Panasonic NN-C980B, NN-C988B User Manual Download

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Technical Guide

Microwave Ovens with Inverters

Panasonic Services Company

National Training

Summary of Contents for NN-C980B, NN-C988B

Page 1: ...Technical Guide Microwave Ovens with Inverters Panasonic Services Company National Training ...

Page 2: ... the general public It does not contain warnings or cautions to advise non technical individuals of potential dangers in attempting to service a product Products powered by electricity should be serviced or repaired only by experienced professional technicians Any attempt to service or repair the product or products dealt with in this service information by anyone else could result in serious inju...

Page 3: ...vens Upon successful completion of this course the student will learn the differences between the high voltage circuit used in most microwave ovens and the Inverter technology used in this line of Panasonic microwave ovens The student will also have a better understanding of the new features and the function of the major components of the microwave oven ...

Page 4: ......

Page 5: ...o check the steam sensor function 10 Inverter Circuit 11 Test and Measuring Procedures 15 Procedure to check the Inverter using an Amp Meter 15 Measurement of microwave output 16 Procedure for measuring microwave energy leakage 17 Safety Tips 19 Safety tips for operation of microwave ovens 19 Safety tips for installation and maintenance of microwave ovens 19 Models line up 20 Features 21 Functions...

Page 6: ...ople absorb microwave energy If energy is absorbed at a rate greater than the rate at which the material looses energy rate of cooling its temperature increases How do microwaves cook In microwave ovens magnetrons are used to produce the microwaves These microwaves have a frequency of 2 450 MHz which is transmitted into the enclosed metal oven cavity In the cavity they are reflected by the oven wa...

Page 7: ...ff repeatedly Inverter Technology In inverter equipped microwave ovens the power transformer is replaced by a circuit board which converts the 60Hz incoming line frequency to a variable rate of 20 KHz to 45 KHz A relatively small transformer is then required to increase the voltage to the level required by a magnetron By varying the pulse width the output power can be linearly controlled for more ...

Page 8: ...tiple power levels When you ask for 60 power the oven delivers 60 power e g they don t just operate 60 of the time This applies no matter what power level is selected True power levels give you better cooking results and your food would have an even texture and temperature after cooking The constant soft penetration of microwave energy into the center of the food helps prevent overcooking on edges...

Page 9: ...orted magnetron To check for open filament Disconnect the filament leads Measure the resistance across the filament terminals The normal resistance is approximately 1 ohm or less To check for a shorted magnetron Disconnect the filament leads Measure the resistance between each filament terminal and the magnetron case Normally it should read open Note Do not rely on continuity check alone to determ...

Page 10: ... a multimode cavity resonator designed to resonate the microwaves emitted from the magnetron Here is where the food is placed for cooking or heating The oven cavity is made with stainless steel aluminum or painted steel plate to reflect the microwaves Oven Cavity Figure 4 Turntable The microwaves come into the oven s cavity from the side of the oven to ensure that the microwave field evenly covers...

Page 11: ...ent the operation of the microwave oven while the door is opened The short switch creates a short circuit to blow the line fuse and stop microwave oven s operation if the door switches fail to open when the door is opened This switch is normally open when the door is closed Switches Location Primary Switch Short Switch Lower Secondary Switch Upper Side view of Microwave Oven Figure 6 Note When the...

Page 12: ...ook assembly to the oven assembly adjust the door hook assembly by moving it in the direction of the arrows in figure 7 so that the oven door will not have any play in it 3 Check for play in the door by pulling the door assembly 4 Make sure that the latch keys move smoothly after adjustment is completed Tighten the screws holding the door hook assembly to the oven assembly 5 Reconnect the short sw...

Page 13: ...re 8 The thermal cutout sensor is used to stop the flow of AC to the oven if the cavity surface overheats for any reason The thermistor will shut the oven down and reset the display when the magnetron overheats and reaches a temperature of 257 F The cooking program can be re started after the magnetron cools down The value of this thermistor is 30K to 120K at 50 F 86 F Temperature Sensors Location...

Page 14: ...this effect is called pyroelectricity where electricity is generated when heat shock hot steam is applied to the general dielectrics material See the figure below Principle of Steam Sensor Dielectrics Pyroelectricitic Material Steam Sensor Figure 9 When the food is heated by the microwave oven the food temperature gradually increases and steam is generated from the food The steam sensor which is l...

Page 15: ...ensor re heat pad 3 Press start Note Steam is normally detected approximately 1 5 to 4 minutes after pressing power This period is named The detection period T1 After going through this period the unit automatically jumps to another period called The remaining cooking time period T2 The T2 time ranges from 8 seconds to 23 seconds 4 The steam sensor function is normal if after jumping to the T2 per...

Page 16: ... information about the inverter power supply turn to pages 2 and 3 Inverter Power supply CN702 AC Input CN701 Control Signals line High Voltage Transformer CN703 High Voltage output to the magnetron Heat sink Figure 12 11 ...

Page 17: ... change in load or the power level affects the frequency of the drive signal Typically the frequency ranges between 20KHz to 40KHz The high voltage transformer generates approximately 2 000V DC or more in the secondary winding and approximately 3V AC in the filament winding The half wave rectifier circuit D701 D702 generates the necessary 4 000V DC needed to drive the magnetron A signal from the c...

