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SERVICE MANUAL - Appliance Factory Parts

1. TURNTABLE MOTOR ie mE EM031EZN POOA CIRCUIT DESCRIPTION As the door is closed the contact of MONITOR SWITCH opens This switch creates the short circuit to blow fuse during operation under abnormal condition ie should the contacts of primary and secondary switch to open the circuit The latches are secured by latch board The oven light turns on while the oven is in operation WHEN MICROWAVE POWER LEVEL AND COOKING TIME SET contacts of the timer switch changes to ON position when the timer knob is rotated While power control knob is set contacts of primary and secondary switch close the circuit Input Volts AC is applied to the high voltage transformer through V P C POWER PRIMARY TIMER CONTROL SWITCH SWITCH SWITCH Q 07 9 MONITOR RESISTOR 30 000000 O SECONDARY SWITCH e Turntable rotates fan motor rotates and cools the magnetron by blowing the air coming from the intake holes on the baseplate over the magnetron air is also directed into the oven to exhaust the vapor in the oven through the upper plate e Timer starts rotating 3 2 volts AC is generated from the filament winding of the high voltage transforme
2. 1 Change the fan motor within 2 3 minutes but 2 The fan falls off 2 Change the fan can not heat from the 3 The plug of the fan motor falls off 3 Insert the plug fourth minutes 4 The turntable shaft is griped with the motor 4 Overhauling them bearing 5 Repairing it 5 The cooling vent blocked 6 When starting the The high voltage diode was punctured Change a new diode oven it can t heat and with wenwen noise 7 The oven can heat but with sound shishi noise The iron core of the transformer loosed Change a new transformer 8 Large amount of 1 The door deformed 1 Mend the door microwave leakage 2 The door metal net cracked 2 Change the door 3 The gap of the door crack is too large 3 Adjust the gap 4 The welding point of the oven fall off 4 Change the oven 5 The screws which fix the magnetron loosed 5 Tighten the screws 6 The wave guide connection oxidized 6 Scrape the oxidized and 7 The magnetron copper filament washer is too tighten the screws thin cause the wave guide opening not in good 7 Thick the copper filament earth washer 9 The door can t open 1 After long time using the wear and the rust 1 Adjust the hinge to rectify eaten enlarged the gap of the door shaft and the position of the door the shaft hole thus cause the door crooked 2 Change the hook 2 The door hook broken 10 The door button fall off release Wore aged after long time operating Overhaul
3. by a new same model one If the resistance value is between 15 22k it indicates the turntable motor is normal then check the connecting shaft weave If the plastic that the shaft insert in has broken a new shaft weave should replace it Repair when the oven can heat but the lamp is not on Pull out the power plug take down the outer case and discharge the capacitor Pull out the two terminal plugs of the lamp measure the two plugs of the lamp with the Rx100 grade of a multi meter If it is open circuited it indicates the lamp has broken and should be replaced by a same model one Means of repair when the oven stop working after several minutes operating The phenomenon indicated the thermal cutout is playing its protective role and you should check whether the fan is working in normal Turn off the oven pull out the power plug take down the outer case discharge the capacitor then turn the fan with hand to see whether it is moving flexibly If not it indicates that the oil bearing of the fan motor has run off the oil and should take down the fan combination to repair the motor Loosen the two screws which fix the bearing out the shaft and the bearing and rinse them with kerosene ATTENTION The bearing can only be wiped with a silk which moistened with kerosene rather than be washed in the kerosene because there are felt on it If the felt are soaked with kerosene then the engine oil can not be sucked up After the bearing being cleaned th
