Sharp R-351NW User manual

R-351NW
CONTENTS
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE EXPO-
SURE TO EXCESSIVE MICROWAVE ENERGY
BEFORE SERVICING
CHAPTER 1. WARNING TO SERVICE PERSONNEL
CHAPTER 2. MICROWAVE MEASUREMENT PRO-
CEDURE
CHAPTER 3. FOREWORD AND WARNING
CHAPTER 4. PRODUCT DESCRIPTION
CHAPTER 5. GENERAL INFORMATION
CHAPTER 6. OPERATION
Cronometro
Minuto Extra
1 Mantequilla
2 Chocolate
1 Helados
2 Queso crema
1 Coberturas de
postres
DESCONGELACION RECALENTARCOCCION
1 Verdura
Fresca
2 Came Molida
3 Papa Asada
4 Arroz
5 Verdura
6 Entradas
Congelada
Congeladas
1 Came Molida
2 Aves
3 Bistec/
Deshuesadas
Chuletas
4 Aves
1 Caserola
2 Sopa
3 Pizza
4 Bebida
5 Plato Principal
6 Pan Presco
7 Pan Congelada
8 Veroura Bnlatada
Derretir Suavizar Calentar
Function Rapida
Reloj
Nivel de
Potencia
Comienzo
Detencion
Cancelacion
Palomitas de Maiz
S3910R351NPAL
MICROWAVE OVEN
R-351NW
In the interest of user-safety the oven should be restored to
its original condition and only parts identical to those speci-
fied should be used.
WARNING TO SERVICE PERSONNEL: Microwave ovens
contain circuitry capable of producing very high voltage
and current, contact with following parts may result in a se-
vere, possibly fatal, electrical shock. (High Voltage Capaci-
tor, High Voltage Power Transformer, Magnetron, High
Voltage Rectifier Assembly, High Voltage Harness etc..)
SERVICE MANUAL
This document has been published to be used for after sales service only.
The contents are subject to change without notice.
CHAPTER 7. TROUBLESHOOTING GUIDE
CHAPTER 8. TEST PROCEDURES
CHAPTER 9. TOUCH CONTROL PANEL ASSEMBLY
CHAPTER 10. PRECAUTIONS FOR USING LEAD-
FREE SOLDER
CHAPTER 11. COMPONENT REPLACEMENT AND
ADJUSTMENT PROCEDURE
CHAPTER 12. CIRCUIT DIAGRAMS
Parts List
MODEL
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PRECAUTIONS TO BE OBSERVED BEFORE
AND DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
BEFORE SERVICING
CHAPTER 1. WARNING TO SERVICE PERSONNEL
[1] Before Servicing ...........................................1-1
[2] When the testing is completed ....................1-1
[3] After repairing..............................................1-1
CHAPTER 2. MICROWAVE MEASUREMENT
PROCEDURE
[1] Requirements: ..............................................2-1
[2] Preparation for testing: ................................2-1
[3] Leakage test:...............................................2-1
CHAPTER 3. FOREWORD AND WARNING
[1]
FOREWORD ................................................3-1
[2] WARNING ...................................................3-1
[3] DANGER .....................................................3-1
CHAPTER 4. PRODUCT DESCRIPTION
[1] SPECIFICATIONS.......................................4-1
CHAPTER 5. GENERAL INFORMATION
[1] GROUNDING INSTRUCTIONS ..................5-1
[2] OVEN DIAGRAM.........................................5-1
CHAPTER 6. OPERATION
[1] DESCRIPTION OF OPERATING SE-
QUENCE .....................................................6-1
[2] OVEN SCHEMATIC ....................................6-2
[3] DESCRIPTION AND FUNCTION OF
COMPONENTS...........................................6-3
CHAPTER 7. TROUBLESHOOTING GUIDE
[1] TROUBLESHOOTING CHART ...................7-1
CHAPTER 8. TEST PROCEDURES
[1] A: MAGNETRON ASSEMBLY TEST...........8-1
[2] B: POWER TRANSFORMER TEST............8-1
[3] C: HIGH VOLTAGE RECTIFIER TEST .......8-1
[4] D: HIGH VOLTAGE CAPACITOR TEST......8-2
[5] E: TEMPERATURE FUSE OR THERMAL
CUT-OUT TEST...........................................8-2
[6] F: SECONDARY INTERLOCK SWITCH
TEST ...........................................................8-2
[7] F: PRIMARY INTERLOCK SYSTEM
TEST ...........................................................8-3
[8] G: MOTOR SWITCH TEST .........................8-3
[9] H: BLOWN MONITOR FUSE TEST ............8-4
[10] I: NOISE FILTER TEST ...............................8-4
[11] J: TOUCH CONTROL PANEL ASSEMBLY
TEST ...........................................................8-4
CONTENTS
[12] K: KEY UNIT TEST ..................................... 8-5
[13] L: RELAY TEST .......................................... 8-6
[14] M: DEFROST TEST ................................... 8-6
[15] N: FOIL PATTERN ON THE PRINTED
WIRING BOARD TEST .............................. 8-6
CHAPTER 9. TOUCH CONTROL UNIT ASSEMBLY
[1] OUTLINE OF TOUCH CONTROL PANEL .... 9-1
