Mitsubishi Electric HITACHI VS-50111 Troubleshooting Manual page 40

V20 Chassis Technical Training
and Troubleshooting Guide
Sync Signal Path
Figure 1 illustrates the Sync Signal Path for both the
Main and Sub Picture signals. IC2L00, IC2L01,
IC2N00 and IC2P01 comprise the Main Picture Sync
Select Circuitry. Sync must be extracted from NTSC
and Component Format Y Signals. NTSC signal are
480i scanning format. Component signals can be 480i,
480p or 1080i.
IC2L00, the Main NTSC Decoder, extracts horizon-
tal and vertical sync when the source signal is 480i for-
mat. IC2L01 extracts composite sync (combined hori-
zontal and vertical sync) from the Y signal when the
source is 480p or 1080i.
IC2N00 selects 480p/1080i sync from IC2L01, or
separate 1080i H and V sync from the DTV inputs.
IC2P01 selects 480p or 1080i sync from IC2N00, or
480i sync from IC2L00.
The selected sync is directed to the Doubler circuitry.
If the selected source is 480i, the number of horizontal
lines are doubled in the Doubler circuit. When the se-
lected source is 480p or 1080i, no line doubling is re-
quired.
Since all sync signals, 480i, 480p and 1080i pass
through the PCB-DOUBLER, the TV cannot be op-
erated with the PCB-DOUBLER unplugged.
6-2