R-1750
R-1751
R-1752
R-1754
SERVICE MANUAL
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ONE TOUCH |
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SENSOR |
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12 : 45 |
PM |
Reheat |
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1 |
2 |
3 |
Popcoon |
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4 |
5 |
6 |
Baked |
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7 |
8 |
9 |
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Potatoes |
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Minute |
0 |
Kitchen |
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Plus + |
Timer |
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Beverage |
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Center |
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Keep |
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MINUTE |
STOP/ |
START |
Warm |
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PLUS |
CLEAR |
Defrost |
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6x6 NO GUESS COOKING |
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6 Categories + 36 Foods |
3+6 |
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Meats |
Vegetables |
Poultry |
MORE |
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FROM YOUR |
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Fish/ |
Frozen |
Pasta |
MICROWAVE |
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Seafood |
Food |
Grains |
6 x 6 |
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Fan |
Light |
Turntable |
Set Up |
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Options |
Options |
On/Off |
S8019R1750X//
OVER THE RANGE
MICROWAVE OVEN
MODELS R-1750
R-1751
R-1752
R-1754
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 the following parts may result in a severe, possibly fatal, electrical shock. (Inverter unit that includes High Voltage Capacitor, High Voltage Power Transformer, High Voltage Rectifier and Heat sink etc., and Magnetron, High Voltage Harness etc..)
TABLE OF CONTENTS |
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PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO |
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AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY ................... |
INSIDE FRONT COVER |
BEFORE SERVICING ...................................................................................................... |
INSIDE FRONT COVER |
WARNING TO SERVICE PERSONNEL ................................................................................................................ |
1 |
MICROWAVE MEASUREMENT PROCEDURE ................................................................................................... |
2 |
FOREWORD AND WARNING ............................................................................................................................... |
3 |
PRODUCT SPECIFICATIONS .............................................................................................................................. |
4 |
GENERAL INFORMATION ................................................................................................................................... |
4 |
OPERATION .......................................................................................................................................................... |
6 |
TROUBLESHOOTING GUIDE ............................................................................................................................ |
14 |
TEST PROCEDURE ............................................................................................................................................ |
16 |
TOUCH CONTROL PANEL ASSEMBLY ............................................................................................................ |
27 |
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ................................................................ |
33 |
PICTORIAL DIAGRAM ........................................................................................................................................ |
41 |
POWER UNIT CIRCUIT ...................................................................................................................................... |
42 |
LSI UNIT CIRCUIT ............................................................................................................................................... |
43 |
PRINTED WIRING BOARD ................................................................................................................................. |
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PARTS LIST ........................................................................................................................................................ |
45 |
PACKING AND ACCESSORIES ......................................................................................................................... |
50 |
SHARP CORPORATION
This document has been published to be used for after sales service only.
The contents are subject to change without notice.
R-1750
R-1751
R-1752
R-1754
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/cm2. The owner of the unit should be instructed not to use the unit until the oven has been brought into compliance.
DANGER CAUTION
HIGH VOLTAGE
Do not energize a microwave oven with the outer case cabinet removed, because a microwave oven generates High Voltage in the circuit.
If you intend to operate the oven employing the high frequency switching power converter circuit, you should take special precautions to avoid an electrical shock hazard.
The high voltage transformer, high voltage capacitor and high voltage diode have energized high voltage potential approx. 8 KV.
The aluminium heat sink is connected to the switching power transistor Collector pole, and has an energized high voltage potential approx. 650V peak.
DO NOT ACCESS THE HIGH VOLTAGE TRANSFORMER, HIGH VOLTAGE CAPACITOR, HIGH VOLTAGE DIODE AND HEAT SINK WHEN THE POWER SUPPLY IS CONNECTED TO AN ELECTRICAL OUTLET.
R-1750
R-1751
R-1752
R-1754
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)
Inverter unit that includes High Voltage Capacitor, High Voltage Power Transformer, High Voltage Rectifier, Heat sink etc., and Magnetron, High Voltage Harness etc..
Read the Service Manual carefully and follow all instructions.
Don't Touch !
Danger High Voltage
Before Servicing
1. Disconnect the power supply cord |
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remove outer case. |
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2.Open the door and block it open.
3.To discharge high voltage capacitor, wait for 60 seconds.