4. indicates the high voltage diode has been punctured and should be replaced by a new one If high voltage diode is also normal then test the pilot switch FIG 5 10 Pull out the two plugs of the switch Measure it with the Rx1 grade of a multi meter the two rod connect the plug of the switch the resistance value should Then press down the pilot switch with a screwdriver if the reading of the multi meter pointed to zero it indicates the pilot switch has broken and should replace it with a new same model one FIG 5 8 5 5 FIGS 10 FIG5 9 M REPAIRING METHOD OF SEVERAL BREAKDOWN 1 Repair when there occurred large amounts microwave leakage There are many factors which may cause microwave leaking Following mentioned may be the main cause of microwave leakage 1 The door deformed the hinge loosed or damaged that caused the door can not close tightly 2 3 The door pressing cover or the embed piece damaged or come off 4 There are filth between the door and the oven Obvious damage or uneven of the oven 5 6 5 The door and the oven are serious loosed after the door closed 6 The crack of the door shielding net cover Before repairing check whether the above listed point are existed if not you can start the microwave oven Place a graduate of about 275ml water at the middle of the glass tray close the door time set at 3 minutes power at high makes the oven operat
5. it or renew it 11 Electricity leaking The earthing insulation resistances of all the Test where is the leaking motors or the transformer are less than 2 mega place then repair it or ohm change those damaged components 5 9 2 3 4 THINGS DO PRIOR CRITICAL PART SERVICING following instructions are CRITICAL to the owners safety Be sure to follow all the instructions Contact the manufacturer of distributor if you have any question 1 1 1 2 1 3 If the oven is operative prior to servicing a Microwave Leakage Test Microwave Emission Check should be performed prior to servicing the oven in the event that any microwave oven found to have microwave emission level in excess of 1 mW em The following procedures should be followed a Inform the distributor importer or manufacture the finding Record itinthe logbooks well b Repair the unit at no cost to the owner c Investigate the oven and ascertain the cause of the excessive leakage d Hold the oven in your facility and instruct the owner not to use the unit until the oven has been brought into compliance In the event that the oven operates with the door open The following procedures should be followed a Tell the user not to operate the oven b Hold the oven in your facility until it is investigated and repaired c Contact the manufacturer immediately Interlock Assembly Replacement an
6. low and would produce much heat When the frequency is too high as the swing of the polar molecule is with rotating inertia it made the swing do not in line with the changing rhythm of the electric field because of the friction drag thus actually lowed the polar molecule swaying speed The friction dragging degree is concerning about the magneto electric wave frequency polar molecule shape and the matter s sticky degree To different matter s molecule there are different special frequency zone Those ado absorb microwave energy from these zone are most capable to turn microwave energy to heat energy Apart from the above said action there is another action which is electric ion under the action of microwave field act fiercely accompanied with the acceleration of electric field The positive ion transfer to the negative polarity of the field while the negative ion do opposite Accompanying with the changing electric field the electric ion changing accordingly During the transferring heat produced with the crash among the ion This kind of action take the main effect to those microwave heating of high salt molecule No matter it is the polar molecule swaying or the ion transferring they both are turning the microwave energy which the heating matter got from the microwave field to hear energy From the analysis of theory we can draw such a conclusion that the power which a unit of volume matter absorbed from the microwave field as the following f
7. meter connect the two polarity of the capacitor When they just connected the reading of the multi meter should be zero then enlarge to nine mega ohm slowly Change the rod to different polarity the reading repeat from zero to 9 mega ohm FIG 5 5 it means the capacitor is normal If the indicator of the multi meter can t point out from zero to 9 mega ohm it indicates the high voltage capacitor has broken and should be replaced by a new one FIG5 5 FIG5 6 If it is normal between the two pole of the capacitor then the insulation between the capacitor pole and the cabinet FIG 5 6 should be checked If the resistance value between the capacitor pole and the cabinet is capacitor is normal Then check the earth of the magnetron s two filament to see whether they are short circuited FIG 5 7 If they are short circuited and the filament strikes the shell of the magnetron it indicates the magnetron has broken and should be replaced by a new same model one If there is no problem with the magnetron check the high voltage diode then Measure the diode with Rx10k grade of a multi meter the rod end of the multi meter connect the cathode of diode the rod end of the multi meter connect the anode of the diode FIG 5 8 The multi meter reading should be about 150 thousand ohm Then change the rod to different electrode FIG 5 9 the reading should be o If the reading is very small and near to short circuit it
