SHARP SERVICE MANUAL

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) Perform the following safety checks on all ovens before activating the magnetron or other microwave source, and make necessary repairs:

• (1) Interlock operation
• (2) Proper door closing
• (3) Seal and sealing surfaces (check for arcing, wear, or 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, waveguide, or transmission line, and cavity for proper alignment, integrity, and connections.

(d) Repair, replace, or adjust any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation and transmission systems according to the procedures in this manual before releasing the oven to the owner.

(e) Perform a microwave leakage check to verify compliance with the Federal Performance Standard on each oven prior to release to the owner.

BEFORE SERVICING

Perform a microwave emission check as per the Microwave Measurement Procedure outlined in this service manual. If microwave emissions exceed the specified limit, contact SHARP ELECTRONICS CORPORATION immediately at 1-800-237-4277.

If the unit operates with the door open, instruct the user not to operate the oven and contact SHARP ELECTRONICS CORPORATION and the Food and Drug Administration's Center for Devices and Radiological Health immediately.

Inform SHARP ELECTRONICS CORPORATION of any certified unit found with emissions exceeding 4mW/cm². Instruct the owner not to use the unit until it is brought into compliance.

CHAPTER 1. WARNING TO SERVICE PERSONNEL

Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with the following parts may result in severe, possibly fatal, electrical shock:

(Example) High Voltage Capacitor, High Voltage Power Transformer, Magnetron, High Voltage Rectifier Assembly, High Voltage Harness, etc.

Read the Service Manual carefully and follow all instructions.

Don't Touch! Danger High Voltage

[1] Before Servicing

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor. WARNING: RISK OF ELECTRIC SHOCK. DISCHARGE THE HIGH-VOLTAGE CAPACITOR BEFORE SERVICING. The high-voltage capacitor remains charged for about 60 seconds after the oven has been switched off. Wait for 60 seconds and then short-circuit the connection of the high-voltage capacitor (connecting lead of the high-voltage rectifier) against the chassis using an insulated screwdriver.

Whenever troubleshooting is performed, the power supply must be disconnected. In some cases, it may be necessary to connect the power supply after the outer case has been removed. In such events:

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the 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 the oven chassis using insulation tape.
6. Reconnect the power supply cord.

[2] When the testing is completed,

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.

[3] After repairing

1. Reconnect all leads removed from components during testing.
2. Reinstall the outer case (cabinet).
3. Reconnect the power supply cord after the outer case is installed.
4. Run the oven and check all functions.

Microwave ovens should not be run empty. To test for microwave energy presence, place a cup of cold water on the oven turntable, close the door, set power to HIGH, and set the timer for two (2) minutes. After the timer reaches zero, check if the water is hot. If the water remains cold, perform the 'Before Servicing' procedure and re-examine component connections. After all service work is completed and the oven is fully assembled, check microwave power output and perform a microwave leakage test.

CHAPTER 2. MICROWAVE MEASUREMENT PROCEDURE

[1] Requirements:

1. Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven should not exceed 1mW/cm² at any point 5cm or more from the external surface of the oven, measured prior to acquisition by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm² at any point 5cm or more from the external surface of the oven.
2. Safety interlock switches: Primary interlock relay and door sensing switch shall prevent microwave radiation emission in excess of the requirement as above mentioned. The secondary interlock switch shall prevent microwave radiation emission in excess of 5 mW/cm² at any point 5cm or more from the external surface of the oven.

[2] Preparation for testing:

1. Ensure the instrument is operating normally as specified in its instruction booklet. Important: Use 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)).
2. Place the oven tray in the oven cavity.
3. Place a load of 275±5 ml (9.8 oz) of tap water, initially at 20±5°C (68°F), in the center of the oven cavity. The water container should be a low-form 600 ml (20 oz) beaker with an inside diameter of approximately 8.5 cm (3-1/2 in.) made of electrically nonconductive material (e.g., glass or plastic). Using this standard load is important for oven protection and accurate leakage measurement.
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 boils before the survey is completed, replace it with 275 ml of cool water.

[3] Leakage test: (Closed-door leakage test)

1. Grasp the survey instrument probe and hold it perpendicular to the gap between the door and the oven body.
2. Move the probe slowly (not faster than 1 in./sec. or 2.5 cm/sec.) along the gap, observing the maximum meter indication.
3. Check for leakage at the door screen, sheet metal seams, and other accessible positions where metal continuity is breached (e.g., around switches, indicators, and vents).
4. While testing leakage around the door, pull the door away from the oven front as far as permitted by the closed latch assembly.
5. Measure carefully at the point of highest leakage. Ensure the highest leakage is no greater than 4mW/cm², and that the secondary interlock switch and primary interlock relay turn the oven OFF before any door movement.

NOTE: After servicing, record data on the service invoice and microwave leakage report.

CHAPTER 3. FOREWORD AND WARNING

[1] FOREWORD

This manual provides Sharp Electronics Corp. Service Personnel with Operation and Service Information for the SHARP MICROWAVE OVEN, R-21LCF. It is recommended that service personnel study the entire manual to render satisfactory customer service. Carefully check interlock switches and the door seal. Pay special attention to avoid electrical shock and microwave radiation hazards.

[2] WARNING

Never operate the oven until the following conditions are ensured:

• (A) The door is tightly closed.
• (B) The door hinges and brackets are not defective.
• (C) The door packing (seal) is not damaged.
• (D) The door is not deformed or warped.
• (E) There is no other visible damage to the oven.

