Sharp DV-5145, Service Manual

Page: 8 / 32

1. Outline of
PAL signal demodulation and R/G/B matrix output
2) White peak limiter control circuit
3) R/G/B mixing circuit included
4) Sand castle pulse processor
2. Pins arrangement
Figure 5.
3. Circuitry behaviors
Pin 12V power supply
Pin Generation of ACC detector control voltage
(generation of killer on/off control voltage)
Pin Chroma input
Pin Reference voltage for ACC detector
Pin ACC control voltage
The peak detector ACC works to detect the
voltage which is proportional to the burst signal
level.
Pin Colour saturation control
Pin Contrast control
Pin Sand castle puise input
The sand castle pulse is divided into two pulses;
the first pulse is set at
DC and used for
blanking of the output signal, and the
second pulse is set at DC and used for
black level clamping and burst keying.
Pin Video data switching
Switching between R/G/B input and video input
is performed:
input at High level, video
input at Low level.
Pin Luminance signal input
Pin Brightness control
Pin Red output
Pin Input of external red
Pin Green output
Pin Input of external green
Pin Blue output
Pin Input of external blue
Pin
Pin
Pin Black level clamping (only with R/G/B signal
input) to provide the same black level in both
R/G/B input mode and video mode.
Pin B-Y input demodulator
Pin R-Y input demodulator
Pin Burst phase detector output
Pin These are used to compare the burst gate
signal with the reference signal coming from
the reference oscillator, so that the resultant
signal in applied to the external low pass filter
(R804, C818) to produce a phase control vol-
tage.
Pin
Pin Reference oscillator
8.86 MHz of the reference oscillator is halved
to be 4.43 MHz (this makes esier a 90” phase
shift operation).
Pin Ground
Pin Chroma output