Saturday, January 1, 2011

Weak current College】 【monitor maintenance start surf】.

<br> Maintenance Fundamentals <br> I. how to judge the quality of common components. <br> In the amateur condition we should try to learn to use multimeter to determine some of the common components of good or bad and components of positive and .negative features. [Of course, these basics not available in the monitor's maintenance, by analogy to other parts of the computer maintenance is also very useful. <br> 1. capacitance: <br> How to recognize capacitor capacitance common tag? how is .direct marking of the common unit has two pF, uF, such as Electrolytic Capacitor 470uF capacitor, such as tiles, and so on, it is easy to 2200pF would be recognized. But some small-capacity capacitor, takes a digital marking method. It .has three digits, in General, first, the second digit is a valid number, and the third digit multiples, which indicates how many back to 0. For example, 343 represents 34X1000pF, if a third digit is 9, meaning 10X-1 instead .of 9-10, for example, the expression as is 479 4.7pF. <br> When the capacitor replacement main attention should be paid to the requirements of the capacitance of the pressure resistance is generally not less than the original capacitive voltage requirements. Its .capacity on demand stricter circuit, usually not exceeding the original capacity of plus or minus 20%. In less strict circuit, such as a bypass circuit, the General requirements of not less than the original capacitance of 1 / 2, generally not greater than the .capacitance of the 2-6 times. <br> 2. resistance: <br> How to identify the main resistance? resistance have carbon resistance carbon film resistor metal film resistors third class, the most widely used for carbon film resistors, the most upscale .for metal film resistors. If you want to use resistance, first of all to ascertain the resistance of resistance. Resistance of resistance in addition to direct annotation, often opposite points to mark, one of the most common is 4 color ring marking and 5 color .ring. If a 4 color ring title, the first color ring is the second of ten digits, each digit color ring as the third color ring to be riding bits, the fourth color ring is staggering. For example 4 color-ring of the resistance .of colors arranged into red and blue brown gold. The only resistance of resistance value is 260 euro error rate of 5%. As with 5 color ring represents, its first color ring for hundreds, the second color ring is 10 digits, the third color .ring is a digit, the fourth color ring should take the digits, the multicolored is staggering. For example, 5 color ring of resistance of colors arranged into Hong-dark-brown, its resistance to 420X1 = 420 euro, a tolerance of 1% .. 5 opposite points of resistance is usually the error is 1% resistor metal film. Their relationships visible schedule. <br> Color of digits corresponding values should take the staggering temperature coefficient <br> Black 0X1 200ppm <br> Brown 1X101% 100ppm < .br> Red 2X1002% 50ppm <br> Orange 3X1000 15ppm <br> Yellow 4X10000 25ppm <br> Green 5X1000000.5% 20ppm <br> Blue 6X10000000.25% 10ppm <br> Purple 7X100000000.1% 5ppm <br> Ash 8X100000000 .1ppm <br> White 9X1000000000 <br> Black 0 <br> Gold X0.15% <br> Silver X0.0110% <br> Natural colour 20% <br> Multimeter measuring resistance of resistance, if its resistance is greater or is .infinite, may be its internal has broken pole or bad; if measured its resistance value is too small or is zero, it may be that their internal breakdown or short circuit. <br> 3. the transistor: <br> With colour display of .transistors used in mainly in the Crystal diode, transistor, MOSFET SCR and so on, one of the most commonly used is the transistor and diode, how to correct judgment, transistor or bad, is one of the keys to the maintenance of the monitor. .<br> A. Crystal diode: <br> To determine whether two meter tube is good or bad, the first thing we need to know the diode is silicon tube or pipe, it is well known in germanium, germanium pipe forward voltage drop General .0.1-0.3 Volt, silicon tube General 0.6-0.7 volts. Its measurement is used two multimeter, when a multimeter measuring its forward resistance when using a multimeter measuring its pipe pressure drop. Last may, under its authority to judge the value of pressure drop .is Silicon Germanium pipe or tube. How to judge the diode is good or bad and polarity? SI tube available multimeters to measure RX1K stalls, germanium tube available RX100 stalls to logging. Generally speaking, the testing of diode difference between forward and reverse resistance the .more uneven the better. Generally it is the resistance of a few hundred to several thousand euro Europe, its reverse resistance to tens of thousands of euro or more, you can determine this diode initially is good. While judgment diode anode and cathode. When the .measured resistance to hundreds or