-3). Relays RY-2 and RY-3 are operated by the con-
trol unit within an interval 54 second time base. Microwave power
operation is as follows:
NOTE: The ON/OFF time ratio does not exactly correspond with
the percentage of microwave power, because approx. 3
seconds are needed for heating of the magnetron fila-
ment.
4. TWO MAGNETRON OPERATION SYSTEM
Two magnetrons MG1, MG2 are equipped in order to get higher micro-
wave power output. The primary windings of the power transformers
T1, T2 are connected so that each magnetron can be oscillated alter-
natively according to the frequency of the power supply. Refer to the
Figure B-1.
Figure B-1. Operation of Magnetron
VARI-MODE ON TIME OFF TIME
100% 54 sec. 0 sec.
90% 49 sec. 5 sec.
80% 45 sec. 9 sec.
70% 40 sec. 14 sec.
60% 36 sec. 18 sec.
50% 29 sec. 25 sec.
40% 24 sec. 30 sec.
30% 18 sec. 36 sec.
20% 13 sec. 41 sec.
10% 9 sec. 45 sec.
0% 0 sec. 54 sec.
COMMERCIAL
FREQUENCY
(60HZ)
POWER OUTPUT
BY MAGNETRON MG1
POWER OUTPUT
BY MAGNETRON MG2
OPERATION OF
MAGNETRON

R1500AT
4 – 2
[2] DESCRIPTION AND FUNCTION OF COMPONENTS
1. DOOR OPEN MECHANISM
1. The handle lever is pulled.
2. The upper and lower latch heads are lifted up by the linked latch
lever.
3. The latch lever is lifted up by the handle lever.
4. Now both latch heads are lifted up, so they can be released from
the latch hook.
5. Now the door can be opened.
Figure D-1. Door Open Mechanism
2. DOOR SENSING SWITCH: SW5
The door sensing switch is activated by the latch head of the door and
switch lever C. When the door is opened, the contacts of the switch
open and interrupt the circuit to the coils of the primary interlock relay.
The contacts of the primary relay then open and interrupt the circuit to
the primary winding of the power transformers T1, T2.
3. SECONDARY INTERLOCK SWITCHES: SW1, SW2
The secondary interlock switches SW1, SW2 are activated by the
upper latch head of the door and switch lever B. When the door is
opened, the contacts (COM-NO) of the switch open and interrupt the
circuit to the primary winding of the power transformers T1, T2. When
the door is opened, the contacts (COM-NC) of the switch SW1 close
and the line voltage is supplied to the switching power supply unit. At
the same time, the contacts of relay RY4 are closed.
4. MONITOR SWITCHES: SW3, SW4
The monitor switches SW3, SW4 are mounted in the upper position of
the latch hook. The monitor switches are activated by the upper latch
head of the door and switch lever A. When the door is opened, the
contacts of the monitor switches close. Monitor switch SW3 is
intended to render the oven inoperative by means of blowing the weak
point (F1), when the contacts of the primary interlock relay and sec-
ondary interlock switch SW1 fail to open when the door is opened.
Monitor switch SW4 is intended to render the oven inoperative by
means of blowing the weak point (F2), when the contacts of the pri-
mary interlock relay and secondary interlock switch SW2 fail to open
when the door is opened.
Functions:
With the door shut, the contacts of the door sensing switch SW5 and
the secondary interlock switches SW1, SW2 are closed and the con-
tacts of the monitor switches SW3, SW4 are open.
1. When the door is opened, the contact of the door sensing switch
SW5 and secondary interlock switches SW1, SW2 are opened first,
then the contact of the monitor switches SW3, SW4 are closed.
2. As the door goes to a closed position, the contacts of the monitor
switches SW3, SW4 are opened first, then the contacts of the door
sensing switch SW5 and the secondary interlock switches SW1,
SW2 close.
3. If the door is opened, and the contacts of the primary interlock relay
RY1 and secondary interlock switch of the same circuit fail to open,
the weak point blows simultaneously with closing of the monitor
switch contacts of that circuit.
CAUTION: BEFORE REPLACING A BLOWN FUSES F8 (F1, F2)
TEST THE DOOR SENSING SWITCH SW5, PRIMARY
INTERLOCK RELAY RY1, SECONDARY INTERLOCK
SWITCHES SW1, SW2, DOOR SENSING SWITCH SW5
AND MONITOR SWITCHES SW3, SW4 FOR PROPER
OPERATION. (REFER TO CHAPTER “TEST PROCE-
DURE”).
