Sony KP 48S70, Training Manual

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13
Video Processing
Overview
The following section covers the video processing section of the RA-3
chassis. This drawing on the following page is a simplified schematic
from the KP-53V80. It is nearly identical to the schematic for the S mod-
els.
This circuit creates main picture RGB signals from either the Y and C
signals from a composite, S video or tuner input, or YUV inputs from the
main component video path. It also combines the PIP with the main pic-
ture if PIP is selected.
YUV Controller
IC1407 YUV Controller has three functions. They are:
ƒ
Switch the appropriate external YUV input to the YCJ.
ƒ
Switch the Main Y input to the TV out line for processing by the YCJ.
ƒ
Adjust the sub color and sub hue of the U and V signals.
There are two sets of YUV inputs to IC1407 YUV Controller. They are
from IC1405 PIP Controller and from the component video (DVD) inputs.
The PIP inputs at IC1407/1, 3 and 2 are selected when the signal from
IC1409/1 Full DVD is HIGH, allowing the signal from IC1405/93 DFB to
control the switching at IC1407/6 YUV SW. When the output from IC1409/
1 Full DVD is LOW, it disables the signal from IC1405/93 DFB. This
places a low on IC1407/6 and the inputs at pins 21, 22 and 23 are se-
lected. The selected signal is output from IC1407/8, 9 and 10.
The Main Y input is from either a composite/S video input or a component
input. This signal is input to IC1407/23 DVD Y and IC1407/19 TV In. If
the main Y is from a composite/S video input, then the TV Out signal will
be used for the main picture and for sync at the YCJ. If the main Y signal
input to IC1407 YUV Controller is from the component input, it will be
used by the YCJ for sync only. The Y Out at IC1407/8 would be used for
the picture.
The inputs at IC1407/16 Color and IC1407/17 Hue are DC voltages that
control the level of Sub Color and Sub Hue for the PIP picture. These
voltage levels were preset at the factory and should
not need adjustment.
However, if necessary they can be changed by adjusting UVSC (Color)
and UVSH (Hue) in the service mode.
YCJ
Here we will be discussing the following three functions of IC206 YCJ:
ƒ
Process the Main Y and C input and output them as RGB.
ƒ
Process the YUV inputs from IC1407 YUV Controller and output RGB
signals for either a full picture from a component video input or a child
picture from a PIP input.
ƒ
Output an FSC signal to be used as a reference by the comb filter.
The main Y and C signals are input to IC206 YCJ at pins 63 and 64
respectively. The C signal is demodulated to its color difference signals
B-Y (U) and R-Y (V). These YUV signals are referred to as “internal”.
These internal YUV signals developed from the Y and C inputs then go to
a switch controlled from the input at IC206/5 YUV SW. This line switches
the internal YUV or the external YUV from the YUV Controller onto the
next stage of processing. If the external YUV inputs at IC206/7, 8 and 10
originated from a component video input, IC206/5 would be two volts and
a Full DVD picture will be displayed. If the external input were from the
PIP, there would be a waveform present at IC206/5. This would insert
these inputs into the main picture to be output from IC206/20, 24 and 26
as RGB. Q220, Q219 and Q218 buffer these signals. After buffering,
these signals are output to the CG board via CN204. The R and B out-
puts will be routed to their C board from the CG board.
IC206 YCJ outputs a 3.58 MHz signal at pin 57. It is created using X202.
This signal is used as a clock by the 3D Comb Filter in V models.