8. XPLODED VIEW isisa a 6 1 REPLACEMENT PARTS LIST ia a aa 6 1 CAUTIONS Unlike other appliances the microwave oven is high voltage and high current equipment Though it is free from danger in ordinary use extreme care should be taken during repair e DO NOT operate on a 2 wire extension cord during repair and use NEVER TOUCH any oven components or wiring during operation BEFORE TOUCHING any parts of the oven always remove the power plug from the outlet For about 30 seconds after the oven stops an electric charge remains in the high voltage capacitor When replacing or checking you must discharge the high voltage capacitor by shorting across the two terminals with an insulated screwdriver Ee Remove your watches whenever working close to or replacing the Magnetron DO NOT touch any parts of the control panel circuit A resulting static electric discharge may damage this P C B NEVER operate the oven with no load NEVER injure the door seal and front plate of the oven cavity NEVER put iron tools on the magnetron NEVER put anything into the latch hole and the interlock switches area 1 1 MICROWAVE RADIATION Personnel should not be exposed to the microwave energy which may radiate from the magnetron or other microwave generating device if it is improperly used or connection All input and output microwave connections waveguide flange and gasket must be sec
9. ave power output measurement is made with the microwave oven supplied at its rated voltage and operated at its maximum microwave power setting with a load of 1000 5 g of potable water The water is contained in a cylindrical borosilicate glass vessel having a maximum material thickness of 3 mm and an outside diameter of approximately 190mm oven and the empty vessel at ambient temperature prior to the start of the test initial temperature T1 of the water is 10 2 C It is measured immediately before the water is added to the vessel After addition of the water to the vessel the load is immediately placed on the center of the turntable which is in the lowest position and the microwave power switched on The time T for the temperature of the water to rise by a value T of 10 2 K is measured where is the time in seconds and T is the temperature rise The initial and final water temperatures are selected so that the maximum difference between the final water temperature and the ambient temperature is 2 K 5 3 microwave power output P in watts is calculated approximately from the following formula P 4187 x A is measured while the microwave generator is operating at full power Magnetron filament heat up time is not included about 3 sec water is stirred to equalize temperature throughout the vessel prior to measuring the final water temperature Stir
10. butor Magnetron Replacement 4 1 4 2 Check for the presence of the wire mesh gasket before installation Conduct a Microwave Leakage Test at the magnetron area prior to installing the top cover 5 10 SAFETY CHECKS AND TESTS AFTER SERVING Constructional Checks If mechanical or electrical electronic parts have been replaced be sure to follow the following steps 1 1 Check for correct wiring adequate mechanical decrements of parts and firm connectors 1 2 Check for adequate grounding 1 3 Check the following items before turning the oven ON 1 Proper door closing seal choke surfaces and hinges 2 No outer case damage 3 Proper interlock and monitor operations Insulation Resistance Test If the low voltage power supply has been repaired use a 500 V Mega ohmmeter to measure the resistance between the primary Line and Neutral of the power plug and operator accessible metal parts The resistance should be no less than 2 Mega Ohms Repair the oven again when necessary 5 11 C18 tik Barrier Screen 0 1 ASSY Barrier Screen 1 LEVER DOOR OPEN went ASSY BRKT Hinge T 1 KNOB DIAL Spring Latch 1 BUTTON DOOR OPEN Latch 1 i DECO MEMBRANE ASSY Door Frame 1 p ASSY DOOR 1 C00 A PAN CY T Fait EMOBTEZN POOA F
