What is a Kinescope?

CRT is an electron (cathode) ray tube, and it is the key device for TV receiver and monitor to reproduce the image. Its main function is to reproduce the electrical signal (image signal) captured and converted by the camera at the transmitting end (TV station) on the fluorescent screen at the receiving end in the form of brightness changes. In order to reproduce the image with high quality, the screen size of the picture tube must be large, the image sharpness must be high, and the fluorescent screen must have sufficient luminous brightness. In addition, there are various specific requirements for picture tubes for different purposes.

CRT is an electron (cathode) ray tube, and it is the key device for TV receiver and monitor to reproduce the image. Its main function is to reproduce the electrical signal (image signal) captured and converted by the camera at the transmitting end (TV station) on the fluorescent screen at the receiving end in the form of brightness changes. In order to reproduce the image with high quality, the screen size of the picture tube must be large, the image sharpness must be high, and the fluorescent screen must have sufficient luminous brightness. In addition, there are various specific requirements for picture tubes for different purposes.

Chinese name

Picture tube

Types of

Ray tube

Appear

March 29, 1950

Appear

American radio corp.

Classification

Picture tube

Classification

Projection picture tube

CRT Development History

On March 29, 1950, American Radio successfully demonstrated an all-electronic color television picture tube. The chairman of the company David Sarnov announced

The position of the picture tube

"We have stepped on the threshold of a new era of television-the era of color television."

American Radio actually exhibited two color picture tubes. One uses a single electron gun and the other uses three electron guns to produce a color image. The specifications of these two picture tubes are the same as those of current black and white televisions. American Radio is competing with CBS, which uses mechanical scanning discs to produce color images. The advantage of the American Radio Corporation's picture tube is that it is consistent with existing black and white television transmission equipment, so viewers can use the television in their home. This is not the case with Columbia's television system. ^[1]

Picture tube classification

Picture tube overview

1. According to the supporting functions of the TV, there are: picture tube and projection picture tube.

Second, according to the fluorescent screen display colors are: black and white picture tube and color picture tube; according to the size of the fluorescent screen (diagonal size): 9, 12, 14, 17, 18, 19, 20, 21, 22, 24, 25, 29 Inches and so on; according to the deflection angle of the picture tube: 70 °, 90 °, 100 °, 110 °, 114 ° and so on. According to the shape of the screen surface of the picture tube, there are: spherical rounded corners and flat right angles. According to the length and height of the rectangle on the screen, there are 4: 3, 5: 4, 16: 9.

Picture tube black and white

A black and white picture tube is an electric vacuum device that displays black and white images. A standard black and white picture tube can be divided into three parts: neck, cone and screen.

(1) Neck: an electron gun inside, including a cathode that emits electrons, a control electrode that controls the amount of electrons emitted, a first anode and a second anode that accelerate electrons to form an electron beam, and focus the electron beam on a third anode on a fluorescent screen Wait. The electron distribution in an electron gun is similar to an optical lens system, so it is called an "electron optical system".

(2) Cone: Its inner and outer walls are coated with a conductive graphite layer. The inner wall is connected to the second anode. A capacitor is formed between the inside and outside, which can absorb secondary electrons and perform high-voltage filtering on the second anode. In addition, the graphite layer can also block stray light from the rear of the picture tube, expand the deflection angle of the picture tube, and reduce the conical portion, so that the thickness of the picture tube becomes thin.

(3) Fluorescent screen (screen): The surface of the inner wall glass of the picture tube is coated with a thin layer of phosphor. The phosphor will emit light when the electron beam emitted by the electron gun hits it. This part is called the phosphor screen. Its luminous colors are blue-white, yellow-white, and gray-white. After the electron beam stops functioning, the phosphor screen will not emit light after a period of time. This is called "afterglow". The afterglow time of general television picture tubes belongs to short and afterglow. In order to reduce the decrease of the contrast caused by the halo and light reflection, the tube surface of the picture tube adopts smoky gray glass. In order to prevent the fluorescent film from being damaged by the bombardment of the center of the fluorescent screen by negative ions in the electron beam, and to improve the screen brightness, modern picture tubes use metallized fluorescent screens.

