CONTENTS SAFETY PRECAUTIONS............................1 THE HEATING PRINCIPLE OF MICROWAVE ......................2 THE STRUCTURE AND WORKING PRINCIPLE OF MICROWAVE OVEN ............3 HIGH VOLTAGE RECTIFYING CIRCUIT ...................3 MICROWAVE GENERATER.......................4 COOLING SYSTEM..........................4 ELECTRIC CONTROL SYSTEM......................4 TYPICAL CIRCUIT ANALYASIS OF MICROWAVE OVEN ..................7 HOW TO ASSEMBLE AND DISASSEMBLE MICROWAVE OVEN COMPONENTS ..........8 THE CABINET ............................8 THE DOOR COMBINATION.......................9 THE CONTROL PANEL AND THE DOOR RELEASE MECHANISM ..........10...
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.
Microwave is one kind of radio wave whose wavelength 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 the 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.
Pa=KE fErtgδ Pa Stands for the power the heated matter adsorbed from the microwave field. K Stands for a constant E Stands for the microwave frequency. f Stands for the microwave frequency. tgδ Stands for loss angle tangent of the heated matter. Er Stands for relative dielectric constant of the heated matter.
Microwave generator is the heart of microwave oven. The quality of a microwave oven mostly depends on the quality of the microwave generator. A microwave generator is mainly composed of magnetron and its power supply circuit, FIG.2-3 is the typical circuit diagram of the present used microwave oven’s generator. The power supply circuit is composed of rectifying circuit and filament circuit.
Drawing 2-5(a) is the circuit and construction diagram fuse main latch switch of the door interlock switch of a microwave oven. It mainly consists of interlock switches (S1, S2), and monitor switch (S3), door hook and starting mechanism of the door interlock switch. There fixed hooks on the oven door, and opened two pilot switch rectangle hole at the corresponding place at the right of...
microwave ovens which have the power control function. FIG.3-1 is the power control circuit diagram of brand microwave oven, WP700. This is a typical instance of conduction ratio control. This oven adopt time and power controller as a whole. When a 120V, 60Hz alternating current is inputted, the time and power motor is always at working condition.
8). It is the most liable place where microwave leakage occurs. Especially, after a long time using, the microwave leakage would enlarge at the hinge and the hook. Anyway, mechanic damage would also cause large amount of microwave leakage. Therefore, the main methods designed for preventing microwave leakage of the door are as follows: 1) Assemble a layer of steel filament or a thin metal plate with many holes at the middle of the window to make it possible to observe the heating as well as shielding the microwave.
Fig.3–1 is the practical circuit diagram of a microwave oven. Its corresponding working conditions are as follows: The door closed, SW1 and SW2 turned on, SW3 closed, power control relay has no power, R1, R2 is cut off. When cooking, touch the starting switch to power the timer and the power relay. RY1, RY2 closed the power supply to the anode of the magnetron and the filament, changing the power frequency electric energy to microwave energy, the microwave energy then transferred to the heating chamber for food heating.
six-angle screw To disassemble, Pull out the power plug. Take off the cabinet. hinge(up) Loosen the two six –angle screws of left hinge (up) with a socket wrench (FIG.4 - 2). oven Push the door release button to have the hook out (FIG.4 -3).
Tear off the adhesive protective paper of the lining and stick it on the door as FIG.4 – 1, slip the hook on the doorframe, and fix the doorframe on the door, tighten it with “+” – screws. After assembled, check whether the hook working in normal and whether the hinge (UP) is its position.
magnetron vertically, and also tighten the screws of the lampshade (FIG.4 - 8). Plug in the two terminals of the magnetron filament and the thermal cutout. Firstly, do as the 1,2, and 3 steps at Ⅲ of this part. Dismantling steps for the transformer: (as FIG.4 -9). Pull out all the terminal of the transformer.
Insert one end of the diode to one lead of the capacitor’s connect piece. Fix the diode with one screw (pay attention to the polarity of the diode, refer to FIG.4 - 16). Firstly, do as the 1, 2, and 3 steps of Ⅲ of this part. To disassemble, Turn the microwave oven over (FIG.
door to check whether the door is flexible. If it does, back screw and front position of the holder should be adjusted. latch switch hold Provided the up hook is loose, the door should be pushed front door pla more closely to the oven, and pull the holder inside closely after loosen the screw which fix the holder, then, tighten the screw and check whether it is still loose.
Before overhauling a 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 over-working 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.
speed of the probe should not exceed 25mm per second, and the measuring direction should be the same with the outing direction of the probe should not exceed 25mm per second, and the measuring direction should be the same with the outing direction of the microwave leakage (FIG.5 - 2)..
pliers. Pull out the power plug, take off the cabinet, discharge the capacitor, measure the resistance value of the primary winding and the secondary winding of the transformer with an multimeter (FIG.5 – 10 and FIG.5 - 9). The resistance value of the primary winding should be about 2.2 ohms, the secondary winding should be about 130 ohms.
same model one. 1. Repair when there occurred large amounts microwave leakage. There are many factors which may cause microwave leaking. Following mentioned may be the main causes of microwave leakage: (1) The door deformed, the hinge loosed or damaged that caused the door cannot close tightly.
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 comply 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 (fig.5 - 16).
Place a graduate of about 250ml water on the turntable tray. Close the door, power set high, time set 4 minutes (To those 700W microwave oven) to make the oven operating in normal. When the bell of the timer rings, open the oven door, the water should have boiled.
PHENOMENON CAUSE REPAIRING MEANS 8A fuse broken. Change a new fuse. The primary and secondary winding of the Change a new transformer. transformer are short – circuited. Change a new capacitor. When starting The earthing or the polarity of the polarity of Change a new pilot switch.
The wave guide connection oxidized tighten the screws The magnetron copper filament washer is Thick the copper filament too thin cause the wave guide opening not washer in good earth. After long time using, the wear and the rust –eaten enlarged the gap of the door shaft Adjust the hinge to rectify the and the shaft hole, thus cause the door position of the door.
& & PART NO. COMPONENT CODE NO. Name GA-EM-U1000C01 P.C board GA-EM-U1000C02 turntable motor 1 GA-EM-U1000W03 power cord GA-EM-U1000C03 power cord GA-EM-U1000C04 wire harness GA-EM-U1000C05 transformer GA-EM-U1000C06 microswitch GA-EM-U1000C07 microswitch GA-EM-U1000C08 magnetron...
GA-EM-U1000C09 lamp GA-EM-U1000C10 capacitor GA-EM-U1000C11 diode GA-EM-U1000C12 fuse PART NO. PART CODE NO NAME QTY PART NO. PART CODE NO NAME GA-EM-U1000W01 touch key pad GA-EM-U1000W27 window GA-EM-U1000P01 touch key pad GA-EM-U1000P27 window GA-EM-U1000W02 control board GA-EM-U1000W28 door frame GA-EM-U1000P02 control board GA-EM-U1000P28 door frame...