11. d Adjustment 2 1 2 2 2 3 2 4 2 5 If you suspect defective primary secondary or monitor interlock switches use your ohmmeter digital or analog type the check the electrical continuity Make sure the power cord is pulled out and the high voltage capacitor is discharged before the electrical continuity check Set the ohmmeter to Low Resistance range and connect both leads alligator clips to the switch terminals Open the door and notice the meter reading The primary or secondary interlock switch should show an infinite resistance when the door is open Replace it when it is defective The monitor interlock should show a 2 or near zero resistance when the door is open When the door is closed the readings will be opposite If the oven has been received inoperative due to the failure of the monitored safety primary and or secondary interlock s you should replace all of the monitored safety interlock switched and the monitor switch Door and Hinge Replacement and Adjustment 3 1 3 2 Pull the power cord from the outlet Check the door for warped or damaged areas Check the hinges for broken or worn areas Check other areas such as cracked from glass broken door latched worn cracked viewing screen and etc After determining the door assembly should be replaced check the parts list for the correct part number All oven door components must be ordered directly from the manufacturer or its authorized distri
12. e MEASURING MICROWAVE ENERGY LEAKAGE e Pour 275415 of 2045 C 68 9 F water a beaker which is graduated to 600 cc and place the beaker on the center of the turntable e Set the energy leakage monitor to 2 450 MHz and use it following the manufacturer s recommended test procedure to assure correct result e When measuring the leakage always use the 2 inch 5 cm spacer supplied with the probe e Operate the oven at its maximum output Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the surface being measured Move probe along shaded area Probe scanning speed Less than 2 5 cm sec a m l f fe jA ee MEASUREMENT WITH OUTER CASE REMOVED When you replace the magnetron measure for microwave energy leakage before the outer case is installed and after all necessary components are replaced or adjusted Special care should be taken in measuring the following parts Around the magnetron waveguide WARNING AVOID CONTACTING ANY HIGH VOLTAGE PARTS Magnetron H V Transformer H V Capacitor H V Cable Ass y H V Fuse MEASUREMENT WITH A FULLY ASSEMBLED OVEN After all components including the outer case are fully assembled measure for microwave energy leakage around the door viewing window the exhaust opening and air inlet openings Microwave energy leakage must
13. e felt should be refueled fully with engine oil for when the oven is operating the engine oil empty into the oil bearing slowly Fix the bearing cover with two screws turn the fan around till it can move flexibly Than install them to the oven and plug in the two terminal plugs If the fan can move flexibly then the winding of the fan motor should be examined Measure the winding with Rx100 grade of a multi meter if it is open circuited it indicates the winding of the fan motor has broken and should be replaced by a new same model one MOTOR TEST PROCEDURE COMPONENTS TEST PROCEDURE RESULTS Fan Motor Wire leads removed Measure the resistance Ohm meter scale Rx 100 Normal Approx 470 Abnormal c or Several Q Turntable Motor Wire leads removed Measure the resistance Ohm meter scale Rx 1000 Normal Approx 3 2kQ Abnormal or Several NOTE e A MICROWAVE LEAKGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON e MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION e WHEN REMOVING THE WIRE LEADS FROM THE PARTS BE SURE TO GRASP THE CONNECTOR NOT THE WIRES 5 8 COMMON BREAKDOWN AND MEANS OF REPAIRING PHENOMENON CAUSE REPAIRING MEANS 1 fuse broken 1 Change a new fuse 2 The primary and secondary winding of the 2 Change a new transformer are short circuited transformer 1 When starting the 3 earthing
14. er E A microwave leakage check should be performed on each oven prior to release to the owner CAUTION MICROWAVE RADIATION DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR OTHER PARTS CONDUCTING MICROWAVE ENERGY TABLE OF CONTENTS pagel SAFETY 6 Inside front cover CAUTION S se te ee ne aaia aaa ae 1 1 THE HEATING PRINCIPLE OF MICROWAVE 2 1 5 5 3 1 OPERATING 5 5 4 1 SCHEMATIC DIAGRAM 4 1 GIRGUIT DESCRIP TION sees eee RE 4 2 SERVICE INFORMATION Se 5 1 TOOLS AND MEASURING INSTRUMENTS 5 1 MICROWAVE LEAKAGE Se 5 2 MEASUREMENT OF MICROWAVE OUTPUT 5 3 TROUBLE SHOOTING PROCEDURES 5 4 COMMON BREAKDOWN AND MEANS OF REPAIRING 5 8 IMPORTANT THINGS TO DO PRIOR TO CRITICAL PART SERVICING 5 9 SAFETY CHECKS AND TESTS AFTER SERVING 5 10 E
