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R306LW
SERVICE MANUAL
S2603R306KPW/
MICROWAVE OVEN
MODELS R-306LK
R-306LW
In the interest of user-safety the oven should be restored to its original condition and only parts identical to those specified 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 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 EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
BEFORE SERVICING
CHAPTER 1. WARNING TO SERVICE PERSONNEL
CHAPTER 2. MICROWAVE MEASUREMENT PROCEDURE
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 LEADFREE SOLDER
CHAPTER 11. COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
CHAPTER 12. CIRCUIT DIAGRAMS
Parts List
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SHARP CORPORATION |
This document has been published to be used |
for after sales service only. |
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The contents are subject to change without notice. |
CONTENTS
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE 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- |
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CEDURE |
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[1] |
Requirements: ............................................ |
2-1 |
[2] |
Preparation for testing: ............................... |
2-1 |
[3] |
Leakage test: .............................................. |
2-1 |
CHAPTER 3. FOREWORD AND WARNING |
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[1] |
FOREWORD .............................................. |
3-1 |
[2] |
WARNING .................................................. |
3-1 |
[3] |
DANGER .................................................... |
3-1 |
CHAPTER 4. PRODUCT DESCRIPTION |
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[1] |
SPECIFICATIONS...................................... |
4-1 |
CHAPTER 5. GENERAL INFORMATION |
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[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 |
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[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
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TEST .......................................................... |
8-3 |
[10] |
Procedure I: NOISE FILTER TEST............. |
8-4 |
[11] |
Procedure J: TOUCH CONTROL PANEL |
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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 |
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[15] Procedure N: FOIL PATTERN ON THE |
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PRINTED WIRING BOARD TEST............. |
8-6 |
CHAPTER 9. TOUCH CONTROL PANEL ASSEMBLY
[1] |
OUTLINE OF TOUCH CONTROL PANEL..... 9-1 |
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[2] |
DESCRIPTION OF LSI.............................. |
9-1 |
[3] SERVICING FOR TOUCH CONTROL |
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PANEL ....................................................... |
9-3 |
CHAPTER 10. PRECAUTIONS FOR USING LEAD-
FREE SOLDER |
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[1] |
Employing lead-free solder ...................... |
10-1 |
[2] Using lead-free wire solder ...................... |
10-1 |
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[3] |
Soldering.................................................. |
10-1 |
CHAPTER 11. COMPONENT REPLACEMENT AND |
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ADJUSTMENT PROCEDURE |
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[1] |
WARNINGS .............................................. |
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 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
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SWITCH REPLACEMENT........................ |
11-3 |
[9] |
TURNTABLE MOTOR REMOVAL ............ |
11-4 |
[10] |
COOLING FAN MOTOR REMOVAL......... |
11-4 |
[11] |
POWER SUPPLY CORD REPLACE- |
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MENT........................................................ |
11-5 |
[12] DOOR SENSING SWITCH/SECONDARY |
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INTERLOCK SWITCH AND MONITOR |
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SWITCH REMOVAL ................................. |
11-5 |
[13] DOOR SENSING SWITCH/SECONDARY |
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INTERLOCK SWITCH AND MONITOR |
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SWITCH ADJUSTMENT .......................... |
11-5 |
[14] DOOR REPLACEMENT ........................... |
11-6 |
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CHAPTER 12. CIRCUIT DIAGRAMS |
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[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
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
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.
BEFOR SERVICING
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/cm2. The owner of the unit should be instructed not to use the unit until the oven has been brought into compliance.
i
R306LW
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] 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 reexamine 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 leakage test should be carried out.
1 – 1
R306LW
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/ cm2 at 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/cm2 at 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/cm2 at 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.
2 – 1
R306LW
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.
3 – 1
R306LW
CHAPTER 4. PRODUCT DESCRIPTION
[1] SPECIFICATIONS
ITEM |
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DESCRIPTION |
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120 Volts |
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Power Requirements |
60 Hertz |
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Single phase, 3 wire grounded |
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Power Consumption |
1530W / Approx. 13 Amperes |
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Power Output |
1100 W nominal of RF microwave energy (IEC Test procedure) |
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Operating frequency 2450 MHz |
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Width |
20-1/2" (520mm) |
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Outside Dimensions |
Height 12-1/4" (310mm) |
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Depth 17-1/4" (439mm) |
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Cooking Cavity Dimensions |
Width |
14-3/4" |
(375mm) |
NOTE: Internal capacity is calculated by measuring |
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Height |
8-1/8" |
(206mm) |
maximum width, depth and height. |
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(1.0 Cubic feet) |
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Depth 15-1/4" (387mm) |
Actual capacity for holding food is less. |
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Touch Control System |
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Clock (1:00 - 12:59) |
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Timer (0 - 99 minutes 99 seconds) |
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Microwave Power for Variable Cooking |
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Repetition Rate; |
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P-HI -------------------- |
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Full power throughout the cooking time |
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P-90 -------------------- |
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approx. 90% of FULL Power |
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P-80 -------------------- |
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approx. 80% of FULL Power |
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P-70 -------------------- |
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approx. 70% of FULL Power |
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P-60 -------------------- |
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approx. 60% of FULL Power |
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P-50 -------------------- |
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approx. 50% of FULL Power |
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P-40 -------------------- |
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approx. 30% of FULL Power |
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P-30 -------------------- |
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approx. 40% of FULL Power |
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Control Complement |
P-20 -------------------- |
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approx. 20% of FULL Power |
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P-10 -------------------- |
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approx. 10% of FULL Power |
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P-0 ---------------------- |
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No power throughout the cooking time |
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POPCORN pad |
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MINUTE PLUS pad |
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SHORT CUTS pads |
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REHEAT pad |
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COOK pad |
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DEFROST pad |
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Number selection pads |
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POWER LEVEL pad |
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TIMER / CLOCLK pad |
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STOP/CLEAR pad |
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START pad |
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Oven Cavity Light |
Yes |
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Safety Standard |
UL listed FCC Authorized |
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DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J |
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4 – 1
R306LW
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 wallreceptacle 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.
