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Model R90GC or R-90GC or R-90GC(S).
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R-90GC
SERVICE MANUAL
S7212R90GC///
HIGH SPEED CONVECTION MICROWAVE OVEN MODEL
R-90GC
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..)
TABLE OF CONTENTS
Page PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICE TO 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 ............................................................................................................................ 13 TEST PROCEDURE ............................................................................................................................................ 15 TOUCH CONTROL PANEL ................................................................................................................................. 25 PRECAUTIONS FOR USING LEAD-FREE SOLDER ......................................................................................... 29 COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ................................................................ 30 PICTORIAL DIAGRAM ........................................................................................................................................ 38 POWER UNIT CIRCUIT ...................................................................................................................................... 39 CPU UNIT CIRCUIT ............................................................................................................................................ 40 GRID ASSIGNMENT OF FLUORESENT DISPLAY TUBE ................................................................................. 41 PRINTED WIRING BOARD ................................................................................................................................. 42 PARTS LIST ........................................................................................................................................................ 43 PACKING AND ACCESSORIES ......................................................................................................................... 49
SHARP CORPORATION
This document has been published to be used for after sales service only. The contents are subject to change without notice.
R-90GC
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.
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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
Before Servicing
1. Disconnect the power supply cord remove outer case. 2. Open the door and block it open. 3. Discharge high voltage capacitor. , and then
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. Discharge high voltage capacitor. 4. Disconnect the leads to the primary of the power transformer. 5. Ensure that the leads remain isolated from other components and oven chassis by using insulation tape. 6. After that procedure, reconnect the power supply cord.
When the testing is completed, 1. Disconnect the power supply cord, and then remove outer case. 2. Open the door and block it open. 3. Discharge high voltage capacitor. 4. Reconnect the leads to the primary of the power transformer. 5. Reinstall the outer case (cabinet). 6. Reconnect the power supply cord after the outer case is installed. 7. Run the oven and check all functions.
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 a microwave leakage test should be carried out.
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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.
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SERVICE MANUAL
PRODUCT DESCRIPTION HIGH SPEED CONVECTION MICROWAVE OVEN R-90GC FOREWORD This Manual has been prepared to provide Sharp Electronics Corp. Service Personnel with Operation and Service Information for the SHARP HIGH SPEED CONVECTION MICROWAVE OVEN, R-90GC. 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. TOUCH CONTROL PANEL 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.
GENERAL INFORMATION
OPERATION
TROUBLESHOOTING GUIDE AND TEST PROCEDURE
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
WIRING DIAGRAM
PARTS LIST
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. SHARP ELECTRONICS CORPORATION
SHARP PLAZA, MAHWAH, NEW JERSEY 07430-2135
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R-90GC
SPECIFICATION
ITEM
Power Requirements
DESCRIPTION
240 Volts 7.5 Amperes (Microwave) / 13.0 Amperes (Convection)/ 13.5 Amperes (Speed Cooking) 60 Hertz / Single phase, 3 wire grounded 1000 watts (IEC Test Procedure) Operating frequency of 2450MHz 1700 Watts 1200 Watts Width 21-5/8" Width 16-1/8" Height 16" Height 8-3/8" Depth 24-5/8" Depth 13-5/8"
Power Output Top Heater Power Output Side Heater Power Output Case Dimensions Cooking Cavity Dimensions (1.1 Cubic Feet ) Control Complement
Touch Control System Timer (0 - 99 min. 99 seconds) Microwave Power for Variable Cooking Repetition Rate; HIGH POWER ......................................... Full power throughout the cooking time 90 PERCENT .............................................................. approx. 90% of Full Power 80 PERCENT .............................................................. approx. 80% of Full Power 70 PERCENT .............................................................. approx. 70% of Full Power 60 PERCENT .............................................................. approx. 60% of Full Power 50 PERCENT .............................................................. approx. 50% of Full Power 40 PERCENT ............................................................... approx. 40% of Full Power 30 PERCENT ............................................................... approx. 30% of Full Power 20 PERCENT .............................................................. approx. 20% of Full Power 10 PERCENT ............................................................... approx. 10% of Full Power 0 PERCENT .............................................. No power throughout the cooking time Convection Temperature for Variable Cooking CONVECTION ............................................................. 100 - 450°F Temp. control
CUSTOM HELP pad, MINUTE PLUS pad, SPEED GRILL pad, SPEED ROAST pad SPEED BAKE pad, PREHEAT pad, CONVECTION pad, REHEAT pad, POPCORN pad COMPU COOK pad, COMPU DEFROST pad, BASIC COOK pad, RECIPES pad UP / DOWN pads, ENTER pad, Number and temperature selection pads, TIMER / CLOCK pad, STOP/CLEAR pad, POWER LEVEL pad, START pad
Oven Cavity Light Safety Standard
Yes UL Listed FCC Authorized DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J
GENERAL INFORMATION
GROUNDING INSTRUCTIONS
This appliance must be grounded. This oven is equipped with a cord having a grounding wire with a 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 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 240 volt 60 Hz, AC only, 15 amp. protected electrical supply. It is recommended that a separate circuit serving only this appliance be provided. The 240 volt circuit is absolutely necessary for optimum cooking performance. The oven is equipped with a 3-prong grounding plug. It must be plugged into a wall receptacle that is properly installed and grounded.
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Extension Cord
If it is necessary to use an extension cord, use only a 3-wire extension cord that has a 3-blade grounding plug and a 3-slot receptacle that will accept the plug on the high speed oven. The marked rating of the extension cord should be AC 240 volt, 15 amp. or more. Be careful not to drape the cord over the countertop or table where it can be pulled on by children or tripped over accidentally.
Receptacle Box Cover 3 Pronged Plug (6-15P) 3 Pronged Receptacle (6-15R)
CAUTION: DO NOT UNDER ANY CIRCUMSTANCES CUT OR REMOVE THE ROUND GROUNDING PRONG FROM THIS PLUG.
