قاتل اللون (Colour Killer) .. كتاب التلفزيون الملون والعادي

10-20 Color Killer:

Figure (20-27) This circuit works to stop the color amplification circuits working during the black and white mono transmission. This is to prevent any trace of fake colors from reaching the detection circuits or the screen - and the color killer circuit is made automatically - in the circuit we find that the signal (7.8 kilohertz) comes from the co-radiator circuit to the binary D and this signal is then filtered in circuit (B A positive voltage (7.5) volts is generated from the rectification process, which feeds the resistance R6 of the color amplifier and provides the necessary bias voltage for this amplifier. The diode D2 and resistors (3) (R) determine the value of the voltage connected to the base of the color amplifier. When transmitting in black and white, there is no signal to the subcarrier so no output voltage is produced from the diode: nor is there any bias voltage on the base of the color amplifier. This amplifier is closed permanently and does not allow any signal of noise or interference to pass through to the color amplifier, so it appears as fake colors called (Cross Color). It should be noted that the color amplifier does not give any output until the crystal local oscillator becomes the same page as the transmitted oscillator, because the frequency of 7.8 kHz does not appear finally unless this condition is guaranteed. In the case of the (BAL) system, the burst signal is sent with 10 cycles from the sub-carrier and installed on the back threshold of each line on the image in the figure - at the entrance of the decoder circuit (waveform 1), and the face of the burst changes at a scanning rate of 45 Lagging behind the BY signal selector, i.e. at an angle of 135 to an angle of 545 prior to the B-Y axis.

20-16 Barst Suppression circuit in PAL system:

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ in infographics, in Figure 20-28 to the base of the detector transistor VT13, the color signal from the collector of VT11 transistor VT11 to the base of the detector transistor VT13 is shorted by capacitor C40 when A positive pulse (wave 3) of the line pulse is placed below VT12. Thus, the burst quenching occurs at this point in the circuit.
17-20 Automatic color control circuit ACC:

It is a circuit found in some types of encoding analyzers - it gives a kind of AGC to the color amplifiers - and the amplitude of the color signal depends on the lighting condition in the instrument room - as well as on both fine tuning and gain adjustment in the TV set. It is necessary to adjust the appropriate ratio between color and luminance, and thus adjust Correct saturation - Also feed a fixed amplitude of the burst to the auxiliary carrier oscilloscope to ensure constant synchronization. The amplitude of the color signal depends on the saturation of the imaged color and therefore it is not appropriate to subject it to automatic color control. And with the burst (BURST) transmission (which is equal to the amplitude of the (sync) pulse, but it will change with the change of fine tuning and other conditions. The measurement of the amplitude of the burst may be the appropriate reference voltage for adjusting the gain of the color phases. Figure (20-29) shows the automatic color adjustment circuit.

The resulting DC negative voltage reduces the bias given to the base of the transistor (VT11) by controlling the level (ACC) and the resistance (R48). And it corrects (VT11) to extract the color signal from the image signal that it detected, and feeds it to the splash gate and color amplifiers in the coding analyzer stage, and the resistance VDR: (21) prevents the ACC voltage from increasing significantly in the absence of the splash, and such a rise makes the transistor (VT11) operate in The direction of the forward gain, or in other words: the highest voltage on the base gives the lowest voltage on the collector, and therefore the lowest gain, and this will give a steady state, and the color signal will not pass through the transistor (VT11).

The z1 can be thought of as having a dual-clamp function in an ACC circuit. The correct setting of the ACC level control depends on the design of the device. And each type has a special method for this adjustment, and if the adjustment is too low, it gives unsaturated colors, or it may lose color completely.