(4) Image scanning process: In order to realize the scanning of the electron beam, a deflection coil is installed at the root of the picture tube. When a sawtooth wave current synchronized with the scanning of the transmitting end flows through the field and the deflection coil, the electron beam will be controlled. The light spot on the fluorescent screen moves up, down, left and right, at this time the image video signal is added to the control electrode (G) of the picture tube, so that the intensity of the electron beam changes, that is, the brightness of the light spot on the fluorescent screen changes, thus showing the same Black and white image.

Picture tube color

Color picture tube is a key device in color TV. Its structure and principle are similar to black and white picture tubes, but it is much more complicated than black and white picture tubes, and the fluorescent screen displays color images.

(1) Types and characteristics of color picture tubes: color picture tubes are divided into three colors: three-shot three-beam tubes with shadow masks, single-shot three-beam tubes with baffle color bars, three-shot three-beam tubes with rectangular baffle color bars There are several types of single-gun three-beam tube.

Shadow color spot type three-gun three-beam color picture tube: equipped with three electron guns arranged at an inclination angle of 1 ° with the tube axis and symmetrically arranged at 120 ° with each other to form an equilateral triangle "pin" shape, each emitting red ( R), green (G), blue (B) three electron beams. Unlike the black and white tubes, there is a third anode (converging pole) connected to the second and fourth anodes inside the three electron guns, which can be adjusted by the influence of external magnetic fields. The phosphor screen is a spherical thin metal plate coated with nearly 1 million groups of phosphor dots (pigments) composed of three primary colors of R, G, and B, and a distance of 15 mm from the spherical thin metal steel plate with approximately 1/3 phosphor dots. (Shadow mask). After the electron beams converge, they can hit the corresponding fluorescent spots through the small holes, and there will be no dyeing and color mixing, so we see a color image.

Baffle color bar type single-gun three-beam color picture tube: it and the shadow mask color point type three-gun three-beam tube

Picture tube principle

The structure is completely different. Equipped with three sets of electron guns consisting of filaments, cathodes, and control electrodes arranged horizontally in the order of R, G, and B, and the rest are composed of the first anode, the second anode, the fourth anode, the third anode, and the two pairs for convergence. Metal deflector consisting of a common gun body. The phosphor screen is composed of 1200 to 1500 phosphor stripes and 400 to 500 metal wire slits arranged in the order of R, G, B. Each gap of the baffle corresponds to the phosphor stripes, and the shape is cylindrical. In the same way, after the electron beams converge on the slits of the baffle and cross, they are shot on the corresponding color bars, and 700,000 to 800,000 groups of color points appear, so that the fluorescent screen presents a color image.

(2) New types of color picture tubes

High-resolution picture tube: improve the resolution by reducing the modulation electron beam hole and increasing the number of holes (slots) of the shadow mask plate;

Penetrating picture tube: Since the shadow mask is removed, the anti-vibration and impact resistance are particularly good.

Picture tube type

1.Spherical tube

The original display, the section of the picture tube was a spherical surface, and the early 14-inch color displays were basically spherical. The display using a spherical picture tube is curved in both the horizontal and vertical directions, and the image is also curved according to the shape of the screen. This kind of display has many disadvantages: the curvature of the spherical surface causes serious distortion of the image, which also makes the actual display area smaller, and the curved screen can easily cause reflections ^[2] .

2.Flat right angle tube

In order to reduce the distortion of spherical screens, especially the four corners of the screen, and the reflection of the display, picture tube manufacturers have made many improvements. In 1994, a "flat right-angle picture tube" was born. The so-called "planar right-angle picture tube" is far from being a real flat surface, except that the curvature of the picture tube is smaller than that of the spherical picture tube, the screen surface is close to the plane, the radius of curvature is greater than 2000 mm, and all four corners are right angles. Because the production process and cost are not much different from ordinary spherical tubes, all display manufacturers have stopped producing spherical displays, and have introduced displays manufactured using flat-angle right-angle picture tubes. Flat-angle right-angle picture tubes quickly replaced spherical picture tubes. Most of the displays that people use today, including the 14-inch displays produced in recent years and most of the 15, 17-inch and larger displays, belong to this type of flat right-angle displays. The flat right-angle picture tube reduces the reflection phenomenon and distortion on the four corners of the screen. With the adoption of new technologies such as screen coating, the display quality of the display has been greatly improved.