Servicing and repair work must be performed only by trained service personnel.

[3] DANGER

Certain initial parts are intentionally not grounded and present a risk of electrical shock during servicing. Service personnel must not contact the following parts while the appliance is energized:

• High Voltage Capacitor
• Power Transformer
• Magnetron
• High Voltage Rectifier Assembly
• High Voltage Harness
• Vent Hood (if provided)
• Fan assembly
• Cooling Fan Motor

Parts marked "*" on the parts list are used at voltages over 250V. Removal of the outer wrap provides access to voltages above 250V.

Parts marked "*" on the parts list may cause undue microwave exposure if they are damaged, loosened, or removed.

CHAPTER 4. PRODUCT DESCRIPTION

[1] SPECIFICATIONS

NOTE: Internal capacity is calculated by measuring maximum width, depth, and height. Actual capacity for holding food is less.

CHAPTER 5. GENERAL INFORMATION

[1] GROUNDING INSTRUCTIONS

This oven is equipped with a three-prong grounding plug. It must be plugged into a wall receptacle that is properly installed and grounded in accordance with the National Electrical Code and local codes and ordinances.

In the event of an electrical short circuit, grounding reduces the risk of electric shock by providing an escape wire for the electric current.

WARNING: Improper use of the grounding plug can result in a risk of electric shock.

Electrical Requirements

The electrical requirements are a 120 volt, 60 Hz, AC only, 15 amp. or more protected electrical supply. It is recommended that a separate circuit serving only this appliance be provided. Observe all applicable codes and ordinances during installation. A short power-supply cord is provided to reduce risks of entanglement or tripping. If a two-pronged wall receptacle is encountered, the customer must contact a qualified electrician to replace it with a properly grounded three-pronged receptacle or a properly grounded and polarized grounding adapter.

If an extension cord is necessary, use a 3-wire, 15 amp. or higher rated cord. Do not drape it over a countertop or table where it can be pulled on by children or tripped over accidentally.

CAUTION: DO NOT CUT OR REMOVE THE ROUND GROUNDING PRONG FROM THIS PLUG UNDER ANY CIRCUMSTANCES.

Diagram: Grounding

A diagram illustrates a grounded receptacle box with a 3-pronged plug, showing the grounding pin and 3-pronged receptacle.

[2] OVEN DIAGRAM

1. OVEN

A diagram shows the oven with numbered components:

• 1. Back splash cover
• 2. Side splash cover
• 3. Oven light
• 4. Ceramic shelf
• 5. Control panel
• 6. Cavity face plate
• 7. Door latch openings
• 8. Door latches
• 9. Door hinges
• 10. Door seals and sealing surfaces
• 11. Door handle
• 12. Oven door with see-through window
• 13. Air ventilation cover and openings
• 14. Power supply cord
• 15. Air intake openings
• 16. Outer case cabinet

2. TOUCH CONTROL PANEL

A diagram shows the touch control panel with a 'TIME GUIDE FOR ONE SERVING' indicating cooking times for various food items (e.g., Bagel, Roll, Beverage, Soup, Hot Dog, Pizza Slice, Popcorn) and a Light Up Dial for setting cooking time. Instructions for operation are also present: 'With the door closed, turn the timer to the desired time. Oven will begin operating immediately. To shut oven off manually, return timer to "0".'

CHAPTER 6. OPERATION

[1] DESCRIPTION OF OPERATING SEQUENCE

This section describes component functions during oven operation.

1. OFF CONDITION

Closing the door activates the door sensing switch and secondary interlock switch. The monitor switch contacts are open. When plugged in, 120 volts AC is supplied to the noise filter and control unit (Figure O-1).

2. COOKING CONDITION

When the Light Up Dial is turned, the following occurs:

1. Relay contacts close, activating connected components: RY-1 (oven lamp/antenna motor/fan motor), RY-2 (power transformer).
2. 120 volts AC is supplied to the power transformer's primary winding, converting to approximately 3.2 volts AC on the filament winding and approximately 2150 volts AC on the high voltage winding.
3. The magnetron filament is heated by the filament winding voltage, and the HV winding voltage is sent to a voltage doubler circuit.
4. Microwave energy from the magnetron is channeled through the waveguide into the cavity feed-box and then into the cavity to cook food.
5. Upon cooking time completion, the power transformer, oven lamp, etc., are turned off, stopping microwave generation. The oven returns to the OFF condition.
6. If the door is opened during a cook cycle, the monitor switch, door sensing switch, secondary interlock switch, relay (RY2), and primary interlock relay (RY1) are activated. This de-energizes circuits for the antenna motor, cooling fan motor, and high voltage components. The oven lamp remains on, and the digital display shows the remaining cook time.
7. The monitor switch monitors the secondary interlock switch and control relay (RY1) operation. It is mechanically linked to the door for the following sequence:
• a) When the door opens, the primary interlock relay (RY1) and secondary interlock switch open their contacts, and the monitor switch contacts close.
• b) When the door closes, the monitor switch contacts open first, followed by the secondary interlock switch and door sensing switch contacts closing. (These switches operate inversely when the door is opened.)

If the secondary interlock switch and primary interlock relay (RY1) fail to open their contacts when the door is opened, the monitor switch contacts will short-circuit the monitor fuse, secondary interlock switch, and primary interlock relay (RY1), causing the monitor fuse to blow.