15. er at the middle of the glass tray of the oven FIG 5 1 Close the door power set high time set to 3 minutes press the starting button to operate the oven After rectified the microwave leakage measure measure around the door crack those hole position of the window and the air vent at four sides of the oven with the probe of the measure When measure the moving speed of the probe should not exceed 2 5cm per second and the measuring direction should be the same with the outing direction of the microwave leakage FIG 5 2 When measuring the ultimate value of microwave leakage of all the measured position should not exceed 1 0 mili watt cm or should be considered as abnormal Probe scanning speed Less than 2 5 Tin sec FIG 5 2 5 4 4 when the oven at operating but the food can t be heated Pull out the power plug take off the outer case discharge the capacitor measure the resistance value of the primary winding and the secondary winding of the transformer with a multi meter FIG 5 3 and FIG 5 4 The resistance value of the primary winding should be about 2 2 ohm the secondary winding should be about 130 ohm otherwise it indicates the transformer has broken and should be replaced by a new one If the transformer is normal then the high voltage capacitor should be checked Pull out the connecting plug of the capacitor and measure it with Rx1 grade of a multi meter the two rod of the multi
16. ey may damage the electronic or mechanical parts of the unit As the colors of the wires in the mains lead of this Do not install the oven next to a conventional appliance may not correspond with the colored surface unit or above a conventional wall oven markings identifying the terminals in your plug proceed as follows 5 Use microwave oven in an ambient temperature less than 104F 40C The wire which is colored green and yellow must be connected to the terminal in the plug which is marked 6 Place the microwave oven on a sturdy and flat L with the letter or the earth symbol surface at least 10 cm 4 inches from the wall colored green or green and yellow 7 Place the microwave oven as far away as possible from TV RADIO COMPUTER etc to prevent The wire which is colored blue must be connected to interference the terminal in the plug which is marked with the letter N or colored black 10cm a The wire which is colored brown must be connected to the terminal in the plug which is marked with the letter L or colored red INIERLOCK PRIMARY INTERLOCK SWTCH UPPER MONTOR m POWER SUPPLY SINGLE PHASE ONLY CAPACITOR DIODE RD ol ol w isp sts SECONDARY i INTERLOCK SWITCH LV TRANSFORM CONDITION NOTE DOOR CLOSED QD OVEN LAMP gt BLACK COOK OFF W lt FAN MOTOR RED BR BROWN lt WHITE GE GREEN YELLOW
17. idea On MICROWAVE OVEN MODEL EM031EZN POOA 1000W 120 6 2 SERVICE MANUAL CAUTION BEFORE SERVICING THE UNIT READTHE SAFETY PRECAUTIONS IN THIS MANUAL SAFETY PRECAUTIONS This device is to be serviced only by properly qualified service personnel Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be taken to avoid possible exposure to excessive microwave energy 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 own
18. ing in normal Rectify the microwave leakage measure measure the amount of the microwave leakage around the oven with its probe If there are places which the leakage exceed the standard requirement then repair them accordingly If the leakage amount exceed 1 0 mW cm at the left door crack then pull out the power plug take down the outer case adjust the screws of the hinge to less the gap between the door and the oven Then measure again the leakage amount should less than 1 0 mW cm Generally it should be controlled below 0 8 mill wattcm2 with some allowance If the leakage occurred at the right door crack adjust the screws that fix the interlock holder and the hook If the leakage is on the larger side at the right above of the oven then adjust the upper screw Loosen out the screw push the door close to the oven to hook the door hook with the plastic parts then tighten the screw again If the leakage is larger at the right below then adjust the lower screw Loosen the screw push the door close to the oven to hook the door hook with the switch holder tightly then tighten the screw again and open and close the door repeatedly to check whether the door can operate flexibly whether the hook and the switch are in their normal position If it is not in position then adjust the door hook and the switch holder the loose between the door and the oven then measure the leakage with microwave leakage measure again If there still exist microwave lea