3.Cylinder tube

The cylindrical picture tube adopts a shadow grid structure. Its surface is still slightly convex in the horizontal direction, but it is straight and cylindrical in the vertical direction, so it is called a "cylindrical tube". Because the cylindrical tube is flat in the vertical direction, it has less geometric distortion than the spherical tube, and can reflect the light above the screen to the bottom instead of directly into the human eye, thereby greatly reducing the glare. Cylindrical picture tubes are currently divided into two categories: Sony's Trinitron and Mitsubishi's Diamond Long ^[2] .

4, flat tube

Traditional CRT display picture tubes, from spherical picture tubes to flat right-angle picture tubes (FST), to cylindrical picture tubes, the radian has become smaller and smaller, and the cylindrical tube has achieved zero radian in the vertical direction, which can be regarded as a progress from generation to generation. However, the above-mentioned picture tubes still do not reach the complete plane. Therefore, the displayed picture will be more or less deformed and distorted, which is still not completely satisfactory. Until now, the appearance of some flat-screen kinescopes has finally brought the traditional CRT display to a completely flat road. Unlike the cylindrical tube, which is just two strong competitors, there are many manufacturers who have introduced flat-screen tube technology ^[2] .

5, short neck tube

In recent years, in addition to pure flat, various short tube displays have also become a major trend in new displays. Because the deflection angle of the electron beam in a general picture tube cannot be too large, otherwise it will bring distortion that is difficult to correct, so that the length of the picture tube is proportional to the screen size, so the large picture tube must also be made longer, resulting in a display. The body is huge ^[2] .

Standard display kinescopes require that the angle of the electron beam from one side to the other cannot be greater than 90 degrees, which makes the thickness of the display at least as long as the diagonal of the screen. For displays larger than 17 inches, the greater the The apparent area also means a thicker body and greater volume and weight. One way to "slim out" a display is to use a short picture tube (ShortDepth), the core of which is the wide-angle deflection coil technology, which can make the maximum angle of the electron beam reach 100 degrees or higher, so that it can be at a short distance Achieve complete coverage of the electron beam, thereby reducing the thickness of the picture tube and the body. This method can reduce the thickness of the display by about two inches. This means that the 19-inch display occupies the same desktop area as the 17-inch display, and the 17-inch display occupies the same area as the 15-inch display. Contrast and focus are improved than before, and it is more comfortable to watch. Although there is a slight difference in dot pitch, it will not be noticed by the naked eye. It should be said that this is a big improvement overall. In addition, the use of smaller parts at the end of the electron gun of the picture tube to replace the original parts can also reduce the thickness of the display by about one inch ^[2] .

Kinescope tube base

The tube base of the picture tube is a small circuit board at the very end of the screen, that is, the thin neck. The tube base is on the board. It is white and is inserted on the picture tube. There are many soldering pins. It is estimated that the high-voltage line (red) on the socket is corroded and broken in the socket, which is also the reason for the blurring of the TV (first, it seems to be unbroken, it is blurred. After it is moved, it is broken, no image) and the ground is generated Shock, as long as no cracked deflation sound is heard, the picture tube is generally not broken ^[3] .

model

Kinescope tube sockets have seven-pin inner, seven-pin outer, nine-pin universal, 12-pin, 13-pin and other models. The nine-pin universal is most common. There are dozens of models of TV picture tube sockets, and only the same model can be replaced. Different models can not only be used, but even hard-plug the picture tube ^[3] .