5. WEAK POINT: F1, F2
1. The weak point blows when the contacts (COM-NO) of the primary
interlock relay (RY1) and secondary interlock switch SW1 or SW2
remain closed with the oven door open and when the monitor
switch (SW3 or SW4) closes.
2. If the wire harness or electrical components are short-circuited, this
weak point (F1, F2) blows to prevent an electric shock or fire haz-
ard.
3. The weak point also blows when the asymmetric rectifier, H.V. rec-
tifier, H.V. wire harness, H.V. capacitor, magnetron or secondary
winding of power transformer is shorted.
6. 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 condition develops in the tube due to
blower motor failure, obstructed air ducts, dirty or blocked air intake,
etc., the circuit to the magnetrons are interrupted. Under normal oper-
ation, the temperature fuses remains closed. However, when abnor-
mally high temperatures are generated within the magnetron, the
temperature fuse will open at 302°F (150°C) causing the microwave
energy to stop. The defective temperature fuse must be replaced with
new rated one.
7. OVEN TEMPERATURE FUSE: TF3
The temperature fuse, located on the side of the exhaust duct assem-
bly, is designed to prevent damage to the oven by fire. If the food load
is overcooked, by either error in cook time or defect in the control unit,
the temperature fuse will open. Under normal operation, the oven tem-
perature fuse remains closed. However, when abnormally high tem-
peratures are generated within the oven cavity, the oven temperature
fuse will open at 248°F (120°C), causing the oven to shut down. The
defective temperature fuse must be replaced with new rated one.
8. EXHAUST THERMISTOR
The exhaust thermistor is located on the side of the exhaust duct
assembly. 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
“EE8” and the oven will stop.
9. MAGNETRON THERMISTOR: TH
The thermistor is a negative temperature coefficient type. The air tem-
perature around the upper and lower magnetrons 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 protect the magne-
trons against overheat. If the magnetron thermistor is open, the control
panel will display “EE8” and the oven will stop.
Latch hook
Latch
lever
SW4: Monitor switch
Secondary
interlock switch
Secondary
interlock switch
Door sensing
switch
SW3: Monitor switch
Switch lever A
Switch lever B
Switch lever C
Latch
head
Latch
head
Handle
lever
SW2:
SW1:
SW5:

R1500AT
4 – 3
10. FAN MOTORS: FM
The fan motors drive blades which draw external cool air into the oven.
This cool air is directed through the air vanes surrounding the magne-
trons and cools the magnetrons. This air is channelled through the
oven cavity to remove steam and vapours given off from the heating
foods. It is then exhausted through the exhausting air vents at the
oven cavity. During cooking, they operate. After cooking, the fan
motors will operate at least for 1 minute and the maximum operating
time is 4 minutes. When the temperature of the magnetron thermistor
becomes bellow 110°C, the fan motors will stop.
These two (2) fan motors are D.C. motors.
11. EXHAUST MOTOR: EM
The exhaust motor is located on the side of the exhaust duct assem-
bly. This motor drives a blade in the exhaust duct assembly. The
driven blade draws the external cool air into the oven from the intake
duct assembly. Then it sends the air out of the oven through the
exhaust duct assembly. During cooking, the exhaust motor operates.
After cooking, it will operate at least for 1 minute and the maximum
operating time is 4 minutes. When the temperature of the exhaust
thermistor becomes bellow 65°C, the exhaust motor will stop. This
motor is D.C. motor.
NOTE: Do not disconnect the power supply from the exhaust motor
when it is turned on. Or it may be out of order.
12. ANTENNA MOTORS: AM
The upper and lower antenna motors drive antennas to radiate the
microwave.
13. EXHAUST FAN: EF
The exhaust fan is located to the rear cover. It sends the air (which is
at the top of the oven cavity) out of the oven. This motor is D.C. motor.
14. ANTENNA SENSOR
The antenna sensors are located to the top and bottom of the oven
cavity. And they watch if the antennas are rotating or not.
15. MIROWAVE SENSOR
The microwave sensor is located on the top of the oven cavity. And it
watch if the microwave is radiated into the oven cavity or not.