OVEN DIAGRAM
1 Door handle To open the door, pull the handle down and forward. Never hold the door handle when moving the oven. 2 Oven door with see-through window 3 Safety door latches The oven will not operate unless the door is securely closed. 4 Door hinges 5 Door seals and sealing surfaces 6 Turntable motor shaft 7 Removable turntable support Carefully place the turntable support in the center of the oven floor. After cooking, always clean the turntable support, especially around the rollers. These must be free from food splashes and grease. Built-up splashes or grease may overheat and cause arcing, begin to smoke or catch fire. 8 Removable turntable Place the turntable on the turntable support securely. The turntable will rotate clockwise or counterclockwise. Only remove for cleaning. 9 Ventilation openings 9 18 13 3 10 Oven light It will light when oven is operating or 12 8 door is open. 11 W a v e g u i d e c o v e r : D O N O T 11 14 10 REMOVE. 6 12 Auto-Touch control panel 7 13 Time display: 99 minutes, 99 seconds 5 16 14 Convection air openings 15 15 Removable low rack 17 16 Removable high rack 17 Splash guard 2 1 4 3 18 Ventilation cover: DO NOT REMOVE.
TOUCH CONTROL PANEL
Each indicator shows what function is in progress.
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OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during oven operation. 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 is electrically monitoring the operation of the primary interlock relay (RY2) and the secondary 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 relay (RY2) and the secondary interlock switch open their contacts. And contacts of the relay (RY1) remain closed. Then the monitor switch contacts close. (2) When the door is closed from the open position, the monitor switch contacts first open, and then the contacts of the secondary interlock switch close. And contacts of the relay (RY1) open. If the primary interlock relay (RY2) and the secondary 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, relay (RY1), primary interlock relay (RY2) and the secondary interlock switch, causing the monitor fuse to blow.
OFF CONDITION
Closing the door activates the door sensing switch and secondary interlock switch. (In this condition, the monitor switch contacts are opened.) When oven is plugged in, 240 volts A.C. is supplied to the control unit. (Figure O-1). 1. The display will show "SHARP SIMPLY THE BEST PRESS CLEAR AND PRESS CLOCK". To set any program or set the clock, you must first touch the STOP/CLEAR pad. The display will clear, and " : " will appear. NOTE: When the door is opened, the oven lamp comes on. 2. A signal is input to the control unit, energizing the coil of shut-off relay (RY-4). RY4 contacts close, completing a circuit to the damper motor. The damper motor now operates moving the damper to the open position, thereby closing the contacts of the damper switch inputs a signal to the control unit. The coil of relay RY-4 is de-energized, opening its contacts, thereby turning off the damper motor.
MICROWAVE COOKING CONDITION
Program desired cooking time Variable Cooking Control by touching the NUMBER pads and 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 RY-1 RY-2 RY-3 RY-4 RY-5 RY-6 CONNECTED COMPONENTS Oven lamp/Turntable motor Power transformer Convection motor Damper motor Fan motor Convection motor
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the 240 volts A.C. is supplied to the power transformer intermittently through the contacts of relay (RY-2). RY-2 is operated by the control unit within an varying time base. Microwave power operation is as follows:
VARI-MODE HIGH POWER (100% power) 90 PERCENT (approx. 90% power) 80 PERCENT (approx. 80% power) 70 PERCENT (approx. 70% power) 60 PERCENT (approx. 60% power) 50 PERCENT (approx. 50% power) 40 PERCENT (approx. 40% power) 30 PERCENT (approx. 30% power) 20 PERCENT (approx. 20% power) 10 PERCENT (approx. 10% power) 0 PERCENT (0% power) ON TIME 32 sec. 30 sec. 26 sec. 24 sec. 22 sec. 18 sec. 16 sec. 12 sec. 8 sec. 6 sec. 0 sec. OFF TIME 0 sec. 2 sec. 6 sec. 8 sec. 10 sec. 14 sec. 16 sec. 20 sec. 24 sec. 26 sec. 32 sec.
2. 240 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 2300 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 feedbox, and then into the cavity where the food is placed to be cooked. 5. Upon completion of the cooking time, the power transformer, oven lamp, etc. are turned off, and the generation of microwave energy is stopped. The oven will revert to the OFF condition. 6. When the door is opened during a cook cycle, monitor switch, door sensing switch, relay (RY1), the primary interlock relay (RY2) and the secondary interlock switch
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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.
CONVECTION COOKING CONDITION
PREHEATING CONDITION Program desired convection temperature by touching the PREHEAT pad and the Temperature pad. When the START pad is touched, the following operations occur: (Figure O-3) 1. The coil of shut-off relays (RY1, RY3 and RY5) are energized, the oven lamp, cooling fan motor, turntable
R-90GC
motor and convection motor are turned on. 2. The coil of relay (RY4) is energized by the control unit. The damper is moved to the closed position, closing the damper switch contacts. The closing of the damper switch contacts sends a signal to the LSI on the control unit de-energizing the relay (RY4) and opening the circuit to the damper motor. 3. The solid-state relays are energized by the control unit and the main supply voltage is applied to the top and side heating elements. 4. When the oven temperature reaches the selected preheat temperature, the following operations occur: 4-1 The solid-state relays are de-energized by the control unit temperature circuit and thermistor, opening the circuit to the heating elements. 4-2. The oven will continue to function for 30 minutes, turning the heating elements on and off, as needed to maintain the selected preheat temperature. The oven will shutdown completely after 30 minutes
(Figure O-3) 1. The contacts of the relays RY1, RY3 and RY5 are closed, and the oven lamp, turntable motor, convection motor and fan motors are energized. NOTE :The rotate direction of the convection motor is the same as one of the convection cooking. 2. The damper is moved to the closed position. 3. The solid-state relays are energized and the main supply voltage is applied to the top and side heating elements. NOTE :After cooking, the operation of the fan motors, damper motor is the same as one of the convection cooking.
SPEED GRILL COOKING
Touch the GRILL pad and then enter cooking time. When the start pad is touched, following operations occur; (Figure O-4) 1. The contacts of the relays RY1, RY3, RY5 and RY6 are closed, and the oven lamp, turntable motor, convection motor and fan motors are energized. NOTE :The rotate direction of the convection motor is reverse to one of the convection cooking by the relay RY6. 2. The damper is moved to the closed position. 3. The solid-state relays are energized and the main supply voltage is applied to the top and side heating elements. NOTE :After cooking, the operation of the fan motors, damper motor is the same as one of the convection cooking.
