Essential for literacy, basic knowledge of electronic components

Can you name the small components on the circuit board and their functions, whether you are a radio enthusiast or a maintenance technician? If you want to become a component (chip) level expert, mastering some relevant electronic knowledge is essential. For example, when repairing a certain hardware, using a multimeter to measure the resistance of a resistor to infinity, although it can be concluded that the resistor is damaged, due to the lack of circuit diagrams for various boards and peripherals (only a few products have local circuit diagrams), the specific resistance value of the resistor before damage is unknown, so it is impossible to replace the damaged component. If you can understand the color ring markings on the resistor, you will know the nominal resistance value of the damaged resistor, and replacing it will not be a problem. The fault will naturally be eliminated. There are many situations like the ones mentioned above, such as the correct selection of components. I will not list them one by one here. Below, I will share some very practical electronic knowledge, hoping that everyone can take another step towards becoming a master. Note: It is recommended to read the following content in conjunction with Figure 1 and subsequent images. 1、 Voltage and current are siblings. Current flows from a high voltage point to a low voltage point, and the presence of voltage does not necessarily result in current. If there is only voltage and no current, it indicates that there is a circuit break (such as a switch in the circuit). In addition, sometimes measuring voltage is normal but measuring current may not be normal, such as slight short circuits or increased resistance of a component. Therefore, in maintenance, it is necessary to combine voltage and current values for analysis. When testing unknown voltage or current with a multimeter, be sure to set the gear to the highest gear. If the measurement cannot be obtained, gradually lower the gear. Note: The symbol for voltage is "V", and the symbol for current is "A". 2、 Resistors are made of various materials that exhibit a certain resistance to the current they pass through. This resistance is called resistance, and entities (components) with the physical property of lumped resistance are called resistors (simply put, conductors with resistance). Its function is very important in circuits, and there are also a large number of computer boards and peripherals. Its classification is also diverse. If classified by purpose, it includes: current limiting resistor, voltage reducing resistor, voltage divider resistor, protection resistor, starting resistor, sampling resistor, decoupling resistor, signal attenuation resistor, etc; If classified by appearance and manufacturing materials, there are: gold film resistors, carbon film resistors, cement resistors, non inductive resistors, thermistors, varistors, wire resistors, patch resistors, etc; If classified by power, there are: 1/16W, 1/8W, 1/4W, 1/2W, 1W, etc. The above resistors are common resistors, so we must know their resistance values. Below, I will take the most common surface mount resistors on various boards in the computer host as an example to introduce them (the same applies to other resistor naming methods): there are two methods for naming surface mount resistors: digital method and color ring method. Let's talk about the number method first. Usually, there are three numbers XXX on a resistor. The first two numbers are ten and one, and the last number is 10 to the power of X. The specific resistance value of this resistor is the two digits composed of the first two numbers multiplied by 10 to the power of X ohms. For example, the resistance value of the resistor labeled 104 is 100000 ohms (100K Ω), and the resistance value of the resistor labeled 473 is 47000 ohms (47K Ω); Next, the author will talk about the color ring method, which is the most common among all resistor naming methods (with relatively few surface mount designs). Common color rings usually have four rings, and we designate the gold or silver ring as the last ring. The colors of the first three rings correspond to the corresponding numbers. After knowing the numbers, we need to use the numerical method mentioned above to read their resistance values. However, we must first know what color represents what number, so we must remember this mnemonic - black brown red orange yellow green blue purple gray white, which correspond to 0123456789 respectively. As for gold and silver, which represent 10-1 and 10-2 respectively, these two colors are only marked with errors in four-color ring resistors. It's just a value, so as long as you understand it, it's enough. Below, I will give two examples to illustrate for better understanding and memory. For example, the resistance of a resistor marked with a brown, black, yellow, and silver ring is 100000 ohms (100K Ω), and the resistance of a resistor marked with a yellow, purple, orange, and