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 highvoltage capacitor (that is the connecting lead of the highvoltage 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.To discharge high voltage capacitor, wait for 60 seconds.
4.Disconnect the leads to the primary of the inverter unit.
5.Ensure that these 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.To discharge high voltage capacitor, wait for 60 seconds.
4.Reconnect the leads to the primary of the inverter unit.
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.
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
R-1750
R-1751
R-1752
R-1754
SERVICING FOR INVERTER UNIT
WARNING
This inverter unit contains circuitry capable of producing high voltage and high current. Contact with any part of the high voltage will result in electrocution.
DO NOT ACCESS ANY PARTS OF INVERTER UNIT WITH POWER SUPPLY CONNECTED. DO NOT OPERATE INVERTER UNIT ITSELF.
It is dangerous because this unit contains high voltage components.
MICROWAVE MEASUREMENT PROCEDURE
A. Requirements:
1)Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven should not exceed 1mW/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.
B. Preparation for testing:
Before beginning the actual measurement of leakage, proceed as follows:
1)Make sure that the actual instrument is operating normally as specified in its instruction booklet.
Important:
Survey instruments that comply with the requirement for instrumentation as prescribed by the performance standard for microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.
2)Place the oven tray in the oven cavity.
3)Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5˚C (68˚F) in the center of the oven cavity.
The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-1/2 in.) and made of an electrically nonconductive material such as glass or plastic.
The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any leakage is 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.
C. 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 does turn the oven OFF before any door movement.
NOTE: After servicing, record data on service invoice and microwave leakage report.
2
SERVICE MANUAL
OVER THE RANGE
MICROWAVE OVEN
R-1750 / R-1751 / R-1752 / R-1754
FOREWORD
This Manual has been prepared to provide Sharp Electronics Corp. Service Personnel with Operation and Service Information for the SHARP OVER THE RANGE MICROWAVE OVEN, R-1750, R-1751, R-1752, R-1754.
It is recommended that service personnel carefully study the entire text of this manual so that they will be qualified to render satisfactory customer service.
Check the interlock switches and the door seal carefully. Special attention should be given to avoid electrical shock and microwave radiation hazard.
WARNING
Never operate the oven until the following points are ensured.
(A)The door is tightly closed.
(B)The door brackets and hinges are not defective.
(C)The door packing is not damaged.
(D)The door is not deformed or warped.
(E)There is no other visible damage with the oven.
Servicing and repair work must be carried out only by trained service personnel.
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;
Inverter unit that includes High Voltage Capacitor, High Voltage Power Transformer, High Voltage Rectifier, Heat sink, etc., and Magnetron, High Voltage Harness etc.;
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 wrapper 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.
SHARP ELECTRONICS CORPORATION
SHARP PLAZA, MAHWAH,
NEW JERSEY 07430-2135
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R-1750
R-1751
R-1752
R-1754
PRODUCT DESCRIPTION
GENERAL INFORMATION
OPERATION
TROUBLESHOOTING GUIDE AND TEST PROCEDURE
TOUCH CONTROL PANEL
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
WIRING DIAGRAM
PARTS LIST
R-1750
R-1751
R-1752
R-1754
PRODUCT SPECIFICATION
ITEM |
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DESCRIPTION |
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Power Requirements |
120 Volts / 14 Amperes / 1600 W |
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60 Hertz |
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Single phase, 3 wire grounded |
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Power Output |
1100 watts (IEC TEST PROCEDURE) |
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Operating frequency of 2450MHz |
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Case Dimensions |
Width |
29-15/16" |
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Height |
16-3/8" |
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Depth |
16- 1/8" (Not including the door handle) |
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Cooking Cavity Dimensions |
Width |
21" |
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Height |
8-7/8" |
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1.6 Cubic Feet |
Depth |
14-7/16" |
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Hood lamp |
2 bulbs, 20W x 2, |
Incandescent light bulbs |
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Hood fan |
Approx. 300 C.F.M. |
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Control Complement |
Touch Control System |
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Clock ( 1:00 - 12:59 ) |
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Timer (0 - 99 min. 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. 40% of Full Power |
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P-30 .................................................................... |
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approx. 30% of Full Power |
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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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TOUCH SCREEN, ONE TOUCH SENSOR pads, Beverage Center pad |
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Keep Warm pad, Defrost pad, MINUTE PLUS pad, STOP/CLEAR pad |
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START pad, 6 x 6 NO GUESS COOKING pads |
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MORE FROM YOUR MICROWAVE 6 x 6 pad, Fan Options pad |
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Light Options pad, Turntable On/Off pad, Set Up pad |
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Oven Cavity Light |
20W x 1 Incandescent light bulb |
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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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Weight |
Approx. 46 lbs. |
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GENERAL INFORMATION
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.