CONVECTION COOKING CONDITION
Touch the CONVECTION pad first and then touch the Temperature pad. And program desired cooking time by touching the Number pads. When the START pad is touched, the following operations occur: (Figure O-3) 1. The numbers on the digital read-out start to count down to zero. 2. The oven lamp, turntable motor, cooling fan motor and convection motor are energized. 3. The damper is moved to the closed position. 4. The solid-state relays are energized (if the cavity temperature is lower than the selected temperature) and the main supply voltage is applied to the heating elements to return to the selected cooking temperature. 5. Upon completion of the cooking time, the audible signal will sound, and oven lamp, turntable motor, cooling fan motor and convection motor are de-energized. At the end of the convection cycle, if the cavity air temperature is above 230°F, the circuit to RY5 will be maintained (by the thermistor circuit) to continue operation of the cooling fan motor until the temperature drops below 195°F, at which time the relay will be de-energized, turning off the fan motor. Relay RY3 will however, open as soon as the convection cycle has ended, turning off the convection fan motor. 6. At the end of the convection cook cycle, if the cavity air temperature is below 250°F, shut-off relay (RY4) is energized turning on the damper motor. The damper is returned to the open position, closing the damper switch contacts which send a signal to the control unit, deenergizing shut-off relay (RY4). NOTE: W h e n " P r e h e a t " a n d " C o n v e c t i o n " i s programmed continuously, after preheat, the heating elements operate as follows. When one of 100°F to 375°F is selected, for the first 1 minute, the top and side heating elements are not energized. When one of 400°F to 450°F is selected, for the first 2 minutes, the top and side heating elements are not energized.
SPEED ROAST COOKING
Touch the ROAST pad and then enter cooking time. When the start pad is touched, following operations occur; (Figure O-5) 1. The contacts of the relays RY1, RY3 and RY5 are closed, and the oven lamp, turntable motor, convection motor and fan motors are energized. NOTE :The rotate direction of the convection motor is the same as one of the convection cooking for the first time. But for the last 15 minutes, the direction is reverse by the relay RY6. 2. The damper is moved to the closed position. 3. The solid-state relays and relay RY2 are energized alternately, and the main supply voltage is applied to the top and side heating elements and the power transformer alternately. NOTE :After cooking, the operation of the fan motors, damper motor is the same as one of the convection cooking.
SPEED COOKING OF AUTOMATIC COOKING
(BASIC COOK, RECIPES) Speed cooking of Automatic cooking will automatically compute the oven temperature, microwave power and cooking time. And the oven will cook according to the special cooking sequence.
MICROWAVE OPTIONS OF AUTOMATIC COOKING
(REHEAT, POPCORN, COMPU COOK, COMPU DEFROST) Microwave options of Automatic cooking will automatically compute the microwave power, cooking time or defrosting
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SPEED BAKE COOKING
Touch the BAKE pad and then enter cooking time. When the start pad is touched, following operations occur;
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time. And the oven will cook according to the special cooking sequence.
FIRE SENSING FEATURE (MICROWAVE MODE)
This model incorporates a sensing feature which will stop the oven's operation if there is a fire in the oven cavity during microwave cooking. This fire sensing feature will operate when the microwave power level is set to 80% or more. This is accomplished by the LSI repeatedly measuring the voltage across the temperature measurement circuit (thermistor) during it's 32-seconds time base comparing the obtained voltage measurements. If the most recent voltage measured is 300 mV greater than the previous voltage measured, the LSI judges it as a fire in the oven cavity and switches off the relays to the power transformer, fan motor and convection motor. The LSI also stops counting down and closes the damper door so that no fresh air will enter the oven cavity. Please refer to the following section for a more detailed description. Operation Please refer to the timing diagrams below. 1. The fire sensing will start after 30 minutes when the oven is started. 2. The thermistor operates within a 32-seconds time base and it is energized for three (3) seconds and off for 29 seconds. Two (2) seconds after the thermistor is energized, the voltage across the temperature
measurement circuit is sampled by the LSI and twenty five (25) seconds after the thermistor is cut off the LSI turns on the convection fan for three (3) seconds. 3. The above procedure is repeated. If the difference between the first voltage measured (in step 1) and the voltage measured when the procedure is repeated (step 2) is greater than 300 mV the LSI makes the judgment that there is a fire in the oven cavity and will switch off the relays to the power transformer, fan motor and convection motor. The LSI also stops counting down and closes the damper door so that no fresh air will enter the oven cavity. 4. Once the fire sensor feature has shut the unit down, the programmed cooking cycle may be resumed by pressing the "START" pad or the unit may be reset by pressing the "CLEAR" pad.
0 23 28 3 sec. 31 32 (sec.) 64 (sec.)
CONVECTION MOTOR
ON OFF
3 sec.
THERMISTOR
ON OFF ON
Sensing Voltage OFF
Sensing the voltage across temperature measurement circuit.
SCHEMATIC DIAGRAM
SCHEMATIC NOTE: CONDITION OF OVEN 1. DOOR CLOSED. 2. CLOCK APPEARS ON DISPLAY.
NOTE: " " indicates components with potential above 250V.
T/C TRANSFORMER
MONITOR FUSE 20A
MAGNETRON TEMPERATURE FUSE 150°C SIDE HEATER THERMAL CUT-OUT 150°C
PRIMARY INTERLOCK RELAY
N.O.
A8
A6
A4
A3 A2 A1
D9
TOP HEATER THERMAL CUT-OUT 170°C
SOLID-STATE RELAY
COM.
COM.
COM.
N.O.
C2
SIDE HEATIMG ELEMENT
TOP HEATIMG ELEMENT
POWER TRANSFORMER WITH 160°C THERMOSTAT IN PRIMARY WINDING
FUSE F10A
C1
RY2
CONTROL UNIT
C4
RY6
C3
240V ~60Hz
E1
E3
E5
COM.
CONVECTION MOTOR
B3
B4
B1
B2 B5
B6 D1 D7
D5
D3
COM.
