Sharp R-306LK User manual

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
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
SERVICE MANUAL
R306LW
CONTENTS
SHARP CORPORATION This document has been published to be used
for after sales service only.
The contents are subject to change without notice.
S2603R306KPW/
MICROWAVE OVEN
R-306LK
R-306LW
MODELS
In the interest of user-safety the oven should be restored to its origi-
nal condition and only parts identical to those specified should be
used.
WARNING TO SERVICE PERSONNEL: Microwave ovens con-
tain circuitry capable of producing very high voltage and cur-
rent, contact with following parts may result in a severe,
possibly fatal, electrical shock. (High Voltage Capacitor, High
Voltage Power Transformer, Magnetron, High Voltage Rectifier
Assembly, High Voltage Harness etc..)

CONTENTS
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE EXPO-
SURE TO EXCESSIVE MICROWAVE ENERGY
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 PRO-
CEDURE
[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] Procedure A: MAGNETRON ASSEMBLY
TEST ..........................................................8-1
[2] Procedure B: POWER TRANSFORMER
TEST ..........................................................8-1
[3] Procedure C: HIGH VOLTAGE RECTIFI-
ER TEST ....................................................8-1
[4] Procedure D: HIGH VOLTAGE CAPACI-
TOR TEST..................................................8-2
[5] Procedure E: TEMPERATURE FUSE OR
THERMAL CUT-OUT TEST .......................8-2
[6] Procedure F: SECONDARY INTERLOCK
SWITCH TEST ...........................................8-2
[7] Procedure F: PRIMARY INTERLOCK
SYSTEM TEST...........................................8-2
[8] Procedure G: MONITOR SWITCH TEST.....8-3
[9] Procedure H: BLOWN MONITOR FUSE
TEST ..........................................................8-3
[10] Procedure I: NOISE FILTER TEST.............8-4
[11] Procedure J: TOUCH CONTROL PANEL
ASSEMBLY TEST ......................................8-4
[12] Procedure K: KEY UNIT TEST ................... 8-5
[13] Procedure L: RELAY TEST......................... 8-6
[14] Procedure M: DEFROST TEST.................. 8-6
[15] Procedure N: FOIL PATTERN ON THE
PRINTED WIRING BOARD TEST.............. 8-6
CHAPTER 9. TOUCH CONTROL PANEL ASSEM-
BLY
[1] OUTLINE OF TOUCH CONTROL PANEL..... 9-1
[2] DESCRIPTION OF LSI ............................... 9-1
[3] SERVICING FOR TOUCH CONTROL
PANEL ........................................................ 9-3
CHAPTER 10. PRECAUTIONS FOR USING LEAD-
FREE SOLDER
[1] Employing lead-free solder ....................... 10-1
[2] Using lead-free wire solder ....................... 10-1
[3] Soldering................................................... 10-1
CHAPTER 11. COMPONENT REPLACEMENT AND
ADJUSTMENT PROCEDURE
[1] WARNINGS ...............................................11-1
[2] OUTER CASE REMOVAL .........................11-2
[3] POWER TRANSFORMER REMOVAL ......11-2
[4] HIGH VOLTAGE COMPONENTS RE-
MOVAL(HIGH VOLTAGE CAPACITOR
AND HIGH VOLTAGE RECTIFIER AS-
SEMBLY) ...................................................11-2
[5] MAGNETRON REMOVAL .........................11-2
[6] POSITIVE LOCK CONNECTOR (NO-
CASE TYPE) REMOVAL ...........................11-3
[7] CONTROL PANEL ASSEMBLY REMOV-
AL ..........................................................
....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 REPLACE-
MENT.........................................................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 ...........................11-5
[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 (Figure S-3) ............ 12-3
Parts List

R306LW
i
R306LW Service Manual
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID
POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
BEFOR 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

R306LW
1 – 1
R306LW Service Manual
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.
[1] Before Servicing
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 connect 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) 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 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 Before Servicing procedure 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 microwave leak-
age test should be carried out.
Don't Touch !
Danger High Voltage

R306LW
2 – 1
R306LW Service Manual
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 use-
ful 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
non conductive 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 measured 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.