16. WEAK POINT (IN THE NOISE FILTER)
If the wire harness or electrical components make a short-circuited,
this weak point blows to prevent an electric shock or fire hazard.
17. H.V. ASYMMETRIC RECTIFIER (1) (2)
The H.V.asymmetric rectifiers (1) (2) are solid state devices that pre-
vent current flow is both directions. And they prevent the temperature
rise of the power transformers (1) (2) by blowing the fuses weak point
F1, F2 when the high voltage rectifiers (1) (2) are shorted. The rated
peak reverse voltage of D1 of the asymmetric rectifier is 6 KV. The
rated peak reverse voltage of D2 of the asymmetric rectifier is 1.7 KV.
D1 and D2 of the asymmetric rectifier or high voltage rectifier are
shorted when the each peak reverse voltage goes beyond the each
rated peak reverse voltage. (The process of the blowing the weak
point.)
NOTE: The H.V.asymmetric rectifier is assembled with the high volt-
age rectifier actually.
1. The high voltage rectifier is shorted by some fault when microwave
cooking or dual cooking.
2. The peak reverse voltage of D2 of the rectifier goes beyond the
rated peak reverse voltage 1.7 KV in the voltage doubler circuit.
3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high voltage winding of
the power transformer.
5. The large electric currents beyond 8A flow through the primary
winding of the power transformer.
6. The fuse 8A blows by the large electric currents.
7. The power supplying to the power transformer is cut off.
18. OVEN LAMP: OL
The oven cavity light illuminates the interior of the oven so that food
being cooked can be examined visually through the door window with-
out having to open the door.
19. NOISE FILTER
The noise filter prevents the radio frequency interference that might
flow back in the power circuit.
D2 D1
ASYMMETRIC
RECTIFIER HIGH VOLTAGE
RECTIFIER

R1500AT
5 – 1
R1500AT ServiceManual

CHAPTER 5. 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 weak point F1 (or F2), check the monitor switches SW3 (or SW4), primary interlock relay RY1,
door sensing switch SW5 and secondary interlock switch SW1 (or SW2), before replacing the weak point F1 (or F2).
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
Home fuse blows when power cord is plugged into wall receptacle " . " does not appear in display when power cord is first plugged into wall receptacle. Oven lamp does not go on for 1 minute after door is opened. Oven lamp and antenna motors do not go on in cook cycle. Fan motor does not operate. Exhaust fan does not operate. Exhaust motor does not operate.
OFF CONDITION CONDITION
PROBLEM
COOKING CONDITION
POSSIBLE CAUSE AND
DEFECTIVE PARTS
TEST PROCEDURE
MAGNETRON MG1, MG2
POWER TRANSFORMER T1, T2
H.V. RECTIFIER ASSEMBLY (1), (2)
HIGH VOLTAGE CAPACITORC1, C2
SECONDARY INTERLOCK SWITCH SW1, SW2
PRIMARY INTERLOCK SYSTEM
DOOR SENSING SWITCH SW5
MONITOR SWITCH SW3, SW4
WEAK POINT (in Noise filter)
MAGNETRON TEMP. FUSE TF1, TF2
OVEN TEMPERATURE FUSE TF3
OVEN LAMP OR SOCKET
FAN MOTORS FM
EXHAUST FAN EF
EXHAUST MOTOR EM
FUSE F8 F1, F2
WEAK POINTS (for Fan motors)
WEAK POINT
(for Exhaust fan motor)
EXHAUST THERMISTOR
MAGNETRON THERMISTOR TH
NOISE FILTER
KEY UNITS
POWER UNIT
RELAY UNIT
CONTROL UNIT
SWITCH UNIT.
AIR FLOW BLOCKED
LOOSE WIRING
SHORT IN POWER SUPPLY CORD
NO POWER AT OUTLET
LOW POWER SUPPLY VOLTAGE
ABCDEF FG JKK HI I ML OQRP
N
Weak point (in noise filter) blows when pow- er cord is plugged into wall receptacle. Oven doen not go into cook cycle when START pad on the door is touched. Oven does not go into cook cycle when START pad is touched. Variable cooking does not operates proper- ly, except HIGH power functions. Low or no power is produced during cook- ing condition. (The food is heated incom- pletely or not heated at all.)
Oven goes into a cook cycle but shuts down before and off cooking cycle. It seems that the output power is low- er or higher than the rated one.