[2] SERVICING FOR TOUCH CONTROL
PANEL ......................................................... 9-1
CHAPTER 10. PRECAUTIONS FOR USING LEAD-
FREE SOLDER
CHAPTER 11. COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
[1] WARNING ...................................................11-1
[2] OUTER CASE REMOVAL...........................11-2
[3] POWER TRANSFORMER REMOVAL........11-2
[4] HIGH VOLTAGE COMPONENTS REMOVAL
(HIGH VOLTAGE CAPACITOR AND HIGH
VOLTAGE RECTIFIER ASSEMBLY) ...........11-2
[5] MAGNETRON REMOVAL...........................11-2
[6] POSITIVE LOCK CONNECTOR (NO-
CASE TYPE) REMOVAL.............................11-3
[7]
CONTROL PANEL ASSEMBLY REMOVAL ..11-3
[8] GRAPHIC SHEET AND MEMBRANE
SWITCH REPLACEMENT ..........................11-3
[9] TURNTABLE MOTOR REMOVAL...............11-4
[10] COOLING FAN MOTOR REMOVAL ...........11-4
[11] POWER SUPPLY CORD REPLACEMENT...11-5
[12] DOOR SENSING SWITCH/SECONDARY
INTERLOCK SWITCH AND MONITOR
SWITCH REMOVAL ....................................11-5
[13] DOOR SENSING SWITCH/SECONDARY
INTERLOCK SWITCH AND MONITOR
SWITCH ADJUSTMENT .............................11-6
[14] DOOR REPLACEMENT..............................11-6
CHAPTER 12. CIRCUIT DIAGRAMS
[1] Pictorial Diagram (Figure S-1).....................12-1
[2] Control Panel Circuit (Figure S-2) ...............12-2
[3] Printed Wiring Board of Power Unit
(Figure S-3) .................................................12-3
Parts List
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R-351NW
i
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID
POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
BEFORE SERVICING
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE
ENERGY
(a) Do not operate or allow the oven to be operated with the door open.
(b) Make the following safety checks on all ovens to be serviced before activating the magnetron or other
microwave 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
compartments, 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
Measurement 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.
Service personnel should inform SHARP ELECTRONICS CORPORATION of any certified unit found
with emissions in excess of 4mW/cm . The owner of the unit should be instructed not to use the unit
until the oven has been brought into compliance.
2
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1 - 1
[1] Before Servicing
CHAPTER 1. WARNING TO SERVICE PERSONNEL
Microwave ovens 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 Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness etc..
Read the Service Manual carefully and follow all instructions.
Don't Touch !
Danger High Voltage
1. Disconnect the power supply cord , and then remove outer
case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
WARNING:
RISK OF ELECTRIC SHOCK. DISCHARGE THE
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 con-
nect the power supply 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.
[2] 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.
[3] After repairing
1. Reconnect all leads removed from components during testing.
2. Reinstall the outer case (cabinet).
3. Reconnect the power supply cord after the outer case is installed.
4. Run the oven and check all functions.
Microwave ovens should not be run empty. To test for the pres-
ence 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 Before
Servicing procedure and re-examine the connections to the
component being tested.
When all service work is completed and the oven is fully as-
sembled, the microwave power output should be checked and
microwave leakage test should be carried out.
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2 - 1
CHAPTER 2. MICROWAVE MEASUREMENT PROCEDURE
[1] 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 and door sensing switch shall prevent microwave radiation emission in excess of
the requirement as above mentioned, secondary interlock switch shall prevent microwave radiation emission in excess of 5 mW/
cm2at any point 5cm or more from the external surface of the oven.
[2] 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 oven tray in the oven cavity.
3. Place the load of 275±5 ml (9.8 oz) of tap water initially at 20±5°C (68°F) 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.
The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any leakage is mea-
sured accurately.
