Saturday, May 7, 2011

【 Weak current College 】 common circuit repair basics "3" 】

How to identify common components?
A, resistance
Resistor in a circuit using the "R" with figures, such as: R1 indicates that the number 1 of resistance. Resistor in a circuit's main role is: triage, current limiting, divider, bias, and so on.
1, parameter identification: units for Ohm resistance (Ω), multiplying the unit: thousand euro (K Ω), megohm (M Ω), etc. Conversion
By: 1 megohm = 1000 thousand euro = 1000000 Europe
Resistance of parameter annotation methods are 3, i.e. direct standard method, color standard method and a few standard method.
A number of standard method, mainly for the patch and other small volume of the circuit, such as: 472 represents 47 × 100 Ω (i.e. 4.7K); 104 indicates 100K
B, color ring marking method most used are for example: four color ring resistance multicolored resistors (precision resistors)
2, resistance of color stops location and rate relationships as shown in the table below:
Color number times the rate of the allowed deviation (%) silver/x0.01 ± 10 Golden/x0.1 ± 5 black 0 + 0/Brown 1x10 ± 1 red 2x100 ± 2 Orange 3x1000/yellow/green 4x10000 5x100000 ± 0.5 blue 6x1000000 ± 0.2 grey purple 7x10000000 ± 0.1 8x100000000/white 9x1000000000/
Two, capacitance
1, capacitance in the circuit of general use "C" with a number (such as C13 represents number is 13 capacitance). Capacitor consists of two pieces of metal film immediately, separated by the insulating material is separated from the composition of elements. Capacitance characteristics mainly at DC-AC.
The size of the capacitor capacity is expressed to the size of the storage of electrical energy, capacitance on AC signal impediment is known as the capacitance, and AC signal frequency and power capacity.
Capacitance XC = 1/2 to π f c (f represents the AC signal frequency, the c = capacity) telephones are commonly used in a variety of capacitance electrolytic capacitors, ceramic capacitors, chip capacitors, monolithic capacitors, tantalumcapacitor and polyester capacitors, etc.
2. identification: identification of capacitance and resistance of recognition method is basically the same, divided into direct standard method, color standard method and a few standard method 3. The basic unit of capacitance for farad (F) that the other units also: MW (mF), micro (uF), NA (nF), skin (pF). Of which: 1 Farah = 103-method = 106-method = 109 na method = 1012 skin method
Capacity of the capacitor capacity values marked directly on the capacitor, 10uF/16V
Capacity of small capacitor capacitance values in its capacity on the letter or number
Letter notation: 1m = 1000uF1P2 = 1.2PF1n = 1000PF
Digital presentation: generally uses a three-digit number represents the size, the first two digits represent a valid number, first 3 digits is multiplying.
Such as: 102 represents 10 × 102PF = 1000PF224 represents 22 × 104PF = 0.22uF
3. capacitance tolerance table
Allowable error of ± 1% ± 2% ± 5% ± 10% ± 15% ± 20% if: a porcelain capacitor-104J represents a capacity 0.1uF, a tolerance of ± 5%.

3. Crystal diode
Crystal diode in circuit common "D" with a number, such as: D5 represents number 5 of the diode.
1, role: main character is a diode in one-way conductivity, which is in the forward voltage, on-resistance is very small; in reverse voltage of on-resistance of great or infinity. Because of these characteristics, a diode with a cordless phone in it is used in commutation, isolation, voltage and polarity protection, coding control, FM modulation and static noise and other circuits. Telephones in use of Crystal diode by role can be divided into: rectifier diode (such as 1N4004), isolation diode (such as 1N4148), Schottky diodes (such as BAT85), light emitting diodes, Zener diodes, etc.
2. identification: identification of the diode is very simple, small power diodes n pole (anode), most of the diode appearance using a color circle marked out, some diodes with dedicatedsymbols to represent diode P pole (cathode) or n pole (anode), also have a symbolic sign for the "P" and "N" to determine the diode polarity. Light-emitting diode polarity can be identified from PIN length, long foot is positive, negative short legs.
3. test considerations: use digital multimeters to measure diode, diode red table pen, black table of cathode diode anode of the pen, the measured resistance is the diode is Wizard-resistance, this pointer table pen connected multimeter method is exactly the opposite.
4, commonly used 1N4000 series diode voltage comparisons are as follows:
Model 1N40011N40021N40031N40041N40051N40061N4007
Withstand voltage (V) 501002004006008001000
Current (A) are all 1
Fourth, the Zener diode
Zener diode in circuit common "ZD" plus digital representation, such as: ZD5 represents number 5 voltage tube.
1 Zener diode voltage principle: Zener diode is characterized by the breakdown of both ends of the voltage has remained virtually unchanged. Then, when the regulator hose access circuit, if due to the power supply voltage fluctuations, or other causes circuit voltage changes in various points, load both sides voltage will remain unchanged.
2, fault characteristics: Zener diode breakdown mainly in open circuit, short circuit and voltage values are not stable. In these three failures, previous failures shows the power supply voltage to rise; after 2 failure performance for the power supply voltage to low to zero volts or output stability.
The model of the common Zener diode and voltage values are as follows:
Model 1N47281N47291N47301N47321N47331N47341N47351N47441N47501N4751
Voltage value 3.3V3.6V3.9V4.7V5.1V5.6V6.2V15V27V30V75V
V, inductance
Inductor in circuit common "L" with figures, such as: L6 represents number 6 of the inductance. Inductance coil is insulated wire skeleton in insulation around a certain number of turns. DC to DC resistance through the coil, it is the resistance of thewire itself, pressure drop is very small; when the AC signal through the coil, coil ends will produce from EMF EMF, since the direction of the applied voltage in the opposite direction, obstacles to communicate through, inductance characteristics is pass DC resistance, the higher the frequency, the greater the impedance of the coil. Inductance in the circuit can be composed of the oscillation circuit capacitance. Inductance General direct standard method and color stop method, the stop method is similar to the resistance. Such as: Brown, black, gold, gold said 1uH (error 5%) of the inductance. The basic unit of inductance: Heng (H) conversion units are: 1H = 103mH = 106uH.
6. variable capacitance diode
Varactor diodes are based on normal diode internal "pn" junction capacitance can vary plus reverse voltage changes this principle specially designed a special diode. Varactor diodes in the cordless telephone is mainly used in mobile or fixed-frequency modulation circuit, the realization of low-frequency signal modulated to high-frequency signals, and fired away. In working order, normal voltage variable capacitance diode modulation to the anode, the internal junction capacitance diode capacitance with the modulation voltage changes.
Variable capacitance diode failure, mainly for leakage or performance variation:
(1) occurs leakage phenomenon, high-frequency modulation circuit will not work or a performance variation.
(2) the evolution of performance variation, high-frequency modulation circuits of precarity, the modulation of high-frequency signal is sent to the other side is received after distortion.
One of the above situation occurs, you should replace the same model of varactor diodes.

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