Page 18: ...d is very dangerous 3 Do not touch the heat sink during operation of the microwave oven The heat sink handles high voltage and becomes very hot 4 Always discharge the high voltage capacitors located on the inverter circuit board before beginning any troubleshooting 5 Only test the inverter circuit board by installing it completely into the oven and refitting the outer panel 6 Always connect the in...

Page 19: ...Inverter Power Supply Figure 14 14 ...

Page 20: ...en at high power for 1 minute and press start The Oven operates for approximately 15 seconds and then it stops showing the error code H98 During operation the AC line current should be between 1A and 1 7A 4 Unplug the 3 pins connector from CN701 on the inverter power supply 5 Set the oven at high power for 1 minute and press start The Oven operates for approximately 27seconds and then it stops sho...

Page 21: ...tron output Take the temperature readings and heating time as accurately as possible 1 minute 1 liter test Fill the beaker with exactly one liter of tap water Stir the water using the thermometer and record the water s temperature 1 Place the beaker on the center of glass tray 2 Set the oven for High power and heat it for exactly one minute 3 Stir the water again and read the temperature of the wa...

Page 22: ...or Glass thermometer 212 F or 100 C 600cc glass beaker Figure 16 Procedure for measuring radiation leakage 1 Do not exceed the meter full scale deflection The leakage monitor should initially be set to the highest scale 2 To prevent false readings the test probe should be held by the grip portion of the handle only 3 Pour 275 15cc 9Oz 1 2oz of 68 9 F water in a 600cc beaker and place in the center...

Page 23: ...d the cover at a very slow speed no faster than 1 inch sec 2 5cm sec Leakage reading for a fully assembled oven with door normally closed should be less than 2mW cm 2 1mW cm 2 for Canada Leakage reading for a fully assembled oven Before the latch switch primary is interrupted while pulling the door should be less than 2mW cm 2 Leakage reading for an oven with the outer panel removed should be less...

Page 24: ...ation and maintenance of microwave ovens Take special care to ensure that no damage occurs to the part of the oven making contact with the door or door seals Ensure that the microwave is unplugged or disconnected from electrical power before reaching into any accessible openings or attempting any repairs Ensure that the adjustment of applied voltages replacement of the microwave power generating c...

Page 25: ...dels line up Mid and Family Size NNS504W M NNS614W NNH664B W NNH764B W NNT694S NNP794B W NNP794S Full Size NNH964B W NNP994B W NNP994S NNS254W NNH264B W Q NNP294B W NNP294S Convection NNC980W B NNC994S 20 ...

Page 26: ...arying levels of power produce uneven results when attempting to cook on 2 levels But thanks to Inverter Technology multiple food preparation is a possibility Preparing food has never been this fast or this easy Lightweight Design Panasonic s Inverter Microwave Ovens are lighter sleeker and more compact than ever before yet also offer more space inside to prepare food Panasonic Inverter technology...

Page 27: ...le instructions There s even a multi lingual display that easily guides you through cooking instructions in English Spanish or French Food weight can be programmed for English or metric measurement Menu Action Screen Figure 17 Word Prompting The LCD screen provides word by word instructions on features such as setting the clock Auto Defrost and using one touch cooking In total there are over 50 in...

Page 28: ... you to defrost foods in almost half the time than previous Panasonic Auto Defrost Panasonic Inverter Turbo Defrost technology is an advanced microwave sequencing system using the Inverter low power delivery feature It was developed on the basis of what scientists call Chaos Theory This design makes it possible to distribute microwave energy with the most appropriate combination of regularity and ...

Page 29: ...very time Movable Louvers Over the Range models They open when needed for ventilation purposes when the oven s in use However when the cooking or defrosting task is complete the louvers automatically close for a more streamlined appearance Dimension 4 Type With this type of convection microwave oven besides having the advantage of a combination oven it is also possible to bake brown re heat and br...

Page 30: ...vides optional built in trim kits which allow you to neatly and securely position a Panasonic microwave oven into an open area of your kitchen Each kit includes all the necessary assembly pieces and hardware to give your Panasonic microwave oven a custom finish look Figure 21 25 ...

Page 31: ...29WR NNTK929S 68 7 cm x 47 3 cm 27in x 18 5 8 in NNP994S NNP994W NNP994B NNH964B NNH964W NNS960B NNS960W NNS951B NNS951W NNT991S NNS962B NNS962W NNS952B NNS952W NNS963B NNS963W NNS953W NNT993S NNTK939BR NNTK939WR NNTK939S 76 2 cm x 47 3 cm 30 in x 18 5 8 in 63 2 cm 0 16 cm x 44 2 cm 0 16 cm x 53 3 cm minimum 24 7 8 in 1 16 in x 17 3 8 in 1 16 in x 21 in minimum NNTK729B NNTK729W NNTK729S 68 7 cm x...