SOLID-STATE RELAY
TURNTABLE MOTOR
MONITOR SWITCH
DAMPER MOTOR
FAN MOTOR
CM
OVEN LAMP
CONVECTION MOTOR CAPACITOR
SECONDARY INTERLOCK SWITCH
Figure O-1. Oven Schematic-OFF Condition
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H.V. RECTIFIER
DOOR SENSING SWITCH
DAMPER SWITCH
THERMISTOR
CAPACITOR 1µ AC 2300V
TTM
FM
DM
FM
OL
MAGNETRON
RY3
RY4
RY5
RY1
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SCHEMATIC NOTE: CONDITION OF OVEN 1. DOOR CLOSED. 2. COOKING TIME PROGRAMMED. 3. "START" PAD TOUCHED.
NOTE: " " indicates components with potential above 250V.
T/C TRANSFORMER
MONITOR FUSE 20A
MAGNETRON TEMPERATURE FUSE 150°C SIDE HEATER THERMAL CUT-OUT 150°C
COM. COM. COM.
PRIMARY INTERLOCK RELAY
N.O.
A8
A6
A4
A3 A2 A1
D9
TOP HEATER THERMAL CUT-OUT 170°C
SOLID-STATE RELAY
N.O.
C2
SIDE HEATIMG ELEMENT TOP HEATIMG ELEMENT
POWER TRANSFORMER WITH 160°C THERMOSTAT IN PRIMARY WINDING
FUSE F10A
C1
RY2
CONTROL UNIT
C4
RY6
C3
240V ~60Hz
E1
CONVECTION MOTOR
B3 B4 B1 B2 B5 B6 D1 D7 D5 D3
E3
E5
COM.
COM.
SOLID-STATE RELAY
TURNTABLE MOTOR
MONITOR SWITCH
DAMPER MOTOR
FAN MOTOR
CM
OVEN LAMP
CONVECTION MOTOR CAPACITOR
SECONDARY INTERLOCK SWITCH
Figure O-2. Oven Schematic-Microwave Cooking Condition
SCHEMATIC (CONVECTION) NOTE: CONDITION OF OVEN 1. DOOR CLOSED. 2. CONVECTION PAD TOUCHED. 3. DESIRED TEMPERATURE SELECTED. 4. COOKING TIME PROGRAMMED. 5. "START" PAD TOUCHED.
SCHEMATIC (SPEED REHEAT) NOTE: CONDITION OF OVEN 1. DOOR CLOSED. 2. REHEAT PAD TOUCHED. 3. DESIRED TEMPERATURE SELECTED. 4. COOKING TIME PROGRAMMED. 5. "START" PAD TOUCHED.
SCHEMATIC (SPED BAKED) NOTE: CONDITION OF OVEN 1. DOOR CLOSED. 2. BAKED PAD TOUCHED. 3. COOKING TIME PROGRAMMED. 4. "START" PAD TOUCHED.
T/C TRANSFORMER
MONITOR FUSE 20A
MAGNETRON TEMPERATURE FUSE 150°C SIDE HEATER THERMAL CUT-OUT 150°C
PRIMARY INTERLOCK RELAY
N.O.
A8
A6
A4
A3 A2 A1
D9
TOP HEATER THERMAL CUT-OUT 170°C
SOLID-STATE RELAY
COM.
COM.
COM.
N.O.
C2
SIDE HEATIMG ELEMENT
TOP HEATIMG ELEMENT
POWER TRANSFORMER WITH 160°C THERMOSTAT IN PRIMARY WINDING
FUSE F10A
C1
RY2
CONTROL UNIT
C4
RY6
C3
240V ~60Hz
E1
E3
E5
COM.
CONVECTION MOTOR
B3
B4
B1
B2 B5
B6 D1 D7
D5
D3
COM.
SOLID-STATE RELAY
TURNTABLE MOTOR
MONITOR SWITCH
DAMPER MOTOR
FAN MOTOR
CM
OVEN LAMP
CONVECTION MOTOR CAPACITOR
SECONDARY INTERLOCK SWITCH
Figure O-3. Oven Schematic-Convection, Reheat, Speed Bake Cooking Condition
9
H.V. RECTIFIER
DOOR SENSING SWITCH
DAMPER SWITCH
THERMISTOR
CAPACITOR 1µ AC 2300V
TTM
FM
DM
FM
OL
MAGNETRON
RY3
RY4
RY5
RY1
H.V. RECTIFIER
DOOR SENSING SWITCH
DAMPER SWITCH
THERMISTOR
CAPACITOR 1µ AC 2300V
TTM
FM
DM
FM
OL
MAGNETRON
RY3
RY4
RY5
RY1
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SCHEMATIC NOTE: CONDITION OF OVEN 1. DOOR CLOSED. 2. GRILL PAD TOUCHED. 3. COOKING TIME PROGRAMMED. 4. "START" PAD TOUCHED.
NOTE: " " indicates components with potential above 250V.
T/C TRANSFORMER
MONITOR FUSE 20A
MAGNETRON TEMPERATURE FUSE 150°C SIDE HEATER THERMAL CUT-OUT 150°C
COM. COM. COM.
PRIMARY INTERLOCK RELAY
N.O.
A8
A6
A4
A3 A2 A1
D9
TOP HEATER THERMAL CUT-OUT 170°C
SOLID-STATE RELAY
N.O.
C2
SIDE HEATIMG ELEMENT TOP HEATIMG ELEMENT
POWER TRANSFORMER WITH 160°C THERMOSTAT IN PRIMARY WINDING
FUSE F10A
C1
RY2
CONTROL UNIT
C4
RY6
C3
240V ~60Hz
E1
CONVECTION MOTOR
B3 B4 B1 B2 B5 B6 D1 D7 D5 D3
E3
E5
COM.
COM.
SOLID-STATE RELAY
TURNTABLE MOTOR
MONITOR SWITCH
DAMPER MOTOR
FAN MOTOR
CM
OVEN LAMP
CONVECTION MOTOR CAPACITOR
SECONDARY INTERLOCK SWITCH
Figure O-4. Oven Schematic-Speed Grill Cooking Condition
SCHEMATIC NOTE: CONDITION OF OVEN 1. DOOR CLOSED. 2. ROAST PAD TOUCHED. 3. COOKING TIME PROGRAMMED. 4. "START" PAD TOUCHED.