[2] OVEN SCHEMATIC

1. Off Condition

A schematic diagram (Figure O-1) illustrates the oven's electrical circuit in the OFF condition (Light Up Dial OFF, Door CLOSED). It shows the AC power input, noise filter, fuse, thermal cut-outs, door sensing switch, secondary interlock switch, primary interlock relay (RY1), control unit, cook relay (RY2), and output components like the oven lamp, fan motor, and antenna motor, connected to the power transformer and magnetron assembly.

2. Cooking Condition

A schematic diagram (Figure O-2) illustrates the oven's electrical circuit in the COOKING condition (Door CLOSED, Light Up Dial ON). It shows the same components as the OFF condition, indicating their active state during cooking.

[3] DESCRIPTION AND FUNCTION OF COMPONENTS

1. DOOR OPEN MECHANISM

Opening the door involves grasping the handle, which pulls a lever. This lever moves upper and lower latch heads upward, releasing them from the latch hook, allowing the door to open. A diagram (Figure D-1) illustrates the door open mechanism with components like the door handle, latch lever, latch heads, latch hook, and various latch switch levers (A, B, C), door sensing switch, secondary interlock switch, and monitor switch.

2. DOOR SENSING AND SECONDARY INTERLOCK SWITCHES

The secondary interlock switch is located at the upper latch hook position, and the door sensing switch is at the lower latch hook position. They are activated by latch switch levers A and C, respectively, which are moved by the upper and lower latch heads. When the door opens, these switches interrupt power to high voltage components. A cook cycle requires both interlock switches to be activated by a firmly closed door. The primary interlock system includes the door sensing switch and primary interlock relay (RY1) on the control circuit board.

3. MONITOR SWITCH

The monitor switch is activated (contacts open) by latch switch lever B on the latch hook when the door is closed. Its purpose is to render the oven inoperative by blowing the monitor fuse if the primary interlock relay (RY1) and secondary interlock switch contacts fail to open when the door is opened.

• When the door opens, the normally closed monitor switch contacts close. At this time, the primary interlock relay (RY1) and secondary interlock switch (normally open contacts) are in the OFF condition (contacts open).
• When the door closes, the monitor switch contacts open first, followed by the door sensing switch and secondary interlock switch contacts closing. (These switches operate inversely when the door is opened.)

If the door is opened and the primary interlock relay (RY1) and secondary interlock switch contacts fail to open, the monitor fuse blows simultaneously with the closing of the monitor switch contacts.

CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE DOOR SENSING SWITCH, PRIMARY INTERLOCK RELAY (RY1), SECONDARY INTERLOCK SWITCH, AND MONITOR SWITCH FOR PROPER OPERATION (REFER TO CHAPTER "TEST PROC").

NOTE: The monitor fuse and monitor switch are replaced as an assembly.

4. ANTENNA MOTOR

The antenna motor rotates the stirrer antenna on the bottom of the oven cavity to ensure even cooking of food on the ceramic shelf. The motor may turn in either direction.

5. COOLING FAN MOTOR

The cooling fan motor draws external cool air through air vanes to cool the magnetron. This air is channeled through the oven cavity to remove steam and vapors from heating food, and is then exhausted through vents.

6. MONITOR FUSE

1. The monitor fuse blows when the contacts (COM-NO) of the primary interlock relay (RY1) and secondary interlock switch remain closed with the oven door open and the monitor switch closes.
2. If the wire harness or electrical components are short-circuited, this fuse blows to prevent electric shock or fire hazard.

7. THERMAL CUT-OUT 145°C (MAGNETRON)

This thermal cut-out protects the magnetron from overheating. If the temperature exceeds 293°F (145°C) due to fan motor interruption or blocked ventilation, it opens, cutting off line voltage to the high voltage transformer and stopping magnetron operation. The thermal cut-out does not reset.

8. THERMAL CUT-OUT 125°C (OVEN)

This thermal cut-out prevents oven damage if food catches fire due to overheating from improper cooking time settings or control unit failure. It remains closed during normal operation. If abnormally high temperatures are reached within the cavity, it opens at 257°F (125°C), shutting down the oven. It does not reset.

9. NOISE FILTER

The noise filter prevents radio frequency interference from flowing back into the power circuit.

CHAPTER 7. TROUBLESHOOTING GUIDE

Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.

When troubleshooting, follow the Sequence of Operation. Many trouble causes require specific tests detailed in the "Test Procedure" section.

IMPORTANT:

If the oven is inoperative due to a blown monitor fuse, check the monitor switch, primary interlock relay (RY1), door sensing switch, and secondary interlock switch before replacing the fuse. If the monitor fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA033WRKZ as an assembly.

IMPORTANT:

Whenever troubleshooting, disconnect the power supply cord. In some cases, it may be necessary to connect the power supply after the outer case is removed. In such events:

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the 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 the oven chassis using insulation tape.
6. Reconnect the power supply cord.

When the testing is completed:

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.

[1] TROUBLESHOOTING CHART

The troubleshooting chart lists conditions, problems, and possible causes/defective parts, indicating which test procedures (A-M) apply to each.

CHAPTER 8. TEST PROCEDURES

[1] Procedure A: MAGNETRON ASSEMBLY TEST

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check across the magnetron filament leads should indicate less than 1 ohm.
5. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads and chassis ground. This test should indicate infinite resistance. If there is little or no resistance, the magnetron is grounded and must be replaced.
6. Reconnect all leads removed from components during testing.
7. Reinstall the outer case (cabinet).
8. Reconnect the power supply cord after the outer case is installed.
9. Run the oven and check all functions.