thousands of Central Europe, the diode forward resistance, then just the table amount received as a negative, as reported in the table amount as the cathode. <br> In addition, if the forward and backward resistance is infinite, .which means that its internal breakage: forward and backward resistance as big, this diode has a problem; forward and backward resistance is zero represents that it has a short circuit. <br> B. triode: <br> Transistor is a colour TV in .one of the most common components, how to tell if a triode or bad is the key colour TV repair. To judge the transistor is good or bad, we must first distinguish the three pole transistor. Available two multimeter measuring the multimeter in RXIK stalls or .RX100 stalls for NPN-type pipe, when the two negative table amount received base, table pens respectively collector and emitter, measured by two PN forward resistance should be hundreds or thousands of Central Europe, and should be reversed and then measuring the table amount for .two pn junction resistive, should generally be reversed as tens of thousands or hundreds of thousands of Central Europe. Then use multimeter emitter and collector, measuring between resistance and transposes the table after the pen and then measure once, twice, the resistance should be in .the tens of thousands of euro or more, so you can basically tell of transistor is good. <br> Triode main role plays zoom, then how to sentence the zoom capacity measured triode? byThe multimeter to RX100 or RXIK stalls when measuring NPN-type .tube, as table pen pick set negative table launches pen pick set electrode, the resistance should generally be measured as more than a few thousand euro; and then in the base-level and collector-level between threaded a 100K European resistance when the logging multimeter .should clear of resistance, the larger the variation, the transistor's zoom capabilities, normal. If you change very little or no change, the transistor is not enlarged capacity or on a large number of very small. <br> If triode damage, preferably using .the same model, unable to find the same model of triode, must, in accordance with reverse voltage BVceo [this value is most important, it is also important to choose the replacement with the same or greater than the pressure values for substitution of transistors] ., working frequency ft, penetrating current Iceo, power consumption, and other technical indicators to Pcm rational use substitution triode. <br> 4. integrated circuit block: <br> Judging the quality of the integrated circuit block, all available multimeter measuring manifold blocks .on foot working voltage, ground resistance values, the operating current is normal. You can also remove the manifold, measuring the feet and earthing circuit block feet is normally between resistance, while removing the manifold can be measured when the external circuit to the feet of .the ground resistance values correctly. To say that, in replacement of the integrated circuit block, it is important to note that the quality of welding and welding time. Some of the more integrated circuit block pin, such as welding improperly exposed to new fault. .Welding time is too long, it is easy to damage the internal circuit manifold block, or even make their printed circuit foil and substrate from by adding unnecessary workload, it is best to use a dedicated welding tip of to speed up the welding time and attention .to the heat. If the PIN is too much a welding is not good, you can wait and then welded. Or buy back the same PIN IC socket, socket welding fine, then insert the integrated circuit block, can do is the best. In .replacement of the integrated circuit block General requirements under the same model, with the specifications of the integrated circuit to be replaced. It cannot find the original model, the specifications of the integrated circuit, consider using similar features integrated circuit block in place, but it .is important to note that when you want to know the place of the supply voltage and impedance matching, pin position and the external control circuit. <br> 5. output transformers [commonly known as 'high package']: <br> High voltage .package is monitor more frequently one of the big problems. Today's display of multiple high-voltage package for integration [of course, there is a split of], model and specification, but the most common for Sanyo. Makes maintenance more difficult. Its easy .of major problems for the internal short circuit. You can check the power supply voltage multimeter to determine whether it is normal. If output transformer insulation performance degradation or turn to local short circuit, causing rows to scan current surges, switching power supply output voltage drop .. Thus, by measuring the voltage to determine output transformer is shorted. As the power supply voltage drops to normal value of about 1 / 2, disconnect the line load powered, with 300 Ω/50 W bulb forgery