دارة AFC الأفقية بالعناصر الصلبة (Solid-Dtate) ١_a ..

​Horizontal AFC Solid-Date Circuit:

This circuit is similar to the fuse circuit used in the past. The phase detector diodes D2 and D1 are connected in opposite shapes (16-5) and they are inside one plastic cover. R502 R501 represents the output of the load circuit and with it the control voltage is generated - the resistance R500 and the capacitor C500 connect the negative synchronization pulses to the phase detector to form the reference frequency, to compare the frequency and the page of the oscillator, the capacitor C500 and the resistance R502 separate the vertical and horizontal synchronization pulses, and so they connect only the horizontal pulses to the AFC circuit and perform Capacitors and resistors C501 - R505 - C503 - C510 - by connecting the positive pulses from the horizontal output transformer - this pulse is repeated in the frequency of the oscillator - to the phase detector circuit to compare the frequency with the horizontal synchronization pulses. C504 - R504 - C502 - R503 - Forms horizontal AFC protection, this prevents any changes in AC from entering the horizontal oscillator circuit, which may cause instability of AFC

AFC work:

To explain the work of the AFC circuit, we start from the synchronization pulse separator circuit 21. Before the positive synchronous pulses reach its base, Q is in the cut-off state and has a large collector voltage. When C500 is connected to its collector, it charges to a value close to the supply voltage - when a positive synchronization pulse comes, 2 is connected and the collector voltage decreases

The capacitor C500 now discharges, connecting the synchronization pulse to the cathode ​ and D. This discharge voltage makes both diodes in the forward bias (D1 and D2), causing them to be connected simultaneously and equally, and currents of equal value and different in polarity pass through the two load resistors (R501 - R502 ) which leads to the formation of a drop in voltage on each of them equal to the other, and different in polarity so that one of them opposes the other - and the output voltage becomes zero - as it reaches from the deviation circuit to the circuit (D and D2) the sawtooth voltage through the capacitor C510 - if it is a wave Sawtooth in an elevator: not zero, when the synchronization pulse arrives, this indicates that there is a difference in the page between the horizontal oscillator and the synchronization pulses, and D connection: it will affect a wave from the saw on its elevator, so when the pulse ends and the C500 is recharged, the voltage generated on both ends of my resistance Pregnancy remains opposite, but not equal. That is, it is non-existent (zero) - and now the correction voltage is generated on C501 - applied to the oscillator to correct its frequency.​

Figure (4-16) shows the forms of waves D-C-B-A. Wave A and B indicate that the page matches between the oscillator and the synchronization pulses, and no correction voltage is generated via C501. As for the wave A and C, they indicate that the frequency of the oscillator is higher than the frequency of the synchronization pulses. And cause to connect the binary: more than D2. The voltage on both ends of the R501 is greater than the voltage on both ends of the R502. A negative correction voltage is generated across the C501, and this negative voltage reduces the frequency of the oscillator and returns it to matching in with the horizontal synchronization pulses. As for wave A and D, it turns out that there is a difference in the page and that the frequency of the oscillator is less than the frequency of the synchronization pulses - and the connection is less than D2, and it is The voltage on R501 is lower than on R502 - a positive voltage is generated across C501 - and this voltage now has the correct polarity to increase the frequency of the horizontal oscillator and bring it back into line with the sync pulses.

16-3 Horizontal oscillator circuit in Seronix TV (SR 270LS):

Figure (6-16) and (7-16) are used in this circuit. A multi-oscillator is part of the integrated circuit (TBA950) = (IC501). The composite visual signal with positive polarity enters the pole (7) in the integrated circuit, and the vertical synchronization pulses are separated. And it exits from pole (5) to the vertical deviation circuit via the base of the T451 transistor through the integration circuit C461 - C452 - R451 - As for the horizontal synchronization pulses, it enters the (AFC) circuit, which is the page difference detector - its page is set by controlling the resistance R542, and it comes out To the horizontal oscillator via pole (2) after it passes through a pulse modulator, which is a (Schmidt trigger), it makes regular square pulses, and reaches the resistance R546 connected with the diode D424 that is in the horizontal pulse amplification circuit and the horizontal synchronization pulses come out from the pole ( 10) for the integrated circuit and up to the base of the T581 transistor. Its work is to clear or extinguish the return line. The voltage of this circuit is (9) volts. The positive pole is connected to pole (3) and the ground is pole (1), and the horizontal deviation pulses enter the base of the transistor (T562) through the capacitor (C562). The transistor acts as a drive stage for the horizontal output transistor T563 - the amplified pulses are delivered to its base.