Switching Process; Sensing And Priorities - Zenith H19F34DT Series Service Manual

SWITCHING PROCESS

Video switching is done between the CV inputs and the
Y/C inputs. There are three CV signals to consider:
CAMPORT VIDEO enters at pin 7 of IC2901.
REAR VIDEO enters at pin 5 of IC2901.
IF Video enters at TV pin 12 of IC2901.
These signals exit from VOUT1 (pin 11) to be processed
and returned to the switch as Y/C signals (Y-COMB and
IC2902).
The second part of the switching is between:
Y/C COMB signals enter at pins 10 and 7 of IC2902 and
Y/C EXT signals entering at pins 12 & 5 of IC2902.
The selected Y/C signals exit from pins 11 & 8 to be
sent to the video processor as main signals.
ICM2200
M61250FP
Tuner
VIDEO OUT
63
IF
PIFIN
SAW Filter
64
FSC 29
2
SCL
26
27 SDA
C-IN
Y-IN
14 ROUT
To
Video
GOUT
15
Output
Board
16
BOUT
YSW-OUT
FBLNK
ROSD
GOSD
BOSD
"CAMPORT" JK PK inputs
V R L
"REAR" JK PK inputs
V
R
L
SR25-3828VD0171B
SERVICE ADJUSTMENTS (continued)
VIDEO PROCESSING & SWITCHING WITH Y/C INPUT
Main Board
IC2400
Audio
COMB FILTER
58
Trap
C-MAIN
38
Y-MAIN
41
Y-Main for MICRO
31
24
Micro
Processor
25
26
27
Video Sense Line
Close caption is achieved by taking a signal from the
YSW-OUT pin (31) of the video processor.

SENSING AND PRIORITIES

CL-Series 34 & 39 models do not have a source menu.
Software sensing the inputs based on their priorities
does switching between sources.
The camport input always has first priority, it is sensed
directly through the microprocessor. The S-Video input
has the second level. The Y/C connector does the S-
Video sensing. The third level corresponds to rear video
and antenna signal (RF), they would be selected by
remote control.
TC90 A45P
IC2902
5
8
7
10
11
12
9
5
7
8
IC2901
3-5
BPF
3.58
TRAP
3.58
Y/C IN
Y
EXIT
C
EXIT
YC SENSE LINE
CL - SERVICING