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R-1750
R-1751
R-1752
R-1754
Electrical Requirements
The oven is equipped with a 3-prong grounding plug. DO NOT UNDER ANY CIRCUMSTANCES CUT OR REMOVE THE GROUNDING PIN FROM THE PLUG.
The power supply cord and plug must be connected to a separate 120 Volt AC, 60 Hz, 15 Amp. or more dedicated line, using a grounded receptacle. The receptacle should be located inside the cabinet directly above the Microwave Oven/Hood system mounting location.
3-Pronged Plug
Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
OVEN DIAGRAM
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9
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8
3 5
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14
2 4
6
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12 |
13 |
10 |
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1.Oven door with see-through window.
2.Door hinges.
3.Stirrer cover.
4.Turntable motor shaft.
5.Oven lamp.
It will light when oven is operating or door is open.
6.Door latches.
The oven will not operate unless the door is securely closed.
7.Auto-Touch control panel.
8.Touch Screen.
9.Ventilation openings.
10.Light Cover.
11.Grease filters.
12.Removable turntable.
The turntable will rotate clockwise or counterclockwise. Only remove for cleaning.
13.Removable turntable support.
14.Power supply cord
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R-1750
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R-1752
R-1754
CONTROL PANEL
12 : 45 PM
1 2 3
4 5 6
7 8 9
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Minute |
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Kitchen |
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Plus + |
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Timer |
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T O U C H S C R E E N
See note. |
MINUTE |
STOP/ |
START |
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PLUS |
CLEAR |
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6x6 NO GUESS COOKING
6 Categories + 36 Foods
Meats |
Vegetables |
Poultry |
Fish/ |
Frozen |
Pasta |
Seafood |
Food |
Grains |
Fan |
Light |
Turntable |
Options |
Options |
On/Off |
ONE TOUCH
SENSOR
Reheat
Popcoon
Baked
Potatoes
Beverage
Center
Keep
Warm
Defrost
3+6
MORE
FROM YOUR MICROWAVE
6 x 6
Set Up |
See note.
See note.
NOTE:
The directed features 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.
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during oven operation.
OFF CONDITION
Closing the door activates the stop switch, primary interlock switch and secondary interlock switch. (In this condition, the monitor switch contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the control unit (Figure O-1).
1."Set clock" key and "Video demo" key will be appeared on the touch screen.
2.Touch "Set clock" key and set the clock referring to the operation manual.
NOTE: If no keys are touched within 30 seconds, the touch screen will go on to the Video Demo mode. To cancel the Video Demo mode, touch the STOP/ CLEAR pad. And then set the clock.
3.The touch screen will show the home page after setting the clock.
4.The following is an example of the Home page when the time of the day is set to 12:30 p.m..
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12 : 30 PM |
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1 |
2 |
3 |
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4 |
5 |
6 |
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7 |
8 |
9 |
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Minute |
0 |
Kitchen |
Plus + |
Timer |
NOTE: Even if the clock is not set, the display will show the Home page by touching the STOP/CLEAR pad within 30 seconds after being plugged in.
COOKING CONDITION
Program desired cooking time touching the NUMBER pads. When the START pad is touched, the following operations occur:
6
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 |
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RY1 |
Oven lamp / Fan motor / Stirrer motor |
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RY2 |
Turntable motor |
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RY3, RY4 |
Hood fan motor |
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2.120 volts A.C. is supplied to the inverter unit and is converted in order to power of the magnetron by the high
frequency switching power circuit. The frequency is approx. 27 _ 40 KHz.
3.The filament winding voltage of H.V. transformer heats the magnetron filament and the H.V. winding gives a high voltage approx. 2 KV to activaite a voltage doubler circuit. Then approx. 4KV peak voltage power is supplied to the magnetron cathode terminal.