R1500AT
5 – 2
SPECIFICATION OF ERROR
Outline Operation when error occurs Display in operation usually
When a basic performance and the function are ruined Displaying and heating stop EE0, EE1, EE2, EE3, EE8
When the dangers of the state of the high temperature and the ignition, etc. are
foreseen Displaying and heating stop EE7
When you mistake the setting of the heating time Operation stop EE9
When neither the power supply nor the environmental condition are proper Operation stop EE4, EE5, EE6
When informing of the exchange time of parts Display Only CC1, CC2, CC3, CC4
Display for maintenance Error his-
tory display Content of maintenance Check item Parts to be
replaced
CC1 CC2 CC3 CC4
– MG1 exchange time information Using time of MG1 MG1
– MG2 exchange time information Using time of MG2 MG2
– Exhaust Fan motor exchange time information Using time of Exhaust motor Exhaust motor
– T/C unit exchange time information Using number of times of RY2/RY3 Relay unit
ATEST PROCEDURE
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
BDC E FH I KL M RPSS T
EE0
EE0
EE0
EE0
EE0
EE0
EE0
EE1
EE1
EE2
EE2
EE3
EE3
EE3
EE4
EE5
EE6
EE6
EE60
EE7
EE7
EE7
EE8
EE8
EE8
EE8
EE8
EE8
EE8
EE8
EE8
EE9
Magnetron MG1and /or MG2 Power transformer T1 & T2 High voltage capacitor C1 and /or C2 H.V.rectifier assembly 1 and/or 2 Secondary interlock switch SW1 and/or SW2 Primary interlock system Fuse 8A F1 and/or F2 Weak points for Fan motors
(DC24V)
Magnetron temp. fuse TF1 and/or TF2 Magnetron thermistor 1 and/or 2 TH Exhaust thermistor Fan motors FM Exhaust motor EM Antenna motor 1 and/or 2 AM Air flow blocked Low or High power supply voltage No load or small load operation Loose wiring Exceeding of maxmum cooking time Burned food Relay unit Control unit Antenna sensor (1) (Upper) Antenna sensor (2) (Lower) Microwave sensor Frequency of power supply is high.
EE 1
Failer of high voltage circuit 1
EE 2
Failer of high voltage circuit 2
EE 3
Failer of high voltage circuit 1&2
EE 4
Too high of input voltage(+13%)
EE 5
Too low of input voltage(-13%)
EE 7
Food burned (temp., too high)
EE 8
Melted contacts of relays
EE 9
Over maximum cooking time
EE 10
EEPROM error
EE 11
Life end of magnetron MG1
EE 21
Life end of magnetron MG2
EE 31
Life end of magnetron MG1, 2
EE 81
Life end of relays RY2/RY3
EE 83
Over Current error
EE 14
MG1 Cooling Fan lock judge
EE 24
MG2 Cooling Fan lock judge
EE 44
Exhaust motor lock judge
EE 54
Life end of exhaust motor
EE 15
MG1 antenna rotation error
EE 25
MG2 antenna rotation error
EE 35
MG1/2 antenna rotation error
EE 16
MG1 thermistor open
EE 26
MG2 thermistor open
EE 17
MG1 temperature, too high
EE 27
MG2 temperature, too high
EE 18
Magnetron MG1
EE 28
Magnetron MG2
EE 38
Magnetron MG1& MG2
EE 29
Exhaust thermistor open/short
EE 19
No food
EE 39
EE 60
Small food
Not correct frequency
Error history
display
Usual error
display
Content of error
If the power supply voltage is higher than 240V+10% (264V), EE4 will be displayed.
If the power supply voltage is lower than 230V-12% (202V), EE5 will be displayed.
NOTE 1:
1) If the magnetrons are used for more than 4000 hours, EE11, EE21 or EE31 will appear when error histories are checked.
2) If the on/off counts of the relay (RY2 or RY3) become more than 400000 times, EE81 will appear when error histories are checked.
3) Even if EE11, EE21, EE31 or EE81 appears when error histories are checked, if the oven is not operated for 3 minutes or more,
or if the oven is disconnected from the power supply once and then the oven is connected to the power supply, the oven can
be operated once more. But after that when the oven is going to be used again, EE1, EE2, EE3 or EE8 will appear and the oven
will not operate.