gold ring is 47000 ohms (47K Ω). There is also a type of five color ring resistor, which is a resistor with relatively low resistance and high accuracy. As it is also used in computer peripherals, I would like to introduce it: it is a resistor with gold or silver as the second to last ring, the first three color rings are the hundred bit, ten bit, and one bit, and the last color ring is the error value. The specific resistance value of such a resistor is the three digit number represented by the first three color rings multiplied by 10 to the negative 1st or negative 2nd power ohm. For example, the resistance value of a resistor labeled with brown purple green silver brown ring is 1.75 Ω. There are only so many basic knowledge about resistors, but when replacing them, we also need to pay attention to the power of the resistor. Usually, using 1/4 or 1/8 resistors to replace surface mount resistors is not a problem. Note: Surface mount resistors using numerical methods are mostly black, and the symbol for the resistor in the circuit is "R". 3、 The most common type of capacitor, apart from resistors, is a capacitor. Simply put, a capacitor is a container that stores electric charge. Most hardware professionals may know about the appearance of capacitors, so I will only briefly explain it. Common capacitors can be classified according to their appearance and manufacturing materials into: surface mount capacitors, tantalum electrolytic capacitors, aluminum electrolytic capacitors, OS solid capacitors, non-polar electrolytic capacitors, ceramic capacitors, mica capacitors, and polypropylene capacitors. Among them, surface mount capacitors are the most common on various boards inside computer hosts, but only a small number of surface mount capacitors are labeled. The capacity reading method for labeled surface mount capacitors is the same as that for surface mount resistors, except that the unit symbol is pF (1000000pF=1 μ F). As for why most surface mount capacitors are not labeled, I think it may be related to their difficulty in damage. In computer power boxes, color displays, and many peripherals, there are many ceramic capacitors and various metalized capacitors. Therefore, the author also wants to mention that these capacitors belong to non-polar capacitors. Their capacity nominal method is the same as digital resistors, but some capacitors will use an "n", which means 1000, and their location and capacity value are also related. For example, the capacity of a capacitor with a nominal 10n is 10000pF (0.01 μ F), and the capacity of a capacitor with a nominal 4n7 is 4700pF (4.7n) instead of 47000pF. As for the withstand voltage values of these two capacitors, they are marked on the capacitors, such as 65V and 100V. 400V, etc. (only a few are not labeled, but they are usually above 65V). Next, let me talk about aluminum electrolytic capacitors. Their characteristics are large capacity and low cost, so they are widely used in various boards, power boxes, and the vast majority of peripherals. Some manufacturers use capacitors with relatively low withstand voltage values in order to reduce production costs, such as filter capacitors with a withstand voltage of 6.5V for 5V voltage. Although it can also be used, the failure rate is slightly higher, and its thermal stability is not very high, so replacing aluminum electrolytic capacitors is a common thing. When replacing, it is necessary to use capacitors with a withstand voltage value of 1.5 times or more than the actual voltage, and it is also important to note that the positive and negative poles cannot be reversed, especially for electrolytic capacitors in the power supply section. Otherwise, capacitor rupture events may occur. In addition, capacitors also have a brand issue. Different brands of resistors only have different error values, but different brands of capacitors have different lifetimes and qualities, such as various losses, insulation resistance, and temperature coefficients. Below, the author will introduce several good brands to everyone: PHILIPS, RubyconBLACK GATE, Rubycon, ELNA, ROE, SOLEN, Nichicon, DECON, WIMA (capacitors with a capacity of over 1 μ F are very expensive) RIFA、ERO， If you really can't recognize it, just remember not to buy any capacitors with the letters C and D (both prefixes) on them. Such capacitors are not produced by world-renowned factories, and some capacitors used in computer boards may even have negative effects. These capacitors can only be used in products that do not have very high requirements for capacitor performance (such as radios that cost 4 yuan each), and their errors in capacity and other performance indicators are very large. Even newly manufactured products can guarantee good performance for about 4 years, so they cannot be installed in computer accessories at all. Note: Surface mount capacitors are mostly gray, and the symbol for capacitors in circuits is "C". 