4. Set the cooking control on Full Power Cooking Mode
5. Close the door 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.
[3] Leakage test:
Closed-door leakage test (microwave measurement)
1. Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door 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 door 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 door pull the door 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 secondary interlock switch and the primary interlock relay do turn the oven OFF before any door movement.
NOTE: After servicing, record data on service invoice and microwave leakage report.
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R-351NW
3 - 1
CHAPTER 3. FOREWORD AND WARNING
[1] FOREWORD
This Manual has been prepared to provide Sharp Electronics Corp. Service Personnel with Operation and Service Information for the
SHARP MICROWAVE OVENS, R-351NW.
It is recommended that service personnel carefully study the entire text of this manual so that they will be qualified to render satisfac-
tory customer service.
Check the interlock switches and the door seal carefully. Special attention should be given to avoid electrical shock and microwave
radiation hazard.
[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 personnel.
[3] DANGER
Certain initial parts are intentionally not grounded and present a risk of electrical shock only during servicing. Service personnel - Do
not contact the following parts while the appliance is energized;
High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness;
If provided, Vent Hood, Fan assembly, Cooling Fan Motor.
All the parts marked “S” on parts list are used at voltages more than 250V.
Removal of the outer wrap gives access to voltage above 250V.
All the parts marked “*” on parts list may cause undue microwave exposure, by themselves, or when they are damaged, loosened or
removed.
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R-351NW
4 - 1
NOITPIRCSEDMETI
Power Requirements
120 Volts
60 Hertz
Single phase, 3 wire grounded
Power Consumption 1530W / Approx. 13 Amperes
Power Output 1100 W nominal of RF microwave energy (IEC Test procedure)
Operating frequency 2450 MHz
Case Dimensions
Width 20-1/2” (520mm)
Height 12-1/4” (310mm)
Depth 17-3/8” (441mm)
Cooking Cavity Dimensions
(1.0 Cubic feet)
Width 14-3/4” (375mm)
Height 8-1/8” (206mm)
Depth 15-1/4” (387mm)
NOTE: Internal capacity is calculated by measuring maximum
width, depth and height. Actual capacity for holding food is
less.
Control Complement
Touch Control System
Clock (1:00 - 12:59)
Timer (0 - 99 minutes 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
“Palomitas de Maíz” pad
“Minuto Extra” pad
Number selection pads
“Nivel de Potencia” pad
“Cronómetro / Reloj” pad
“Detencion / Cancelacion” pad
“Comienzo” pad
“Derretir” pad
“Functión Rápida Suavizar” pad
“Calentar” pad
“1 Mantequilla 2 Chocolate” pad
“1 Helados 2 Queso crema” pad
“1 Coberturas de postres” pad
“COCCIÓN” pad
“DESCONGELACION” pad
“RECALENTAR” pad
Oven Cavity Light Yes
CHAPTER 4. PRODUCT DESCRIPTION
[1] SPECIFICATIONS
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R-351NW
[2] OVEN DIAGRAM
1. OVEN
1. Door open button
Push to open door.
2. Oven door with see-through window
3. Safety door latches
The oven will not operate unless the
door is securely closed.
4. Door hinges
5. Door seals and sealing surfaces
6. Turntable motor shaft
7. Removable turntable support
Carefully place the turntable support
in the center of the oven floor.
8. Removable turntable
Place the turntable securely on the turntable support. The turntable will rotate clockwise or counterclockwise. Only remove for
cleaning.
9. Ventilation openings (Rear)
10. Oven light
It will light when oven is operating or when the door is open.
11. Waveguide cover: DO NOT REMOVE.
12. Auto-Touch control panel
13. Time display: 99 minutes, 99 seconds
14. Power supply cord
14
8
9
7
12
13
1
5
32
46
11 310
5 - 1
CHAPTER 5. GENERAL INFORMATION
[1] GROUNDING INSTRUCTIONS
This oven is equipped with a three prong grounding plug. It must be plugged into a wall receptacle that is properly installed and
grounded in accordance with the National Electrical Code and local codes and ordinances.
In the event of an electrical short circuit, grounding reduces the risk of 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. A short power-
supply cord is provided to reduce risks of becoming entangled in or tripping over a longer
cord. 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 properly
grounded and polarized. If the extension cord must be used, it should be a 3-wire, 15 amp.
or higher rated cord. Do not drape over a countertop or table where it can be pulled on by
children or tripped over accidentally.
CAUTION: DO NOT UNDER ANY CIRCUMSTANCES CUT OR REMOVE THE ROUND
GROUNDING PRONG FROM THIS PLUG.