NOTE 3:
""
means that the parts should be replaced if EE11, EE21, EE31 or EE81 is indicated on the display when error histories are checked. NOTE 2:

R1500AT
6 – 1
R1500AT ServiceManual

CHAPTER 6. TEST PROCEDURES
[1] A: MAGNETRON TEST
CARRY OUT 3D CHECKS.
Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.
To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron filament terminals, the meter should show a
reading of less than 1 ohm.
To test for short circuit filament to anode condition, connect ohmmeter between one of the filament terminals and the case of the magnetron (ground).
This test should be indicated an infinite resistance. If a low or zero resistance reading is obtained then the magnetron should be replaced.
1. 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 IEC test procedure, i.e. it can be measured by using water load how much it can be absorbed by the water
load. To measure the microwave output power in the microwave oven, the relation of calorie and watt is used. When P(W) heating works for t (sec-
ond), 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 of the test.
3) Temperature of the water
The initial temperature of the water is (10±1)°C
4) Select the initial and final water temperature so that the maximum difference between the final water temperature and the ambient temperature is
5°C.
5) Select stirring devices and measuring instruments in order to minimize addition or removal of heat.
6) The graduation of the thermometer must be scaled by 0.1°C at minimum and an accurate thermometer.
7) The water load must be (1000±5) g.
8) “t” is measured while the microwave generator is operating at full power. Magnetron filament heat-up time is not included.
NOTE: The operation time of the microwave oven is “t + 3" sec. (3 sec. is magnetron filament heat-up time.)
Measuring method:
1) Measure the initial temperature of the water before the water is added to the vessel.
(Example: The initial temperature T1 = 11°C)
2) Add the 1 litre water to the vessel.
3) Place the load on the centre of the shelf.
4) Operate the microwave oven at HIGH 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 OPER-
ATION.
SERVICE INFORMATION
IMPORTANT:When the magnetron MG1 and/or MG2 is replacing, the relays (RY3 and RY4) on control unit must be replaced at the
same time. Because if the magnetron's life has been over, the relay's life may also be over.
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
Water load ........................................................1000 g
Heating time ................28 sec. [R-1500AT]/ 20 sec. [R-2100AT]
T2 .................................................... Final Temperature
Power supply Voltage ........................... Rated voltage
Initial temperature (T1) .................................... 10±1°C
Mass of container (mc) ...................................... 330 g
P = 150 x T [R-1500AT] P = 210 x T [R-2100AT]

R1500AT
6 – 2
JUDGEMENT: The measured output power should be at least ±15% of the rated output power.
CAUTION: 1°C CORRESPONDS TO 150WATTS (for R-1500AT)/ 210WATTS (for R-2100AT). REPEAT MEASUREMENT IF THE POWER IS INSUF-
FICIENT.
[2] B: POWER TRANSFORMER TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and secondary winding connections from the rest of
the HV circuitry. Using an ohmmeter, set on a low range, it is possible to check the continuity of all three winding. The following readings should be
obtained:
a.Primary winding -------------------- approximately 1.3 Ω
b.Secondary winding --------------- approximately 76 Ω
c.Filament winding --------------------------- less than 1 Ω
If the readings obtained are not stated as above, then the power transformer is probably faulty and should be replaced.
3. CARRY OUT 4R CHECKS.
[3] C: HIGH VOLTAGE RECTIFIER (1) AND/OR (2) TEST
1. HIGH VOLTAGE RECTIFIERFTEST
1. CARRY OUT 3D CHECKS.
2. Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested using an ohmmeter set to its highest range.
Connect the ohmmeter across the terminal B+C of the high voltage rectifier and note the reading obtained. Reverse the meter leads and note this
second reading. The normal resistance is infinite in one direction and more than 100k ohms in the other direction.
3. CARRY OUT 4R CHECKS.
2. ASYMMETRIC RECTIFIER TEST
1. CARRY OUT 3D CHECKS.
2. Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be tested using an ohmmeter set to its highest range
across the terminals A+B of the asymmetric rectifier and note the reading obtained. Reverse the meter leads and note this second reading. If an
open circuit is indicated in both directions then the asymmetric rectifier is good. If the asymmetric rectifier is shorted in either direction, then the
asymmetric rectifier is faulty and must be replaced with high voltage rectifier. When the asymmetric rectifier is defective, check whether magne-
tron, high voltage rectifier, high voltage wire or filament winding of the power transformer is shorted.