MICROWAVE OUTPUT POWER

This test procedure is performed with the oven fully assembled (outer case fitted). HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD BE OBSERVED.

Magnetron power output can be measured by a water temperature rise test. This test is only used if other tests do not indicate a faulty magnetron and there are no defects in the silicon rectifier, high voltage capacitor, or power transformer. This test requires a 16 oz (453cc) measuring cup and an accurate mercury thermometer or thermocouple temperature tester.

1. Fill the measuring cup with 16 oz. (453cc) of tap water and measure its initial temperature. Stir the thermometer/thermocouple until the temperature stabilizes, then record it.
2. Place the cup of water in the oven. Operate the oven at full power for more than 60 seconds. Measure the heating time using a stopwatch or digital countdown.
3. Remove the cup and measure the temperature again, stirring until the maximum temperature is recorded.
4. Subtract the cold water temperature from the hot water temperature. A normal result shows a rise of 34.7 to 64.6°F (19.3 to 35.9°C). If water temperatures are accurately measured and tested for the required time, this indicates magnetron power output. Low power output (low rise) extends cooking time; high power output (high rise) reduces it. The magnetron tube assembly should be replaced only if the water temperature rise test indicates power output well beyond normal limits. The test is accurate only if the power supply line voltage is 120 volts and the oven cavity is clean.

[2] Procedure B: POWER TRANSFORMER TEST

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the primary input terminals and measure the transformer's resistance with an ohmmeter. Check coil continuity. On the R x 1 scale, the primary coil resistance should be less than 1 ohm, the high voltage coil approximately 83.7 ohms, and the filament coil less than 1 ohm.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.

(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO MEASURE THE FILAMENT AND HIGH VOLTAGE.)

[3] Procedure C: HIGH VOLTAGE RECTIFIER TEST

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Isolate the rectifier from the circuit. Using the highest ohm scale, read resistance across terminals, then reverse leads and observe meter reading. If a short is indicated in both directions, or if infinite resistance is read in both directions, the rectifier is likely defective and should be replaced.
5. Reconnect all leads removed from components during testing.

CHAPTER 9. TOUCH CONTROL PANEL ASSEMBLY

[1] OUTLINE OF TOUCH CONTROL PANEL

1. Control Unit

The control unit comprises the LSI, power source circuit, synchronizing signal circuit, reset circuit, buzzer circuit, encoder circuit, and indicator circuit.

• LSI: Controls encoder signals, relay driving signals for oven function, buzzer signals, and LED signals.
• Power Source Circuit: Generates necessary voltages for the control unit. (VC +5V for LSI, VR +20V for RELAY RY1, RY2). Voltage VR varies with the number of LEDs lit.
• Synchronizing Signal Circuit: Provides a synchronizing signal to compose a basic standard time in the clock circuit, with minor error due to commercial frequency operation.
• Reset Circuit: Generates signals to reset the LSI to its initial state when power is supplied.
• Buzzer Circuit: Responds to LSI signals to emit audible sounds (completion sound).
• Door Sensing Switch: Informs the LSI if the door is open or closed.
• Relay Circuit: Drives the magnetron, fan motor, antenna motor, and lights the oven lamp.
• Encoder: Generates pulse signals sent to the LSI.
• Indicator Circuit: Uses Light-emitting diodes (LD1-LD20) and consists of 4 digits and 5 segments.

[2] SERVICING FOR TOUCH CONTROL PANEL

1. Precautions for Handling Electronic Components

This unit uses CMOS LSI. Handle with care due to its high impedance input/output terminals, which are susceptible to influence from high voltage power sources and static electricity. Protect CMOS LSI by wrapping them in aluminum foil for storage and transport, and by grounding the technician, soldering iron, and work table during soldering.

2. Servicing of Touch Control Panel

Procedures for servicing the touch control panel are described, along with necessary precautions. Power can be supplied from the oven itself or an external source.

1. Servicing with Oven Power Supply:

CAUTION: THE HIGH VOLTAGE TRANSFORMER OF THE MICROWAVE OVEN IS STILL LIVE DURING SERVICING AND PRESENTS A HAZARD.

Before checking performance:

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure these leads remain isolated from other components and the oven chassis using insulation tape.
6. Reconnect the power supply cord.

After checking performance:

1. Disconnect the power supply cord.
2. Open the door and block it open.
3. Reconnect the leads to the primary of the power transformer.
4. Reinstall the outer case (cabinet).
5. Reconnect the power supply cord after the outer case is installed.
6. Run the oven and check all functions.

Note: For models with short power cords, check and repair controls while connected. For models with longer cords, separate the panel and jumper the door sensing switch (on PWB) to simulate a closed door. Use dummy resistors for sensor-related controls.

2. Servicing with External Power Source:

Disconnect the touch control panel from the oven and jumper the door sensing switch (on PWB) to simulate a closed door. Connect an external power source to the panel's input terminal to check and repair controls, using dummy resistors for sensor-related controls.

3. Servicing Tools

• Soldering iron: 60W (with grounding terminal recommended).
• Oscilloscope: Single beam, DC-10MHz frequency range or more advanced.
• Hand tools.