NOTE: The solid-state relays and relay RY2 are energized alternately. For last 15 minutes, the contacts of relay RY6 will contact D5.
T/C TRANSFORMER
MONITOR FUSE 20A
MAGNETRON TEMPERATURE FUSE 150°C SIDE HEATER THERMAL CUT-OUT 150°C
COM. COM. COM.
PRIMARY INTERLOCK RELAY
N.O.
A8
A6
A4
A3 A2 A1
D9
TOP HEATER THERMAL CUT-OUT 170°C
SOLID-STATE RELAY
N.O.
C2
SIDE HEATIMG ELEMENT TOP HEATIMG ELEMENT
POWER TRANSFORMER WITH 160°C THERMOSTAT IN PRIMARY WINDING
FUSE F10A
C1
RY2
CONTROL UNIT
C4
RY6
C3
240V ~60Hz
E1
CONVECTION MOTOR
B3 B4 B1 B2 B5 B6 D1 D7 D5 D3
E3
E5
COM.
COM.
SOLID-STATE RELAY
TURNTABLE MOTOR
MONITOR SWITCH
DAMPER MOTOR
FAN MOTOR
CM
OVEN LAMP
CONVECTION MOTOR CAPACITOR
SECONDARY INTERLOCK SWITCH
Figure O-5. Oven Schematic-Speed Roast Cooking Condition
10
H.V. RECTIFIER
DOOR SENSING SWITCH
DAMPER SWITCH
THERMISTOR
CAPACITOR 1µ AC 2300V
TTM
FM
DM
FM
OL
MAGNETRON
RY3
RY4
RY5
RY1
H.V. RECTIFIER
DOOR SENSING SWITCH
DAMPER SWITCH
THERMISTOR
CAPACITOR 1µ AC 2300V
TTM
FM
DM
FM
OL
MAGNETRON
RY3
RY4
RY5
RY1
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DESCRIPTION AND FUNCTION OF COMPONENTS
DOOR OPEN MECHANISM
The door is opened by pulling the door handle down and forward, referring to the figure D-1. When the door handle is pulled down, the latch heads are moved upward. And then when the door handle is pulled forward, the latch heads are released from the latch hooks right and left. Now, the door will open.
Monitor switch Latch hook left Latch head Secondary interlock switch
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 DOOR SENSING SWITCH, PRIMARY INTERLOCK RELAY, 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.
Latch hook right Latch head Door sensing switch
THERMISTOR
The thermistor is a negative temperature coefficient type. The temperature in the oven cavity is detected through the resistance of the thermistor, and then the control unit causes the heater relay to operate, thus the current to the heating elements is turned ON/OFF. If the convection cooking or some cooking modes which use the top / side heating elements is started and the oven temperature does not rise above 100°F (37.8°C), the control unit will stop the oven after 10 minutes. In this case, the thermistor may be opened.
Door handle
Figure D-1. Door Open Mechanism
MAGNETRON TEMPERATURE FUSE.
The temperature fuse located on the waveguide flange is designed to prevent damage to the magnetron if an over heated condition develops in the magnetron 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.
DOOR SENSING AND SECONDARY INTERLOCK SWITCHES
The door sensing switch in the primary interlock system is mounted in the lower position on the latch hook right, the secondary interlock switch is mounted in the lower position on the latch hook left. They are activated by the latch heads on the door. When the door is opened, the switches interrupt the circuit to all components except for the oven lamp. 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.
TOP HEATER THERMAL CUT-OUT
The thermal cut-out located on the thermal cover upper is designed to prevent damage to the top heating element unit if an over heated condition develops in the top heating element unit due to convection fan failure, thermistor failure, obstructed air ducts, dirty or blocked air intake, etc. Under normal operation, the thermal cut-out remains closed. However, when abnormally high temperature are reached within the top heating element unit, the thermal cut-out will open at 338°F (170°C) causing the oven to shut down. When the thermal cut-out has cooled, the thermal cut-out closes at 311°F(155°C).
MONITOR SWITCH
The monitor switch is mounted on the upper position of latch hook left. It is activated (the contacts opened) by the left latch head 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 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 door sensing and secondary interlock switches are in the OFF condition (contacts open) due to their 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 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 relay and
11
SIDE HEATER THERMAL CUT-OUT
The thermal cut-out located on the thermal cover left is designed to prevent damage to the side heating element unit if an over heated condition develops in the top heating element unit due to convection fan failure, thermistor failure, obstructed air ducts, dirty or blocked air intake, etc. Under normal operation, the thermal cut-out remains closed. However, when abnormally high temperature are reached within the side heating element unit, the thermal cut-out will
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open at 302°F (150°C) causing the oven to shut down. When the thermal cut-out has cooled, the thermal cut-out closes at 266°F (130°C).
tion time reaches 0, the heating elements are de-energized and the convection fan stops operating and the oven shuts off. Flow of hot air: The rotation direction of the convection motor is controlled by relay RY6. When the convection fan rotates clockwise, the hot air from the oven cavity left side wall blows stronger than one from the oven cavity top wall. ( This mode is called "Convection mode".) When the convection fan rotates counterclockwise, the hot air from the oven cavity top wall blows stronger than one from the oven cavity left side wall. (This mode is called "JET mode".)
Top heating element unit
TOP HEATING ELEMENT
The top heating element is located at the top of the oven cavity. It is intended to heat air driven by the convection fan. The heated air is kept in the oven and force-circulated and reheated by the top heating element.
SIDE HEATING ELEMENT
The side heating element is located at the left side of the oven cavity. It is intended to heat air driven by the convection fan. The heated air is kept in the oven and force-circulated and reheated by the top heating element.
TURNTABLE MOTOR
The turntable motor rotates the turntable located in the bottom of the oven cavity, so that the food on the turntable is cooked evenly during cooking. The turntable may turn in either direction.
Side heating element unit Convection fan Convection mode
JET mode
FAN MOTOR (MAGNETRON SIDE)
The 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 vapors given off from the heating foods. It is then exhausted through the exhausting air vents at the oven cavity.