Room temperature .................................................................... To = 21°C
Initial temperature ..................................................................... T1 = 11°C
Temperature after (28 + 3) = 31 sec. (for R-1500AT).................... T2 = 21°C
Temperature after (20 + 3) = 23 sec. (for R-2100AT).................... T2 = 21°C
Temperature difference Cold-Warm ..................................... T1 = 10°C
Measured output power
The equation is “P = 150 x T" (for R-1500AT).............. P = 150 x 10°C = 1500 Watts
The equation is “P = 210 x T" (for R-2100AT).............. P = 210 x 10°C = 2100 Watts
WARNING: High voltages and large currents are present at the secondary winding and filament winding of the power transformer. It is
very dangerous to work near this part when the oven is on. NEVER make any voltage measurements of the high-voltage cir-
cuits, including the magnetron filament.
1000g
1000g
1000g
T1 C T2 C
Heat up for 31 sec.(for R-1500AT)
Heat up for 23 sec.(for R-2100AT)
D2 D1
ASYMMETRIC
RECTIFIER HIGH VOLTAGE
RECTIFIER
AB
C

R1500AT
6 – 3
3. CARRY OUT 4R CHECKS.
NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts.
[4] D: HIGH VOLTAGE CAPACITOR (C1) AND/OR (C2) TEST
1. CARRY OUT 3D CHECKS.
2. If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads and check for short or open between the termi-
nals using an ohmmeter.
Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate continuity for a short time and should indicate an
open circuit once the capacitor is charged. If the above is not the case, check the capacitor with an ohmmeter to see if it is shorted between either
of the terminals and case. If it is shorted, replace the capacitor.
3. CARRY OUT 4R CHECKS.
[5] E: SECONDARY INTERLOCK SWITCH (SW1) AND/OR (SW2) TEST
1. CARRY OUT 3D CHECKS.
2. 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 door open and a closed circuit with the door closed. If improper operation is indicated, replace the secondary interlock switch.
3. Isolate the switch (SW1) and connect the ohmmeter to the common (COM.) and normally close (NC) terminal of the switch (SW1). The meter
should indicate a close circuit with the door open and an open circuit with the door closed. If improper operation is indicated, replace the switch
(SW1).
4. CARRY OUT 4R CHECKS.
[6] F: PRIMARY INTERLOCK SYSTEM TEST
1. DOOR SENSING SWITCH (SW5)
1. CARRY OUT 3D CHECKS.
2. 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 door open and a closed circuit with the door closed. If improper operation is indicated, replace the door sensing switch.
3. CARRY OUT 4R CHECKS.
2. PRIMARY INTERLOCK RELAY (RY1)
1. CARRY OUT 3D CHECKS.
2. Disconnect two (2) wire leads from the male tab terminals of the Primary Interlock Relay RY1. Check the state of the relay contacts using a ohm-
meter. The relay contacts should be open. If the relay contacts are closed, replace the circuit board entirely or the relay itself.
3. CARRY OUT 4R CHECKS.
[7] G: MONITOR SWITCH (SW3) AND/OR (SW4) TEST
1. CARRY OUT 3D CHECKS.
2. Before performing this test, make sure that the secondary interlock switches SW1, SW2 and the primary interlock relay RY1 are operating prop-
erly, according to the above Switch Test Procedure. Disconnect the wire lead from the monitor switches SW3, SW4 (COM) terminals. Check the
monitor switches SW3, SW4 operation by using the ohmmeter as follows. When the door is open, the meter should indicate a closed circuit. When
the monitor switch actuator is pushed by a screw driver through the upper latch hole on the front plate of the oven cavity with the door 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. After testing the monitor switches, reconnect the wire lead to the monitor switch (COM) terminals and check the continu-
ity of the monitor circuit.
3. CARRY OUT 4R CHECKS.
Screw Driver
Ohmmeter
Monitor switch (2)
Latch hook
Monitor switch (1)

R1500AT
6 – 4
[8] H: WEAK POINT F1, F2 TEST
1. CARRY OUT 3D CHECKS.
2. If the weak point F1 or F2 is blown when the door is opened, check the primary interlock relay RY1, secondary interlock switches SW1, SW2 and
monitor switches SW3, SW4 according to the “TEST PROCEDURE” for those switches before replacing the blown weak point F1 or F2.