Features

As a key element in color TVs and displays, the tube base of the picture tube, due to its complex working environment, is prone to a variety of failures during use. After the color TV is turned on, the sound is normal, the image is blurry, and it looks like a color cloud. After a few minutes or tens of minutes, the image gradually becomes clear, which is a typical socket failure. Due to the structure of the tube base, the shape of the electrode, and the level of the manufacturing process, the tube focusing pole is in a long-term high-voltage working state. When it is affected by harsh environments such as high air humidity and severe air pollution, the two poles of the tube focusing discharge cavity are generated. Corona discharge phenomenon, and produce highly corrosive ozone (O3, a strong oxidant, smells like fishy smell). In addition, when abnormal high-voltage pulses are generated during color TV operation, arc discharge is generated, and high-energy charged particles are bombarded in focus. The surface of the cavity electrode causes the plating on the electrode surface to be destroyed and the metal ions to be sprayed out, so that the burning phenomenon occurs and the electrode plating is destroyed, and at the same time, O3 corrodes the electrode with the injured coating. In addition, the bromine flame retardants in ordinary PBT plastics can easily release corrosive bromide-induced discharges under the above-mentioned environment. All these corrosive substances undergo chemical reactions under the action of electric fields to generate acids or salts Substances are adsorbed on the plastic surface inside the discharge chamber, which reduces the insulation resistance in the focus chamber of the tube holder, increases the leakage current, decreases the focus voltage, and eventually results in blurred images. Color TV images are dim and lack of color, usually caused by oxidative rusting of the socket contact parts, resulting in increased contact resistance, poor contact between the display pin and the socket, such as severe oxidation corrosion, resulting in the contact resistance between the display pin and the socket Large, it will produce slow, lack of color, or even no raster. The image is blurred and accompanied by flicker, which is caused by poor contact of the socket, and the image is clear. If there is flicker, it is not a problem with the socket, and it is mostly caused by a power failure. The start-up image is clear. After a period of time, the image is blurred, poor focus, and it is not a problem with the socket. It is caused by the failure of the focus circuit and the focus voltage. It is mostly caused by the poor focus of the line output potentiometer. If this fault occurs, replace the line output. In short, the appearance of the failure of the socket in the color TV machine, the screen performance includes: blurry image caused by defocus, low brightness, lack of color, no grating, black bars, etc., as long as the maintenance personnel find the source of the failure, and select reliable performance The problem of natural pipe sockets is solved easily ^[3] .

Features of damaged tube sockets

The plastic tube socket of the picture tube is broken, which will make the picture blurry after the TV series is turned on, but there will be sound. It will be better after a period of time (about 10-20 minutes). This phenomenon is especially wet and rainy It is more obvious when you need to replace the base of the picture tube to solve the problem ^[3] .

Replacement process

1. Remove the socket first-some special tools are needed. Take the removed socket to match an identical one. There are many types of sockets, and some of the same models also need to be modified to adapt to different circuit boards (remove one pin to prevent short circuit to ground). So this is very important, otherwise it will damage the TV. After that, it's much simpler. How to disassemble it can be installed ^[3] .

2. Find a section of wire, which can be a straight line (Note: the wire to be insulated cannot be a naked wire). One end is connected to the ground, and the other end is connected-the place where the high voltage package is connected to the picture tube (the place is covered by a very soft rubber cover), of course you have to lift the cover first. When you lift it, be careful to touch the high voltage, it is best not to lift it by hand. For safety, I usually lift it with an insulated screwdriver. After peeling off, the wire touched the metal part of the place. About a few seconds, the high voltage was completely eliminated. It is also worth noting that some parts of the circuit board are also live, so try not to touch them. ^[3]

Picture tube imaging principle

In the television receiver, the amplified video image signal is sent to the cathode of the picture tube by the final stage of the video amplifier, which is used to control the intensity of the electron beam current, so as to reproduce the image. If the image signal is applied between G and K of the picture tube at the same time as the static voltage. In the following, the linearized picture tube modulation curve is used to analyze the change of the beam current after the image signal is added, and the working relationship between the picture displayed by the picture tube and the modulation curve.

Picture tube modulation characteristics

The gray scale of each point forming an image on the phosphor screen is determined by the magnitude of the grid cathode current, and the change in the cathode current is modulated by the grid cathode voltage. We call the control relationship between the grid cathode voltage Ugk and the cathode current i, as the modulation characteristics of the picture tube. Therefore, the modulation characteristic of the picture tube actually refers to the relationship between the electron beam current and the picture tube grid-cathode voltage. The modulation characteristic of the cathode ray tube has an exponential curve relationship, and the relationship curve is expressed as follows: In the formula, the index value is called the value of the picture tube. Usually black and white picture tube = 2.2, color picture tube = 2.8.

