Assessments - 1, GPA: 5
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In NTSC and Component format signals, horizontal and vertical sync must be extracted from the Y signal by the NTSC Decoder. For the DTV Input, the signal can be either Y,Pr,Pb or RGB/HV, sometimes referred to as “5-wire.” (Sync on green is no longer an option.) Obviously all 5-wire inputs have separate horizontal and vertical sync. Sync Select circuitry selects the Main picture sync source. The selected output is used to synchronize the Horizontal and Vertical Deflection Generators. If the source signal is 480i, horizontal sync is doubled, before synchronizing the Horizontal Drive Generator. Horizontal deflection drive is amplified by the Horizontal Output circuitry and directed to the horizontal windings in the Deflection Yokes. The signal from the Horizontal Output is also directed to HV Drive circuitry. HV Drive is amplified at directed to the Flyback transformer. Vertical sync synchronizes the Vertical Deflection Generator. Output from the Vertical Generator is amplified in the Vertical Output circuitry and directed to the vertical windings in the Deflection Yokes. 6-2 Sync Signal Path Figure 6-1 illustrates the Sync Signal Path for the Main Picture signals on the PCB-Terminal. IC2K00, IC2A00, IC2B00 and IC2A95 comprise the Main Picture Sync Select Circuitry. Sync must be extracted from NTSC, Composite and Component Format Y Signals. NTSC and Composite signals are 480i scanning format. Component signals can be 480i, 480p or 1080i. IC2F00, the Main NTSC Decoder, extracts horizontal and vertical sync when the source signal is composite or component video. IC2A95 selects the already seperate vertical and horizontal sync from the 5-wire sources. • DTV (when the source is 5-wire) • VGA • DVI (decoded from the digital signal) • DM (also decoded from a digital signal) The selected sync is directed to the PCB-Signal via connector JA, pins 32 and 33, and then to the Doubler circuitry. 6-3 Figure 6-2 illustrates the Sub Sync Signal Path for the Sub-Picture signals on the PCB-Terminal. It functions the same as the Main Sync Signal Path using different pin sets on the same ICs. The sub sync signals are used by Doubler circuitry for POP/ PIP signal processing. Figure 6-3 shows the sync signal functions performed by the PCN-Signal. It serves to interface the sync signals as follows: • DVI and DM inputs to the PCB-Terminal • Selected Main and Sub sync signals from the Terminal to the Doubler PCBs. • Sync from the doubler to the VCJ The selected sync is directed to the Doubler circuitry. If the selected source is 480i, the number of horizontal lines are doubled. When the selected source is 480p or 1080i, no line doubling is required. However, since all sync signals, 480i, 480p and 1080i pass through the PCB-DOUBLER, the TV cannot be operated with the PCB-DOUBLER unplugged. IC2X10 and IC2X11 are flip-flops serving as schmitt triggers. They effectively remove any spikes or noise that may be riding on the sync, preventing false triggering. 6-4 From the flip-flops, sync pulses are directed to the VCJ, IC2V01. Both Horizontal and Vertical Drive Generators are in the VCJ. Horizontal drive is output at pin 40, and vertical drive is output at pins 52 and 53. The signals are directed to their respective output circuitry on the PCB-MAIN. 6-5 Vertical Deflection Figure 6-4 shows the Vertical Deflection circuitry. The Vertical Deflection Generator in the VCJ outputs push-pull type of vertical deflection drive signal. +VDR at pin 53 and –VDR atz pin 52. Both signals are applied to the Vertical Output IC, IC4B01. The amplified output from IC4B01 is directed to the vertical coils in the Deflection Yokes. D4B01 and C4B04 make up the pump-up circuitry. Feedback from the Deflection Yokes ground return at pin 4 of DY, to pin 1 of IC4B01, provide linearity and S correction. Horizontal Deflection Figure 6-4 illustrates the Horizontal Deflection Drive and Output circuitry. Horizontal drive signal from the VCJ is amplified by Horizontal Drive circuitry including transistors Q2V40, Q5A40, Q5A33, Q5A39 and Q5A32. The output from Q5A32 is directed to Q5A31, the Horizontal Output transistor. The output from Q5A31 takes three paths: 1) To the horizontal windings in the Deflection Yokes 2) Through C5A34 and Q5A37 to the HV Drive circuitry. 3) Through T5A31, providing the source for the CRT filament supply. 6-6 Horizontal Deflection DC Supply Circuitry The DC supplies for Q5A32 and Q5A31 are derived from Horizontal Deflection DC Supply circuitry. The 31K line from the Control .PC controls the DC voltage for Q5A31. Q5A31 supply voltage is approximately 10 volts higher for the 33.75 kHz scan format (1080i), than that for the 31.5 kHz scan (480p), The H-Deflection DC Supply circuitry is also used to: • Add side pincushion correction, controlled by the EWDRV signal from the VCJ. • Reduce the Deflection DC supply during scanning frequency changes. Figure 6-6 shows the Horizontal Deflection DC Supply circuitry. The conduction of Q5A01 determines the valu...
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