Video Signal Flow with Double Window
(Figure 14)
The XXPT91 versions of the H8 chassis have
the DOUBLE WINDOW panels. This allows
for both a single PIP window and a split
screen. Each Time the PIP On/Off button on
the remote is selected, the PIP window goes
from a small window to a large window and
then to a split screen. Composite Video and
YUV switching between the PIP panel and the
SSB is the same as the standard PIP. Two
other differences are the Histogram IC 7403
and the Gemstar module. The component
YUV input is routed through the Gemstar
module. If there is a Component input to the
set, such as the output of a DVD, it is
combined with the on-screen Gemstar
information in the Gemstar module and output
from the Gemstar module as RGB. The RGB
signal is then fed to the RGB/YUV switch in
7301. Another addition to this chassis version
is the Histogram IC, 7403. The Histogram cir-
cuit is a Contrast improvement circuit. The Y
or Luminance signal is divided into 5 discrete
histogram sections for processing. Each level
is adjusted to improve the overall contrast
level. The Blue Stretch circuit shifts colors
near white toward Blue to give a brighter
impression. The HIS-OFF is used to switch
the Histogram circuit On and Off.
Double Window Tuner and Video Switching
(Figure 15)
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 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 for
feedback to the SSB on Pin 15 or Video for
the PIP window on Pin 14. IC 7401 selects
Composite Video or Luminance (Y) from AV1,
AV2, or AV3. The other part of 7401 selects
Chroma from the rear Jack or the Side Jack
panel. These selections are fed to 7301
on Pins 24, 29, and 20. If Composite
Video is selected, it is fed to a YC
separator, then to a Delay Line and
Demodulator. If it is a 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.
Double Window Output (Figure 16)
The PIP or Double Window YUV signal is
fed to the PIP/DW processor, 7801. The
I2C buss controls the IC from the
Microprocessor on the SSB. The PIP/DW
processor outputs YUV for the PIP window
or Split Screen to the YUV switch 7803
where it is mixed with the YUV signal from
the SSB for the main picture. The Fast
Blanking line from 7801 on Pin 68 controls
the switch point in which the PIP window
or Split Screen is inserted. The SDA and
SCL lines are switched by the +3VD line.
The PIP processor is powered by the +3
volt supply. The +3.3 volt, +3 volt, and
+3VD volt supplies are produced by the
regulator 7802 which is driven by the +5VS
supply. This supply is switched On when
the PIP window is selected.
Double Window Control and Power Supply
(Figure 17)
The PIP/Double Window module is
controlled by the I2C buss through 7403 on
the PIP module. Pins 4, 5, 6, and 7
perform Video selection functions. Pin 10
produces a reset signal for the Guide Plus
module. Pin 12 controls the +5VS and
+8VS supplies.
Page 19
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