Sony UP-980 - 4-1. VIDEO CIRCUIT

4-1. VIDEO CIRCUIT
4-1-1. Input Trap Filter Circuit, CCSYNC Process Circuit
The composite video signal is inputted to MA-91 board from BNC connector (CN1-VIDEO IN). 75 ohm termination is
controlled by system control (IC505) using relay (RY!) according to setting of menu. After that, it is divided three signal
systems, high scan signal for (fH=31.5 kHz), normal scan signal for (fH=15.75 kHz) and for C-SYNC processing via input
buffer. For high scan signal is not processed and sent it to the video amplifier 2. And for normal scan signal is passed
through the buffer and divided more three systems, the signal passed through trap filter (FL1) for NTSC, the signal passed
through trap filter (FL2) for PAL, no processed signal is inputted to the analog switch (ICI pins 1, 3 and 5). Selection of
signal is performed by system control (IC505) and inputted to the video amplifier 1 (1C2). C-SYNC processing signal is
extracted the sync signal from the composite signal by the transistor Q10 and IC3.
4-1-2. Sharpness and AGC Circuit
The signal from analog switch (IC1) is divided two systems, one is inputted to the video amplifier | (IC2 pins 15 and 16),
another is inputted to the peak detection circuit for AGC. Sharpness is switched Soft and Hard by changing the voltage that
is inputted to the video amplifier 1 (C2 pin 13). The voltage is switched by analog switch (IC5) and controlled by system
control (IC505). AGC is performed by using contrast amplifier in the video amplifier 1 (IC2). When setting AGC to ON,
the voltage is peak voltage of input video signal that is obtained by peak detection circuit (Q13, Q14, IC 4), when setting
AGC to OFF, the reference voltage is outputted from analog switch (ICS) by controlling system control ([C505), both
voltages are fed back to video amplifier 1 (IC2 pin 11) and controls gain of amplifier. C-SYNC signal for AGC circuit is
used the signal outputted from video amplifier 1 (IC2 pin 3).
Peak Detection Circuit
CLAMP
PULSE
GENERATOR
PEDESTAL INTEGRATION
CLAMP CIRCUIT
GAIN ADJUSTMENT
4-1-3. Brightness, Contrast Control and A/D Conversion
The signal from video amplifier 1 (IC2 pin 10) via low pass filter (Q6, Q7) and the nothing processed signal for high scan
are inputted to relay (RY2). This relay is controlled by system control. This relay selects high scan or normal scan signal
and it is inputted to the video amplifier 2 (IC6 pin 16). In video amplifier 2, amplitude of input video signal according to
the value of BRIGHTNESS or CONTRAST in the menu item of front section is adjusted. That method is, key controller
(IC20 1) make the voltage (IC203 pins 10 and 11) that is corresponded each setting value by D/A converter (C203). Its
voltage is inputted to the video amplifier 2 (IC6 pins 4 and 6) and its amplitude and etc. are changed. After that, the video
signal (1C6 pin 9) adjusted at video amplifier 2 is converted digital signal at A/D converter (IC7, 8) and stored the memory.
4-4 UP-980(UC)
UP-980CE(CE)