31
Video Path 24” and Under
Overview
The following section will discuss the video path for 24” and under BA-5
chassis models. These models have two sets of video inputs and a tuner
input. The rear jack may also have an S Video input. These signals are
routed through the video switch to the YCJ, then to the Comb Filter if
necessary, back through the YCJ, and then output as RGB.
Switching
The composite video signals from the rear jack J201, the front jack J202
and the tuner are all input to IC1304 Video Switch. IC1304 has two inputs
that are used to control the switching. These inputs are V0 and V1 at
IC1304/2 and 4. The input to these pins comes from IC1001 Control
Tuning System at pins 10 and 11. The following table shows the voltage
level at these pins for different input selections:
Input
IC1304/2 V0
IC1304/4 V1
Tuner
0 Volts
0 Volts
Video 1
3.3 Volts
0 Volts
Video 2
0 Volts
3.3 Volts
Whichever input is selected will be output from IC1304/7 and then input to
IC1301/41.
The separate Y and C signals from the S video jack are input directly to
IC1301/2 and 4. If the input chosen is composite video, that signal will be
switched through the YCJ and output at pin 6. Pin 6 is the monitor out line
and would have the Y signal present at its output if an S video source
were chosen. This signal will be used by IC1001 Control Tuning System
for V Chip and Closed Captioning, and by IC1302 Digital Comb Filter.
Digital Comb Filter
The Digital Comb Filter is used when composite video inputs are used.
The composite video signal output at IC1301/6 is buffered and filtered by
Q1311, Q1312, FL1301 and Q1310. You should note that the chroma
signal has a very low amplitude at FL1303. The signal is then input to
IC1302/14 A In. There is also a 3.58 MHz clock signal output at IC1301/
43 FSC and input to IC1302/13. This signal is used by IC1302 Digital
Comb Filter for timing. The Digital Comb Filter has separate Y and C
outputs at pins 20 and 17, respectively. These signals are both buffered
and filtered before being re-input to IC1301 at pins 9 and 7.
Y/C Processing
The YCJ selects which Y and C signal to use for processing. If S video is
selected then the inputs at pins 2 and 4 are used. If composite video is
selected, the inputs at pin 7 and 9 are chosen. Whichever input is cho-
sen, the Y and C signals will be used to create the RGB outputs of IC1301.
These signals will eventually be sent to the tube cathodes.
The YCJ also contains an input for IK to control AKB. The YCJ samples
this signal and determines if each color’s cathode is drawing adequate
current. If the YCJ determines that there is a problem with the IK loop,
video will be blanked. IC1301 YCJ communicates this to IC1001 Control
Tuning System through the I²C bus. This IC will then flash the Standby/
Timer LED in sequences of five to indicate an IK problem.
Summary of Contents for FD TRINITRON WEGA KV-13FM12
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