Basic knowledge of the hottest display components

Basic knowledge of maintenance of display components

display is the basic international science and technology feast in computer "dinner" nbsp; From the perspective of new material industry, Ningbo export equipment is a window for people to talk with computers. It is a durable device in computer configuration, and many computer upgrades are carried out under the premise of retaining the monitor. Generally, the computer host can only be used for twoorthree or fourorfive years, but it is eliminated due to the improvement of the technical requirements of the new software used; But for ordinary users, the monitor can be used for about ten years, but in the process of use, they often encounter problems with the monitor. Now let's make a brief introduction to some basic knowledge of display components, hoping to be beneficial to you

1. Capacitance: the common marking method of capacitance is direct marking, and its common unit is PF, μ F two, easy to recognize. However, some capacitors with small capacity are marked by numbers, which generally have three digits. The first and second digits are valid digits, and the third digit is a multiple, that is, how many zeros should be followed. For example, 343 means 34000pf. In addition, if the third digit is 9, it means 10-1, not the 9th power of 10. For example, 479 means 4.7PF

when replacing the capacitor, it should be noted that the withstand voltage value of the capacitor is generally not lower than that of the original capacitor. In the circuit with strict requirements, its capacity generally does not exceed ± 20% of the original capacity. In circuits with less strict requirements, such as bypass circuits, it is generally required to be no less than 1/2 of the original capacitance and no more than 2 ~ 6 times of the original capacitance

2. Resistance: resistance mainly includes carbon resistance, carbon film resistance and metal film resistance. The most widely used is carbon film resistance, and the highest grade is metal film resistance. The resistance value of the resistance is marked by a color ring, of which the most common are four-color ring and five color ring. If a four-color ring is used for marking, the first color ring is ten digits, the second color ring is single digits, the third color ring is multiplicative digits, and the fourth color ring is the error rate. For example, if the color of the resistance of the four-color ring is red, blue, brown and gold, the resistance value of this resistance is 260 Ω, and the error rate is 5%

3. Transistors: transistors used in color display mainly include crystal diodes, crystal triodes, thyristors, field effect tubes, etc., of which the most commonly used are triodes and diodes. How to correctly judge the quality of diodes and diodes is one of the keys to learn and maintain displays

1 crystal diode: first of all, we need to know whether the diode is a silicon tube or a germanium tube. It can be seen from table 3 that the forward voltage drop of the germanium tube is generally between 0.1 V and 0.3 V, while the silicon tube is generally between 0.6 V and 0.7 v. The measurement method is: use two multimeter to measure. When one multimeter measures its forward resistance, use another multimeter to measure its tube voltage drop. Finally, we can judge whether it is germanium tube or silicon tube according to the value of its tube pressure drop. The silicon tube can use the R of the multimeter × 1K gear to measure, germanium tube can use r in that month × 100 gears to measure. Generally speaking, the greater the difference between the forward and reverse resistances of the measured diodes, the better. Generally, if the forward resistance is hundreds to thousands of ohms and the reverse resistance is more than tens of thousands of ohms, it can be preliminarily concluded that this diode is good. At the same time, the positive and negative poles of the diode can be determined. When the measured resistance value is hundreds of ohms or thousands of ohms, it is the positive time of the diode flashing back to hellip 1 year ago; hellip; At this time, the negative probe is connected to the negative pole, and the positive probe is connected to the positive pole. In addition, if the forward and reverse resistance is infinite, it means its internal disconnection; The forward and reverse resistances are the same, so there are problems with such diodes; Zero resistance in both directions indicates a short circuit

2 crystal triode: crystal triode is one of the most common components in color display. How to judge the quality of triode is the key to the maintenance of color display. To judge the quality of the crystal triode, the method is to use the R of the multimeter × 1K gear or R × 100 gear measurement. For NPN type tubes, when the negative probe is connected to the base and the positive probe is connected to the collector and emitter respectively, the measured positive resistance of the two PN junctions should be hundreds of ohms or thousands of ohms, and then the probes should be adjusted to measure the reverse resistance of the two PN junctions, which should generally be tens of thousands of ohms or more. Then use a multimeter to measure the resistance between the emitter and collector, and then adjust the probe to measure it again. The resistance value of both times should be more than tens of kiloohms. Such a triode can be judged to be basically good

crystal triode mainly plays the role of amplification, so how to judge the amplification ability of triode? The method is: set the multimeter to R × 100 gear or R × 1K gear. When measuring NPN type tubes, the positive probe is connected to the emitter and the negative probe is connected to the collector. The measured resistance value should generally be more than several thousand ohms; Then connect a 100 kohm resistance between the base and collector in series. At this time, the resistance measured by the multimeter should be significantly reduced. The greater the change, the stronger the amplification ability of the triode. If the change is small or there is no change at all, the amplification ability of the triode is not strong or weak

4. Integrated circuit block: to judge the quality of the integrated circuit block, use a multimeter to measure whether the working voltage, resistance to ground and working current of each pin of the integrated circuit block are normal. The integrated block can also be removed to measure whether the resistance between each pin of the integrated block and the grounding pin is normal. When the integrated block is removed, the resistance to ground of each pin of its external circuit can be measured to see whether it is normal. In particular, when replacing integrated circuit blocks, we must pay attention to the welding quality and welding time. When replacing integrated circuit blocks, it is generally required to replace them with integrated circuits of the same model and specification. When the original model and specification of integrated circuit blocks cannot be found, it can be considered to replace them with integrated circuit blocks with similar functions, but it should be noted that when replacing, it is necessary to clarify the supply voltage, impedance matching, pin position and peripheral control circuit

5. Row output transformer: row output transformer (commonly known as high-voltage package) is one of the big pieces that often have problems in the display. The main problem that easily occurs is internal short circuit. At this time, check the power supply voltage with a multimeter to determine whether it is normal. If the insulation performance of the row output transformer decreases or there is a local short circuit between turns, the row scanning current will surge and the output voltage of the switching power supply will drop. Therefore, whether the row output transformer is short circuited can be judged by measuring the power supply voltage. (end)