4.The microwave energy produced by the magnetron is channelled through the waveguide into the cavity feedbox, and then into the cavity where the food is placed to be cooked.
5.Upon completion of the cooking time, the inverter unit, 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, stop switch, secondary interlock switch and primary interlock switch are activated with the following results. The circuits to the stirrer motor, the cooling fan motor, the turntable motor, and the inverter unit are de-energized, and the touch screen displays the time still remaining in the cook cycle when the door was opened.
7.The monitor switch is electrically monitoring the operation of the secondary interlock switch and primary interlock switch and is mechanically associated with the door so that it will function in the following sequence.
(1)When the door opens from a closed position, the primary interlock switch and secondary interlock switch open their contacts, and then the monitor switch contacts close. And contacts of the relay (RY1) remain closed.
(2)When the door is closed from the open position, the monitor switch contacts first open and the stop switch contacts open, and then the contacts of the secondary interlock switch and primary interlock switch close. And contacts of the relay (RY1) open.
If the secondary interlock switch and primary interlock switch fail with their 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, primary interlock switch and relay (RY1) causing the monitor fuse to blow.
VARIABLE COOKING
When Variable Cooking Power is programmed, the 120 volts A.C. is supplied to the inverter unit which is operated by the control unit. Microwave power operation is as follows: The oven can be set for any of 11 power levels: 0% to 100%(HIGH). The variable cooking power less than 40% is
R-1750
R-1751
R-1752
R-1754
programmed at the ratio of ON time and OFF time within 32 sec./ cycle time base.
CONNECTION BETWEEN POWER SETTING AND ON/ OFF TIME OF INVERTER UNIT.
OUTPUT POWER SETTING |
ON TIME |
OFF TIME |
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Power 100% |
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Power 90% |
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Power 80% |
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Power 70% |
Continue operation |
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Power 60% |
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Power 50% |
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Power 40% |
26 sec. |
6 sec. |
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Power 30% |
22 sec. |
10 sec. |
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Power 20% |
16 sec. |
16 sec. |
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Power 10% |
8 sec. |
24 sec. |
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Power 0% |
0 sec. |
32 sec. |
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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.
SENSOR COOKING CONDITION
Using the Sensor cooking function (See sensor cooking menus), the food is cooked without figuring time, power level or quantity. When the oven senses enough steam from the food, it relays the information to its microprocessor which will calculate the remaining cooking time and power level needed for best results. When the food is cooked, water vapor is developed. The sensor “senses” the vapor and its resistance increases gradually. When the resistance reaches the value set according to the menu, supplementary cooking is started. The time of supplementary cooking is determined by experiment with each food category and input into the LSI.
An example of how sensor works: (BAKED POTATOES)
1.Potatoes at room temperature. Vapor is emitted very slowly. MICROWAVE
2.Heat Potatoes. Moisture and humidity is emitted rapidly. You can smell the aroma as it cooks.
AH SENSOR |
MICROWAVE |
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R-1750
R-1751
R-1752
R-1754
3.Sensor detects moisture and humidity and calculates cooking time and variable power.
Cooking Sequence.
1.Operate the oven in sensor cooking mode by referring to the operation manual.
NOTE: The oven should not be operated on SENSOR immediately after plugging in the unit. Wait two minutes before cooking on SENSOR.
2.The coil of shut-off relay (RY-1) is energized, the turntable motor, oven lamp and cooling fan motor are turned on, but the inverter unit is not turned on.
3.After about 32 seconds, the cook relay (RY-2) is energized. The power transformer is turned on, microwave energy is produced and first stage is started. The 32 seconds is the cooling time required to remove any vapor from the oven cavity and sensor.
NOTE: During this first stage, do not open the door or touch STOP/CLEAR pad.
4.When the sensor detects the vapor emitted from the food, the display switches over to the remaining cooking time and the timer counts down to zero.
At this time, the door may be opened to stir, turn, or season food.
5.When the timer reaches zero, an audible signal sounds. The shut-off relay is de-energized and the inverter unit, oven lamp, etc. are turned off.
6.Opening the door or touching the STOP/CLEAR pad, the time of day will reappear on the display and the oven will revert to an OFF condition.