4、 Inductors are made of coils, and their main functions are to choke and filter out high-frequency noise. They come in various shapes, some resembling resistors, some resembling diodes, and some resembling coils at first glance. Usually only inductors like resistors can read the inductance value, because there are only these colored rings and nothing else. The appearance of a surface mount inductor is the same as that of a digital labeled surface mount resistor, except that it does not have a number and is replaced by a small circle. Due to the limited usage of inductors, everyone just needs to understand them. In a certain sense, various transformers are actually composed of inductors. Note: The symbol for inductance in a circuit is "L". 5、 A diode belongs to the semiconductor category and is composed of N-type and P-type semiconductors. A PN junction is formed at the interface where they intersect. The main characteristic of a diode is unidirectional conduction and reverse cutoff, where a positive voltage is applied to the P pole and a negative voltage is applied to the N pole. Therefore, the directionality of the diode is very important. From the perspective of their functions, diodes can be classified into rectifier diodes, voltage reducing diodes, voltage stabilizing diodes, switching diodes, detection diodes, and varactor diodes; From the perspective of manufacturing materials, it can be divided into silicon diodes and germanium diodes. No matter what diode it is, there is a forward conduction voltage below which the diode cannot conduct. The forward conduction voltage of silicon tubes is between 0.6V and 0.7V, and that of germanium tubes is between 0.2V and 0.3V. Among them, 0.7V and 0.3V are the maximum forward conduction voltages of the diode - that is, at this voltage, no matter how much the voltage rises (not higher than the rated withstand voltage of the diode), the voltage applied to the diode will not rise again. The forward conduction characteristics of diodes were mentioned above, and diodes also have reverse conduction characteristics. However, the conduction voltage is relatively higher than that in the forward direction, and the rest is not much different from forward conduction. Zener diodes are made using this principle, but since the theory may be too lengthy to explain further, we will only provide a brief introduction. Just remember that the smaller the reverse leakage current, the better the quality of the diode. High quality silicon transistors range from a few milliamps to tens of milliamps, and germanium transistors range from tens of milliamps to hundreds of milliamps. Below, the author will explain the different functions of different diodes: there are many rectifier diodes in color displays, and four rectifier diodes are used to convert 220V AC power into 300V DC power, which is the most famous rectifier bridge circuit. Of course, a considerable number of color displays have integrated these four diodes into a silicon stack. However, whether they are discrete components or integrated components, the diodes they use are low-frequency diodes, but after passing through the switching power supply circuit, the output voltage needs to use switching diodes or fast recovery diodes. This must be remembered, because if low-frequency diodes are used to rectify high-frequency voltages, they will burn out the diodes and even other components. However, if high-frequency diodes are used in low-frequency circuits, there is no problem. In addition, diodes, like capacitors, have a withstand voltage value, so only diodes with a withstand voltage value higher than the actual voltage can be used with confidence. Zener diodes are also common, as they can stabilize higher voltages to their rated voltage values. However, their connection is opposite to that of diodes, as they utilize the principle of reverse conduction. Note: The symbol of a diode in a circuit is "VD" or "D", and the symbol of a voltage regulator diode is "ZD". 6、 The function of a transistor is to amplify, switch, or regulate. It is rare in computer hosts, but its number is not very small in displays and some peripherals. It can be divided into PNP and NPN types according to the different semiconductor substrate materials, and it is not difficult for everyone to understand that a transistor is just a combination of two diodes. But here, P and N are no longer simply positive or negative, but are divided into B (base), C (collector), and E (emitter) poles. Whether it is PNP or NPN, the B pole is the control pole, but the B pole of PNP transistor needs to be controlled with a voltage lower than the emitter for conduction, while the B pole of NPN transistor needs to be controlled with a voltage higher than the emitter for conduction. In addition, the transistor also has a maximum withstand voltage and maximum power value, so it is important to avoid the feeling of a small horse pulling a big car as much as possible, otherwise the consequences may be very serious. Note: The symbol for a transistor in a circuit is "VT" or "Q" or "V". 