R306LW
3 – 1
R306LW Service Manual
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-306LK and R-306LW.
It is recommended that service personnel carefully study the entire text of this manual so that they will be qualified to render satisfactory customer
service.
Check the interlock switches and the door seal carefully. Special attention should be given to avoid electrical shock and microwave radiation hazard.
[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 “ “ 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.

R306LW
4 – 1
R306LW Service Manual
CHAPTER 4. PRODUCT DESCRIPTION
[1] SPECIFICATIONS
ITEM DESCRIPTION
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
Outside Dimensions
Width 20-1/2" (520mm)
Height 12-1/4" (310mm)
Depth 17-1/4" (439mm)
Cooking Cavity Dimensions
(1.0 Cubic feet)
Width 14-3/4" (375mm) NOTE: Internal capacity is calculated by measuring
Height 8-1/8" (206mm) maximum width, depth and height.
Depth 15-1/4" (387mm) 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. 30% of FULL Power
P-30 -------------------- approx. 40% 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
POPCORN pad
MINUTE PLUS pad
SHORT CUTS pads
REHEAT pad
COOK pad
DEFROST pad
Number selection pads
POWER LEVEL pad
TIMER / CLOCLK pad
STOP/CLEAR pad
START pad
Oven Cavity Light Yes
Safety Standard UL listed FCC Authorized
DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J

R306LW
5 – 1
R306LW Service Manual
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 accor-
dance 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.
[2] OVEN DIAGRAM
1. OVEN
1. Door opening button
Push to open door.
2. Oven door with see-through win-
dow
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 sup-
port in the center of the oven floor.
8. Removable turntable
Place the turntable securely on the turntable support securely. 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
3-Pronged
Plug
Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
14
8
9
7
12
13
1
5
32
46
11 310

R306LW
5 – 2
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 fea-
tures are automatically enabled when the door is opened and closed or the STOP/ CLEAR pad is pressed.

R306LW
6 – 1
R306LW Service Manual
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 inter-
lock switch. (In this condition, the monitor switch contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the noise filter
and the control unit. (Figure O-1).
1) The display will show flashing "88:88".
To set any program or set the clock, you must first touch the STOP/
CLEAR pad. The display will clear, and " : " will appear.
2. COOKING CONDITION
Program desired cooking time by touching the NUMBER pads. Pro-
gram the power level by touching the POWER LEVEL pad. When the
START pad is touched, the following operations occur:
1) The contacts of relays are closed and components connected to
the relays are turned on as follows.
(For details, refer to Figure O-2)
2) 120 volts A.C. is supplied to the primary winding of the power trans-
former and is converted to about 3.3 volts A.C. output on the fila-
ment winding, and approximately 2360 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 channelled
through the waveguide into the cavity feed-box, and then into the
cavity where the food is placed to be cooked.
5) Upon completion of the cooking time, the power transformer, oven
lamp, etc. are turned off, and the generation of microwave energy
is stopped. The oven will revert to the OFF condition.
6) When the door is opened during a cook cycle, the 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, the oven lamp remains on,
and the digital read-out displays the time still remaining in the cook
cycle when the door was opened.
7) The monitor switch electrically monitors the operation of the sec-
ondary interlock switch and primary interlock relay and is mechani-
cally associated with the door so that it will function in the following
sequence.
a) When the door opens from the closed position, the primary
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-90 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:
NOTE: The ON/OFF time ratio does not correspond with the per-
centage 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 automatically adjust
itself to 70% power to avoid overcooking.
RELAY CONNECTED COMPONENTS
RY-1 oven lamp/turntable motor/fan motor
RY-2 power transformer
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.