CAUTION: CAUTION: BEFORE REPLACING A BLOWN WEAK POINT F1 OR F2, TEST THE PRIMARY INTERLOCK RELAY RY-1, SECONDARY
INTERLOCK SWITCHES SW1, SW2, DOOR SENSING SWITCH SW5 AND MONITOR SWITCHES SW3, SW4 FOR PROPER OPERA-
TION.
3. If the weak point is blown, check the magnetron, high voltage capacitor, high voltage rectifier assembly, according to the “TEST PROCEDURE”
before replacing the blown weak point. Then replace the weak point.
4. CARRY OUT 4R CHECKS.
[9] I: WEAK POINT (FOR FAN MOTOR ) TEST
CARRY OUT 3D CHECKS.
If the weak point is blown, the fan motor or exhaust fan could be locked or there could be a shorts in the fan motor or exhaust fan. Check them and
replace the defective parts.
CARRY OUT 4R CHECKS.
CAUTION: Only replace weak point with the correct value replacement.
[10] J: WEAK POINT (IN NOISE FILTER) TEST
CARRY OUT 3D CHECKS.
If the weak point is blown, there could be a shorts or grounds in electrical parts or wire harness. Check them and replace the defective parts or repair
the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace weak point with the correct value replacement.
[11] K: TEMPERATURE FUSE TEST
1. CARRY OUT 3D CHECKS.
2. A continuity check across the temperature fuse terminals should indicate a closed circuit unless the temperature of the temperature fuse reaches
specified temperature as shown below.
3. CARRY OUT 4R CHECKS.
CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE, REPLACE TEMPERATURE FUSE.
[12] L: MAGNETRON THERMISTOR TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the connector of the magnetron thermistor from the harness. Measure the resistance of each thermistor with an ohmmeter. Connect
the ohmmeter leads to the connector of each thermistor.
If the meter does not indicate above resistance, replace the thermistor.
3. CARRY OUT 4R CHECKS.
[13] M: EXHAUST THERMISTOR TEST
The exhaust thermistor can be checked by using the Special function (SF-6). Check the exhaust thermistor, referring to the pages of the Exhaust ther-
mistor check (SF-6).
If the display shows “OH”, the exhaust thermistor is normal. If the display shows “no”, the exhaust thermistor is abnormal and it should be replaced.
Open temperature Close temperature Display or
Condition
Check point
Magnetron temperature
fuse (1)
150°C Non resetable type
EE1 Magnetron (MG1) Failure:
Test magnetron (MG1) and fan motor.
Magnetron temperature
fuse (2) EE2 Magnetron (MG2) Failure:
Test magnetron (MG2) and fan motor.
Magnetron temperature
fuse (1), (2) EE3
Magnetron (MG1), (MG2) Failure: Test magnetron
(MG1), (MG2).
Check fan motor and ventilation opening.
Oven temperature fuse 120°C Non resetable type Oven shut off Food has been burned in oven.
Temperature of oven inside is very high.
Room temperature Resistance
20°C Approx. 750KΩ

R1500AT
6 – 5
[14] N: NOISE FILTER TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the lead wires from the terminal the noise filter. Using an ohmmeter, check
between the terminals as described in the following table. If incorrect reading are obtained,
replace the noise filter.
3. CARRY OUT 4R CHECKS.
[15] O: KEY UNIT TEST
1. CARRY OUT 3D CHECKS.
2. Check Key unit ribbon connection before replacement.
3. If key unit ribbon connection is normal, carry out the following procedures.
4. Re-install the rear cover and the outer case (cabinet).
5. Reconnect the power supply cord.
6. The following symptoms indicate a defective key unit.
1) When touching the pads, a certain pad produces no signal at all.
2) When touching a number pad, two figures or more are displayed.
3) When touching the pads, sometimes a pad produces no signal.
7. When you can not judge if the key unit is normal or not by using the item 8 above, carry out following test procedures.
1) Disconnect the power supply cord, and then remove outer case and rear cover.
2) Open the door and block it open.
3) Discharge two high voltage capacitors.
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.
6) Reconnect the power supply cord.
7) 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 prop-
erly; that is the contacts are closed when the door is closed and open when the door 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 door sensing switch is closed (either close
the door or short the door sensing 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.