Grounded
Receptacle Box
3-Pronged Plug
Grounding Pin 
3-Pronged Receptacle
[2] OVEN DIAGRAM
1. OVEN
1. |
Door opening button |
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5 |
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Push to open door. |
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2. |
Oven door with see-through win- |
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13 |
14 |
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dow |
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3. |
Safety door latches |
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12 |
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The oven will not operate unless |
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4 |
6 |
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the door is securely closed. |
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4. |
Door hinges |
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1 |
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5. |
Door seals and sealing surfaces |
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8 |
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6. |
Turntable motor shaft |
3 |
2 |
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11 |
10 |
3 |
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7. |
Removable turntable support |
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7 |
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Carefully place the turntable sup- |
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9 |
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port in the center of the oven floor. |
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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
5 – 1
R306LW
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
R306LW
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 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. Program 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)
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 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 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 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:
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 automatically adjust itself to 70% power to avoid overcooking.
6 – 1
[2] OVEN SCHEMATIC
1. Off Condition
SCHEMATIC
NOTE: CONDITION OF OVEN
1.DOOR CLOSED
2.CLOCK APPEARS ON DISPLAY
L |
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FUSE |
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20A |
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FILTER |
0.22μF / AC 250V |
SUPPRESSIONNOISE COIL |
LINE BYPASS |
CAPACITOR |
0.0033μF / AC125V |
LINECROSSCAPACITOR |
BYPASSLINE |
CAPACITOR |
125VAC/0.0033μF |
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NOISE |
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GRN |
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120V AC |
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60 Hz |
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N |
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R306LW
TEMPERATURE
FUSE 150ºC (OVEN)
or
THERMAL CUT-OUT
150ºC (MAGNETRON)
TEMPERATURE FUSE 145ºC (OVEN) NOTE: " " indicates components with potentials above 250V
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POWER |
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TRANSFORMER |
A1 |
(RY-1) |
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(RY-2) |
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PRIMARY |
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INTERLOCK |
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RELAY |
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CAPACITOR |
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0.91μF |
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AC2100V |
CONTROL UNIT |
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A3 |
B2 |
B1 |
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DOOR |
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SENSING |
MONITOR |
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SWITCH |
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SWITCH |
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OL |
TTM |
FM |
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RECTIFIER |
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OVEN |
TURN- |
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FAN |
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MAGNETRON |
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LAMP |
TABLE |
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MOTOR |
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MOTOR |
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SECONDARY |
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INTERLOCK |
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SWITCH |
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Figure O-1. Oven Schematic-Off Condition
2. Cooking Condition
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
L
NOISE FILTER
GRN
N
FUSE |
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20A |
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LINE CROSS CAPACITOR 0.22μF / AC 250V |
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NOISE SUPPRESSION COIL |
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LINE BYPASS |
CAPACITOR |
0.0033μF / AC125V |
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LINE BYPASS |
CAPACITOR |
0.0033μF / AC 125V |
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TEMPERATURE |
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FUSE 150ºC (OVEN) |
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or |
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TEMPERATURE FUSE |
THERMAL CUT-OUT |
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145ºC (OVEN) |
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150ºC (MAGNETRON) |
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POWER |
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TRANSFORMER |
A1 |
(RY-1) |
(RY-2) |
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PRIMARY |
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INTERLOCK |
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RELAY |
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CAPACITOR |
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0.91μF |
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AC2100V |
CONTROL UNIT |
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A3 |
B2 |
B1 |
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DOOR |
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SENSING |
MONITOR |
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SWITCH |
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SWITCH |
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OL |
TTM |
FM |
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RECTIFIER |
OVEN |
TURN- |
FAN |
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MAGNETRON |
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LAMP |
TABLE |
MOTOR |
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MOTOR |
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SECONDARY |
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INTERLOCK |
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SWITCH |
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Figure O-2. Oven Schematic-Cooking Condition
6 – 2
R306LW
[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.
Door
Latch Hook
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Door Sensing |
Latch |
Switch |
Heads |
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Monitor Switch
Switch Lever
Secondary
Interlock Switch
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 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.
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. TEMPERATURE FUSE (MAGNETRON)
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. 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 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.
10. NOISE FILER
The noise filter prevents the radio frequency interference that might flow back in the power circuit.
6 – 3
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