Zenith H19F34DT Series, Service Manual

Page: 34 / 62

SR25-3828VD0171B
3-5
CL - SERVICING
SERVICE ADJUSTMENTS (continued)
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.
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.
VIDEO PROCESSING & SWITCHING WITH Y/C INPUT
63
64
26
27
14
15
16
ICM2200
M61250FP
58 VIDEO OUT
“CAMPORT” JK PK inputs
V R L
“REAR” JK PK inputs
C-IN
Y-IN
YSW-OUT
FBLNK
ROSD
GOSD
BOSD
31
24
25
26
27
Audio
Trap
Y-Main for MICRO
Micro
Processor
IC2902
8
11
5
7
12
10
5
IC2400
COMB FILTER
TRAP
3.58
BPF
3.58
Y
EXIT
C
EXIT
YC SENSE LINE
Y/C IN
SCL
SDA
ROUT
GOUT
BOUT
PIFIN
Video Sense Line
C-MAIN
Y-MAIN
Main Board
V
R
L
Tuner
IF
SAW Filter
2
To
Video
Output
Board
FSC 29
TC90 A45P
7
38
41
9
8
IC2901