4. Other Precautions

• Before powering the control unit, remove aluminum foil used for static electricity protection.
• Connect the key unit connector to the control unit, ensuring wires are not twisted.
• After removing foil, be cautious of abnormal voltage from static electricity.
• Ensure all connections (connectors, capacitors) to the PWB are tight.
• Use specified components where high precision is required.

CHAPTER 10. PRECAUTIONS FOR USING LEAD-FREE SOLDER

[1] Employing lead-free solder

The "Main PWB" uses lead-free solder, indicated by the "LF" symbol on the PWB and in the manual. The suffix letter denotes the alloy type (e.g., Sn-Ag-Cu).

[2] Using lead-free wire solder

When repairing a PWB with the "LF" symbol, use only lead-free solder. Using standard tin/lead alloy solder may result in cold joints and damage to printed patterns.

Lead-free solder has a melting point approximately 40°C higher than tin/lead solder. Use a dedicated bit and adjust iron temperature accordingly.

[3] Soldering

Lead-free solder (Sn-Ag-Cu) has a higher melting point and poorer wettability. To prevent damage to the PWB land, avoid prolonged bit contact. Remove the bit as soon as good flow is achieved. The high tin content can cause premature bit corrosion. Reduce bit wear by lowering temperature or turning off the iron when not in use. Mixed solder types contaminate alloys, making soldering difficult. Clean and replace bits more often when using lead-free solder. Clean bits thoroughly after each use to reduce wear.

CHAPTER 11. COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE

[1] WARNING

WARNING AGAINST HIGH VOLTAGE:

Microwave ovens contain circuitry capable of producing very high voltage and current. Contact with parts like the High Voltage Capacitor, Power Transformer, Magnetron, High Voltage Rectifier Assembly, and High Voltage Harness may result in severe, possibly fatal, electrical shock.

WARNING:

Avoid possible exposure to microwave energy. Follow these instructions before operating the oven:

1. Disconnect the power supply cord.
2. Visually check the door and cavity face plate for damage (dents, cracks, signs of arcing, etc.). Perform any necessary remedial work before operating.

Do not operate the oven if any of the following conditions exist:

• Door does not close firmly.
• Door hinge, support, or latch hook is damaged.
• Door gasket or seal is damaged.
• Door is bent or warped.
• Defective parts in the door interlock system.
• Defective parts in the microwave generating and transmission assembly.
• Visible damage to the oven.

Do not operate the oven:

• Without the RF gasket (Magnetron).
• If the waveguide or oven cavity are not intact.
• If the door is not closed.
• If the outer case (cabinet) is not fitted.

WARNING FOR WIRING:

To prevent electric shock, take these precautions:

1. Before wiring:
• Disconnect the power supply cord.
• Open the door and block it open.
• Discharge the high voltage capacitor and wait for 60 seconds.
2. Do not let wire leads touch the following parts:
• High voltage parts: Magnetron, High voltage transformer, High voltage capacitor, High voltage rectifier assembly.
• Hot parts: Oven lamp, Magnetron, Power transformer, Oven cavity.
• Sharp edges: Bottom plate, Oven cavity, Waveguide flange, Chassis support, and other metallic plates.
• Movable parts (to prevent faults): Fan blade, Fan motor, Switch, Switch lever, and Antenna motor.
3. Do not catch wire leads in the outer case cabinet.
4. Insert the positive lock connector until its pin is locked, ensuring wire leads do not come off even when pulled.
5. Connect wire leads correctly, referring to the Pictorial Diagram, to prevent error functions.

Refer to "OVEN PARTS, CABINET PARTS, CONTROL PANEL PARTS, DOOR PARTS" for removal procedures.

[2] OUTER CASE REMOVAL

To remove the outer case:

1. Disconnect the power supply cord.
2. Open the oven door and block it open.
3. Remove the five (5) screws from the rear and side edges of the case.
4. Slide the entire case back about 3cm to free it from retaining clips on the cavity face plate.
5. Lift the entire outer case from the unit.
6. Discharge the H.V. capacitor before further work.
7. Do not operate the oven with the outer case removed.

CAUTION: DISCONNECT OVEN FROM POWER SUPPLY BEFORE REMOVING OUTER CASE. DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS OR WIRING.

[3] POWER TRANSFORMER REMOVAL

1. Disconnect the power supply cord and remove the outer case.
2. Open the oven door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the filament leads of the power transformer from the high voltage capacitor and the magnetron.
5. Disconnect the H.V. wire from the power transformer.
6. Disconnect the main wire harness from the power transformer.
7. Remove the two (2) screws and two (2) VCP caps holding the transformer to the base plate.
8. Remove the transformer.
9. The power transformer is now free.

[4] HIGH VOLTAGE RECTIFIER ASSEMBLY AND HIGH VOLTAGE CAPACITOR REMOVAL

To remove these components:

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the H.V. wire of the high voltage rectifier assembly from the magnetron and the power transformer.
5. Disconnect the filament lead of the power transformer from the high voltage capacitor.
6. Remove the one (1) screw holding the earth side terminal of the high voltage rectifier assembly.
7. Disconnect all leads and terminals of the high voltage rectifier assembly from the high voltage capacitor.
8. The high voltage rectifier assembly should now be free.
9. Remove one (1) screw holding the capacitor holder to the oven cavity rear plate.
10. Remove one (1) screw holding the fan duct to the oven cavity rear plate.
11. Release the capacitor holder from the fan duct.
12. Remove the capacitor from the capacitor holder.
13. The capacitor is now free.