Picture tube black and white image

Picture tube (black and white tube) for displaying black and white images. The main components of the black and white tube are a glass bulb, an electron gun and a fluorescent screen. A deflection coil is also mounted on the neck of the glass bulb. Keep the vacuum inside the glass bulb. The electron gun emits a modulated electron beam, which is focused and deflected and hits a fluorescent screen to display a glowing image. The scanning of the modulated electron beam is synchronized with the scanning of the electron beam on the target surface of the camera tube at the transmitting end, and the magnitude of the beam current corresponds to the electrical signal output by the camera tube. Due to the inertness of the human eye, the modulated electron beam is scanned point by point on the fluorescent screen to generate light spots with different brightness, and a light image is formed on the fluorescent screen.

Picture tube glass bulb

The casing of modern picture tubes is made of glass. The glass bulb is divided into three parts: screen, cone and neck

Picture tube picture

. The vacuum degree in the glass bulb is (1-5) × 10 Pa. The screen of the picture tube is rectangular, and the size of the screen is usually expressed by the length of the diagonal. Commonly used are 31 cm (12 inches), 36 cm (14 inches), and 48 cm (19 inches).

Picture tube screen

The inner part of the screen is coated with phosphor. Phosphors emit light when excited by an electron beam. The glass screen is smoke-colored and functions as a neutral filter. The light transmittance is about 50%. The stray light irradiated on the phosphor screen is reflected to the observer through secondary attenuation, while the light on the phosphor screen image is attenuated only once, which reduces the effect of stray light on the image and improves the contrast. The phosphor is composed of a mixture of blue-emitting zinc sulfide: silver (ZnS: Ag) and yellow-emitting zinc cadmium sulfide: silver [(ZnCd) S: Ag]. By controlling the mixing ratio of the two powders, white light with different color temperatures (such as 9300K, 11000K, etc.) can be emitted. A smooth aluminum film with a thickness of 2000-3000 angstroms is vapor-coated on the phosphor layer. Its role is to: increase the brightness of the screen by 70% to 80% by virtue of the specular reflection of the aluminum film; because the aluminum layer is an isoposition surface, which can prevent ion spots from being bombarded by the phosphor layer; It is opaque and can block reflected light from the inner wall of the cone, thereby improving the contrast of the image.

Kinescope electron gun

The function of the electron gun is to emit electrons, control the electron flow, focus and accelerate the electron beam and hit the phosphor screen to form a small light spot. Black and white picture tubes usually use a single-potential electron gun, which emits electrons from a hot cathode, and the control electrode controls the size of the emission current. The electrons bombard the phosphor screen after focusing and accelerating by a cathode voltage of 12 to 16 kV, and a light spot modulated with the strength of the video signal is generated on the phosphor screen.

Picture tube deflection system

Picture tubes commonly use magnetic deflection systems. The magnetic deflection system includes two sets of coils that are perpendicular to each other. One set of coils has a horizontal deflection of the electron beam when a scanning current flows, and the other set of coils has a horizontal scanning line of the electron beam that gradually moves from top to bottom. In the progressive scanning system, the horizontal scanning period is 1/625 of the vertical scanning; in the interlaced scanning system, it is 2/625. One of the characteristics of the appearance of the picture tube is the deflection angle. It refers to the deflection angle of the diagonal when scanning across the screen, which is generally 90 ° or 110 °.

Picture tube screen quality

There are three requirements for the screen. Brightness: The unit is Citi or Citi. The brightness varies with the luminous efficiency of the luminescent material, the magnitude of the beam current, and the level of the anode voltage. Contrast: The ratio of the brightness of the brightest part of the image on the picture tube screen to the brightness of the darkest part. Resolution: the ability to distinguish the details of an image, usually expressed by the number of scanning lines. The resolution is mainly determined by the structure of the electron gun and the anode voltage, as well as the magnitude of the beam current. The size of the phosphor particles also affects the resolution.

Picture tube color image

Picture tubes (color tubes) for displaying color images. The display of color images is based on the principle of three primary colors. Any color can be combined with the three primary colors of red, green and blue to produce basically the same visual effect. A color tube is different from a black and white tube in that it has a phosphor screen that generates three primary colors and three electron beams that excite tens of thousands of three primary color cells on the phosphor screen. As long as the components of light generated by the three primary color phosphors are different, various colors in nature can be formed.