19. inor wen wen noise cycling kala noise and shishi noise should be consider as normal But it is abnormal if the following noise occurred 1 Sound wenwen noise 2 Long time shishi noise 3 Strike voice like pipa pipa I SPOT EXAMINING STEPS OF THE MICROWAVE OVEN 1 the microwawe insulating resistance Measure the insulating resistance with a multi meter or a mega ohmmeter The value should not less than 2 mega ohm Otherwise part examination should be taken at once Such as checking whether the motor the thermal cutout the transformer or the capacitor are electricity leaking 2 Examination of the resistance value of the microwave oven Close the door set the time the oven is at operating condition but the power plug haven t been plugged in measure the two feet L N of the power plug with Rx1 grade of a multimeter the resistance value should be about 22 ohm If open circuit occurred then you must check whether the 10 A fuse is broken the primary winding of the transformer is open circuit the thermal cutout is open circuit or not you must check whether the interlock device is put through or all the plugs are connected well If short circuit occurred you should check whether the primary winding of the power transformer is short circuited or part short circuited 3 Examination of microwave leakage Measure the microwave leakage with a microwave leakage Measure Place a graduate of 275ml wat
20. kage measure near the magnetron with the probe of the microwave leakage measure If the leakage is larger the oven should be turned off and check whether the 2 or 4 screws which fix the magnetron have been loosed if loosed twist them tightly with socket wrench If the screws are fixedly then the magnetron should be take down to check the copper filament weaved washer of the magnetron has been placed well or whether the wave guide housing coupling has been oxidized or have lacquer on it If do have scrape the oxidized layer or the lacquer off when fix the magnetron the copper filament weaved washer must be placed well the screws must be twist tightly Then turn on the oven and measure again until it complies with the requirement If the microwave leakage is larger at those hole position of the window board the oven should be turned off to inspect whether there are crack among them If several holes formed a crack it would enlarge the microwave leakage If that is the case it indicates the door has broken and should be replaced with a new door 5 6 Means of repair when the oven can heat but the turntable glass cant move Firstly check whether the turntable holder is placed correctly If it is correct then pull out the power plug and take down the turntable combination measure the resistance value of the turntable motor with Rx1k grade of a multi meter If it is open circuited it indicates the turntable motor has broken and should be replaced
21. not exceed the values prescribed below NOTE Leakage with the outer case removed less than 3 mW cm Leakage for a fully assembled oven Before the latch switch primary is interrupted with the door in a slightly opened position less than 1 mW cm 5 2 NOTES WHEN MEASURING Do not exceed meter full scale deflection The test probe must be removed no faster than 1 inch sec 2 5 cm sec along the shaded area otherwise a false reading may result test probe must be held with the grip portion of the handle A false reading may result if the operator s hand is between the handle and the probe When testing near a corner of the door keep the probe perpendicular to the surface making sure the probe horizontally along the oven surface this may possibly cause probe damage RECORD KEEPING AND NOTIFICATION AFTER MEASUREMENT After adjustment and repair of any microwave energy interruption or microwave energy blocking device record the measured values for future reference Also enter the information on the service invoice microwave energy leakage should not be more than 1 0 mW em after determining that all parts are in good condition functioning properly and genuine replacement parts which are listed in this manual have been used At least once a year have the electromagnetic energy leakage monitor checked for calibration by its MEASUREMENT OF MICROWAVE POWER OUTPUT Microw
