Panasonic NN-SD297SR, NN-SD297BR, NN-SD297WR, NN-SD277SR, NN-SD277WR Service Manual

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NN-SD297SR

NN-SD297BR NN-SD297WR NN-SD277SR NN-SD277BR NN-SD277WR NN-SA247SR NN-P295SFR NN-P295WFR NN-S255WFR NN-S245WFR

CPH(CANADA)

Microwave Oven

Please file and use this manual together with the service manual for Model NN-S262SF (Order No.SIMMC0203005C1)

ORDER NO.PHAMOS0902007A1

NN-SD297SR

1 SCHEMATIC DIAGRAM 5

1.1. NN-SD297SR/BR/WR, P295SFR/WFR

1.2. SD277SR/BR/WR

1.3. NN-SA247SR, S245WFR

1.4. NN-S255WFR

2 DESCRIPTION OF OPERATING SEQUENCE

2.1. Variable power cooking control

2.2. Inverter power supply circuit

2.3. Inverter defrost

2.4. Sensor cooking (Only for sensor models)

2.5. Sensor reheat (Only for sensor models)

3 CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING

3.1. Check the grounding

3.2. Inverter warnings

3.3. Part replacement.

3.4. When the 20A fuse is blown due to the malfunction of the

monitor interlock switch:

3.5. Avoid inserting nails, wire etc. through any holes in the

unit during operation.

3.6. Verification after repair

3.7. Sharp edges

4 COMPONENT TEST PROCEDURE

4.1. Primary, Secondary Latch Switch interlocks & Power

Relay RY1

4.2. Monitor Interlock Switch

4.3. Magnetron

4.4. Inverter power supply (U)

4.5. Humidity sensor

5 MEASUREMENTS AND ADJUSTMENTS

5.1. Adjustment of primary latch switch, secondary latch switch

and monitor interlock switch.

5.2. Measurement of microwave output

6 PROCEDURE FOR MEASURING MICROWAVE ENERGY

LEAKAGE

6.1. Equipment

6.2. Procedure for measuring radiation leakage

6.3. Record keeping and notification after measurement

6.4. At least once a year, have the radiation monitor checked

for calibration by its manufacture r.

7 TROUBLESHOOTING GUIDE

7.1. Troubleshooting of inverter circuit (U) and magnetron

7.2. SIMPLE WAY OF H.V. INVERTER/MAGNETRON

TROUBLESHOOTING

7.3. H.V.INVERTER BOARD MAIN PARTS LIST

(F606Y8X00AP)

8 EXPLODED VIEW AND PARTS LIST

8.1. EXPLODED VIEW

8.2. PARTS LIST

8.3. DOOR ASSEMBLY

8.4. ESCUTCHEON BASE ASSEMBLY

8.5. PACKING AND ACCESSORIES

8.6. WIRING MATERIALS

9 DIGITAL PROGRAMMER CIRCUIT

9.1. NN-SD297SR/BR/WR CPH

9.2. NN-P295SFR/WFR CPH

9.3. NN-SD277SR/BR/WR CPH, S255WFR CPH

9.4. NN-SA247SR CPH, S245WFR CPH

9.5. PARTS LIST

CONTENTS

Page Page

NN-SD297SR

1 SCHEMATIC DIAGRAM

1.1. NN-SD297SR/BR/WR, P295SFR/WFR

NN-SD297SR

1.2. SD277SR/BR/WR

NN-SD297SR

1.3. NN-SA247SR, S245WFR

NN-SD297SR

1.4. NN-S255WFR

NN-SD297SR

2.1. Variable power cooking control

High Voltage Inverter Power Supply (U) controls output power by the signal from Digital Programmer Circuit (DPC). Power relay always stay on, but PWM (Pulse Width Modulation) signal controls microwave output power.

NOTE:

The ON/OFF time ratio does not correspond with the percentage of microw ave power since approximately 2 seconds are required for heating of magnetron filament.

Variable Power Cooking

POWER SETTING OUTPUT

POWER(%)

APPROX.

MANUAL MICROWAV E

DUTY

ON(SEC) OFF(SEC)

HIGH P10 100% 22 0

P9 90% 22 0

P8 80% 22 0 MEDIUM-HIGH P7 70% 22 0 MEDIUM P6 60% 22 0

P5 50% 22 0

P4 40% 22 0 MEDIUM-LOW P3 30% 22 0

P2 20% 15 7

P1 10% 8 14 DEFROST P3 30% 22 0

2.2. Inverter power supply circuit

The Inverter Power Supply circuit powered from the line voltage, 120V 60Hz AC input supplies 4,000V DC to the magnetron tube, and function s in place ofthe H.V. transformer, the H.V. capacitor and H.V. diode.

