Daewoo DV-K882SY-AN, Service Manual

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13
2. Signal flow of the PAL colour in the record mode
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).
3. Signal flow of the luminance in the playback mode
The play-back Y-FM from the PREAMP (approximately 60dB amplification) is fed to the PB EQ circuit to perform frequency-
limiting 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 play-back Y-FM signal are deteriorated due to the characteristics of the Tape-
Head system, Y-FM signal (black spike) effect in the play-back picture, and the Double Limited 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 emphasizied high frequency component from the Main Emphasis is de-emphasized. The signal from the Main DE-
emphasis is fed to pin 4 of IC301.
Video input
2
Video
AGC
BPF
ACC
AMP MAIN
CONV
IMHz
LPF
Killer
4.43MHz 4.43MHz
(5.06±4.43)
MHz
5.06MHz
O
u
I
To. PREAMP
2Head: Pin
&
of LA7411
4Head: Pin
)
of LA7416
BLOCK 2. PAL COLOR SIGNAL FLOW
627KHz