3-Pronged
Plug
Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
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R-351NW
2. TOUCH CONTROL PANEL
NOTE: Some one-touch cooking features such as “MINUTE PLUS” are disabled after three minutes when the oven is not in use.
These features are automatically enabled when the door is opened and closed or the STOP/ CLEAR pad is pressed.
5 - 2
Cronometro
Minuto Extra
1 Mantequilla
2 Chocolate
1 Helados
2 Queso crema
1 Coberturas de
postres
DESCONGELACION
RECALENTARCOCCION
1 Verdura
Fresca
2 Came Molida
3 Papa Asada
4 Arroz
5 Verdura
6 Entradas
Congelada
Congeladas
1 Came Molida
2 Aves
3 Bistec/
Deshuesadas
Chuletas
4 Aves
1 Caserola
2 Sopa
3 Pizza
4 Bebida
5 Plato Principal
6 Pan Presco
7 Pan Congelada
8 Veroura Bnlatada
Derretir Suavizar Calentar
Function Rapida
Reloj
Nivel de
Potencia
Comienzo
Detencion
Cancelacion
Palomitas de Maiz
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R-351NW
CHAPTER 6. OPERATION
[1] DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during
oven operation.
1. OFF CONDITION
Closing the door activates 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. (Figure O-1).
1) The display will show flashing “88:88”.
To set any program or set the clock, touch the STOP/CLEAR pad.
The display will clear, and “ : ” will appear.
2. COOKING CONDITION
Program desired cooking time by touching the NUMBER pads.
And program the power level by touching the POWER LEVEL pad.
When the START pad is touched, the following operations occur:
1) The contacts of the relays are closed and components con-
nected to the relays are turned on as follows.
(For details, refer to Figure O-2)
6 - 1
RELAY CONNECTED COMPONENTS
RY-1 oven lamp/turntable motor/fan motor
RY-2 power transformer
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 2400 volts A.C.
on the high voltage winding.
3)
The filament winding voltage heats the magnetron filament and
the H.V. winding voltage is sent to a voltage doubler circuit.
4) The microwave energy produced by the magnetron is chan-
nelled 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 door is opened during a cook cycle, monitor switch,
door sensing switch, secondary interlock switch, relay (RY1)
and primary interlock relay are activated with the following
results. The circuits to the turntable motor, the cooling fan
motor, and the high voltage components are de-energized,
and the digital read-out displays the time still remaining in the
cook cycle when the door was opened.
7) The monitor switch is electrically monitoring the operation of
the secondary interlock switch and primary interlock relay
and is mechanically associated with the door so that it will
function in the following sequence.
a) When the door opens from the closed position, the pri-
mary interlock relay (RY2) and secondary interlock switch
open their contacts. And contacts of the relay (RY1)
remains closed. Then the monitor switch contacts close.
b) When the door 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 door is opened, the closing
of the monitor switch contacts will form a short circuit through the
monitor fuse, secondary interlock switch, relay (RY1) and primary
interlock relay (RY2), causing the monitor fuse to blow.
3. POWER LEVEL P-0 TO P-HI COOKING
When Variable Cooking Power is programmed, the 120 volts
A.C. is supplied to the power transformer intermittently 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
P-HI (100% power) 32 sec. 0 sec.
P-90 (approx. 90% power) 30 sec. 2 sec.
P-80 (approx. 80% power) 26 sec. 6 sec.
P-70 (approx. 70% power) 24 sec. 8 sec.
P-60 (approx. 60% power) 22 sec. 10 sec.
P-50 (approx. 50% power) 18 sec. 14 sec.
P-40 (approx. 40% power) 16 sec. 16 sec.
P-30 (approx. 30% power) 12 sec. 20 sec.
P-20 (approx. 20% power) 8 sec. 24 sec.
P-10 (approx. 10% power) 6 sec. 26 sec.
P-0 (0% power) 0 sec. 32 sec.
NOTE: The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approx. 3 seconds are needed for heating of the
magnetron filament.
4. POWER OUTPUT REDUCTION
If the oven is set for more than 20 minutes at 80, 90 or 100%
power level, after the first 20 minutes the power level will auto-
matically adjust itself to 70% power to avoid overcooking.
