I. Preparatory work
When choosing a second-hand monitor, it is best to bring a graphics card with more than 2M memory, because some merchants only provide low-grade graphics cards of 256KB or 5 12KB to deceive consumers, so it is impossible to make a comprehensive inspection when using it to open the monitor.
In addition, with the permission of the merchant, we can judge the quality of the second-hand monitor more comprehensively by bringing tools such as screwdriver, opening the back cover of the monitor and observing the internal structure.
Second, the selection method
(1) Look at the appearance
There are many kinds of second-hand monitors, which can be roughly divided into high, medium and low grades according to quality. High-end monitors are mainly produced in Japan, the United States and other places, such as Sony, Mitsubishi and Apple. Mid-range products are mainly produced by Korean, China, Taiwan Province, Southeast Asia and domestic joint ventures, such as Samsung, Hyundai and Daewoo. In fact, some famous brand monitors are OEM products in Taiwan Province Province, China; Low-end monitors are produced by some little-known factories.
The monitors produced by well-known brand manufacturers are very standardized. From the appearance, they have beautiful shapes, clear lines, exquisite spraying technology and seamless interfaces. The color of the front and back covers of the monitor is the same, and there is no damage or yellowing. Trademark printing is exquisite and elegant. From the inside of the display, its circuit design is standardized, there is no flying wire, the solder joints are bright and smooth, and the workmanship is fine. Choose famous factory components.
There are two ways to adjust the display: knob adjustment and digital adjustment. The knob adjustment method uses a set of knobs to adjust the parameters such as brightness, contrast, field width, line width and pincushion distortion respectively. According to the adjustment interface, digital adjustment methods can be divided into: ordinary numbers, on-screen menus and shuttle buttons. Ordinary digital uses "+"and "-"keys to adjust a parameter respectively, and it is also useful to select items by one key cycle, display the position through the indicator light, and then use two public keys to adjust the adjustment form of its value; On-screen menu type is a set of keys used to adjust the menu displayed on the screen; Single key shuttle is displayed and operated by a single rotatable key combined with the screen. Compared with the knob adjustment mode, the digital adjustment mode has the characteristics of accurate image control, convenient operation and friendly interface, and has replaced the knob adjustment mode at present. Generally speaking, the fewer keys used in digital adjustment mode, the more advanced its technology. Because the display technology with digital adjustment mode is advanced, and it is generally the product after 1995, so try to choose the display with digital adjustment mode when choosing the second-hand display.
(2) Look at the sign
There is usually a label on the back cover of the monitor. The monitors produced by famous factories attach great importance to the printing of signs, which are beautifully printed, the edges of fonts do not lose hair and the stickers are firm. Brand, production date, model, product serial number (FCC ID), place of origin (XXXXX manufacturing), bar code and various international certification marks are printed on it. Among them, the most important thing is:
1. Date of production
Generally speaking, the production date of the display is one of the important signs of whether the performance of the display is advanced or not. The closer the production date is, the more advanced the technology is and the better the performance is. When selecting second-hand monitors, products after 1996 should be selected, and the screen size should be above 15 inch. It should be noted that individual businesses selling second-hand monitors will cheat consumers by changing or deleting the production date.
2. International certification
Whether a monitor's safety, electromagnetic radiation, environmental protection, energy saving and other important indicators have passed the international authoritative certification is an important condition to judge the internal quality of a monitor. According to the different contents, requirements and nature of certification, there are different certifications in the world. The more international certifications passed, the higher the credibility of product quality. Generally speaking, brand-name monitors have passed several to a dozen international certifications, among which the most common ones are:
UL: safety certification.
TUV: EMC certification.
MPR: low radiation standard.
ISO: international organization for standardization and certification.
TCO'92/95/99: Electromagnetic radiation, energy saving, electric power and safety standards. Because of the high requirements, not many manufacturers passed, so it is rare in the display on the market.
In addition, there are FCC, EN, ISO, CE, CSA, GS, n, FI, d, s, energy star, great wall electrician and other certifications.
Among the international certifications, the most stringent certification is TCO certification, which is a series of standards proposed by the Swedish Expert Union (TCO). After continuous expansion and improvement, it has become a universal authoritative standard in the world.
The signs of inferior monitors are printed roughly, the edges of fonts are rough, the stickers are not firm, and the corners are curled, especially there is no production date and any international certification marks.
It should be noted that some picture tubes of second-hand brand-name monitors have been replaced with inferior ones for one reason or another, which is quite common. Therefore, the key to choosing a second-hand monitor depends on the display effect.
(3) Look at the display effect
It is not enough to choose second-hand monitors only from the appearance and logo, but also from the internal quality display effect.
1. Look at the brightness
Gradually increase the brightness of the display to see if the brightness meets the requirements. If the brightness is not enough, it may be caused by the aging of the picture tube or the low voltage of the accelerating electrode. Of course, the circuit fault is not ruled out. If the acceleration voltage is too low, it can be adjusted. You can open the back cover of the monitor. On the back or side of the printed board, there is an element the size of an ink bottle, and a thick wire leads to the picture tube. This is the line output transformer. There is a knob marked "screen" on the line output transformer. Adjust it to increase the brightness.
If the brightness switch is adjusted to increase the brightness, there is a phenomenon that the peak brightness drops sharply and darkens, indicating that the CRT is seriously aging, and this kind of display is absolutely unnecessary.
When adjusting the brightness, we should pay attention to whether the grating size and definition change greatly with the increase of brightness. If so, the display quality is poor.
In addition, pay attention to the brightness of the edge of the display screen. The screen edge of inferior picture tubes usually has dark corners or uneven brightness around them.
2. Look at the color purity
The color purity of the display has a great influence on the display effect, especially in graphics, image processing and games. Observe the color purity. You can call up the brush in Windows9X to observe whether all colors are realistic and pure, and pay special attention to whether the three primary colors of red, green and blue are short of colors. If the color purity is poor and there is color cast, it can be adjusted by the relevant adjustment knob inside the display. If users can't do it themselves, they can find a TV repairer to solve it.
It should be noted that there are many 14-inch second-hand monitors modified with inferior picture tubes on the market at present. The blue color is impure and dark gray, and the display effect is very poor. This kind of picture tube also has a fatal quality problem. There is a horizontal line under the grating, which is also an obvious feature of this inferior picture tube. When checking, you can see a brown line across the bottom of the screen on the background of white words on a white background, and a big tail is dragged on the left side of the line, just like an inverted "L". It should be noted that this brown line happens to coincide with the prompt line of Windows 9X, and you can't see it unless you pay attention. When observing, drag the prompt line of Windows 9X away, and the fox's tail will be exposed.