22. or the polarity of the capacitor is 3 Change a new capacitor oven the lamp is not on punctured 4 Change a new pilot the turntable tray can t 4 The pilot switch can t cut off switch rotate and the food can t 5 The interlock switch hasn t closed 5 Change a new interlock be heated 6 The power plug and the socket are not in good switch connection 6 Adjust the connection or 7 The door hook broken replace it by a new one 7 Change a new book 2 When starting the 1 The primary and secondary winding the 1 Change a new oven the lamp is on the filament of the transformer are open circuited transformer turntable rotating the fan 2 The magnetron filament is open circuited the 2 Change the magnetron cycling but the food can t magnetic steel of the magnetron broken orthe 3 Change the time power be heated magnetron is air leaking distributor or the micro 3 Time and power distributor broken switch 4 The plugs of the magnetron of the capacitor 4 Fix them loosed 3 The food can be 1 The lamp broken 1 Change a new lamp heated but the lamp is 2 The plug fall off 2 Insert the plug again not on 4 The food 1 The turntable motor broken 1 Change the turntable heated but the turntable 2 The plug fall off motor tray is not rotating 3 Connecting shaft weave broken 2 Insert the plug securely 3 Change the weave 5 The oven can 1 The winding of the fan motor in open circuited
23. ormal condition the molecule is in irregular order due to its thermal action thus the food do not appear polarity FIG 1 1a Under the action of outer electric field the positive end of the polar molecule trend to the negative electric field the negative end of polar molecule trend to the positive electric field and somewhat arrange in order through the direction of the electric field FIG 1 1c This phenomenon usually be called TORQUE POLARITY When the outer electric field apply for the opposite polarity the polar molecule then arrange an opposite direction order accordingly FIG 1 1b If the direction of the outer electric field changed repeatedly the polar molecule would repeatedly sway accordingly During the swaying it understands that the polar molecule would produce heat due to somewhat similar friction among them 1 When the electric field is applied for ultrahigh frequent microwave field from the outside its direction would change tens billion times per second so do the molecule This kind of molecule swaying producing similar frictional heat from the interference and block of the action strength among the molecule and changed to microscopic microwave heating Microwave heating not only concerned the nature of the matter itself but also closely connected with the electric field strength and frequency When the frequency is low the molecule swaying rate and the acute degree of the mutual friction among the molecule is
24. ormula F Er tg Stands for the power the heated matter absorbed from the microwawe field K Stands for a constant Stand for microwave field strength F Stands for the microwave frequency Er Stands for relative dielectric constant of the heated matter tg5 Stands for loss angle tangent of the heated matter 2 1 INSTALLATIONS INSTALLING 1 Empty the microwave oven and clean inside it with EARTHING INSTRUCTIONS a soft damp cloth Check for damage such as This microwave oven is designed to be used in a fully misaligned door damage around the door or dents earihed condition inside the cavity or on the exterior It is imperative therefore to make sure it is properly earthed before servicing 2 Put the oven on a counter table or shelf that is WARNING strong enough to hold the oven and the food and utensils you put in it The control panel side of the THIS APPLIANCE oven is the heavy side Use care when handling MUST BE EARTHED IMPORTANT 3 Do not block the vent and the air intake openings Blocking vent or air intake openings can cause damage to the oven and poor cooking results Make sure the microwave oven legs are in place to The wires in this mains lead are colored in accordance with the following code ensure proper air flow Green and yellow Earth 4 The oven should not be installed in any area where Blue Neutral Brown Live heat and steam are generated because th
25. r This 3 2 volts is applied to the magnetron to heat the magnetron filament through two noise preventing choke coils A high voltage of approximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the diode and charging of the high voltage capacitor The negative DC voltage is then applied to the filament WHEN THE DOOR IS OPENED DURING COOKING Both primary switch and secondary switch open to cut off the primary winding voltage to the high voltage transformer to stop microwave oscillation Timer turntable and fan motor stop As the door is opened if the contact of primary switch fail to open the fuse opens due to the large current surge caused by the monitor switch activation which in turn stops magnetron oscillation POWER PRIMARY TIMER CONTROL SWITCH O SWITCH SWITCH RELAY O Q O je MONITOR RESISTOR PYOTOPTYTTYY MOI O o WO MONITOR O SECONDARY SWITCH SERVICE INFORMATION TOOLS AND MEASURING INSTRUMENTS NECESSARY TOOLS Tools normally used for TV servicing are sufficient Standard tools are listed below Diagonal pliers Long nose pliers e Phillips screwdriver Flat blade screwdriver e Wrench size 5mm e Nutdriver size 5mm Adjustable wrench e Soldering iron Solder Vinyl insulation tape e Polishing cloth MICROWAVE LEAKAGE TEST CAUTIONS e Be sure to check microwave leakage prior