7、 Potentiometer can also be understood as an adjustable resistor with variable resistance, but it is different from a variable resistor. The pins of the potentiometer are all at least 3. The function of a potentiometer is mainly to adjust the values of various signals or voltages. In addition to the various boards in the host, its use is still very extensive. Almost all devices, from color displays to active multimedia speakers, have potentiometers. In general, it is best not to touch the potentiometers in the circuit (except for various adjustment knobs and potentiometers outside the machine), especially in the power supply part, because many values cannot be adjusted to the optimal value under manual conditions. Of course, if it is necessary to replace due to damage, it is another matter. However, it is also necessary to use a potentiometer of the same specification and adjust it to similar conditions as the original potentiometer before attempting to operate. This can be safer. In addition, the materials used to make potentiometers are also different, generally divided into three categories: metal film potentiometers, synthetic carbon potentiometers, and metal glass glaze potentiometers. Note: The symbol for potentiometers in circuits is "W".
8、 The function of the voltage regulator block and the fuse regulator block is to reduce the voltage and stabilize it to a fixed value before outputting. For example, the three terminal regulator block 7805 can reduce voltages less than 35V to a stable 5V output voltage. It is much better than circuits that only use one regulator diode for voltage regulation, and the cost is not very high, so it is still widely used. The common three terminal voltage regulator blocks can be divided into two types: positive voltage regulator blocks and negative voltage regulator blocks. There are 78XX series for positive voltage and 79XX series for negative voltage. They cannot be interchanged, so do not confuse them when choosing. Of course, there are not only these two series of voltage stabilizing blocks, but also four terminal voltage stabilizing blocks and five terminal voltage stabilizing blocks, although these two series are the most common in computer systems; In addition, there are different types of voltage stabilizing blocks: small, medium, and high power. When replacing them, do not use low-power ones to replace high-power ones, but there is no problem replacing low-power ones with high-power ones. As for the brand aspect, there are also some considerations. Some low-quality voltage regulators have significant errors between their voltage regulation values and nominal values, and even some brands have very poor thermal stability performance, often causing strange malfunctions. Among the multiple brands of voltage regulators that the author has used, there are four brands with good quality and performance, namely ST (Italian French), AN (Panasonic), LM (American National Half), and MC (Motorola). Their specific brands can be seen from the prefix of their models. When it comes to insurance pipes, some people may say, 'What's there to say about this? It's just fine copper wire!'. In fact, insurance tubes are also very sophisticated. Insurance tubes are divided into two types: DC insurance tubes and AC delay insurance tubes, as well as current insurance and voltage insurance tubes. They cannot be interchanged, otherwise they may not play a protective role, and sometimes even burn out the insurance tube as soon as it is turned on. The melting current of the insurance tube is generally between 1.5 and 2 times the rated current of the electrical appliance to have a good protective effect. Therefore, when it is found that the insurance tube has melted, a new insurance tube with a melting current similar to the original insurance tube should be used as much as possible to replace it; In addition, the fuse also has a pressure resistance value, so everyone should pay extra attention, otherwise it may burn the fuse. Note: The symbol for the voltage regulator block in the circuit is "IC". 9、 Integrated blocks can be said to be the main core parts of various components in computer systems. In addition to some commonly seen analog signal processing integrated blocks, such as CPU, RAM, ROM, south and north bridge chips, and graphics card chips, they all belong to the category of integrated blocks. Although there are many integrated blocks that play the most important role, their failure rate is the lowest. Without high voltage "attacks" and serious short circuits in peripheral components, they are basically not damaged. Even if they are broken, some integrated blocks are difficult to replace. Many people will say that if they accidentally replace the integrated block, the new integrated block will be broken down by static electricity. In fact, not all integrated blocks are afraid of static electricity on the human body or soldering iron. Only low-voltage small signal processing COMS type integrated blocks are afraid of this static electricity, so there is no need to worry too much. The