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R-351NW
1. Off Condition
Figure O-1. Oven Schematic-Off Condition
2. Cooking Condition
Figure O-2. Oven Schematic-Cooking Condition
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED
2. CLOCK APPEARS ON DISPLAY
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
2. COOKING TIME PROGRAMMED.
3. VARIABLE COOKING CONTROL "P-HI".
4. START PAD TOUCHED.
120V AC
60 Hz
OVEN
LAMP
OVEN LAMP
RELAY TURN-
TABLE
MOTOR
FAN
MOTOR
POWER
TRANSFORMER
R
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H
CT
IW
S
RECTIFIER
N
ORTENGA
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SECONDARY
INTERLOCK
SWITCH
TTM
OL FM
DOOR
SENSING
SWITCH
(RY1)
(RY2)
CONTROL UNIT
PRIMARY
INTERLOCK
RELAY
GRN
B2
CAPACITOR
0.91µF
AC 2100V
B1
FUSE
20A
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ROTI
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SAPYBEN
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O
T
ICA
P
AC
V521
C
A
/Fµ3300.0
L
N
RETLIFESION
(MAGNETRON)
NOTE: " " indicates components with potentials above 250V
120V AC
60 Hz
OVEN
LAMP
OVEN LAMP
RELAY TURN-
TABLE
MOTOR
FAN
MOTOR
POWER
TRANSFORMER
R
OTINOM
HCTIWS
RECTIFIER
NO
R
TE
NG
AM
SECONDARY
INTERLOCK
SWITCH
TTM
OL FM
DOOR
SENSING
SWITCH
(RY1)
(RY2)
CONTROL UNIT
PRIMARY
INTERLOCK
RELAY
GRN
B2
CAPACITOR
0.91µF
AC 2100V
B1
FUSE
20A
LIOCN
O
IS
S
ERPPUSES
I
ON
R
O
T
I
CAP
A
C
S
S
O
RC
E
NI
L
V052C
A
/
F
µ22
.
0
SSAP
YB
ENIL
ROTI
C
APAC
V521CA/Fµ3300.0
SSAPY
B
ENIL
ROTICA
PAC
V521CA/Fµ3300.0
LN
RETL
IFES
I
O
N
(MAGNETRON)
NOTE: " " indicates components with potentials above 250V
6 - 2
[2] OVEN SCHEMATIC
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6 - 3
1. DOOR OPEN MECHANISM
The door is opened by pushing the open button on the control
panel, refer to the Figure D-1.
When the open button is pushed, the open button pushes up
the switch lever, and then the switch lever pushes up the latch
head. The latch heads are moved upward and released from
latch hook. Now the door will open.
[3] DESCRIPTION AND FUNCTION OF COMPONENTS
2. DOOR SENSING AND SECONDARY
INTERLOCK SWITCHES
The secondary interlock switch is mounted in the lower position
of the latch hook and the door sensing switch in the primary
interlock system is mounted in the upper position of the latch
hook. They are activated by the latch heads on the door. When
the door is opened, the switches interrupt the power to all high
voltage components. A cook cycle cannot take place until the
door is firmly closed thereby activating both interlock switches.
The primary interlock system consists of the door sensing switch
and primary interlock relay located on the control circuit board.
3. MONITOR SWITCH
The monitor switch is activated (the contacts opened) by the
latch head on the door while the door is closed. The switch is
intended to render the oven inoperative, by means of blowing
the monitor fuse, when the contacts of the primary interlock relay
(RY2) and secondary interlock switch fail to open when the door
is opened.
Functions:
1) When the door is opened, the monitor switch contacts close
(to the ON condition) due to their being normally closed.
At this time the primary interlock relay (RY2) and secondary
interlock switch are in the OFF condition (contacts open)
due to its being normally open contact switches.
2) As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing switch
and secondary interlock switch contacts close.
3) If the door is opened, and the primary interlock relay (RY2)
and the secondary interlock switch contact fail to open, the
monitor fuse blows simultaneously with closing of the
monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE,
TEST THE DOOR SENSING SWITCH, PRIMARY
INTERLOCK RELAY (RY2), SECONDARY
INTERLOCK SWITCH AND MONITOR SWITCH
FOR PROPER OPERATION. (REFER TO CHAPTER
“TEST PROCEDURE”).
NOTE: MONITOR FUSE AND MONITOR SWITCH ARE
REPLACED AS AN ASSEMBLY.
Figure D-1. Door Open Mechanism.
Latch
Heads
Door
Switch Lever
Latch Hook
Door Sensing
Switch
Monitor Switch
Secondary
Interlock Switch
4. TURNTABLE MOTOR
The turntable motor rotates the turntable located on the bottom
of the oven cavity, so that the food on the turntable is cooked
evenly. The turntable may turn in either direction.