FRONT VIEW
Figure D-2. Rotation direction of convection fan
Oven cavity left side
FAN MOTOR (POWER TRANSFORMER SIDE)
The fan motor drives a blade which draws external cool air. This cool air is directed through the air vents surrounding the power transformer and cools the power transformer. 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.
Hot air Oven cavity top wall
Hot air
Convection fan
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where food is not directly heated by the heating element, but is heated by forced circulation of the hot air produced by the heating elements. The air heated by the heating elements is circulated through the convection passage provided on the outer casing of the oven cavity by means of the convection fan which is driven by the convection motor. It then enters the inside of the oven through the vent holes provided on the top and left sides of the oven. Next, the hot air heats the food on the turntable and leaves the oven cavity through the vent in the center of the oven cavity back side wall. Without leaving the oven, this hot air is reheated by the heating elements, passes through the convection passage and enters the inside of the oven cavity again, in a continuing cycle. In this way, the hot air circulates inside the oven cavity to raise its temperature and, at the same time, comes into contact with the food being cooked. When the temperature inside the oven cavity reaches the selected temperature, the heating elements are de-energized. When the temperature inside the oven cavity drops below the selected temperature, the heating elements are energized again. In this way, the inside of the oven cavity is maintained at approximately the selected temperature. When the convec12
Top heating element unit Top heating element unit
Hot air Hot air Side heating element unit Side heating Turntable element unit
Convection Mode
JET Mode
Figure D-3. Flow of hot air
DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except during convection cooking, reheat, speed grill, speed roast, speed bake, or all cooking modes which use the top / side heating elements. Damper position is set automatically by damper motor, damper switch, motor cam and damper shaft. These components are operated by a signal that judges if microwave cooking, convection cooking operation or other cooking operation is selected by the control unit.
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Microwave Cooking: Damper is in the open position, because a portion of cooling air is channelled through the cavity to remove steam and vapors given off from the heating foods. It is then exhausted at the top of the oven cavity into a condensation compartment. Convection, Preheat, Speed Grill, Speed Roast, Speed Bake, or all cooking modes which use the top / side heating elements: Damper is in the closed position, so that no hot air will be allowed to leak out the oven cavity. Damper Operation 1. When power supply cord is plugged in: 1-1. When power supply cord is plugged in, a signal is sensed in the control unit, and operates shut-off relay (RY4). 1-2. Contacts of shut-off relay (RY4) close, the damper motor is energized, opening the damper door. 1-3. When the damper is moved to the open position by the damper cam the damper switch is opened (OFF position). 1-4. The signal from damper switch is re-sensed in the
control unit and shut-off relay (RY4) is turned off. 1-5. The 240 volts A.C. to the damper motor is removed and the motor turns off. 2. When oven is microwave cooking: Damper is in the open position. 3. When oven is convection cooking: 3-1. Damper motor is energized by touching the convection, temperature and START pads. 3-2. When damper is in the closed position (damper switch is ON), its signal is sensed by the control unit, and shut-off relay (RY4) is de-energized. 3-3. The damper is held in the closed position during the convection cooking operation. 3-4. At the end of the convection cooking, if the cavity air temperature is below 250°F, shut-off relay (RY4) is energized, and the damper is returned to the open position. NOTE: If the damper door is not in the proper position, closed during convection or open during microwave, the control unit will stop oven operation after 1 minute.
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 relay (RY2), door sensing switch and secondary interlock switch before replacing the monitor fuse. If the monitor fuse is replaced, the monitor switch must also be replaced. Use part FFSBA033WRKZ 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 2. Remove the outer case cabinet, referring to "OUTER CASE CABINET REMOVAL". 3. Open the door and block it open. 4. Discharge high voltage capacitor. 5. Remove the back plate from the oven, referring to "BACK PLATE REMOVAL". 6. Disconnect the leads to the primary of the power transformer. 7. Ensure that the leads remain isolated from other components and oven chassis by using insulation tape. 8. 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) and theback plate. 6. Reconnect the power supply cord after the outer case and the back plate are installed. 7. Run the oven and check all functions.
13
S
A B C D E F G H J K M O P Q U V W W W W W W Y Z X X
Check
Check
Check
Check
Replace
Replace
Replace
Replace
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R
U I
L N
TEST PROCEDURE
POSSIBLE CAUSE AND DEFECTIVE PARTS
CONDITION
CONVECTION MOTOR CAPACITOR
MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR SECONDARY INTERLOCK SWITCH PRIMARY INTERLOCK SYSTEM MONITOR SWITCH MONITOR FUSE MAGNETRON TEMPERATURE FUSE THERMAL CUT-OUT (TOP) TOP HEATING ELEMENT THERMISTOR DAMPER MOTOR DAMPER SWITCH TOUCH CONTROL PANEL TACT SWITCH RELAY RY-1 RELAY RY-2 RELAY RY-3 RELAY RY-4 RELAY RY-5 RELAY RY-6 COMP. DEFROST FUSE1 ON PWB. SOLID-STATE RELAY (TOP) SOLID-STATE RELAY (SIDE) OVEN LAMP FAN MOTOR (MAGNETRON) TURNTABLE MOTOR CONVECTION MOTOR LOOSE WIRING SHORTED IN POWER CORD NO POWER AT OUTLET LOW VOLTAGE THERMAL CUT OUT (SIDE) SIDE HEATING ELEMENT FAN MOTOR (POWER TRANSFORMER) T/C TRANSFORMER FUSE F10A
PROBLEM
Home fuse blows when power cord is plugged into wall receptacle. Monitor fuse blows when power cord is plugged into wall receptacle 88:88 does not appear in display when power cord is first plugged into wall receptacle. Display does not operate properly when STOP/CLEAR pad is touched. (The time of day should appear on the display with beep sound.) Oven lamp does not light with door opened. Oven lamp does not light in cook cycle. (It light when door is opened). Cooking cycle runs 1 minute then shuts down. Oven lamp light, but turntable motor does not operate. Turntable motor operates normally but cooling fan motor does not operate. Oven does not go into a cook cycle, when START pad is touched. Low or no power is produced during microwave cooking (The food is heated incompletely or not heated at all) Extremely uneven heating is produced in oven load (food). Function of variable cooking does not operate properly except HIGH power. Function of COMPU DEFROST does not operate properly. Oven does not go into cook cycle when START pad is touched. Heating elements do not heat. Temperature in the oven cavity is lower or higher than preset. Convection cycle runs for 10 minutes then shuts down. Convection motor does not operate of all or properly.