CAUTION: WHEN REPLACING THE HIGH VOLTAGE RECTIFIER AND HIGH VOLTAGE CAPACITOR, THE GROUND SIDE TERMINAL OF THE HIGH VOLTAGE RECTIFIER MUST BE SECURED FIRMLY WITH A GROUNDING SCREW.

[5] MAGNETRON REMOVAL

1. Disconnect the power supply cord and remove the outer case.
2. Open the oven door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the high voltage wire of the high voltage rectifier assembly and the filament lead of the transformer from the magnetron.
5. Remove the one (1) screw holding the airguide to the magnetron and remove the airguide.
6. Remove the one (1) screw holding the insertion plate A to the magnetron and remove the insertion plate A.
7. Remove the one (1) screw holding the chassis support to the magnetron.
8. Release the tabs of the air intake duct from the chassis support and the oven cavity.
9. Move the air intake duct to the left.
10. Carefully remove four (4) screws holding the magnetron to the waveguide. Hold the magnetron to prevent it from falling while removing screws.
11. Remove the magnetron from the waveguide carefully, ensuring the magnetron antenna is not hit by any surrounding metal objects.

CAUTION: WHEN REPLACING THE MAGNETRON, ENSURE THE R.F. GASKET IS IN PLACE AND THE MAGNETRON MOUNTING SCREWS ARE TIGHTENED SECURELY.

[6] CONTROL PANEL ASSEMBLY REMOVAL

CONTROL PANEL ASSEMBLY

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the main wire harness from the control unit.
5. Remove the one (1) screw holding the control panel assembly to the oven cavity front plate.
6. Lift up the control panel assembly.
7. The control panel assembly is now free.

CONTROL UNIT

1. Remove the five (5) screws holding the control unit to the control panel frame.
2. Remove the control unit from the control panel frame.
3. The control unit is now free.

TIMER KNOB

1. After removing the control unit, remove the ring holding the timer knob to the control panel.
2. Release the tab of the timer knob from the control panel hole.
3. The timer knob is now free.

NOTE:

1. Before attaching a new timer sheet, wipe off old adhesive from the control panel frame surfaces with a soft cloth soaked in alcohol.
2. When attaching the timer sheet, align the upper and right edges with the correct position on the control panel frame.
3. Stick the timer sheet firmly by rubbing with a soft cloth to avoid scratches.

[7] OVEN LAMP AND LAMP SOCKET REMOVAL

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Lift the oven lamp socket from the air intake duct.
5. Pull the wire leads from the oven lamp socket by pushing the terminal hole with a small flat-type screwdriver.
6. The oven lamp socket is now free.

A diagram shows the oven lamp socket with terminal, wire lead, terminal hole, and a flat-type small screwdriver.

[8] POSITIVE LOCK CONNECTOR (NO-CASE TYPE) REMOVAL

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Push the lever of the positive lock® connector.
5. Pull down on the positive lock® connector.

CAUTION: WHEN CONNECTING THE POSITIVE LOCK® CONNECTORS TO THE TERMINALS, INSTALL THE POSITIVE LOCK® SO THAT THE LEVER FACES YOU.

A diagram illustrates the positive lock connector with lever, terminal, push, and pull down actions.

[9] ANTENNA MOTOR REMOVAL

1. Disconnect the power supply cord.
2. Remove the one (1) screw holding the base plate cover to the base plate and remove the base plate cover.
3. Disconnect the wire leads from the antenna motor and remove the one (1) screw holding the antenna motor.
4. Remove the antenna motor shaft from the antenna motor.
5. The antenna motor is now free.

[10] COOLING FAN MOTOR REMOVAL

1. REMOVAL

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the wire leads from the fan motor.
5. Remove the one (1) screw holding the capacitor holder to the oven cavity rear plate.
6. Remove the one (1) screw holding the fan duct to the oven cavity rear plate.
7. Release the tabs of the capacitor holder from the fan duct.
8. Remove the fan duct from the oven.
9. Remove the fan blade from the fan motor shaft following the procedure below.
10. Hold the edge of the fan motor rotor with groove joint pliers.

CAUTION: MAKE SURE THAT ANY PIECES DO NOT ENTER THE GAP BETWEEN THE ROTOR AND STATOR OF THE FAN MOTOR, AS THE ROTOR IS EASILY SHAVED BY PLIERS, PRODUCING METAL PIECES. DO NOT TOUCH THE PLIERS TO THE FAN MOTOR COIL, AS IT MAY BE CUT OR INJURED. DO NOT DISFIGURE THE BRACKET BY TOUCHING WITH PLIERS.

11. Remove the fan blade assembly from the fan motor shaft by pulling and rotating the fan blade by hand.
12. The fan blade is now free.

CAUTION: DO NOT RE-USE THE REMOVED FAN BLADE, AS THE HOLE (FOR SHAFT) MAY BE LARGER THAN NORMAL.

13. Remove the two (2) screws holding the fan motor to the fan duct.
14. The fan motor is now free.

2. INSTALLATION

1. Install the fan motor to the fan duct using the two (2) screws.
2. Install the fan blade to the fan motor shaft according to the following procedure:
• Hold the bracket supporting the fan motor shaft on a flat table.
• Install the fan blade to the shaft by pushing it with a small, light-weight ball peen hammer or rubber mallet.