5. COOLING FAN MOTOR
The cooling fan motor drives a blade which draws external cool
air. This cool air is directed through the air vents surrounding
the magnetron and cools the magnetron. 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.
6. MAGNETRON TEMPERATURE FUSE
The temperature fuse located near the magnetron is designed
to prevent damage to the magnetron if an over heated condition
develops in the tube due to cooling fan failure, obstructed air
guide, dirty or blocked air intake, etc. Under normal operation,
the temperature fuse remains closed. However, when abnormally
high temperatures are reached within the magnetron, the
temperature fuse will open at 302°F(150°C) causing the oven to
shut down.
7. THERMAL CUT-OUT (OVEN)
The thermal cut-out, located on the top of the oven cavity, 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 thermal cutout will open. Under normal operation, the
oven thermal cut-out remains closed. However, when abnormally
high temperatures are reached within the oven cavity, the oven
thermal cut-out will open at 293°F(145°C), causing the oven to
shut down.
8. MONITOR FUSE
1) The monitor fuse blows when the contacts (COM-NO) of the
primary interlock relay (RY2) and the secondary interlock
switch remain closed with the oven door open and when the
monitor switch closes.
2) If the wire harness or electrical components are short-
circuited, this monitor fuse blows to prevent an electric
shock or fire hazard.
9. NOISE FILER
The noise filter prevents the radio frequency interference that
might flow back in the power circuit.
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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 monitor fuse, check the monitor switch, primary interlock relay (RY2), door
sensing switch and secondary interlock switch before replacing the monitor fuse. If monitor fuse is replaced, the monitor switch must
also be replaced. Use part QFS-BA009WRE0 and QSW-MA086WRE0 as an assembly.
7 - 1
CHAPTER 7. TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
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.
[1] TROUBLESHOOTING CHART
RE CK A B C D E F F G H RE RE CK J CK CK CK K L N I
POSSIBLE CASE
AND DEFECTIVE PARTS
DROCREWO
P
NITROHS
GNIRIWDENEPOROTROHS
NORTENGAM
REMROFSNARTREW
O
P
YLBMESSAREI
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ITCER.V.H
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EG
A
TLOVHGI
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ES
UFER
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TA
R
EPME
T
TUO-TU
CLA
MR
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HTro
METSYSKCOLRE
T
NIYRAMI
RP
HCTIWSKCOLRETNI
Y
RA
D
NO
C
ES
HCTIWSROTINOM
E
S
U
F
ROT
I
NOM
PMA
L
NEVO
ROTOMNA
F
GN
IL
OO
C
ROT
OM
ELBATN
R
U
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LENAPLOR
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CUOT
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ORW
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I
N
UYE
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)
1YR(YALER
BW
P
NO
N
RE
T
TAP
LIO
F
RETLIFESION
CONDITION PROBLEM
OFF
CONDITION
TEST PROCEDURE
COOKING
CONDITION
M
T
S
O
R
FE
D
Home fuse or circuit breaker blows when
power cord is plugged into wall receptacle
Monitor fuse blows when power cord is plug-
ged into wall receptacle.
All letters and indicators do not appear in dis-
play when power cord is first plugged into
wall outlet.
Display does not operate properly when
STOP/CLEAR key is touched. (Buzzer
should sound and ":" or time of day should
appear in display.)
Oven lamp does not light when door is
opened.
Oven lamp does not go out when door is
closed.
Oven lamp lights but fan motor and turntable
motor do not operate.
Oven does not go into cook cycle when
START pad is touched
Oven seems to be operating but little or no
heat is produced in oven load. (Food incom-
pletely cooked or not cooked at all at end of
cook cycle.)
Oven goes into a cook cycle but extremely
uneven heating is produced in oven load
(food).
Oven does not cook properly when program-
med for Cooking Power P-50 mode. (Oper-
ates properly on Cooking Power P-HI (HIGH)
mode.)
Oven goes into DEFROST but food is not
defrosted well.
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[1] A: MAGNETRON ASSEMBLY TEST
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. 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. Reinstall the outer case (cabinet).
8. Reconnect the power supply cord after the outer case is installed.
9. Run the oven and check all functions.
1. MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled condition (outer case fitted).
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: silicon rectifier, high voltage ca-
pacitor and power transformer.
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 thermo
couple temperature tester. Stir the thermometer or thermocouple through the water until the temperature stabilizes. Record the tem-
perature of the water.
2. Place the cup of water in the oven. Operate oven at P-HI (100% Power) 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 32.1 to 59.7°F(17.9 to 33.2°C)
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.