R306LW
6 – 2
[2] OVEN SCHEMATIC
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.
POWER
TRANSFORMER
RECTIFIER
MAGNETRON
CAPACITOR
0.91μF
AC2100V
OVEN
LAMP
TURN-
TABLE
MOTOR
FAN
MOTOR
MONITOR
SWITCH
SECONDARY
INTERLOCK
SWITCH
TTM
OL FM
A1
DOOR
SENSING
SWITCH
B2 B1
(RY-1) (RY-2)
CONTROL UNIT
PRIMARY
INTERLOCK
RELAY
A3
TEMPERATURE
FUSE 150ºC (OVEN)
TEMPERATURE FUSE
150ºC (MAGNETRON)
THERMAL CUT-OUT
145ºC (OVEN)
120V AC
60 Hz
GRN
FUSE
20A
NOISE SUPPRESSION COIL
LINE CROSS CAPACITOR
0.22μF / AC 250V
LINE BYPASS
CAPACITOR
0.0033μF / AC125V
LINE BYPASS
CAPACITOR
0.0033μF / AC 125V
LN
NOISE FILTER
or
NOTE: " " indicates components with potentials above 250V
POWER
TRANSFORMER
RECTIFIER
MAGNETRON
CAPACITOR
0.91μF
AC2100V
OVEN
LAMP
TURN-
TABLE
MOTOR
FAN
MOTOR
MONITOR
SWITCH
SECONDARY
INTERLOCK
SWITCH
TTM
OL FM
A1
DOOR
SENSING
SWITCH
B2 B1
(RY-1) (RY-2)
CONTROL UNIT
PRIMARY
INTERLOCK
RELAY
A3
TEMPERATURE
FUSE 150ºC (OVEN)
TEMPERATURE FUSE
150ºC (MAGNETRON)
THERMAL CUT-OUT
145ºC (OVEN)
120V AC
60 Hz
GRN
FUSE
20A
NOISE SUPPRESSION COIL
LINE CROSS CAPACITOR
0.22μF / AC 250V
LINE BYPASS
CAPACITOR
0.0033μF / AC125V
LINE BYPASS
CAPACITOR
0.0033μF / AC 125V
LN
NOISE FILTER
or

R306LW
6 – 3
[3] DESCRIPTION AND FUNCTION OF COMPONENTS
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.
Figure D-1. Door Open Mechanism.
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 can-
not 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.
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 magne-
tron 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 cav-
ity.
6. TEMPERATURE FUSE (MAGNETRON)
The temperature fuse located near the magnetron is designed to pre-
vent 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 cut-
out 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. TEMPERATURE FUSE (OVEN)
The temperature fuse, 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 cut-out will open. Under normal operation, the temperature
fuse remains closed. However, when abnormally high temperatures
are reached within the oven cavity, the temperature fuse will open at
302°F(150°C), causing the oven to shut down.
9. MONITOR FUSE
1) The monitor fuse blows when the contacts (COM-NO) of the pri-
mary 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.
10. NOISE FILER
The noise filter prevents the radio frequency interference that might
flow back in the power circuit.
Latch
Heads
Door
Switch Lever
Latch Hook
Door Sensing
Switch
Monitor Switch
Secondary
Interlock Switch

R306LW
7 – 1
R306LW Service Manual
CHAPTER 7. 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 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 FFS-BA037WRKZ as an assembly.
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
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
RE CK A B C D E F F G H RE RE CK J CK CK CK K L NI
POSSIBLE CASE
AND DEFECTIVE PARTS
SHORT IN POWER CORD SHORT OR OPENED WIRING MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR TEMPERATURE FUSE or THERMAL CUT-OUT PRIMARY INTERLOCK SYSTEM SECONDARY INTERLOCK SWITCH MONITOR SWITCH MONITOR FUSE OVEN LAMP COOLING FAN MOTOR TURNTABLE MOTOR TOUCH CONTROL PANEL WRONG OPERATION LOW VOLTAGE DIRTY OVEN CAVITY KEY UNIT (MEMBRAINE SWITCH RELAY (RY1) FOIL PATTERN ON PWB NOISE FILTER
CONDITION PROBLEM
OFF
CONDITION
TTEST PROCEDURE
COOKING
CONDITION
M
DEFROST
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 pad 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.