26. ring devices and measuring instruments selected in order to minimize addition or removal of heat WATER LOAD TURNTABLE TROUBLE SHOOTING PROCEDURES Before overhauling microwave oven you should judge the breakdown and the cause correctly then you can repair it with corresponding ways The overhauling must be proceed in order any hasty conclusion is not recommendable otherwise overworking would be done when repair The microwave oven may occur compound breakdown due to all kinds of different reasons thus when overhaul they all should be taken into consideration Special attention must be given to the microwave leakage and the electric insulation when examine because they may do harmful to the repairing staff I MEANS OF THE BREAKDOWN EXAMINING How to examine a microwave oven with breakdown A better means which demonstrated in practical operating are through inspecting and listening On the basis of large amounts of perceptual knowledge you can judge and analysis the breakdown quickly and correctly 1 Inspection Inspect whether the oven shape is disordered and where is the disordered position if any It is normal if the outer case disordered a little but abnormal if the oven the door disordered the door hook broken the door crooked or there are too much looseness between the door and the oven after the door is closed 2 Listening Listening to the voice of the oven operating and the noise of the fan after it conducted M
27. to servicing the oven if the oven is operative prior to servicing service personnel should inform the manufacture importer or assembler of any certified oven unit found to have a microwave emission level in excess of 5 mW cm and should repair any unit found to have excessive emission levels at no cost to the owner and should ascertain the cause of the excessive leakage The service personnel should instruct the owner not to use the unit until the oven has been brought into compliance If the oven operates with the door open the service personnel should Tell the user not to operate the oven Contact the manufacturer service personnel should check all surface and vent openings for microwave leakage e Check for microwave leakage after every servicing The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 5 mW em Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage 5 1 NECESSARY MEASURING INSTRUMENTS TESTER VOLTS DC AC Ohmmeter Microwave survey meter Holaday HI 1710 A Narda 8100 8200 e Inch scale 600 non conductive material beaker glass or plastic inside diameter approx 8 5 cm 31 2 in e Cylindrical and made of borosilicate glass vessel max thickness 3 mm outside diameter approx 190mm height approx 90mm e Glass thermometer 100 C or 212 F 1 deg scal
28. ure never operate the device without a microwave energy absorbing load attached Never look into an open waveguide or antenna while the device is energized e Proper operation of the microwave oven requires that the magnetron be assembled to the waveguide and cavity Never operate the magnetron unless it is properly installed e Be sure that the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron ANTENNA a Gasket COOLING FIH FLAMENT TERMINALS 7 2 MAGNE ROM CHASSIS GROLMD MAGNETRON THE OVEN IS TO BE SERVICED ONLY BY PROPERLY QUALIFIED SERVICE PERSONNEL THE HEATING PRINCIPLE OF MICROWAVE Microwave is one kind of radio wave whose wave length is very short frequency is very high Therefore it is called ultrahigh frequency electromagnetic wave Microwave can heat food mainly result in the mutual affect of the food in the microwave field and microwave field itself Under the affect of microwave field the thermal effect mechanism produced from the mutual affect of the microwave and the food includes two aspects One is Dielectric loss of polar molecule the other is conductive loss of ion Usually food is constitute of organism plant and animal The organism is formed by all kinds of polar water molecule polar protein molecule and all sorts of salt ion The center of gravity of the positive and negative charge in the molecule is not coincide In n

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