OFF CONDITION
14
COOKING CONDITION (MICROWAVE) (CONVECTION, SPEED BAKE/ GRILL/ROAST)
R-90GC
TEST PROCEDURES PROCEDURE LETTER A MAGNETRON ASSEMBLY TEST
1. 2. 3. 4. 5. 6. Disconnect the power supply cord. Remove the outer case cabinet, referring to "OUTER CASE CABINET REMOVAL". Open the oven door and block it open. Discharge the high voltage capacitor. Remove the back plate from the oven, referring to "BACK PLATE REMOVAL". To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check across the magnetron filament leads should indicate less than 1 ohm. 7. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads and chassis ground. This test should indicate an infinite resistance. If there is little or no resistance the magnetron is grounded and must be replaced. 8. Reconnect all leads removed from components during testing. 9. Reinstall the outer case (cabinet). 10. Reconnect the power supply cord after the outer case is installed. 11. Run the oven and check all functions. MICROWAVE OUTPUT POWER The following test procedure should be carried out with the microwave oven in a fully assembled condition (outer case fitted). HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD BE OBSERVED. Power output of the magnetron can be measured by performing a water temperature rise test. This test should only be used if above tests do not indicate a faulty magnetron and there is no defect in the following components or wiring: silicon rectifier, high voltage capacitor and power transformer. This test will require a 16 ounce (453cc) measuring cup and an accurate mercury thermometer or thermocouple type temperature tester. For accurate results, the following procedure must be followed carefully: 1. Fill the measuring cup with 16 oz. (453cc) of tap water and measure the temperature of the water with a thermometer or thermocouple temperature tester. Stir the thermometer or thermocouple through the water until the temperature stabilizes. Record the temperature of the water. 2. Place the cup of water in the oven. Operate oven at HIGH POWER (100%) selecting more than 60 seconds cook time. Allow the water to heat for 60 seconds, measuring with a stop watch, second hand of a watch or the digital read-out countdown. 3. Remove the cup from the oven and again measure the temperature, making sure to stir the thermometer or thermocouple through the water until the maximum temperature is recorded. 4. Subtract the cold water temperature from the hot water temperature. The normal result should be 29.5 to 54.9°F(16.4 to 30.5°C) rise in temperature. If the water temperatures are accurately measured and tested for the required time period the test results will indicate if the magnetron tube has low power output (low rise in water temperature) which would extend cooking time or high power output (high rise in water temperature) which would reduce cooking time. Because cooking time can be adjusted to compensate for power output, the magnetron tube assembly should be replaced only if the water temperature rise test indicates a power output well beyond the normal limits. The test is only accurate if the power supply line voltage is 240 volts and the oven cavity is clean.
COMPONENT TEST
B
POWER TRANSFORMER TEST
1. 2. 3. 4. 5. 6. Disconnect the power supply cord. Remove the outer case cabinet, referring to "OUTER CASE CABINET REMOVAL". Open the oven door and block it open. Discharge the high voltage capacitor. Remove the back plate from the oven, referring to "BACK PLATE REMOVAL". Disconnect the primary input terminals and measure the resistance of the transformer with an ohmmeter. Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance of the primary coil should be approximately 1.3 ohms and the resistance of the high voltage coil should be approximately 75 ohms; the resistance of the filament coil should be less than 1 ohm. 7. Also, the power transformer has the thermostat in the primary coil. Measure the resistance of the primary coil. The resistance of the primary coil should be above resistance unless the temperature of the thermostat in the primary coil reaches approximately 320°F (160°C). The thermostat resets automatically at 221°F(105°C). If an ohmmeter indicates an open circuit under normal condition, replace the power 15
R-90GC
TEST PROCEDURES PROCEDURE LETTER COMPONENT TEST
transformer because the primary coil (thermostat) has opened. An open primary coil (thermostat) indicates overheating of the power transformer. Check for restricted air flow to the power transformer, especially the fan motor (power transformer side). 8. Reconnect all leads removed from components during testing. 9. Reinstall the outer case (cabinet) and the back plate. 10.Reconnect the power supply cord after the outer case and the back plate are installed. 11.Run the oven and check all functions. (HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO MEASURE THE FILAMENT AND HIGH VOLTAGE.)
C
HIGH VOLTAGE RECTIFIER TEST
1. 2. 3. 4. 5. 6. Disconnect the power supply cord. Remove the outer case cabinet, referring to "OUTER CASE CABINET REMOVAL". Open the oven door and block it open. Discharge the high voltage capacitor. Remove the back plate from the oven, referring to "BACK PLATE REMOVAL". Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance across the terminals and observe, reverse the leads to the rectifier terminals and observe meter reading. If a short is indicated in both directions, or if an infinite resistance is read in both directions, the rectifier is probably defective and should be replaced. 7. Reconnect all leads removed from components during testing. 8. Reinstall the outer case (cabinet) and back plate. 9. Reconnect the power supply cord after the outer case and the back plate are installed. 10.Run the oven and check all functions.
NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts. D HIGH VOLTAGE CAPACITOR TEST
Disconnect the power supply cord. Remove the outer case cabinet, referring to "OUTER CASE CABINET REMOVAL". Open the oven door and block it open. Discharge the high voltage capacitor. Remove the back plate from the oven, referring to "BACK PLATE REMOVAL". If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads and check for short or open between the terminals using an ohmmeter. Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate continuity for a short time and should indicate an open circuit once the capacitor is charged. If the above is not the case, check the capacitor with an ohmmeter to see if it is shorted between either of the terminals and case. If it is shorted, replace the capacitor. 7. Reconnect all leads removed from components during testing. 8. Reinstall the outer case (cabinet) and the back plate. 9. Reconnect the power supply cord after the outer case and the back plate are installed. 10.Run the oven and check all functions. 1. 2. 3. 4. 5. 6.
