Samsung SV-DVD50 Service Manual page 142

Circuit Operating Descriptions
7-10 SECAM
(1) REC Mode
12
16
Fig. 7-36 Signal flow in REC mode
Video signals which input to Pin 16, pass 4.3MHz BPF, unnecessary component (ex : sync signal) is removed, and
take component of chroma signal. And to be flat the characteristics when it is sending by REC-BELL circuit.
This REC-BELL circuit is automatically adjusted to be 4.286MHz for center frequency. After that,the pulse width is
limited by limiter amplifier pass the 1/4 divided circuit and converted to 1/4 for chroma signal frequency. As for
converted signal, the noise of non-signal parts of sync signal is amplified by limiter amplifier, in order to be
remove components of the sync signal generates by sync gate circuit. Also this signal is squarewave, and contains
unnecessary components, at first, through 1.1MHz BPF and nextinput to REQ-EQ. REC-EQ has the same
characteristics of BELL characteristics, automaticallyadjust to be 1.0715MHz for center frequency. Afterwards,
unnecessary components around the sync signal are muted, low chroma signal is output to Pin 18 after through
Buffer. This mute circuit also has the function of remove unnecessary component during vertical sync signal and
output control owing to Pin 1.
(2) PB Mode
14 18
Fig. 7-37 Signal flow in PB mode
The signal which input from Pin 14, at first enter AGC amplifier and adjust for lever. Gain of this AGC amplifier
is controlled to be fixed the 4fsc clock generator with PLL circuit of output level(VM) which shows below. Thus,
pass the 1.1MHz BPF, remove unnecessary components, input to PB-EQ which has 1.1MHz Anti-BELL
characteristic. This center frequency of PB equalizer, automatically adjusted to be 1.0715MHz. Next, enter 4fsc
clock generator with PLL circuit. +4.3MHz BPF remove unnecessary, component of frequency generate in 2fsc
clock generator owing to limiter amplifier are cleaned by performance of sync gate circuit. This signal has a
rectangle waveform, for contain unnecessary components of frequency, due to through 4.3MHz BPF, next input to
PB-BELL. PB-BELL automatically adjust to 4.286MHz of center frequency, and return to BELL characteristics when
it is sending.
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