load, and then turn on main .power supply voltage is measured. To return to normal, and load the inspection not short-circuit or variable value, then basically you can determine the output transformer short circuit. When the package is damaged high pressure, only the replacement of lost, there is .more than its species, the more difficult to find the same to replace, then as long as it is the same model in General can direct substitution. But if the alternative line output transformer winding of the same or similar, but not match pin arrangement, .then the original circuit board must be unable to install, you can output transformer additionally installed fixed in build-in a certain position, and use the soft copper wire will pin in the circuit board corresponding to pick the appropriate spot. <br> II. .getting started with the new maintenance and tests <br> 1. the first few lap confidence to believe that through their continuous learning and efforts must be able to fix the problem. In the actual repair, the problems are more than a simple question, really .big problem it is very difficult to meet. In the maintenance to do an audacious, but be sure to pay attention to safety. <br> 2. second to ready a soldering iron, Multimeter, cross the peace of the solution, solder wire, .and other common tools. Soldering iron selected 20-25W to ordinary quality soldering iron; multimeter starter on selected ranges of larger digital multimeter bar; solder wire buy a couple of metres, but be sure to choose the kind of quality within the belt of rosin .flux solder Gee, however dollars welding quality, but it is much better; solutions for large and small knives etc wrench by few. If you have not even those that go buy back, but they add up to a maximum of $ money only, otherwise .you have to use the hand with an eye to repair the <br> 3. repair before you should be aware of the situation when the problem occurred, such as voltage stability, with and without collision, damp from wet, lightning, has no smell .and no image noise, unstable, and so on, so do the number of basic has in mind. Before preparing the folding machine, check the external monitor's power is normal, the voltage is stabilized. Then you can check the switch with colour display and .the knob is normal, there is no obvious dull Gravis phenomenon. Finally you should see the brands with colour display, new and old, dust, and other appearance. <br> 4. press the power switch, the actual observation under xianping. If .there are no grating on the screen, the image is stable image is distorted, the brightness contrast is adjustable, and so on. In addition to note down the monitor whether there are smell or spark. <br> 5. open the rear cover of .the monitor, carefully inspect the monitor's internal components have no damage, breakdown, charred, discoloration and so obvious failure. Secondly you can examine the following components have no detachment, the virtual welding. Inside wiring for loose, whether plug. <br> 6 .. in the absence of clear fault position, not to some of the built-in adjustable components for blind people, so that the failure of more complicated. Encountered within the current limiting resistors, fuses or circuit protection components breakdown or blowing, the first serious .examination of its surrounding circuit problems, no problem, and then replace it with power. <br> 7. replace the components it is important to note that welding quality, careful not to create virtual welding. Besides weldingNext time it should not be too long ., so as to avoid damage to components, resulting in unnecessary economic losses, although some components had some value for money. But after welding times easily lead off from the circuit board on the foil, it should be noted. <br> 8. maintenance .and repair should be in the first part, then the power supply repair parts before grating overhaul of images and image stability in parts of the principle. Why we all know, the power supply is the monitor sections can be good source of energy, and the .grating is the normal display image. <br> 9. Finally, it should be noted that a soldering iron, screws, components, etc., are properly placed, repaired machines of foreign bodies to timely clean, cables and plug-ins you want .to reinstall the plug in place. So in turn caused other human failure. <br> III. the basic structure and the monitor manufacturer Web site: <br> Generally speaking, monitors are primarily by CRT [cathode tube], row, field scan .circuit, video processing circuits, multiple frequency synchronization control circuit, digital tube power supply circuits, switching power supply circuit, and several parts. Today's most monitors at the factory are not random fringe circuit diagram, this had increased to daily maintenance very difficult. If .you need to monitor manufacturers for circuit diagrams and other services and help..

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