The following are the sensor cooking menus.
Reheat
Popcorn
Baked potatoes
Vegetables
Ground beef or Meat
Boneless Chicken Breast, Bone-in Chicken Pieces and Ground Poultry of Poultry
Fish / Seafood
Vegetables, Entrees, Main Dishes and Snacks of Frozen food
White Rice and Brown Rice of Pasta Grains
Frozen breakfast food, Meal in cup, Hot dogs in buns, Soup, Frozen sandwich, Stuffed Acorn Squash, Ratatouille, Bacon, Microwave pizza of More From Your Microwave.
VENTILATION METHODS HOT AIR EXHAUST
1.VERTICAL VENTING
For this venting method, hot air rising from the conventional range below is drawn in by the hood fan motor through the grease filters at the right and left sides of the base cover, up through the right and left sides of the oven cavity, then discharged vertically at rear center top of the oven, into the customer's vent system.
: AIR FLOW
TO DUCT |
TO DUCT |
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HOOD
INTAKE
DUCT
GREASE
FILTER
2.HORIZONTAL VENTING
The air handing is the same as VERTICAL VENTING except that the final air discharge is directed horizontally out from the top rear of the oven into the customer's vent system.
: AIR FLOW
HOOD FAN MOTOR
TO DUCT
HOOD
INTAKE
DUCT
GREASE
FILTER
3.RE-CIRCULATION (INSIDE VENTING)
The air handing is the same as VERTICAL VENTING except that the final air discharge is directed horizontally through the upper front of the oven into the kitchen. In this case, the accessory charcoal filter RK-230 must be provided to filter the air before it leaves the oven.
: AIR FLOW
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HOOD EXHAUST |
CHARCOAL |
HOOD FAN MOTOR |
LOUVER |
FILTER |
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HOOD |
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INTAKE |
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BASIC OPERATION OF INVERTER CIRCUIT
Basic circuit diagram is shown Figure A-1.
AC line voltage is rectified and converted to direct-current voltage (DC. Voltage). By switching the power transistor Q1 ON and OFF, High frequency current (about 27 - 40 KHz) is generated controlled by the IC of the inverter unit. OFF-time of the transistor Q1 is nearly constant. That is, on-time is varied. It is a kind of Pulse Width Modulation (PWM). Because off-time is constant, switching frequency is varied in response to the length of on-time and output power of magnetron is proportional to the length of on-time. Therefore, the frequency of inverter becomes low for high output and high for low output.
8
R-1750 R-1751 R-1752 R-1754
Wave-form of main parts are shown in Figure A-2. During off-time, flyback voltage appears on the primary winding of the high voltage transformer. The off-time depends on the inductance of the transformer and capacitance of the resonant capacitor C3. Synchronous circuit generates the timing signal by detecting the flyback voltage. The power transistor Q1 is periodically switched on when the collector voltage returns to zero (0) volt. High voltage (about 2 KV) appears on secondary winding of the transformer. The full-wave voltage doubler circuit increase to about 4 KV and is applied to the magnetron. The efficiency of the inverter unit itself is approx. 93%, and equal to that of current efficiency. Ferrite core is used for the high voltage transformer. It is superior to silicon steel core at high frequency, low magnetic loss. The power level is determined by the touch control board, and the PWM data corresponding to the level is set to the IC of the inverter unit through the control lines. The IC controls on-time of transistor Q1 by comparing the average value of the primary current with the magnitude of the power level data. The IC has the protection circuit which detects over-current of the main circuit and the high voltage circuit, over-voltage of the power transistor Q1 and AC power interruption. When abnormal phenomenon is detected, the IC pauses on the moment in order to protect the power transistor Q1 from
being destroyed. After approx. 60 millisecond, it starts generating the driving signal from the minimum pulse width and expands the length of on-time slowly until the current of the main circuit reaches the target level.
