أشعة × الصادرة عن صمام الشاشة .. كتاب التلفزيون الملون والعادي

11- 5 x rays emanating from the screen valve:

Increasing the high voltage in the screen valve generates harmful rays on the human body called (X) or (Roentgen) rays. The amount of radiation is measured in Roentgen - and should not exceed
(0.5 milliroentgen / hour). It is measured at a distance of 5 cm from the surface of the television set - and it is the responsibility of the factory to adhere to these values ​​specified by international health organizations, and there is often a warning about the high voltage limits connected to the screen valve and not to exceed this voltage when performing adjustments and maintenance operations.

beam divergence angle:

The horizontal and vertical deflection coils move the beam to scan all points of the screen. If the angle of deviation is (114), this means that the ray emanating from the launcher deviates 57 to the right and 57 to the left. The angle of deviation is related to the screen size and neck length. The greater the angle of deviation, the shorter the neck of the suitable screen, and this is what is better and saves in the thickness of the box of the device, in exchange for the necessity of having stronger and larger deviation files. The neck of the screen has a smaller diameter to surround the beam with a smaller distance.

Example specifications of a 25-inch color LED screen:

Diagonal angle 100

The horizontal angle is 86

The vertical angle is 67

Example: Deflection angle relationship with neck length in color screen valve:

Deflection angle 70 Screen neck diameter 2 inches = 5.08 cm

Deflection angle 90 Screen neck diameter 1 inch = 3.63 cm

Deflection angle 100 - 114 Screen neck diameter 1 inch = 1 inch = 2.9 cm 16

Screen Surface Dimensions:

It is known that the screen measurement is the diagonal dimension. It is usually measured in inches or centimeters, and the length of the screen = 2/3 of its height.

Screen valve base:

There are a large number of models of screen valve base electrodes. In monochromatic television, the number of poles at its base ranges from 8 to 12 poles, while in color TV the number of poles ranges from 13 to 14 poles. Figure (11-17) It is not possible to determine the connection of each pole and its work except by referring to the device diagram. The poles are often fed through a printed board carrying some elements such as transistors, fixed resistors, tuning resistors, etc. - The elevator that feeds the high voltage is connected through the high voltage cable to a carrier slot behind the interface of the screen.
An example of the distribution and function of the poles of a Seronix color TV screen - German design / 27 inch

Pole 1-6 heating filament

Pole 13 - 2 - 4 The cathodes are red - green - blue, respectively


Pole 3 - 14 - 12 The governing networks of the three launchers

Pole 5 - 7 - 11 the second nets of the three launchers

Pole 9 last grid

Feeding the elevator behind the front of the screen with rectified voltage (25 kV). Figure (11-18) and (11)- (19) illustrate the technical information for a black and white screen and a color screen.

11-6 Color reproduction in the screen:

The generation of colors is controlled by two main factors:
1- The phosphorescent blobs that are hit by the beam by one of the three launchers.

2- The number of electrons in each beam. If one of the three rays is interrupted, the effect of the remaining two rays remains. If the beam that stimulates the red phosphorous dots is interrupted, the color turquoise (CYAN) or (bluish-green) will appear on the screen, depending on the intensity of each ray.

Thus, the color (purple) (magneta) appears when the green-induced beam is interrupted. The color close to (yellow) appears when the blue-induced ray is interrupted.

It is known that the phosphorescent dots have a color close to white when they are not exposed to the rays of the bombers

We have mentioned that the number of trichromatic phosphorous granules (distributed in a triangle or a line) reaches 400,000 trichromatic ones. The holes in the mask or its narrow openings in the form of slits or a grid determine the passage of the rays towards the specified points in the specified phosphorescent points. The process of static and dynamic matching is carried out with the aim of aiming the rays towards the specified points in the center and sides of the screen, as we will explain later.