1) Understanding the type of fault Understanding the type of fault is very important for overhauling electronic products. Because different types of faults have different characteristics, the repair methods and methods can be determined according to different types of faults during maintenance, to help quickly solve the fault.
In electronic product overhaul, the faults of electronic products are often divided into three categories:
(1) Faults before power-on commissioning Faults before power-on commissioning refer to faults caused by errors during soldering assembly. The production process of electronic products is: component procurement, screening test, component aging, product welding, complete machine assembly, commissioning, and complete machine aging test. When the product enters the debugging process, it must ensure that the components are welded, the wire connection and the structural parts are assembled correctly, without welding, welding, bridging, short circuit and so on. In other words, the electrical performance of the circuit is normal and basically works normally. As far as the radio is concerned, after the connection is completed, the radio broadcast signal can be received when the power is turned on, and then debugging can be performed. Otherwise, it is necessary to go to the maintenance process. The characteristic of such a fault is that the electronic product has never worked properly and there is a mistake in the soldering assembly.
(2) Faults after normal operation Electronic product repair refers to such faults, which refers to faults that occur after an electronic product has been in use for a period of time. There are many reasons for such failures. The electronic products reach the service life, the components are aging, the components are damaged due to improper operation of electronic products, the soldering of the circuit and the corrosion of the solder joints can cause the electronic products to malfunction and fail. jobs.
(3) Man-made faults Man-made faults generally refer to faults caused when repairing electronic products, and beginners are particularly prone to such faults. Frequent human faults are: when repairing electronic products, suspect that the components are damaged and removed for repair and re-soldering, or when replacing components, reverse the polarity of the components; if you do not understand the circuit, it will take off Solder wire is soldered incorrectly. Therefore, when repairing electronic products that may be subject to human error, the newly replaced or disassembled components should be carefully checked against the schematic. Experienced maintenance personnel will quickly find the replaced components by observing the solder joints and carefully check for human error.
2) Preparations before the repair After understanding the type of fault, before the electronic product is overhauled, the product should be understood. First, the electronic product should be used to understand its performance and main indicators, and master the work of the electronic product. Principle, do a good job before the maintenance.
Preparations before the overhaul include the following:
(1) The inquiry is mainly to understand some situations before and after the electronic product is damaged, such as silent, noisy, components, fever, smoke, and whether others have been repaired. If an inexperienced person disturbs the inductance and trimming resistance, disconnecting the wiring, and replacing the components, it may cause human failure. Therefore, we must try to restore the components and circuits according to the drawings and then repair them. Any electronic product that has been faulty and later caused by human error due to improper maintenance is often difficult to repair. At this time, it is necessary to carefully identify the fault.
By asking, you can find out which type of fault is and find the fault point according to the characteristics of the fault type. This will save us time when repairing electronic products, and it will do more with less.
(2) Trial of electronic products to be repaired For electronic products that have failed, it is necessary to deepen the understanding of electronic product faults through audition, trial and trial. The inspector should try to connect the power supply, dial the relevant switches and plugs, turn the various buttons, listen carefully to the output sound, and observe the displayed image. At the same time, according to the circuit diagram, analyze and judge the place that may cause the fault.
In the process of trying out electronic products, pay attention to whether there is serious damage, such as equipment fire, popping sound, and only a very bright spot on the picture tube. If this phenomenon occurs, it means that the current of the whole electronic product to be repaired is too large, and it cannot be powered on and repaired. Instead, the power should be cut off immediately to further find out the cause.
(3) Understand the schematic diagram and assembly drawing To repair the faulty electronic product, first of all, it must have its schematic diagram and printed circuit wiring diagram (assembly drawing). In the inspection of electronic products, we often perform fault analysis on the circuit schematic by testing the data and combining the fault phenomena. It is very difficult to check the fault without the schematic diagram. Before the maintenance, the circuit schematic diagram should be analyzed to understand the structure and function of each unit circuit and the connection between each unit circuit. Combined with the fault characteristics of the electronic product to be repaired, it is analyzed in which unit circuits the fault may occur, which can narrow the scope of the search fault and quickly detect the fault. The more profound the general rules of the circuit structure of the electronic product to be repaired, the more thorough the understanding of the unique functions of the various unit circuits in the entire complex circuit, the more the blindness in the maintenance process can be reduced, thereby greatly improving the overhaul. Work efficiency. If there is no schematic of the electronic product to be repaired at hand, you can find a schematic with similar circuit structure as a reference.
Printed circuit diagrams help to quickly find the components to be inspected during inspection, because the printed circuit diagrams correspond to the components on the printed circuit board and are printed with the symbol of the components, which can save the search for components. time.