Driving signal
Collector current of Q1
Collector voltage of Q1
Secondary voltage of high voltage transformer
Synchronous signal
Figure A-2. Switching Wave-form
Choke coil
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Bridge diode |
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High voltage |
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C2 |
transformer |
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AC 120V / 60 Hz |
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C3 |
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Power |
D11 |
C11 |
Magnetron |
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transistor |
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A |
Q1 |
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C12 |
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D12 |
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IC |
Synchronous Circuit |
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Synchronous |
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Voltage Detector |
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Signal for AC. |
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Overcurrent and |
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Overvoltage Detector |
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Output Control |
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Signal |
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Average Current |
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Figure A-1. Basic Circuit
9
R-1750
R-1751
R-1752
R-1754
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MAGNETRON |
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SCHEMATIC |
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THERMAL CUT-OUT |
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TEMPERATURE FUSE |
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NOTE: CONDITION OF OVEN |
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CONTROL UNIT |
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COM. |
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2. CLOCK APPEARS ON DISPLAY |
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F1 |
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FUSE |
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F2 |
SENSOR |
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20A |
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F3 |
AH |
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B7 |
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RY3 |
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H1 |
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B5 |
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H2 |
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BLK |
CUT OUT |
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SSR |
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H3 |
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E1 |
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HOOD FAN |
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A3 |
A1 |
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THERMAL |
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FA |
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GRN |
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F |
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B1 |
Low |
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STOP |
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120 V AC. GND |
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HOOD |
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SWITCH |
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FA |
MAGNETRON |
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CAPACITOR |
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E2 |
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AC3 |
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WHT |
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MOTOR |
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60 Hz |
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RY2 |
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RY1 |
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HOOD |
A1 |
A3 |
B9 |
A5 |
A7 |
N.O. |
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TURNTABLE |
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LAMPOVEN |
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PRIMARY |
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M |
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MOTOR |
FAN MOTOR |
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STIRRER MOTOR |
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MONITOR SWITCH |
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HOOD |
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TTM |
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INTERLOCK |
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OL |
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LAMP |
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HL |
HL |
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FM |
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STM |
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INVERTER UNIT |
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INTERLOCK |
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SWITCH |
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Figure O-1. Oven Schematic-Off Condition
OVEN |
MAGNETRON |
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THERMAL CUT-OUT |
TEMPERATURE FUSE |
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SCHEMATIC
NOTE: CONDITION OF OVEN
1.DOOR CLOSED
2.COOKING TIME PROGRAMMED
3.VARIABLE COOKING CONTROL "HIGH"
4."START" PAD TOUCHED
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CONTROL UNIT |
COM. |
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FUSE |
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F1 |
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F2 |
SENSOR |
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20A |
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F3 |
AH |
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B7 |
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RY3 |
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H1 |
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B5 |
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H2 |
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BLK |
CUT OUT |
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RY4 |
SSR |
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H3 |
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E1 |
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HOOD FAN |
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THERMAL |
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High |
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GRN |
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B3 |
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B1 |
Low |
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STOP |
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120 V AC. GND |
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HOOD |
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SWITCH |
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CAPACITOR |
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E2 |
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60 Hz |
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RY2 |
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WHT |
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HOOD |
A1 |
A3 |
B9 |
A5 |
A7 |
N.O. |
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MOTOR |
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TURNTABLE MOTOR |
FAN MOTOR |
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OVEN LAMP |
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STIRRER MOTOR |
PRIMARY |
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MONITOR SWITCH |
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TTM |
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INTERLOCK |
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LAMP |
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OL |
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HL |
HL |
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FM |
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STM |
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SECONDARY |
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INTERLOCK |
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SWITCH |
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A3 |
A1 |
FA |
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FA |
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AC3 |
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M |
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INVERTER UNIT |
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Figure O-2. Oven Schematic-Cooking Condition
10
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MAGNETRON |
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BF20 |
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VC |
F |
FA |
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.V.(HRESISTOR) |
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D17 |
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120M |
100 |
PD2 |
2800V 03.0
C11
D11
H1
T1
P1
R11
3100V 06.0
C12
P2
R101 |
2.2/ 1W |
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D12 |
H2
S2 R102
2.2/ 1W |
R103 |
D100 |
S1
2
1
M2
3
VC 4
M1
(R72) |
/580V |
3.0 |
Q1 |
VE |
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C3 |
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VRS3 |
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39K |
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Q2 |
Q3 |
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33K |
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10K |
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Q4 |
