Theory Of Operation; B Board; Input Section - Decoder Section; Video Signal And Y/C Signal - Sony TRINITRON PVM-14L2 Service Manual

Section 5

Theory of Operation

5-1. B Board

1. Input section - Decoder section

Because the signal paths are different depending on the input signal, the respective signal path for each
input signal, are described below.

(1) Video signal and Y/C signal

The LINE A/B video signal that is selected by the VIDEO switch on the Q board, or the Y signal from
the Y/C input of LINE A connector, is input to the B board from CN103 pin-1, and then to IC104
(CXA2163AQ) pin-1. The C signal from the Y/C input of LINE A connector, is input to the B board from
CN103 pin-3, and then to IC104 pin-48.
When the VIDEO signal is input, the video signal that is input to IC104 pin-1 is output as it is from
IC104 pin-3, passes through the 20 MHz band-pass filter FL107 and is sent to the digital comb filter
IC111 pin-15 where the video signal is separated to the Y signal and the C signal. The Y signal is output
form IC111 pin-6 and the C signal is output from IC111 pin-8. Both of the Y and C signals pass thorough
the 20 MHz band-pass filters FL108/FL109 to remove the digital noise that is added during processing by
IC111, and are sent to IC104 pin-5/pin-7 respectively.
The Y and C signals from IC111, or the LINE A : Y and C signal of the Y/C input from the Q board, is
selected inside IC104 internally. The selected signal is decoded to Y, R-Y and B-Y signals.
The decoded Y, R-Y and B-Y signals, or the component signals (see (2)) that are directly input to IC104
pin-25, -26 and -27, are selected inside IC104 again internally. The selected signals are output from pin-
21 (Y), -22 (Cb) and -23 (Cr), and are sent to IC231 pin-3 (Y), -2 (Cb) and -1 (Cr)
(2) Component signal
The Y/G signal of the component signal that is supplied from the Q board, is input to CN104 pin-1, the
B-Y/B signal to CN104 pin-3 and the R-Y/R signal to CN104 pin-5 of the B board. On the other hand,
the Y/G signal of the component signal that is supplied from the option board, is input to CN101 pin-B12,
the B-Y/B signal to CN101 pin-B14 and the R-Y/R signal to CN101 pin-B16 of the B board respectively.
Either one of the above two component signals is selected by IC101 and routed to the main unit or to
option. The selected signals are sent to IC104 pin-31 (B-Y), -30 (Y) and -29 (R-Y). As described in
paragraph (1), they are selected inside IC104 and are output from pin-21 (Y), -22 (Cb) and -23 (Cr).
(3) OSD insertion
The OSD signals are output from pin-18 (G), -19 (R) and -20 (B) of IC452, buffered by IC109 and are
sent to pin3 of IC112 (G), IC113 (R) and IC114 (B). When the OSD signal is displayed, and when either
Video signal is input or Y/C signal is input or Component signal is input, only the OSD signal alone is
output from pin-7 of the respective ICs and are sent to pin-10 (R), -11 (G) and -12 (B) of IC231 respec-
tively. The OSD signal is superimposed on video signal and is output. When the OSD signal is input
while the RGB signal is being input, the signal processing of the OSD signal will be discussed in para-
graph (4).
(4) RGB input
The RGB input signals take the same input signal path as those of the Component input signals. After the
input circuit, the output signals from IC101 are buffered and clamped by IC115, Q113, Q114, Q115 and
Q116. They are sent to pin-1 of IC112 (G), IC113 (B) and IC114 (R) respectively. Because the OSD
signals are being input to pin-3 of these ICs, the OSD signal is super-imposed on the video signal during
OSD mode, and is output from the respective ICs. The output signals from these ICs are sent to pin-10
(R), pin-11 (G) and pin-12 (B) of IC231 respectively.
5-1
PVM-14L2/20L2