I.Voltage, Current
Voltage and current are brothers, current flows from a place where the voltage (level) is high to a place where the voltage (level) is low, a current must be generated because of the presence of a voltage, but the presence of a voltage does not necessarily generate a current – if there is only a voltage and no current, it can be proved that there is an interruption in the circuit (e.g., there is a switch in the circuit). If there is only voltage but no current, it is evidence of a circuit break (e.g. a switch in the circuit). In addition, sometimes the measurement of voltage is normal but the measurement of current is not necessarily normal, such as a slight short-circuit phenomenon or a component of the resistance value of the phenomenon of large, etc., so in the maintenance must be combined with the voltage value and current value to analyze. When testing the unknown voltage or current with the multimeter, be sure to set the gear into the highest grade, such as measuring the value and then gradually lower the gear.
Note: The symbol for voltage is “V” and the symbol for current is “A”.
II.Resistors
Various materials present a certain resistance to the current that passes through them, and this resistance is called resistance, and the entity (element) that has this physical property of aggregate resistance is called a resistor (simply a conductor with a resistance value). Its role in the circuit is very important, in the computer boards and peripherals in the number is also very large.
Its classification is also varied, if classified by use: current limiting resistors, buck resistors, voltage divider resistors, protection resistors, start-up resistors, sampling resistors, decoupling resistors, signal attenuation resistors, etc.; if classified by shape and production materials: gold film resistors, carbon film resistors, cement resistors, non-inductive resistors, thermistors, varistors, pull-wire resistors, chip resistors, etc.; if categorized by power: 1/ 16W, 1/8W, 1/4W, 1/2W, 1W…… and so on.
These resistors are common resistors, so their resistance value of the nominal method we must know, the following I will take the computer host card on the most common chip resistors as an example (the other resistors nominal method of the same): Chip resistor nominal method of digital and color ring method of these two.
First of all, the digital method, usually there are three resistors on the number XXX, the first two numbers in turn is the number of tens and digits, the last number is 10 of the Xth power, the specific resistance value of the resistor is the first two numbers of the two-digit number multiplied by 10 of the Xth power of the ohms, such as labeled with a 104 resistor resistance is 100000 ohms (i.e., 100KΩ), labeled with a 473 resistor resistance value is 47000 ohms (i.e., 47KΩ); the following author to say a few words about the color ring method, this nominal method is the most common in all the resistor nominal method (patch shape of the relatively few), the common color ring usually has four rings, we will be the gold or silver ring as the last ring, the first three rings of the color corresponds to the corresponding number, we know the number of numbers we need to use the number of the above mentioned method of reading the value of its resistance, but We must first know what color represents what number to do, so we must remember such a mnemonic – black, brown, red, orange, yellow, green, blue, purple, gray and white, which corresponds to 0123456789, as for the gold and silver, respectively, said 10-1 and 10 -2, these two colors in the four-color ring resistor is only marked error value only, so as long as you understand the line. Below I also give two examples to illustrate, in order to understand and remember, such as marked brown, black, yellow and silver ring resistor resistance is 100000 ohms (i.e., 100KΩ), marked yellow, purple, orange and gold ring resistor resistance is 47000 ohms (i.e., 47KΩ).JoinWin is a professional electronic components distributor and partners with original manufacturers, provides genuine integrated circuits and connectors, supply hard-to-find and discontinued parts. To get accurate data for millions of electronic parts.Enjoy affordable prices for quality products.
There is also a five-color ring resistor, this resistor are some relatively small resistance value, relatively high precision resistors, because there are applications in computer peripherals, so I also introduce: it is gold or silver for the penultimate ring, the first three color ring were the hundredths, tenths, digits, and the last color ring is the error value, the specific resistance value of such a resistor is the first three color ring on behalf of the three digits of the three numbers composed of Three digits multiplied by 10 of the negative 1 times or negative 2 times Ohm, such as marked with brown, purple, green, silver and brown ring of the resistor resistance value is 1.75Ω.
About some of the basics of the resistor is so much, just in the replacement of the resistor’s power should also be noted, usually 1/4 or 1/8 of the resistor to replace the chip resistor is not a problem.
Note: Using the digital method of the chip resistor is mostly black, the resistor in the circuit symbol for “R”.
III.Capacitors
In addition to resistors, the most common is capacitors, simply put, capacitors are containers that store electric charge. For the shape of the capacitor may be most of the people engaged in hardware know, so I only briefly say. Common capacitors according to the shape and production materials can be divided into: chip capacitors, tantalum electrolytic capacitors, aluminum electrolytic capacitors, OS solid capacitors, electrodeless electrolytic capacitors, porcelain capacitors, mica capacitors, polypropylene capacitors.
One of the chip capacitors in the computer mainframe within the various boards on the most common, but only a small number of chip capacitors have a logo, have a logo of the chip capacitor capacity reading method and chip resistors, just the unit symbol for pF (1000000pF = 1μF), as for the majority of the majority of chip capacitors why most of them do not have a logo, I think that may not be easy to damage is not unrelated. In the computer power supply box and color display and many peripherals have a lot of ceramic capacitors and a variety of metalized capacitors, so I would also like to say that such capacitors belong to the non-polarized capacitors. Their capacity nominal method and digital resistors, only some capacitors will use a “n”, the “n” means 1000, and it is located in the position and the capacity of the value also has a relationship, such as the nominal capacity of 10n capacitor is 10000pF (i.e., 0.01μF), labeled as 4n7 capacitor capacity is 4700pF (i.e., 4.7n) rather than 47000pF, as for the two kinds of capacitor voltage withstand value, are marked on the capacitor, such as 65V, 100V, 400V …… and so on (only a few do not mark, but usually above 65V). usually above 65V).
Here I say a little more about aluminum electrolytic capacitors, which are characterized by large capacity and low cost, so they are widely used in various boards and power supply boxes, as well as most of the peripherals. In order to reduce the production cost, some manufacturers use a lot of relatively low withstand voltage value of capacitors, such as for the 5V voltage withstand voltage 6.5V filter capacitors. Although it can be used, but the failure rate is slightly higher, coupled with its thermal stability is not very high, so the replacement of aluminum electrolytic capacitors is very common. Just in the replacement of the voltage withstand value in the actual voltage 1.5 times more than the capacitor, but also pay attention to the positive and negative poles can not be connected to the reverse, especially the power supply part of the electrolytic capacitors should pay more attention to these two points, otherwise the capacitor may occur burst events.
In addition, there is a brand of capacitors, different brands of resistance is just not the same error value, but different brands of capacitors is the life and quality of the different, such as a variety of losses and insulation resistance and temperature coefficients of the different. The following author will introduce a few good brands to you: PHILIPS (Philips), RubyconBLACK GATE (black gold steel), Rubycon (Ruby), ELNA, ROE, SOLEN, Nichicon, DECON, WIMA (this product is very expensive capacitors above the capacity of 1μF), RIFA, ERO, if you really do not recognize it. You really do not recognize the words you just remember that all capacitors on the C, D two letters (all prefix) capacitors do not buy, such capacitors are not the world’s leading manufacturers, and even some capacitors used in computer boards and cards may also cause a bad influence. These capacitors can only be used to capacitance performance requirements are not very high in the product (for example, to 4 dollars a radio), its capacity and some other performance indicators on the error is very large, even if the new factory products can ensure that 4 years or so can have a better performance, so it can not be loaded into the computer accessories.