[2] B: POWER TRANSFORMER TEST
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 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 155 ohms (RTRN-A767WRZZ) or 150 ohms (RTRN-A729WRZZ) or 125 ohms (RTRN-
A730WRZZ); the resistance of the filament coil should be less than 1 ohm.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO MEASURE THE FILAMENT
AND HIGH VOLTAGE.)
[3] C: HIGH VOLTAGE RECTIFIER TEST
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. Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance across the terminals and observe,
reverse the leads to the rectifier terminals and observe meter reading. If a short is indicated in both directions, or if an infinite resis-
tance is read in both directions, the rectifier is probably defective and should be replaced.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts.
8 - 1
CHAPTER 8. TEST PROCEDURES
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[4] D: HIGH VOLTAGE CAPACITOR TEST
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. If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads and check for short or open be-
tween the terminals 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.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
[5] E: TEMPERATURE FUSE OR THERMAL CUT-OUT TEST
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. Check a continuity across the temperature fuse or thermal cut-out terminals in the table below.
Table: Temperature Fuse and Thermal Cut-out Test
Parts Name Temperature of “ON” condition
(closed circuit).
Temperature of “OFF” condition
(open circuit).
Indication of ohmmeter (When room
temperature is approx. 20°C.)
Temperature fuse 150°C This is not resetable type. Above 150°C (302°F) Closed circuit
Thermal cut-out 145°C This is not resetable type. Above 145°C (293°F) Closed circuit
5. An open temperature fuse (Magnetron) or thermal cut-out (Magnetron) indicates overheating of the magnetron. Check for restricted
air flow to the magnetron, especially the cooling fan and air guide.
An open temperature fuse (Oven) or thermal cut-out (Oven) indicates overheating of the oven, exchange the temperature fuse or
thermal cut-out and check inside of oven cavity and for improper setting of cooking time or operation of control unit. Check for re-
stricted air flow through the vent holes of the oven cavity, especially the cooling fan and air guide.
6. Reconnect all leads removed from components during testing.
7. Reinstall the outer case (cabinet).
8. Reconnect the power supply cord after the outer case is installed.
9. Run the oven and check all functions.
CAUTION: IF THE TEMPERATURE FUSE OR THERMAL CUT-OUT INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE,
REPLACE IT
[6] F: SECONDARY INTERLOCK SWITCH TEST
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. 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, re-
place the secondary interlock switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
8 - 2
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Monitor
Switch
Secondary
Interlock Switch
Screw Driver
Ohmmeter
BLK
GRY
WHT
8 - 3
[7] F: PRIMARY INTERLOCK SYSTEM TEST
1. DOOR SENSING SWITCH
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. 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, re-
place the door sensing switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: If the door sensing switch contacts fail in the open position and the door is closed, the cooling fan, turntable and oven light
will be activated by RY1.
2. PRIMARY INTERLOCK RELAY (RY2)
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 two (2) wire leads from the male tab terminals of the Primary Interlock Relay. Check the state of the relay contacts using
a ohmmeter.
The relay contacts should be open. If the relay contacts are closed, replace the circuit board entirely or the relay itself.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
[8] G: MONITOR SWITCH TEST
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. Before performing this test, make sure that the secondary interlock switch and the primary interlock relay are operating properly,
according to the above Switch Test Procedure. Disconnect the wire lead from the monitor switch (COM) terminal. Check the moni-
tor switch 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 screwdriver through the lower 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 op-
eration is indicated, the switch may be defective. 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. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
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8 - 4
[9] H: BLOWN MONITOR FUSE TEST
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. If the monitor fuse is blown when the door is opened, check the primary interlock relay, secondary interlock switch and monitor
switch according to the “TEST PROCEDURE” for those switches before replacing the blown monitor fuse.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE PRIMARY INTERLOCK RELAY, SECONDARY INTER
LOCK SWITCH, DOOR SENSING 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” part number QFS-BA009WRE0 and QSW-MA086WRE0, 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. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
[10] I: NOISE FILTER TEST
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 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.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
MEASURING POINT INDICATION OF OHMMETER
Between N and L Open circuit.
Between terminal N and WHITE Short circuit.
Between terminal L and RED Short circuit.
[11] J: TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional microwave
ovens, proper maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control panel
assembly is divided into two units, Control Unit and Key Unit, and also the Control Unit is divided into two units, CPU Unit and Power
Unit, and troubleshooting by unit replacement is described according to the symptoms indicated.