R306LW
8 – 1
R306LW Service Manual
CHAPTER 8. TEST PROCEDURES
[1] Procedure 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 indi-
cate a faulty magnetron and there is no defect in the following components or wiring: silicon rectifier, high voltage capacitor 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 thermocouple tempera-
ture tester. Stir the thermometer or thermocouple through the water until the temperature stabilizes. Record the temperature of the water.
2. Place the cup of water in the oven. Operate oven at 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 tempera-
ture. 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] Procedure 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 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] Procedure 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 resistance is read in both direc-
tions, the rectifier is probably defective and should be replaced.
5. Reconnect all leads removed from components during testing.

R306LW
8 – 2
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.
[4] Procedure 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 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.
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] Procedure 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.
5. An open temperature fuse (Magnetron) indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially the cool-
ing 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 restricted 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] Procedure 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, replace 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.
[7] Procedure F: PRIMARY INTERLOCK SYSTEM TEST
1. DOOR SENSING SWITCH
1. Disconnect the power supply cord, and then remove outer case.
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

R306LW
8 – 3
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, replace 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] Procedure 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 monitor 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 screw
driver 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 operation 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.
[9] Procedure 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 INTERLOCK SWITCH,
DOOR SENSING SWITCH AND MONITOR SWITCH FOR PROPER OPERATION.
Monitor
Switch
Secondary
Interlock Switch
Screw Driver
Ohmmeter
BLK
GRY
WHT

R306LW
8 – 4
If the monitor fuse is blown by improper switch operation, the monitor fuse and monitor switch must be replaced with “monitor fuse and monitor
switch assembly” part number FFS-BA037WRKZ, 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] Procedure 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 readings 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.
[11] Procedure 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 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.
6) After that procedure, re-connect the power supply cord.
1. Key Unit
NOTE:
1) Check key unit ribbon connection before replacement.
2) )Re-install the outer case (cabinet).
3) Reconnect the power supply cord after the outer case is installed.
4) 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.
If the key 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 key unit.
5) Reconnect all leads removed from components during testing.
6) Re-install the outer case (cabinet).
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.
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

R306LW
8 – 5
7) Reconnect the power supply cord after the outer case is installed.
8) Run the oven and check all functions.
2. Control Unit.
The following symptoms indicate a defective control unit. Before replacing the control unit, perform the Key unit test (Procedure K) to determine if con-
trol unit is faulty.
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.
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] Procedure 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 ohmme-
ter should indicate open circuit. If incorrect readings are obtained, the key unit is faulty and must be replaced. 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.
G4 G5 G6G1
G8
G9
G10
G2 G3
G7
REHEAT
4
1
7
2
5
8
0
6
3
TIMER
CLOCK
9
COOK
SOFTEN
WARM
POPCORN
MELT
DEFROST
POWER
LEVEL
STOP
CLEAR
START
Pin NO. G1 Pin NO. G10
Key unit ribbon
cable
Key unit (Membrane Switch) front view
MINUTE
PLUS

R306LW
8 – 6
[13] Procedure 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 Pin No. 1 of the 3 pin connector (A) and the lower side terminal of the relay 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.
8. If any abnormal condition is defected, replace the control unit.
9. Disconnect the power supply cord and then remove outer case.
10.Open the door and block it open.
11. Discharge high voltage capacitor.
12.Reconnect all leads removed from components during testing.
13.Re-install the outer case (cabinet).
14.Reconnect the power supply cord after the outer case is installed.
15.Run the oven and check all functions.
[14] Procedure 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.
6. If improper operation is indicated, the control unit is probably defective and should be checked.
[15] Procedure 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.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx. 12.5V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 Approx. 11.2V D.C. Power transformer
MENU 1ST STAGE 2ND STAGE 3RD STAGE
Steaks/Chops LEVEL TIME LEVEL TIME LEVEL TIME
0.5lb 70% 17sec. 60% 27sec. 30% 40sec.
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. *Insert the coil RCILF2003YAZZ between “c” and “d”.

R306LW
8 – 7
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 915Ω±10%). If any abnormal condition is detected,
replace the control unit.
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) 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.
STEPS OCCURRENCE CAUSE OR CORRECTION
1The rated AC voltage is not present between Pin No. 1 of the 3-pin con-
nector (A) and the lower 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 trans-
former.
Low voltage transformer or secondary circuit defective.
Check and replace control unit.
a
d
b
c