DAEWOO DVF24S_44S
Manual de Servicio

B. Signal flow of the PAL colour in the record mode
Video input
(5.06±4.43) MHz

2

Video AGC

BPF

4.43MHz

ACC AMP

4.43MHz

MAIN CONV

IMHz LPF

O
5.06MHz 627KHz

To. PREAMP 2Head: Pin & of LA7411 4Head: Pin ) of LA7416

u

Killer

I
BLOCK 2. PAL COLOUR SIGNAL FLOW A recording composite video signal is fed to the AGC circuit from Pin 12 of IC301, and its output signal is passed through a BPF (Band Pass Filter) to eliminate the luminance components, and then only the colour signal is fed to the ACC (Auto Colour Controller) amplifier. The gain of the ACC amplifier is controlled by the DC voltage at Pin 41 of IC301. The signal from ACC AMP is fed to the Main Converter to transfer 4.43MHz to 627KHz. That is, the summation and substraction of the two input signal frequencies are obtained from this Main Converter. Here, the two input signal frequencies are 4.43MHz and 5.06MHz. The output frequencies from the Main Converter are approximately 627KHz and 9.49MHz. The output from the Main Converter is fed to the killer circuit through the LPF. The LPF is used to eliminate unwanted frequencies (ie: 9.49MHz). The Killer detector gives a reliable operation thanks to the application of both systems i.e. synchronized detection (APC Killer) and the Peak detection (ACC Killer) in the record mode. The signal is obtained from Pin 38 of IC301 as the recording colour signal. The output signal from Pin 38 of IC301 is fed to the PREAMP IC (2 Head: Pin 7 of LA7411, 4 Head: Pin 10 of LA7416). C. Signal flow of the luminance in the playback mode The playback Y-FM from the PREAMP (approximately 60dB amplification) is fed to the PB EQ circuit to perform frequencylimiting and phase compensation. The output signal from the PB EQ circuit is input to Pin 1 of IC301 and then this signal is passed through the FM-AGC so that the signal level is kept constant. The output signal is fed to a Double Limiter. The Double Limiter's function is as follows: As the high frequency components of the playback Y-FM signal are deteriorated due to the characteristics of the TapeHead system, Y-FM signal (black spike) effect may be seen in the playback picture, and the Double Limiter is used to compensate for this. The signal from the Double Limiter is fed to an FM Demodulator. This demodulated video signal is passed through the LPF and the emphasized high frequency component from the Main Emphasis is de-emphasized. The signal from the Main DEemphasis is fed to pin 4 of IC301.

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