(4) Commonly used maintenance tools for preparing inspection tools, equipment and components include electric soldering iron, tweezers, screwdrivers, soldering devices, multimeters, etc. For some more complicated faults, the corresponding testing instruments, such as signal generators and oscilloscopes, are also needed for maintenance.
Prepare commonly used electronic components, such as resistors of various resistances, commonly used capacitors, diodes, and triodes.
3) Troubleshooting The troubleshooting of electronic products can be divided into three levels: the first level is to replace the entire module; the second level is to replace the circuit board and other components; the third level is to replace the components. The first level of maintenance, speed, short downtime, but the maintenance costs are the largest; the second level of maintenance is slightly slower than the first level, but the cost of replacing the circuit board and other components is much lower than the cost of replacing the entire module; the third level of maintenance is the most Economy, but it takes a long time to repair faulty components, replace them, and make circuit adjustments. In the process of maintenance, it should be reasonably selected according to actual technical conditions and economic conditions. The second and third level of maintenance is more in line with China's national conditions. Adhering to the principle of value for money and diligence and thrift is one of the principles that must be followed in the professional ethics of maintenance workers.
Troubleshooting is a necessary means of completing an inspection task. The fault can be eliminated by treating the detected cause of the fault accordingly. The specific methods are as follows:
1 Replace the damaged or deteriorated device with a good device of the same specification and the same model. When there is no identical device and needs to be replaced by other components, the replacement principle should be followed.
2 Re-adjust the relevant circuit or adjustable device to solve the offset fault, and the adjustment after the inspection can make the machine performance better.
8 re-welding, wire-filling to eliminate the problem of virtual welding, desoldering or wire breakage.
4 Cleaning, baking of circuits, devices or equipment that are contaminated, rusted, poorly contacted or leaky can eliminate simple or difficult faults.
5 Flexible use of temporary measures. This method varies from person to person and from place to place, but it must be standardized so that future generations are not good at repairing. If temporary measures are adopted, they must be replaced in time after purchase of the equipment and recorded.
After the troubleshooting is completed, the maintenance personnel should conduct the commissioning operation of the electronic products and verify the finished products to optimize the performance of the electronic products.
4) After the completion of the above work, the maintenance personnel should fill in the maintenance records for future reference and deliver the repaired electronic products to the users.
FBT WDM - Fused Biconic Taper Wavelength Division Multiplex
A fusion taper type wavelength division multiplexer, comprising an input end cone, an output end cone, and a coupling area. The input end cone is located at one end of the coupling area, and the output end cone is located at the coupling area. At the other end of the zone, the input end cone includes an input arm and a backscatter arm, the output end cone includes a through arm and a coupling arm, and the optical power is input from the input arm of the input end cone through the The coupling zone is redistributed after coupling and output from the output end cone. A part of the optical power is output from the through arm and the other part is output from the coupling arm. The coupling zone includes two optical fibers, and the cladding parts of the two optical fibers are mutually connected. Close, when pulling the taper, the two optical fibers are pulled in opposite directions but cannot move relative to each other. The two optical fibers are processed by a fusion taper device.
Further, the melting taper device is formed by two insulation bricks made of aluminum oxide fiber insulation material to form a cavity, and the high temperature heat source is provided by an electric heating wire made of molybdenum disilicide material, and the heating wire is located In the heating tank, the heating temperature is adjusted by adjusting the voltage at both ends of the electrodes connected to it, the optical fiber passes over the heating wire, and the taper speed is adjusted by changing the rotation speed of the programmable stepping motor driver.
Further, the two optical fibers are fused and tapered in the fusion tapering device, one of which is used as the input power of the input arm, and the other is used as the coupling arm fiber. After the tapering length reaches a certain distance, the two fibers are coupled, and the optical power is Continuously couple into the coupling arm fiber, continue to taper, and the optical power is repeatedly and alternately coupled in the two fibers.
At present, the method of making FBT WDM in industry is to use a flame to heat and melt the fiber at a single point and then stretch it. The defect is that the heating area is too short, resulting in a short stretchable length (corresponding to the coupling length), and the fiber diameter is not small enough, so This limits the minimum channel spacing that this type of wavelength division multiplexer can achieve.
FBT WDM, also known as Fused Biconic Taper WDM and FBT WDM Splitter, along with LAN WDM Splitter, Filter WDM splitter, dense WDM splitter and coarse WDM splitter, are the most commonly used WDM device in construction of PON.
FBT WDM, Fused Biconic Taper WDM, FBT WDM Splitter
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