1. The AC input voltage 120V 60Hz is rectified to DC voltage immediately.

2. DC voltage will be supplied to the switching devices called IGBT. These devices are switched ON-OFF by the 20 to 40 kHz PWM (pulse width modulation) signal from the microcomputer in the DPC.

3. This drives the High voltage transformer to increase voltage up to 2,000V AC.

4. Then the half-wave doubler voltage rectifier circuit, consisting of the H.V. diodes and capacitors, generates the necessary 4,000V DC needed for the magnetron.

5. Output power of the magnetron tube is always monitored by the signal output from the current transformer built into the inverter circuit.

6. This signal is fed back to the microcomputer in the DPC to determine operating conditions and output necessary to control PWM signal to the Inverter Power Supply for control of the output power.

2.3. Inverter defrost

When the Auto Control feature is selected and the Start button is tapped:

1. The digital programer circuit determines the power level and cooking time to complete cooking and indicates the operating state in the display window. Table shows the corresponding cooking times for respective serving by categories.

Inverter Turbo Defrost

SELECTED WEIGHT COOKING TIME

1.0 LB 5 min.28 sec.

2. When cooking time in the display window has elapsed, the oven turns off automatically by a control signal from the digital programmer circuit.

2.4. Sensor cooking (Only for

sensor models)

Auto sensor cooking without setting a power level or selecting a time. All that is necessary is to select an Auto Sensor Program before starting to cook.

Understanding Auto Sensor Cooking

As the food cooks, a certain amount of steam is produced. If the food is covered, this steam builds up and eventually escapes from the container. In Auto Sensor Cooking, a carefully designed instrument, called the humidity sensor element, senses this escape of steam. Then, based upon the Auto Sensor Program selected, the unit will automatically determine the correct power level and the proper length of time it will take to cook the food.

NOTE:

Auto Sensor Cooking is successful with the foods and recipes found in the Auto Sensor Cooking Guide. Because of the vast differences in food composition, items not mentioned in the Cooking Guide should be prepared in the microwave oven using power select and time features. Please consult Variable Power Microwave Cookbook for procedures.

2 DESCRIPTION OF OPERATING SEQUENCE

NN-SD297SR

Explanation of the Auto Sensor Cooking process

1. T1 time The total amount of time it takes the microwave oven to switch to T2 time.

2. T2 time When the steam escapes from the cooking container placed in the oven, the humidity sensor detects it and the microprocessor calculates the balance of cooking time. This T2 time is then shown in the display and begins counting down.

Balance of cooking time (T2 time)

The balance of cooking time which is called T2 time, can be calculated by the following formula. T2 time (in sec.) = T1 time X K factor

NOTE:

The coefficient K is programmed into the microprocessor memory and they are listed in the following tables along with the P1 and P2 powers.

NOTE:

When "More" or "Less" button is selected, the K factor varies resulting in T2 time to be increased or decreased.

Example of calculating the T2 time

Example 1: If the T1 time is measured to be 2 minutes and 40 seconds, and the Auto program selected is Oatmeal:

T2 = T1 × K

= 2 min. and 40 sec. × 0.1

= 160sec. × 0.1

= 16 sec.

Category P1

Power

K Factor

Standard

Oatmeal MEDIUM-HIGH MEDIUM-HIGH 0.5

2.5. Sensor reheat (Only for sensor models)

Auto Sensor Reheat is a quick and easy way to reheat refrigerated and room temperature foods.

Simply press the [Sensor Reheat] button. There is no need to select power level and cooking time.

NOTE:

The Auto Sensor Reheat process is same as Auto Sensor Cooking process.

Category P1

Power

K Factor

Standard

Sensor Reheat HIGH MEDIUM 0.5

NN-SD297SR

Unlike many other appliances, the microwave oven is a high voltage, high current device. Though it is free from danger in ordinary use, extreme care should be taken during repair.

CAUTION

Servicemen should remove their watches and rings whenever working close to or replacing the magnetron.

3.1. Check the grounding

Do not operate on a two wire extension cord. The microwave oven is designed to be grounded when used. It is imperative, therefore, to ensure the appliance is properly grounded before beginning repair work.

