Circuit Descriptions, List of Abbreviations, and IC Data Sheets
9.
9.3.7
Sound Trap Switching
Figure 9-14 Sound trap switching circuit
Composite video is output on pin 10 of 7323 and buffered by
transistor 7411. The signal is then applied to the 5.5 MHz trap,
1406. In the PAL/SECAM mode, the LMN line is Low, switching
transistor 7407 "on", causing the signal to bypass 1407, the 4.5
MHz filter. The video is then buffered by transistor 7322 before
being applied to pin 14 of 7323.
In the NTSC mode, the LMN line goes "high" and transistor
7406 turns "on", switching the 4.5 MHz SAW filter "on".
Transistor 7407 is turned "off".
9.3.8
1fH Component Buffer Amplifiers
Figure 9-15 Component (YPbPr) buffers
The Y signal is buffered by transistors 7800 and 7801. This is
an impedance matching and YPbPr to YUV circuit. This circuit
does not invert the signal. The Pb signal is amplified by 7802
and buffered by 7803. The Pr signal is amplified by 7804 and
buffered by 7805. The Pb and Pr signals are inverted.
9.3.9
Double Window PIP
Figure 9-16 DW/PIP input
The PIP/Double Window panel allows for both a standard PIP
window and a split screen. The PIP/Double Window module
has a separate Tuner, SAW filter, and Signal Processor. The
line labelled Reset drives transistor 7332, which switches pin
10 of 1352, to select between PAL/SECAM and NTSC. The
output of the Signal Processor, 7301, on pin 16 is fed to
switching IC 7402, which selects between the PIP Tuner and
composite Video from the SSB. Selected composite Video for
the main picture is output on pin 15 of 7402 and is fed to the
SSB. Selected composite Video for the PIP window is output
on pin 14 and is buffered by 7421. It is fed to 1334, a 5.5 MHz
Trap. It is then buffered by transistor 7331 before being fed to
pin 24, which selects between the selected Tuner Video or
selected composite Video from the SSM. composite Video is
fed to an YC separator, then to a Delay Line and Demodulator.
If it is an YC signal, it bypasses the YC separator. The YUV
signal is then fed to the YUV switch, which selects between the
output of the Delay Line and Demodulator, and external YUV
from the Large Signal Board. The YUV (SY, SU, and SV) is
output to the PIP processor IC. Selected composite Video is
fed to the V-chip processor. V-chip processing for the main
picture is done by the microprocessor on the SSB.
9.3.10
Double Window Output
Figure 9-17 DW/PIP output
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