CAUTION: DO NOT HIT THE FAN BLADE HARD WHEN INSTALLING, AS THE BRACKET MAY BE DISFIGURED. MAKE SURE THE FAN BLADE ROTATES SMOOTHLY AFTER INSTALLATION. MAKE SURE THE SHAFT AXIS IS NOT SLANTED.

3. Install the fan duct to the oven cavity rear plate with one (1) screw.
4. Insert the tabs of the capacitor holder into the fan duct.
5. Install the capacitor holder to the oven cavity rear plate with one (1) screw.
6. Reconnect the wire leads to the fan motor.

Diagrams illustrate fan motor shaft removal and installation, showing pliers, shaft, rotor, stator, bracket, and installation steps.

[11] POWER SUPPLY CORD REPLACEMENT

1. REMOVAL

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Remove the screw holding the green wire to the cavity rear plate.
5. Disconnect the power supply cord wires from the noise filter.
6. Release the power supply cord from the oven cavity rear plate.
7. The power supply cord is now free.

2. REINSTALL

1. Insert the molding cord stopper of the power supply cord into the square hole of the oven cavity rear plate (refer to Figure C-3b).
2. Install the earth wire lead of the power supply cord to the cavity rear plate with one (1) screw and tighten it.
3. Connect the power supply cord wires to the noise filter (refer to the Pictorial Diagram).

Diagrams illustrate power supply cord replacement.

[12] DOOR SENSING SWITCH/SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH REMOVAL

1. REMOVAL

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Remove the control panel assembly (refer to CONTROL PANEL ASSEMBLY REMOVAL section).
5. Disconnect the leads from all switches.
6. Remove the two (2) screws holding the latch hook to the oven cavity.
7. Remove the latch hook.
8. Push the retaining tab outward slightly and remove the switch.

A diagram (Figure C-4) shows the switches: Door Sensing Switch, Secondary Interlock Switch, and Monitor Switch.

2. REINSTALL

1. Re-install each switch in its place. The door sensing switch and monitor switch are in the lower position; the secondary interlock switch is in the upper position.
2. Reconnect wire leads to each switch, referring to the pictorial diagram.
3. Secure the latch hook (with two (2) mounting screws) to the oven flange.
4. Verify proper monitor switch operation and check continuity of the monitor circuit (refer to "Test Procedure" and Adjustment procedure).

[13] DOOR SENSING SWITCH/SECONDARY INTERLOCK SWITCH AND MONITOR SWITCH ADJUSTMENT

1. Adjustment

1. Disconnect the power supply cord and remove the outer case.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.

If the door sensing switch, secondary interlock switch, and monitor switch do not operate properly due to misadjustment, perform the following adjustment:

4. Loosen the two (2) screws holding the latch hook to the oven cavity front flange.
5. With the door closed, adjust the latch hook by moving it back and forth, and up and down. The in-and-out play of the door allowed by the upper and lower position of the latch hook should be less than 0.5mm. Adjust the vertical position of the latch hook so that the door sensing switch and secondary interlock switch are activated when the door is closed. Adjust the horizontal position so that the monitor switch plunger is pressed when the door is closed.
6. Secure the screws firmly with washers.
7. Check the operation of all switches. If any switch has not activated with the door closed, loosen the screw and adjust the latch hook position.

2. After adjustment, check the following:

1. In-and-out play of the door remains less than 0.5mm when latched. Check upper latch hook position by pushing/pulling the upper door portion toward the oven face. Then check lower latch hook position by pushing/pulling the lower door portion toward the oven face. Both results (door play) should be less than 0.5mm.
2. The door sensing switch and secondary interlock switch interrupt the circuit before the door can be opened.
3. Monitor switch contacts close when the door is opened.
4. Re-install the outer case and check for microwave leakage around the door using an approved microwave survey meter (refer to Microwave Measurement Procedure).

A diagram (Figure C-5) illustrates Latch Switch Adjustments.

[14] DOOR PARTS REMOVAL

1. REMOVAL

CHOKE COVER

1. Disconnect the power supply cord.
2. Open the door slightly.
3. Insert a putty knife (approx. 0.5mm thick) into the gap between the choke cover and door frame to free engaging parts (Figure C-6).
4. Pry the choke cover using the putty knife.
5. Release the choke cover from the door panel.
6. The choke cover is now free.

NOTE: When repairing the door, do not bend or warp the slit choke (tabs on the door panel assembly) to prevent microwave leakage.

7. Release the two (2) pins of the door panel from the two (2) holes of the upper and lower oven hinges by lifting up.
8. Remove the one (1) cushion (ferrite) from the lower opening between the door panel and the door frame.
9. The door sub-assembly is now free from the oven cavity.

DOOR PANEL REMOVAL

10. Remove the four (4) screws holding the door panel to the door frame.
11. Release the door panel from seven (7) tabs of the door frame by sliding it downward.
12. The door panel is now free.

DOOR HANDLE REMOVAL

13. Release the latch spring from the tab of the latch angle assembly.
14. Remove the two (2) screws holding the door handle and latch angle assembly through the door frame.
15. The door handle is now free.

LATCH HEADS REMOVAL

16. Remove the one (1) screw holding the latch angle assembly to the door frame.
17. Remove the latch angle assembly, latch lever, latch spring, and upper/lower latch heads from the door frame.
18. Release the latch lever, latch spring, and latch heads from the latch angle assembly.
19. Release the two (2) latch heads from the latch lever.
20. The upper and lower latch heads are now free.