Before testing,
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 these leads remain isolated from other components and oven chassis by using insulation tape.
1. Key Unit
NOTE:
1) Re-install the outer case (cabinet).
2) Reconnect the power supply cord after the outer case is installed.
3) Run the oven and check all functions.
The following symptoms indicate a defective key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
FUSE 20A
NOISE FILTER
NOISE SUPPRESSION COIL
LINE CROSS CAPACITOR
0.22µF / AC 250V
LINE BYPASS
CAPACITOR
0.0033µF / AC 125V
LINE BYPASS
CAPACITOR
0.0033µF / AC 125V
L
REDWHITE
N
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2. Control Unit.
The following symptoms indicate a defective control unit.
1) In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2) 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.
3) 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. If the Key unit or control unit is defective.
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) Replace the control unit assembly.
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.
4. When 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 all leads removed from components during testing.
5) Re-install 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] K: KEY UNIT TEST
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. Using an ohmmeter and referring to the key unit matrix indicated on the control unit circuit, check the circuit between the pins of the
key unit that correspond to the STOP/CLEAR pad. When the pad is pressed, the ohmmeter should indicate short circuit. When the
pad is released, the ohmmeter should indicate open circuit. If incorrect readings are obtained, the key unit is faulty and must be re-
placed. About the other pads, the above method may be used.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
8 - 5
MINUTE
PLUS
STOP
CLEAR
POWER
LEVEL
WARM
COOK POPCORN
SOFTEN
REHEAT
MELT
TIMER
CLOCK
789
3
6
0
5
2
1
4
START DEFROST
G10
G9
G8
G7
G6 G5 G4 G3 G2 G1
Pin NO. G12 Pin NO. G1
Key unit ribbon cable
Key unit (Membrane Switch) front view
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8 - 6
[13] L: RELAY TEST
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 these leads remain isolated from other components and oven chassis by using insulation tape.
6. After that procedure, re-connect the power supply cord.
7. Remove the outer case and check voltage between the cabinet side terminal of the relay RY1 and the oven side terminal of the re-
lay RY2 on the control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
RY1 and RY2 Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
DC. voltage indicated ................. Defective relay.
DC. voltage not indicated ........... Check diode which is connected to the relay coil. If diode is good, control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx. -12V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 Approx. -11V D.C. Power transformer
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.
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 functions.
[14] M: DEFROST TEST
WARNING: The oven should be fully assembled before following procedure.
1. Place one cup of water in the center of the turntable tray in the oven cavity.
2. Close the door, touch the “DEFROST” pad once. And then touch the number pad 2.
3. Touch the number pad 5 and then touch the start pad.
4. The oven is in Defrost cooking condition.
5. The oven will operate as follows.
MENU 1ST STAGE 2ND STAGE 3RD STAGE
Steaks/Chops
0.5lb
LEVEL TIME LEVEL TIME LEVEL TIME
70% 17sec. 60% 27sec. 30% 40sec.
6. If improper operation is indicated, the control unit is probably defective and should be checked.
[15] N: FOIL PATTERN ON THE PRINTED WIRING BOARD TEST
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on the PWB, this foil pattern acts
as a fuse.
1. Foil pattern check and repairs.
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) Follow the troubleshooting guide given below for repair.
STEPS OCCURRENCE CAUSE OR CORRECTION
1 Only pattern at “a” is broken. *Insert jumper wire J1 and solder.
2 Pattern at “a” and “b” are broken. Replace the control unit.
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5) Make a visual inspection of the varistor. Check for burned damage and examine the
transformer with a tester for the presence of layer short-circuit (check the primary coil
resistance which is approximately 563Ω±10%). If any abnormal condition is detected,
replace the control unit assembly.
6) Reconnect all leads removed from components during testing.
7) Re-install the outer case (cabinet).
8) Reconnect the power supply cord after the outer case is installed.
9) Run the oven and check all functions.
2. Follow the troubleshooting guide given below, if indicator does not light up after
above check and repairs are finished.
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 these leads remain isolated from other components and oven chassis by using insulation tape.
6) After that procedure, re-connect the power supply cord.
7) Follow the troubleshooting guide given below for repair.
8 - 7
STEPS OCCURRENCE CAUSE OR CORRECTION
1
The rated AC voltage is not present between the cabinet side terminal
of the relay RY1 and the oven side terminal of the relay RY2.
Check supply voltage and oven power cord.
2The rated AC voltage is present at primary side of low voltage
transformer.
Low voltage transformer or secondary circuit defective.
Check and replace control unit.
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.
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 functions.
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