(1) Look at the appearance

Monitors come in all kinds and varieties, and can be roughly divided into high, medium and low grades according to quality. High-end monitors are mainly products from Japan, the United States and other places, such as Sony, Mitsubishi, Apple, etc.; mid-range main products are mainly products produced by South Korea, Taiwan, Southeast Asia and domestic joint ventures, such as Samsung, Hyundai, Daewoo, etc. In fact, some famous brand monitors are OEM products produced in Taiwan, China; low-end monitors are off-brand monitors produced by some unknown small factories. The monitors produced by famous brand manufacturers are very standardized. In terms of appearance, they are beautiful in appearance, with clear lines, exquisite spray painting, and well-sewn interfaces. The front and rear covers of the monitor have the same color, no damage, and no yellowing. The trademark is beautifully printed and sophisticated. From the inside of the monitor, the circuit design is standardized, there are no flying wires, the solder joints are bright and smooth, the workmanship is fine, and components from famous manufacturers are used.

There are two ways to adjust the monitor: knob adjustment and digital adjustment. The knob adjustment method is to use a set of knobs to adjust parameters such as brightness, contrast, field width, line width, and distortion; the digital adjustment method can be divided into: ordinary digital type, screen menu type, and shuttle single button according to the adjustment interface. Mode. Ordinary digital keys use "+" and "-" to adjust a certain parameter. There is also a key to select an item and the position is displayed through a light, and then two public keys are used to adjust its value. The adjustment form; the screen menu type is a set of buttons to adjust with the menu displayed on the screen; the single-button shuttle uses a single rotatable key combined with the screen to display and operate its parameter size. The digital adjustment method is similar to the knob adjustment method and has the characteristics of precise image control, convenient operation, and friendly interface. It has now replaced the knob adjustment method. Generally speaking, the fewer keys used in a digital adjustment method, the more advanced the technology. Since the technology of digitally adjusted monitors is relatively advanced and is usually produced after 1995, when choosing a second-hand monitor, you should try to choose a digitally adjusted monitor.

(2) Look at the label

Monitors usually have a label on the back cover. The monitors produced by famous manufacturers attach great importance to the printing of signs. The printing is exquisite, the edges of the fonts are lint-free, do not bleed, and are firmly adhered. It is printed with the brand, production date (Manufactured), model number (Model), product serial number (FCC ID), place of origin (Made in XXXXX), barcode and various international certification marks. The more important ones are:

1. Production date

Generally speaking, the production date of the monitor is one of the important indicators of whether the performance of the monitor is advanced or not. Recently, the more advanced the technology used, the better the performance. When choosing a second-hand monitor, you should choose products made after 1996. The best screen size is 15 inches or more. Some merchants selling second-hand monitors will use methods such as altering the production date or cutting out the production date to deceive consumers, so attention should be paid.

2. International certification

Whether the monitor’s safety, electromagnetic radiation, environmental protection and energy saving and other important indicators have passed international authoritative certification, this is an important condition for judging the inherent quality of a monitor. . Depending on the content, requirements, and nature of the certification, there are international certifications with different contents. The more international certifications passed, the higher the credibility of product quality. Generally speaking, brand-name monitors have passed various international certifications ranging from a few to more than ten. The more common ones are:

UL: safety certification.

TUV: Electromagnetic compatibility certification.

MPRⅡ: low radiation standard. ISO: International Organization for Standardization certification.

TCO’92/95/99: Standards for electromagnetic radiation, energy saving, electrical, safety, etc. Due to the high requirements, not many manufacturers have passed it, so it is rare among monitors on the market.

In addition, there are FCC, EN, ISO, CE, CSA, CS, N, FI, D, S, Energy Star, Great Wall Electrician and other certifications. Among international certifications, the most stringent certification is TCO certification, which is a series of standards proposed by the Swedish Federation of Experts (TCO). After continuous expansion and improvement, it has become a universal world authoritative standard.

The labels on inferior monitors have rough printing, blurred edges, weak adhesion and curled corners. In particular, there is no production date or any international certification mark.

It is important to note that some second-hand picture tubes of brand-name monitors have been replaced with inferior picture tubes for one reason or another. This phenomenon is relatively common. Therefore, the key to choosing a second-hand monitor is the display effect.

(3) Look at the display effect

When choosing a second-hand monitor, it is not enough to just check the appearance and label. You also need to look at the internal quality and display effect.

1. Check the brightness

Gradually increase the brightness of the monitor 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 accelerating electrode voltage being too low. , of course does not rule out circuit failure. If the accelerating voltage is too low, it can be adjusted by opening the back cover of the monitor. There is an ink bottle-sized component behind or on the side of the printing board, with a thick wire on it leading to the picture tube, which is the output transformer. There is a knob marked "SCREEN" on the row output transformer. Adjust it to increase the brightness.

If when adjusting the brightness switch to increase the brightness, the brightness drops sharply at a peak point and becomes darker, indicating that the picture tube is seriously aged, and this kind of monitor is absolutely unacceptable.

When adjusting the brightness, you should pay attention to whether the grating size and clarity will change significantly as the brightness increases. If so, it means the monitor is of poor quality.

In addition, pay attention to the brightness at the edge of the monitor screen. The edges of the screen of inferior picture tubes usually have vignetting or uneven brightness around them.

2. Look at color purity

The color purity of the monitor has a greater impact on the display effect, especially graphics, image processing and games that have higher requirements for color purity. To observe the color purity, you can call up the paintbrush in Windows 9X and observe whether the various colors are realistic and pure. Pay special attention to whether the three primary colors of red, green and blue are lacking in color. If the color purity is poor and there is a color cast, it can be adjusted through the relevant adjustment knobs inside the monitor. If the user cannot do it himself, he can find a TV repairman to solve the problem. What needs special attention is that there are currently many 14-inch second-hand monitors on the market that are modified with an inferior picture tube. The blue color is impure and dark gray, and the display effect is very poor. This type of picture tube also has a fatal quality problem. There is a horizontal line at the bottom of the grating, which is also an obvious feature of this inferior picture tube. During the inspection, against the white background, you can see a brown line running across the bottom of the screen, and a large "1" or "7" dragging "Chu Huan" on the left side of the line. It should be noted that yes , this brown line coincides with the prompt line of Windows 9X, and you can't see it if you don't pay attention. When observing, you should drag the prompt line of Windows 9X away, and the fox's tail will be exposed.