8) For the door key unit, check the open/short and/or connection of the switch unit and the harness, too.
8. If the Key unit is defective.
1) Disconnect the power supply cord, and then remove outer case and rear cover.
2) Open the door and block it open.
3) Discharge two high voltage capacitors.
4) Replace the Key unit.
5) Reconnect all leads removed from components during testing.
6) Re-install the rear cover and the outer case (cabinet).
7) Reconnect the power supply cord after the rear cover and the outer case are installed.
8) Run the oven and check all functions.
[16] P: CONTROL UNIT TEST
The following symptoms indicate a defective control unit. Before replacing the control unit, perform the Key units test (Procedure O) to determine if
control unit is faulty.
Connect the power supply cord. And check for followings.
MEASURING POINT INDICATION OF OHMMETER
Between source terminals Approx. 470KΩ
Between source (Black) and load (Black) terminals Short circuit.
Between source (White) and load (White/Brown) terminals Short circuit.
WEAK
POINT
NOISE FILTER
NOISE SUPPRESSION COIL
LINE CROSS CAPACITOR
1.0μF / AC 275V
DISCHARGE RESISTOR
470K 1/2W
LINE BYPASS
CAPACITOR
0.0033μF / AC 250V
LINE BYPASS
CAPACITOR
0.0033μF / AC 250V
Load
(Black)
Load
(Gray/White)
Source
(Blue)
Source
(Brown)
5432
7
8
9
6
1
2
3
4
1
5
6
7
2
3
4
1
5
6
7
2
3
4
1
5
6
7
8
CN-M
CN-R
CN-Z CN-Q
< DOOR KEY UNIT >
< KEY UNIT >
<SWUNIT>

R1500AT
6 – 6
1. In connection with pads.
1) When touching the pads, a certain group of pads do not produce a signal.
2) When touching the pads, no pads produce a signal.
2. In connection with display
1) At a certain digit, all or some segments do not light up.
2) At a certain digit, brightness is low.
3) Only one indicator does not light.
4) The corresponding segments of all digits do not light up; or they continue to light up.
5) Wrong figure appears.
6) A certain group of indicators do not light up.
7) The figure of all digits flicker.
3. Other possible problems caused by defective control unit.
1) Buzzer does not sound or continues to sound.
2) Cooking is not possible.
4. If the protectors F1 and/or F2 on the control unit PWB are open, the control unit is defective. To check, carry out following procedures.
i) Disconnect the power supply cord, and then remove outer case and rear cover.
ii) Open the door and block it open.
iii) Discharge two high voltage capacitors.
iv) Remove the control unit from the control panel, referring to “CONTROL PANEL ASSEMBLY AND CONTROL UNIT REMOVAL”.
v) Check the continuity of the protectors F1 and F2 on the control unit
[17] Q: POWER UNIT TEST
1. Check the out put voltage of power unit at CN21 as follows.
i) Disconnect the power supply cord, and then remove outer case and rear cover.
ii) Open the door and block it open.
iii) Discharge two high voltage capacitors.
iv) Disconnect the leads to the primary of the power transformer.
v) Ensure that these leads remain isolated from other components and oven chassis by using insulation tape.
vi) Check the voltage between Pin No1 and No2 of CN21.
vii) The output voltage should be approx. 24V.
viii) If not so, the power unit is defective.
2. Check the continuity of the fuse F1 and protector F21 on the power unit as follows.
i) Disconnect the power supply cord, and then remove outer case and rear cover.
ii) Open the door and block it open.
iii) Discharge two high voltage capacitors.
iv) Remove the power unit from the oven, referring to “POWER UNIT REMOVAL”.
v) Check the continuity of the fuse F1 and the protector F21.
vi) If they are open, the power unit is defective
[18] R: RELAY UNIT TEST
1. CARRY OUT 3D CHECKS.
2. Remove the relay unit from the oven, referring to “RELAY UNIT REMOVAL”.
3. Check the continuity of the FUSE1 on the relay unit.
1) If it is open, the relay unit is defective.
4. Check the open and /or short of the transformer primary coil on the relay unit.
1) If it is open and /or short, it is defective.
5. Check the state of the relays contacts RY-1, RY-2 and RY-3 using an ohmmeter.
1) The relay contacts should be open. If not so, the relay unit is defective.