For example, the luminous fluxes of the three primary colors of red, green and blue are combined into white light according to a certain proportion. The combination of red and green becomes yellow. The combination of red and blue becomes purple. Only the red gun's electron beam excites red powder to emit red light, only the blue beam excites blue powder to emit blue light, and only the green beam excites green powder to emit green light. If all three beam currents are zero (the phosphor screen is not excited), it is black. Color TV signal transmission is different from black and white TV in that there is a chrominance signal in addition to the luminance signal. A color TV receives these two signals, and after processing, decomposes them into three (red, green, and blue) luminance signals to modulate the corresponding electron guns, respectively.

From 1949, the American RCA company first created the shadow mask-type color tube, until 1972 the world generally used a three-gun three-beam tube arranged in a triangle. After 1972, RCA first announced the production of precision in-line color tubes. The color tube (shadow mask type) has five basic components, namely the glass bulb, the color screen, the shadow mask, the electron gun and the deflection coil that is sleeved on the neck of the glass bulb.

Picture tube glass bulb

The shape and function of the glass tube of the color tube are the same as those of the black and white tube, but the high voltage used for the color tube is 25-32 kV. Such a high-energy electron beam bombards the phosphor screen not only radiates X-rays, but also turns the phosphor screen into a brown color. Therefore, the screen glass uses a special barium strontium cerium glass. The electron beam not only bombarded the phosphor screen, but also 80% of the electron beam hit the shadow mask, so that about 75% of the X-rays leaked out of the cone. Therefore, the cone uses high-lead glass with a lead content (PbO) of more than 21% to absorb 75% -80% of X-rays.

Picture tube screen

In a three-gun three-beam tube arranged in a triangle, there are hundreds of thousands of round holes in the shadow mask, and the number of corresponding phosphor dots is three times that of the shadow mask holes. In the PIL tube, a strip-shaped shadow mask is used, and the corresponding strip is a strip of phosphor powder. The three bundles of the triangular tube and the PIL tube all converge on the round holes or strip holes of the shadow mask, and then hit the three powder spots or noodles respectively. The three-primary phosphors for color tubes have been improved many times, and the luminous efficiency of the white field has increased from 8 streams / watt in 1957 to 45 streams / watt. Commonly used red-emitting phosphors are yttrium oxysulfide: thorium (Y2O2S: Eu), and green-emitting phosphors are zinc cadmium sulfide: copper, lead (ZnCd) S: Cu, Al), or non-toxic zinc sulfide: Gold, copper, and aluminum (ZnS: Au, Cu, Al), and those emitting blue light are zinc sulfide: silver (ZnS: Ag). An aluminum film is also vapor-coated on the phosphor layer, and its effect is the same as that of the aluminum film in the black and white tube. In order to improve the contrast, the screen of the color tube used to be smoky. In 1968, a black background screen appeared, that is, graphite powder pre-coated with external light was absorbed between the screen light powder dots or powder strips. This eliminates the need for smoky screen glass and improves light transmission (85%) and brightness. In the late 1970s, the red and blue phosphors were separately colored. The red powder was coated with a red pigment ( - Fe2O3) and the blue powder was coated with a blue pigment (Co · n Al2O3), thereby improving the contrast.

Kinescope mask

The shadow mask of the color tube is a color blocking mechanism. The three electron beams can pass through a small circular hole or strip hole on the shadow mask plate to hit the corresponding powder dots or noodles respectively. There are about 500,000 round holes on the 64 cm (25 inch) color tube mask, so there are 3 × 500,000 dots of phosphor on the phosphor screen.

Picture tube electron gun and deflection coil

In the color tube of the triangle-arranged electron gun, a complicated convergence system is needed to deflect the three beams together in a uniform magnetic field. Its role is to keep the three beams converging in the round holes or strip holes on the shadow mask at all times during scanning. Now common PIL tubes are self-converging and do not require complex adjustment systems. The three electron guns of this tube are arranged in a line and have an integrated structure, that is, the three guns are punched into a whole to ensure accuracy. In addition to the three guns closely aligned in line, it also relies on an uneven deflection magnetic field to complete the self-convergence. The vertical deflection magnetic field is barrel-shaped, and the horizontal deflection magnetic field is pincushion-shaped. In this way, when the three beams are deflected up and down or left and right, the force of the magnetic field can cause the three beams to converge.