FRONT DOOR GLASS OR SEALER PLATE REMOVAL (After DOOR PANEL REMOVAL)

1. Remove the four (4) screws holding the glass stopper U to the door frame and remove it.
2. Remove the two (2) screws holding the glass stopper R to the door frame and remove it.
3. Slide the front door glass and sealer plate left, then upward to release them from the holding tabs.
4. The front door glass or sealer plate is now free.

DOOR CASE REMOVAL (After DOOR PANEL REMOVAL)

1. Straighten all tabs holding the door case to the door frame.
2. Release the door case from the door frame.
3. The door case is now free.

NOTE: The door badge is attached to the door case at this moment.

2. REINSTALL OF THE DOOR

1. Reinstall all door parts except the choke cover.
2. Catch the two (2) pins of the door panel on the two (2) holes of the upper and lower oven hinges.
3. Insert the one (1) cushion (ferrite) into the lower opening between the door panel and the door frame.
4. Reinstall the choke cover to the door panel by pushing.

NOTE: After any service to the door:

1. Ensure door sensing switch, secondary interlock switch, and monitor switch are operating properly (Refer to chapter "Test Procedures").
2. Use an approved microwave survey meter to ensure compliance with proper microwave radiation emission limitation standards (Refer to chapter "Test Procedures").

3. After any service, make sure of the following:

1. Door latch heads smoothly catch the latch hook through latch holes, and the latch head goes through the center of the latch hole.
2. Deviation of door alignment from the horizontal line of the cavity face plate is less than 1.0mm.
3. The door is positioned with its face pressed toward the cavity face plate.
4. Check for microwave leakage around the door with an approved microwave survey meter (Refer to Microwave Measurement Procedure).

NOTE: The oven door acts as an electronic seal preventing microwave energy leakage. Occasional moisture, light, or gentle warm air movement around the door is not abnormal and does not indicate leakage.

A diagram (Figure C-7) illustrates door replacement components.

[15] ANTENNA MOTOR SHAFT REPLACEMENT

1. REMOVAL

1. Disconnect the power supply cord.
2. Open the door and block it open.
3. Discharge the high voltage capacitor (wait 60 seconds).
4. Remove the antenna motor from the oven cavity bottom plate (refer to "ANTENNA MOTOR REMOVAL").
5. Remove the ceramic shelf from the oven cavity bottom plate.
6. Remove the one (1) screw and washer holding the antenna holder of the stirrer antenna assembly to the oven cavity bottom plate through the square hole of the stirrer antenna (Refer to Figure C-8).
7. Release the antenna holder from the one (1) tab of the oven cavity bottom plate.
8. Remove the stirrer antenna assembly from the oven cavity bottom plate.
9. Remove the antenna motor shaft from the oven cavity bottom plate hole.
10. The antenna motor shaft is now free.

Diagrams (Figures C-8, C-9, C-10) show antenna motor shaft removal and installation, stirrer antenna assembly, and direction of components.

[16] INSTALLATION OF CERAMIC SHELF

1. Disconnect the power supply cord.
2. Open the door and block it open.
3. Ensure the smooth surface of the ceramic shelf faces up.
4. Ensure the rubber packing without a fin of the ceramic shelf faces the front of the oven.

NOTE: Three (3) rubber packings with fins and one (1) without are attached to the shelf edges. The one without a fin is for the front edge.

5. Insert the front edge of the ceramic shelf into the front edge of the oven cavity bottom plate.
6. Push down the rear edge of the ceramic shelf into the oven cavity bottom plate.
7. The ceramic shelf is now installed.

WARNING: Ensure the rubber packing is not caught between the oven door and the oven cavity front plate to avoid possible exposure to excessive microwave energy.

A diagram shows the oven cavity, rear edge, front edge, and ceramic shelf with push action.

CHAPTER 12. CIRCUIT DIAGRAMS

[1] Pictorial Diagram (Figure S-1)

A pictorial diagram shows the overall wiring layout of the oven, connecting various components like the power supply cord, noise filter, fuse, thermal cut-outs, interlock switches, control unit, relays, motors, and high voltage components (magnetron, transformer, capacitor, rectifier).

[2] Control Panel Circuit (Figure S-2)

A detailed schematic diagram of the control panel circuit, showing the integrated circuit (IC), resistors, capacitors, diodes, transistors, LEDs, buzzer (SP1), relays (RY1, RY2), and connectors.

[3] Printed Wiring Board (Figure S-3)

A diagram of the printed wiring board (PWB) layout, showing the placement of components like ICs, resistors, capacitors, diodes, transistors, relays, and connectors, with labels for various test points and connections.

PARTS LIST

How to Order Replacement Parts

To order parts promptly and correctly, provide the following information:

1. MODEL NUMBER
2. REF. NO.
3. PART NO.
4. DESCRIPTION

Parts marked "*" may cause undue microwave exposure. Parts marked " " are used at voltages over 250V.

[1] OVEN PARTS

This section lists Oven Parts, Cabinet Parts, and Miscellaneous items with their part codes, descriptions, and references to diagrams.

[2] DOOR AND CONTROL PANEL PARTS

This section lists Control Panel Parts, Door Parts, and Miscellaneous items with their part codes, descriptions, and references to diagrams.

INDEX

An index cross-references part codes with their corresponding reference numbers and descriptions.

Diagrams and detailed lists of Oven Parts and Door/Control Panel Parts are provided, showing exploded views and specific part numbers, codes, and descriptions.