E
SECONDARY INTERLOCK SWITCH TEST
1. 2. 3. 4. 5. Disconnect the power supply cord. Remove the outer case cabinet, referring to "OUTER CASE CABINET REMOVAL". Open the oven door and block it open. Discharge the high voltage capacitor. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal of the switch. The meter should indicate an open circuit with the door open and a closed circuit with the door closed. If improper operation is indicated, replace the secondary interlock switch. Reconnect all leads removed from components during testing. Reinstall the outer case (cabinet). Reconnect the power supply cord after the outer case is installed. Run the oven and check all functions.
6. 7. 8. 9.
16
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TEST PROCEDURES PROCEDURE LETTER F PRIMARY INTERLOCK SYSTEM TEST DOOR SENSING SWITCH
1. 2. 3. 4. Disconnect the power supply cord, and then remove outer case. Open the door and block it open. Discharge high voltage capacitor. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal of the switch. The meter should indicate an open circuit with the door open and a closed circuit with the door closed. If improper operation is indicated, replace the door sensing switch. Reconnect all leads removed from components during testing. Reinstall the outer case (cabinet). Reconnect the power supply cord after the outer case is installed. Run the oven and check all functions.
COMPONENT TEST
5. 6. 7. 8.
NOTE: If the door sensing switch contacts fail in the open position and the door is closed, the turntable motor and oven light will be activated by RY1. PRIMARY INTERLOCK RELAY (RY2)
1. 2. 3. 4. Disconnect the power supply cord, and then remove outer case. Open the door and block it open. Discharge high voltage capacitor. Disconnect two (2) wire leads from the male tab terminals of the Primary Interlock Relay (RY2). Check the state of the relay contacts using a ohmmeter. The relay contacts should be open. If the relay contacts are closed, replace the circuit board entirely or the relay itself. Reconnect all leads removed from components during testing. Reinstall the outer case (cabinet). Reconnect the power supply cord after the outer case is installed. Run the oven and check all functions.
5. 6. 7. 8.
G
MONITOR SWITCH
1. 2. 3. 4. Disconnect the power supply cord, and then remove outer case. Open the door and block it open. Discharge high voltage capacitor. Before performing this test, make sure that the secondary interlock switch and the primary interlock relay are operating properly, according to the above Switch Test Procedure. Disconnect the wire lead from the monitor switch (COM) terminal. Check the monitor switch operation by using the ohmmeter as follows. When the door is open, the meter should indicate a closed circuit. When the monitor switch actuator is pushed by a screw driver through the lower latch hole on the front plate of the oven cavity with the door opened (in this condition the plunger of the monitor switch is pushed in), the meter should indicate an open circuit. If improper operation is indicated, the switch may be defective. After testing the monitor GRY BLK switch, reconnect the wire lead to the monitor switch (COM) terminal and check the continuity of the monitor circuit. Reconnect all leads removed from components Monitor switch during testing. OHMMETER Screw driver Reinstall the outer case (cabinet). Reconnect the power supply cord after the outer case is installed. Secondary interlock switch Run the oven and check all functions.
Latch hook left
5. 6. 7. 8.
H
BLOWN MONITOR FUSE
1. 2. 3. 4. Disconnect the power supply cord, and then remove outer case. Open the door and block it open. Discharge high voltage capacitor. If the monitor fuse is blown when the door is opened, check the primary interlock relay, secondary interlock switch and monitor switch according to the "TEST PROCEDURE" for those switches before replacing the blown monitor fuse.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE PRIMARY INTERLOCK
17
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TEST PROCEDURES PROCEDURE LETTER COMPONENT TEST RELAY, SECONDARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR SWITCH FOR PROPER OPERATION.
If the monitor fuse is blown by improper switch operation, the monitor fuse and monitor switch must be replaced with "monitor fuse and monitor switch assembly" part number FFS-BA033WRKZ, even if the monitor switch operates normally. The monitor fuse and monitor switch assembly is comprised of a 20 ampere fuse and switch. 5. Reconnect all leads removed from components during testing. 6. Reinstall the outer case (cabinet). 7. Reconnect the power supply cord after the outer case is installed. 8. Run the oven and check all functions.
I
BLOWN FUSE F10A
1. 2. 3. 4. 5. 6. Disconnect the power supply cord. Remove the outer case cabinet, referring to "OUTER CASE CABINET REMOVAL". Open the oven door and block it open. Discharge the high voltage capacitor. Remove the back plate from the oven, referring to "BACK PLATE REMOVAL". If the monitor fuse is blown, there could be short or ground in high voltage rectifier, magnetron, power transformer, high voltage capacitor or high voltage wire. Check them and replace the defective parts or repair the wire harness. Reconnect all leads removed from components during testing. Reinstall the outer case (cabinet) and the back plate. Reconnect the power supply cord after the outer case and back plate are installed. Run the oven and check all functions.
7. 8. 7. 8.
CAUTION: ONLY REPLACE FUSE F10A WITH CORRECT VALUE REPLACEMENT. J MAGNETRON TEMPERATURE FUSE TEST
1. 2. 3. 4. Disconnect the power supply cord, and then remove outer case. Open the door and block it open. Discharge high voltage capacitor. A continuity check across the temperature fuse terminals should indicate a closed circuit unless the temperature of the magnetron reaches approximately 302°F(150°C). An open temperature fuse indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially the cooling duct and cooling fan. Reconnect all leads removed from components during testing. Reinstall the outer case (cabinet). Reconnect the power supply cord after the outer case is installed. Run the oven and check all functions.
5. 6. 7. 8.
CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE, REPLACE TEMPERATURE FUSE. K THERMAL CUT-OUT (TOP HEATER) TEST
1. 2. 3. 4. Disconnect the power supply cord, and then remove outer case. Open the door and block it open. Discharge high voltage capacitor. A continuity check across the thermal cut-out terminals should indicate a closed circuit unless the temperature of the thermal cut-out reaches approximately 338°F(170°C). The thermal cut-out resets automatically at ap