Bi Board - Sony TRINITRON PVM-14L5 Service Manual

5-2. BI Board

1. Y/C Separator Circuit
1-1. NTSC/PAL mode
The composite input signal that is input through the Q board is band-width limited by FL801, amplified
by Q803/Q804, passed through the digital comb filter (IC801 pin-25) so that it is separated to the Y signal
and the chroma signal. Since IC801 uses the digital output, the input signal is converted from digital to
analog in IC802. The Y signal passes through FL804 where the signal components of the unwanted
bandwidth are removed, and is output after passing through the amplifier (Q812, Q813), switch circuit
(IC804, IC804, and IC805) and the Y-level adjustment amplifier (IC806). The chroma signal passes
through FL2801 where the signal components of the unwanted bandwidth are removed, and is sent to the
chroma decoder circuit (IC2804) after passing through the amplifier (Q2803, Q2804) and the switch
circuit (IC2803).
1-2. SECAM mode
The composite input signal is bandwidth limited by FL801, amplified by Q803/Q804 and passes through
the chroma trap (FL802, FL803) where chroma signal component is removed. The Y signal is output after
passing through the switch circuit (IC803, IC804, and IC805) and the Y-level adjustment amplifier
(IC806).
2. Sync Separator and AFC Circuit
The sync signal is separated from the composite input signal by IC2801. The VD signal and the HD
signal whose frequency is stabilized by the AFC circuit are generated. At the same time, the sync signal is
separated from the Y input signal by IC2806. The SYNC signal and the AFC P signal whose frequency is
stabilized by the AFC circuit are generated.
3. Generation of HP and CLP
The HD signal triggers the one shot multi-vibrator (IC2802) that generates the CLP signal for IC801, and
the HP signal and the CLP signal for the SECAM decoder. The HP voltage (IC2805) sets the CLP voltage
(IC2805) sets pulse width of the CLP signal and the pulse width of the HP signal.
4. NTSC/PAL Decoder Circuit
The chroma signal that is output from the Y/C separator circuit, passes through Q2809 and is input to pin-
5 of IC2804 via the phase shift circuit (Q2811, Q2812). The ACC PHASE voltage (IC4803) sets amount
of phase shift of this circuit. The chroma signal takes the two paths at IC2804. One signal is output to pin-
3 via ACC circuit and the other path is input to the APC circuit via the TINT circuit, that controls VCXO
(X2802 : NTSC, X2801 : PAL) at pin-11/-13. The ACC level is set by the ACC LEV voltage (IC4803) at
pin-4. The PHASE voltage (IC4803) and the SUB PHASE voltage (IC4803) at pin-12 set the oscillating
phase of VCXO. The F0 voltage (IC4803) sets the free running frequency of VCXO. The chroma signal
output from the ACC circuit takes the two signal paths. One is the R-Y signal system and other is the B-U
signal system. The chroma signal that is input to the R-Y signal system is input to IC2804 pin-19 via the
phase shift circuit (Q3801, Q3802), where the chroma signal is decoded to the R-Y signal and is output
from pin-23. The R-Y PHASE voltage (IC4803) sets amount of phase shift. The chroma signal that is
input to the B-Y signal system is input to IC2804 pin-15 via the phase shift circuit (Q3803, Q3804),
where the chroma signal is decoded to the B-Y signal and is output from pin-22.
5. NTSC Low-pass Filter
The R-Y signal that is output from IC2804 pin-23 passes through the active low-pass filter (Q3809 to
Q3812) and is output via the switch circuit (IC3804, IC3806) and the level adjustment circuit (IC3807).
The B-Y signal takes the equivalent circuit.
5-3
PVM-14L5/20L5/D14L5A/D20L5A