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1/ |
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R73 |
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R4 |
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7K.4 |
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/35V |
100 |
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VR |
VC C4 |
100p/50V |
R5 |
4.7K |
R6 |
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C35 |
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ZD33 |
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ZD32 |
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1.3K/5W |
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2K.1 |
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C31 |
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1/2W |
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ZD31 |
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D32 |
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R34 |
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D1 RBV-2506 |
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TH2 |
R25 |
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VR1 330 D22 |
D23 |
0.01 /16V |
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47K |
R20 1.2KF |
C20 |
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PH1 |
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D20 |
D21 |
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M |
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ZD70 |
47 |
1 |
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R70 |
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1000p/50V |
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C21 |
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4 |
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100K |
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Q70 |
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R71 |
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1.0 |
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MCK (CN-A) |
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C70 |
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ZD40 |
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10K |
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D50 |
R40 |
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C41 |
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R42 |
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33K |
1/2W |
R54 |
R55 2.2KF 5.6KF |
C50 |
0.01 /50V |
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R43 |
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36K |
1/2W |
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R56 |
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300F |
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R50 |
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3KF.1 |
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430 |
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R51 |
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R45 |
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Q51 |
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D16 |
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R44 |
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1.8K |
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5K.1 |
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R22 |
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18K |
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220p/50V |
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R21 |
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C40 |
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39K |
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+ |
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- |
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R24 |
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C24 |
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18 |
VCC |
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OUT |
AGND |
VS |
VP2 |
VP0 |
VP1 |
IA |
10 |
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CF1 8MHZ |
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LR38166 |
IC1 |
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1 |
OSC |
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EN |
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PA |
GND |
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R62 |
1M |
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39K |
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1000p/50V |
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R63 |
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D30 |
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C30 |
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120K |
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R35 |
4.7K |
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7K.4 |
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R63 |
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PD1 |
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R61 |
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CN-A |
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PWM |
MCK |
VS |
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Figure O-3. Inverter Unit Circuit
R-1750
R-1751
R-1752
R-1754
Q50
11
R-1750 R-1751 R-1752 R-1754
|
PD1 |
R35 |
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D30 |
ZD31 |
J1 |
D21 |
D20 |
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C62 |
+R61 |
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C30 |
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CF1 |
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CN |
R53 |
C61 |
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C31 |
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3 |
9 |
R63 |
R62 |
1 |
+ |
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A- |
Q50 |
E |
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1 |
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E |
R71 |
R56 |
10 |
C70 |
R71 |
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ZD50 |
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C24 |
R21 |
B |
Q70 |
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PD3 |
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R22 |
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C50 |
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R50 |
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EARTH |
D16 |
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ZD30 |
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J11 |
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IC1 |
R6 |
R25 |
E |
Q51 |
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18 |
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R34 |
E |
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R51 |
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R24 |
C51 |
+ |
Q4 |
J2 |
C4 |
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R55 |
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R4 |
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TH1 |
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R54 |
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Q2 |
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Q3 |
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C50 |
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C35 E |
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R30 |
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J3 |
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C21 |
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VR1
D23 |
R20 |
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D22 |
TH2 |
CT1 |
R5 |
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ZD32 ZD33 +
94VR |
P3X-CMK |
M2 |
M1 |
PD2 |
D70 |
R103 |
D100 |
C41 |
ZD40 |
R40 R45 |
D50 |
S1 |
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R70 |
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R44 |
J4 |
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ZD70 |
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J5 |
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0 - |
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R102 |
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R101 |
J6 |
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R43 |
R42 |
0 |
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H1 |
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P2 |
. |
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J9 |
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F006 |
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J10 |
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C12 |
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J7 |
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F |
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H2 |
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P1 |
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FA |
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D12 |
F003.0 |
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HS2 |
C11 |
FA |
F |
D11 |
HS1 |
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SOLDER |
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R11 |
DANGER H.V.
FA930DR
AC3 |
BLUE |
3 |
RED |
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M
VRS2 |
L2 |
D32 |
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R31 |
D1 |
S2
PH1 |
R2 |
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G |
J8 |
C |
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E |
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Q1 |
VRS3 |
VRS4 |
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R72 |
R73 |
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C3 |
WR |
C2 |
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Figure O-4. Printed Wiring Board for Inverter Unit Circuit
12
R-1750
R-1751
R-1752
R-1754
DESCRIPTION AND FUNCTION OF COMPONENTS
DOOR OPEN MECHANISM
The door is opened by pulling the door handle, refer to the
Figure D-1.