Picture tube screen quality

As with black and white tubes, the color tube screen requires high brightness and image resolution, in addition to the chromaticity requirements. The brightness of the color tube refers to the white field brightness. Since the 1960s, the brightness of the white field has increased 14 times due to improved light-emitting materials, black screens and higher anode voltage. The improvement in contrast is mainly achieved through aluminized screens, black backgrounds, and colored phosphors. The development of new electron guns has improved the resolution of images. In terms of chromaticity, it is required that the color of each part of the image and the original object scene have no color distortion.

Picture tube technical parameters

The inspection of the picture tube is divided into routine inspection, technical parameter inspection, safety performance and work durability test.

Routine inspection of picture tubes

Including packaging and visual inspection:

Packaging inspection shall be in accordance with GB191-90 and SJ / T10916-96;

Appearance inspection: The glass tube of the picture tube should be complete without cracks and cracks. The screen glass should have no bubbles or scratches that affect viewing. The needle is complete and parallel to the neck of the tube.

Picture tube inspection

Chinese national standard GB3212-82GB / T5998-94 and GB5960-86 respectively specify 24 photoelectric parameter test methods for black and white picture tubes, and 26 color photoelectric tube test methods and main size inspections for color picture tubes. We put forward 18 main performance indicators and test methods in Table 6-9-49.

Table 6-9-49 Inspection of picture tube

Tube type

Parameter standard black and white color

GB / T321282 GB / T599894

Visual inspection in GB5960-86 3.3

Gas content coefficient 2.15 2.1

Cathode emission current 2.6 2.5

Cut-off voltage 2.9 2.8

Cut-off voltage ratio 2.9 2.8

Panel and screen defects in GB / T5998-94 2.10 2.10

Grating center displacement 2.19 2.15

Grating tilt 2.16

Misconvergence 2.22

Uniformity 2.22 2.23

Resolution 2.17 2.11

Focusing voltage 2.18 2.12

Hot wire current 2.3 SJ / T1108296

Japan completely discontinued crt (picture tube) televisions

Leakage current between hot wire and cathode 2.5.1 2.3.2

Each gate current 2.6 2.4.3

Parasitic emission 2.7 2.6

Flashover 2.8 2.7

Effective screen size 2.16 GB / T943588

Picture tube performance inspection

It consists of two parts:

Explosion-proof test of picture tube: According to GB2037-89.

X-ray radiation protection is in accordance with SJ2484-84.

Picture tube durability test

It shall be in accordance with 3.9.2 of GB5960-86.

Picture tube precautions

CRT products that implement the import safety and quality permit system, foreign production or operating enterprises must obtain the import safety and quality license issued by the State Entry-Exit Inspection and Quarantine Bureau and affix the corresponding mark on the product before importing.

Picture tube recycling technology

Panasonic Corporation of Japan announced on October 2, 2009 that the company has developed a fusion cutting and recycling technology for kinescopes using lasers. Compared with the traditional kinescope recycling technology, the new technology can more efficiently separate and recycle kinescopes.

According to a press release issued by Panasonic, because the new technology uses lasers, the average processing time of each picture tube during the processing is only 50 seconds, which makes the new technology's picture tube processing capacity 3 times that of traditional technology. The bulletin said that the purity of the screen tube and the funnel-shaped glass at the back is different, and it is necessary to separate the two at a certain place during recovery and ensure that the two glasses are not doped with each other. In the past, the cutting picture tube was surrounded by a metal wire around the joint portion of the two parts of the picture tube, and the metal wire was heated to separate the two parts. However, there are disadvantages to using this technique. One is that the metal wire needs a certain amount of time to heat, which affects the processing efficiency. The other is that the glass may be broken due to the thermal stress generated by local heating, which will cause the cutting position to be uneven and must be manually corrected. The new technology allows the laser's focus to always be focused on the glass surface, and adjusts the energy irradiated to the glass surface to achieve stable fusion cutting. The new technology can also automatically measure and determine the size of the picture tube to be processed, and select the appropriate laser intensity and cutting method according to the size for fully automated processing.