3.2. Inverter warnings

WARNING HIGH VOLTAGE AND HIGHTEMPERATURE

(HOT/LIVE) OF THE INVERTERPOWER SUPPLY (U)

The High Voltage Inverter Power Supply generates very high voltage and current for the magnetron tube. Though it is free from danger in ordinary use, extreme care should be taken during repair.

The aluminum heat sink is also energized with high voltage (HOT), do not touch when the AC input terminals are energized. The power device Collector is directly connected to the aluminum heat sink.

The aluminum heat sink may be HOT due to heat energy, therefore, extreme care should be taken during servicing.

H.V. Inverter warning

WARNING FOR INVERTER POWER SUPPLY (U)

GROUNDING

Check the High Voltage Inverter Power Supply circuit grounding. The high voltage inverter power supply circuit board must have a proper chassis ground. The inverter grounding plate must be connected to the chassis. If the inverter board is not grounded it will expose the user to very high voltages and cause extreme DANGER! Be sure that the inverter circuit is properly grounded via the inverter grounding plate.

Grounding of the inverter circuit board

3 CAUTIONS TO BE OBSERVED WHEN

TROUBLESHOOTING

NN-SD297SR

WARNING DISCHARGE THE HIGH VOLATGE

CAPACITORS

For about 30 seconds after the oven is turned off, an electric charge remains in the high voltage capacitors of the Inverter Power Supply circuit board.

When replacing or checking parts, remove the power plug from the outlet and short the inverter output terminal of the magnetron filamen t terminals to the chassis ground with an insulated handle screwdriver to discharge. Please be sure to contact the chassis ground side first and then short to the output terminal.

Discharging the high voltage capacitors

WARNING

There is high voltage present with high current capabilities in the circuits of the primary and secondary windings, choke coil and heat sinkof the inverter. It is extremely dangerous to work on or near these circuits with the oven energized. DO NOT measure the voltage in the high voltage circuit including the filament voltage of the magnetron.

WARNING

Never touch any circuit wiring with your hand or with an insulated tool during operation.

3.3. Part replacement.

When troubleshooting any part or component is to be replaced, always ensure that the power cord is unplugged from the wall outlet.

3.4. When the 20A fuse is blown due to the malfunction of the monitor interlock switch:

WARNING

When the 20A 120V fuse is blown due to the malfunction of the monitor interlock switch, replace all of the components (primary latch switch, monito r interlock switch and power relay RY1).

1. This is mandatory. Refer to “measurements and adjustments” for the location of these switches.

2. When replacing the fuse, confirm that it has the appropriate rating for these models.

3. When replacing faulty switches, be sure the mounting tabs are not bent, broken or deficient in their ability to hold the switches.

3.5. Avoid inserting nails, wire etc. through any holes in the unit during operation.

Never insert a wire, nail or any other metal object through the lamp holes on the cavity or any holes or gaps, because such objects may work as an antenna and cause microwave leakage.

3.6. Verification after repair

1. After repair or replacement of parts, make sure that the

screws of the oven, etc. are neither loosen or missing. Microwave energy might leak if screws are not properly tightened.

2. Make sure that all electrical connections are tight before

inserting the plug into the wall outlet.

3. Check for microwave energy leakage. (Refer to procedure

for measuring microwave energy leakage).

CAUTION OF MICROWAVE RADIATION LEAKAGE

USE CAUTION NOT TO BECOME EXPOSED TO RADIATION FROM THE MICROWAVE MAGNETRON OR OTHER PARTS CONDUCTING MICROWAVE ENERGY.

IMPORTANT NOTICE

1. The following components have potentials above 2000V while the appliance is operated.

• Magnetron

• High voltage transformer (Located on inverter (U))

• High voltage diodes (Located on inverter (U))

• High voltage capacitors (Located on inverter (U))

Pay special attention to these areas.

2. When the appliance is operated with the door hinges or magnetron installed incorrectly, the microwave leakage can exceed more than 5mW/cm

. After repair or exchange, it is very important to check if the magnetron and the door hinges are correctly installed.

3.7. Sharp edges

CAUTION

Please use caution when disassembling or reassembling internal parts. Some exposed edges may be sharp to the touch and can cause injury if not handled with care.

NN-SD297SR

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Panasonic NN-SD297SR, NN-SD297BR, NN-SD297WR, NN-SD277SR, NN-SD277WR Service Manual

Specifications and Main Features

Frequently Asked Questions

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