Latch
Hook
Stop
Switch
Latch
Heads
Primary
Interlock
Switch
Monitor
Fuse
Door |
Monitor |
|
Switch |
Secondary
Interlock
Switch
Figure D-1. Door Open Mechanism
STOP, PRIMARY INTERLOCK AND SECONDARY INTERLOCK SWITCHES
The secondary interlock switch is mounted in the lower position of the latch hook and the stop switch is mounted in the upper position of the latch hook. The primary interlock switch is also 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 circuit to all components. A cook cycle cannot take place until the door is firmly closed thereby activating both interlock switches.
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 switch and secondary interlock switch fail to open when the door is opened.
Functions:
1.When the door is opened, the monitor switch contact close (to the ON condition) due to their being normally closed. At this time the primary interlock switch and secondary interlock switch are in the OFF condition (contacts open) due to their being normally open contact switches. And the contacts of relay (RY1) are in the ON condition (contacts close).
2.As the door goes to a closed position, the monitor switch contacts are first opened and the stop switch contacts close, and then the primary interlock switch and the secondary interlock switch contacts close. (On opening the door, each of these switches operate inversely.)
3.If the door is opened, and the primary interlock switch and secondary interlock switch contacts fail to open, the monitor fuse blows simultaneously with closing of the monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE TEST THE STOP SWITCH, PRIMARY INTERLOCK SWITCH, SECONDARY INTER-
LOCK SWITCH AND MONITOR SWITCH FOR PROPER OPERATION. (REFER TO CHAPTER "TEST PROCEDURE").
NOTE: MONITOR FUSE AND SWITCH ARE REPLACED AS AN ASSEMBLY
TEMPERATURE FUSE (MG)
The temperature fuse located near the waveguide 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, the temperature fuse will open at 302˚F (150˚C) causing the oven to shut down.
THERMAL CUT-OUT (HOOD )
This thermal cut-out located on the right base plate. It is designed to automatically turn on the hood fan motor whenever the hot air rising from the conventional range below causes the temperature at the thermal cut-out to rise to 140˚F (60˚C) or higher, thus removing this hot air from around microwave oven. When the temperature around the thermal cut-out drops to 113˚F (45˚C) or lower, the thermal cut-out shuts off the hood fan motor.
THERMAL CUT-OUT (OVEN )
This thermal cut-out is located on the top of the oven cavity. It is designed to prevent damage to the oven unit if the food in the oven catches fire due to overheating produced by improper setting of cooking time or failure of control unit.
Under normal operation, the thermal cut-out remains closed. However, the thermal cut-out will open at 293˚F (145˚C) causing the oven to shut down.
TURNTABLE MOTOR
The turntable motor rotates the turntable located on the bottom of the oven cavity, so that the foods on the turntable cook evenly during cooking. Turntable will turn in either direction. The turntable motor can be turned off by touching TURNTABLE ON/OFF pad.
COOLING FAN MOTOR
The cooling fan motor drives a blade which draws external cool air. This cool air is directed through the air vanes surrounding the magnetron and cools the magnetron. This air is channelled through the oven cavity to remove steam and vapors given off from the heating foods. It is then exhausted through the exhausting air vents at the oven cavity.
HOOD FAN MOTOR
The hood fan motor is a two-speed, single-phase, double pole induction type, requiring a hood fan capacitor. It is located outside the upper rear part of the oven cavity, is to remove, from around the oven, hot air rising from the conventional electric or gas range over which it is installed. This air is then expelled either vertically or horizontally through the customer supplied duct system, or discharged back into the kitchen.
13
R-1750
R-1751
R-1752
R-1754
STIRRER MOTOR
The stirrer motor drives the stirrer fan to stir the microwave radiation from the waveguide.
HOOD LAMP
The hood lamps are mounted at the hood lamp angle on the base cover. The hood lamps can be turned off and on by touching the Light Options pad. And also the brightness can be varied to high or low by touching the Light Options pad.
TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter 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, relay (RY1) primary interlock 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-BA016/KIT 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 all leads removed from components during testing.
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.
14