Sony TVP-08, Руководство по обучению

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41
Input Switching
Overview
The two tuners’ video outputs, along with all video signals that enter the
unit except the Video 5 component input, are input to IC515 A/V Switch.
In accordance with commands received from IC1008 Main CPU, IC515
A/V Switch switches these video signals to three different paths. The first
is the main video path, second is the sub video path and third is the select
output.
Inputs
The five video inputs each have separate composite and S Video inputs
and all are contained in one package as shown by J505 in the related
drawing. Each package also contains left and right audio inputs. All of
these jacks input to IC515 A/V Switch where they are switched to the
appropriate parts of the circuit by I²C data from IC1008 Main CPU (not
shown).
IC515 A/V Switch is able to determine if the S video input is being used
because of an internal switch in the S video jack. This switch is con-
nected to a voltage divider that is connected to the S Switch input for each
of the 5-video inputs. If there were an S video source connected, then the
S SW input would be LOW. This causes the internal switch in IC515 A/V
Switch to allow the S video input to be passed to the Y and C outputs. If
there is nothing plugged in to the S video jack, the voltage on the S Switch
line will be 2.5 volts. The operation of the Video 5 circuit is somewhat
different because it also has component video input. There is a switch on
the Pr input that goes to an additional circuit that places five volts on the S
switch line. No video will pass to the Y and C outputs when a cable is
plugged in to the Pr input. This will be discussed further in the YUV
Switch section.
In addition to the 5-video inputs, there are also two tuner inputs. These
tuners are all the same type so that this set may have the audio swap
function when using PIP features. The sub tuner will never produce the
main picture. If a picture swap takes place when using PIP, the tuners will
be re-tuned. The main and sub tuner’s video signals each pass through
identical buffers before being input to IC515 A/V Switch. In addition, au-
dio is input to IC515 A/V Switch from each tuner. The tuners are not re-
tuned for the audio swap function.
Outputs
Main Video
IC1008 Main CPU determines what input will be switched to each output
by interpreting the customer’s input and sending commands to IC515 A/V
Switch for proper execution.
Regardless of which input is selected for the main picture, it will follow the
following path: The composite video or Y signal will be output from IC515/
38 V Out 1 to Q533 Buffer. It is then input to IC515/49 Y In and switched
through IC515 A/V Switch to be output at IC515/56 Y Out. The main
composite or Y signal is then sent to the main Y buffer before being input
to IC1309. IC1309 is an A/D Converter that will digitize the composite or
Y signal for input to the 3D Comb Filter.
If an S video input is selected, then the C signal will be output at IC515/58
C Out. It is input to the main C buffer before being input to IC1306/96.
IC1306 is the 3D Comb Filter.
Sub Video
If a composite sub video input is selected, it is output at IC515/42 Sub V
Out and then sent to CM501/4 Glass Comb Filter. CM501 Glass Comb
Filter is used to separate the Y signal from the chroma in the composite
sub video signal. The Y signal is output CM501/1 and input to IC515/38
Sub Y In. The composite signal is also input to the base of Q548, which
uses L523 and C643 and C639 to filter out the 3.58 MHz chroma signal.
The signal is then input to IC515/40 Sub C In. The sub Y and C signals
are output from IC515/45 and 47 respectively. If an S video signal is
input, the signals will be output directly at IC515/45 and 47.
Select Out
The select out outputs one of the input signals as composite video from
IC515/34, along with audio from IC515/34 and 36. The selected output is
determined using the setup menu. These signals leave the set at J502.