Page 32: ...iled menus that help make cooking with this Panasonic over the range microwave a simple task even for the most novice chefs Categories include oatmeal beverages bacon soup frozen entrees frozen pizza frozen pocket sandwiches hot dogs potatoes vegetables fresh or frozen rice frozen dinners fish fillets and pasta Auto Reheat Keep Warm Simmer A pulsing delivery of very low microwave power keeps food ...

Page 33: ...en It scrolls step by step cooking instructions across the display in a choice of English Spanish or French The Function Key simplifies the programming of 10 useful non cooking functions Just press the Function Key and the Menu Action Screen will display easy to follow steps to complete the desired function Quick Minute Set cooking times in one minute intervals or add a minute to a current cooking...

Page 34: ...ause them to vibrate but not enough to change them chemically is referred to as non ionizing radiation Examples of this kind of radiation are sound waves visible light and microwaves Radiation that falls within the ionizing radiation range has enough energy to actually break chemical bonds This is the type of radiation that people usually think of as radiation We take advantage of its properties t...

Page 35: ...have very high frequency in the range of 100 billion billionth Hertz and very short wavelengths 1 million millionth of a meter Radiation in this range has extremely high energy It has enough energy to strip off electrons or in the case of very high energy radiation break up the nucleus of atoms Ionization is the process in which a charged portion of a molecule usually an electron is given enough e...

Page 36: ...m 1 Defective DPC 2 Open or loose connection of the membrane keypad 3 Shorted or open membrane keyboard 4 The Oven lamp and the fan motor turn on when oven is plugged in with door closed 1 Misadjusted secondary switch or loose wiring 2 Defective secondary switch Adjust door and latch switches 5 Timer starts to countdown but there s no microwave oscillation No heat while the oven lamp and the fan m...

Page 37: ...e oven does not operate It returns to plugged in mode as soon as the start pad is pressed 1 Open or loose wiring of temperature sensor Thermistor 2 Defective temperature sensor Thermistor 3 Defective DPC Check for tight contact of screw on thermistor and check the connection on the DPC 10 Loud buzzing noise can be heard 1 Loose fan 2 Noisy fan 11 Turntable motor does not rotate 1 Open or loose wir...

Page 38: ... Condition H97 H98 or H99 appears on the display window Open Magnetron 0V DPC board Loose relay wiring H V Inverter 3V AC 0V DPC board Check the inverter control signal at pins 1 and 2 of CN701 Unplug CN701 and measure at lead wire harness side Check for inverter AC line input at CN702 Unplug CN702 and measure at lead wire harness side Check for magnetron filament continuity Refer to the how to di...

Page 39: ...ing surface ANTENNA PIN See tuning stub BIAS A DC voltage applied to the control electrode of an electronic device to establish the desired operating point CAPACITANCE The property of a capacitor that determines how much charge can be stored in it for a given potential difference across its terminals The basic unit is the farad However the small microfarad unit is more commonly used abbreviated MF...

Page 40: ...F POTENTIAL The voltage existing between two points If a circuit is established between the two points a flow of electrons will result DIRECTLY HEATED CATHODE A wire or filament that is designed to emit electrons when an electric current flows through it The current heats the filament to the point where electrons are emitted DPC Digital Programmer Circuit DUMMY LOAD A device used at the end of a w...

Page 41: ...e collectively all the electric or magnetic lines of force in a given region FREQUENCY The number of times a wave makes one full cycle in one second of time Usually expressed in hertz Hz FULL WAVE RECTIFIER A circuit that uses both positive and negative alternations of an alternating current to produce a direct current GROUND Zero potential with respect to the ground or earth A metallic connection...

Page 42: ...arating conductors so as to prevent undesired current flow between the conductors or to other objects INTERFACE CIRCUITRY Serves to link the otherwise incompatible high impedance circuits of the microprocessor and the high potential circuits of external components ISO International Organization for Standardization IONIZING The dislodging of orbital electrons from atoms creating electrically charge...

Page 43: ...000 MILLIWATT 1 1000 of a watt of electricity MODULATION DEMODULATION Modulation is the ability to impress intelligence upon a transmission medium A transmission medium may be described as radio waves light or infrared beams wire lines sound or other communication systems The characteristics intelligence of one waveform are impressed onto a second waveform by varying the frequency amplitude phase ...

Page 44: ... neutral side of an AC line is always connected to the neutral side of an appliance such as a microwave oven POSITIVE CHARGE An electrical medium that has become deficient in electrons thus having the ability to attract electrons POTENTIAL The amount of charge held by a body as compared to another point or body A difference in voltage potential between two connected points results in current flow ...

Page 45: ... order to complete the circuit SHORT CIRCUIT A low resistance usually zero ohms connection across a voltage source or between two points in a circuit that are of different electrical potential A short circuit usually results in excessive and possibly damaging current flow SOLENOID An electromagnetic coil that contains a movable plunger STANDING WAVE The distribution of waves in a reflective enclos...

Page 46: ...ltage of a circuit is the greatest effective difference of potential between any two conductors of a circuit VOLTAGE DROP Ratio of voltage or electrical pressure lost or dropped across a specified load as a result of forcing current flow through that load WATT The practical unit of electric power In a DC circuit one watt of power is used when one ampere of current flows through a resistance of one...

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