internal structure of integrated blocks is basically entirely composed of semiconductors, which concentrate tens of thousands of transistors into small components. Therefore, many integrated blocks can be interchangeable as long as their pin functions are the same, the operating voltage is consistent, and the voltage of each pin is the same. This feature is very useful for the replacement of some integrated blocks that are not available in the market or have high prices; In addition, the quality of integrated blocks varies depending on their place of origin. Imported products have the best quality, followed by joint venture products, while domestically produced integrated blocks have the worst quality. Therefore, their prices also differ greatly, with a 10:1 gap at the most "hanging" time; It is not difficult to distinguish domestic integrated blocks. Products with the prefix "CD" are definitely domestic products, while those with the prefix "OM" may be domestic or joint venture products. Note: Integrated blocks and what we commonly refer to as integrated circuits are the same concept. The symbol for integrated blocks in circuits is "IC" or "N" or "U". 10、 Crystal oscillator is an oscillator made of quartz crystal, which has high accuracy and can generate very stable frequencies. Its thermal stability is also better than that of discrete component oscillators. In terms of function, it can be said that the crystal oscillator is the "heartbeat" generator of each board. If the "heartbeat" of a person is chaotic, they will get sick. Similarly, if the "heartbeat" of a computer board is chaotic, various strange faults will also occur. Because the frequency of crystal oscillator in computers is generally high and the ambient temperature is relatively high, the failure rate of crystal oscillator is not very low. Usually, new products of the same model should be used when replacing crystal oscillators, because a considerable number of circuits have very strict requirements for crystal oscillators. These circuits not only require that the frequency of new crystal oscillators should be the same as that of the original crystal oscillator, but also that the suffix letters should be identical (crystal oscillators can be in series or in parallel), otherwise they will not work normally. So everyone should pay more attention when replacing crystal oscillators, and try to replace the faulty crystal oscillator with the same new product. Note: The symbol of a crystal oscillator in a circuit is "X" or "G" or "Z". 11、 Switch is a very common component that is present in all accessories. Strictly speaking, jumpers on various boards and buttons on keyboards and mice also belong to switches. The author cannot provide a detailed description of the classification of switches here because there are too many classifications. Therefore, the author roughly divides them into two types: current type switches and voltage type switches. Voltage type switches are only used to control signal potentials, such as jumper switches, switches for keyboards and mice, etc; Current type switches are used to control power sources, such as power switches for active speakers and switches on multifunctional sockets. When such switches are closed, a relatively large current will pass through, and the instantaneous large current will generate sparks inside the switch, which will oxidize the switch. Therefore, do not perform frequent closing and opening operations on current type switches to ensure their long service life. Note: The symbol for the switch in the circuit is "S". 12、 Glue and wire glue are commonly used items in the DIY community, but different objects require different types of glue to stick together. Here are a few examples: if you want to stick thin hard plastic or ABS plastic items, you need to use quick drying strong glue such as 502. If you want to stick relatively fixed items, it is best to use strong chloroprene glue (such as glue on the edges when installing heat sinks). If you want to stick hard objects, AB glue (such as color display shells or metals) can be used. If you want to fix a certain item, hot melt glue (such as fixing chassis bellows or speakers) can be used. There are also some considerations when it comes to the selection of cables. For example, when you want to buy speaker cables for several meters of multimedia speakers, you need to choose oxygen free copper wires with more than 50 cores specifically for audio. Otherwise, the sound will sound lacking in high frequency and low frequency intensity, and it will become increasingly severe; For example, if you want to buy a power extension cord for a computer that is over ten meters long, you need to buy a high-quality multi strand copper wire of 1.5mm2 (a copper wire of 1 square millimeter has a safe current of about 8A~10A). If the quality and wire diameter are not too good, it may cause accidents; In addition, wires also have the highest voltage resistance value, so it is also important to pay attention when purchasing.