Sony DTV-01, Руководство пользователя

Страница: 48 / 132

51
Video Process E
The video output stage has only two functions:
1. Amplify the video signal to sufficient levels to drive the picture tube;
and
2. Combine the IK pulses and return them to the AKB circuit on the B
board.
Video Signal Amplification
The chart below shows the red drive levels with a color bar signal input to
video 1 jack.
R e d D r i v e S i g n a l L e v e l s
N a m e L o c a t io n V p - p *
V id e o I n p u t C N 9 0 0 1 / p in 1 2 V p - p
V id e o O u t p u t I C 9 0 0 1 / p in 8 1 7 0 V p - p
R e d I K o u t p u t I C 9 0 0 1 / p in 5 1 0 V p - p
C o m m o n I K r e t u r n Q 9 0 0 1 / E m it t e r 3 V p - p
* Noise in not included in the peak to peak measurement.
D C V o lt a g e s
C N 9 0 0 1 /p in 1 b o a r d in p u t 4 . 5 V
I C 9 0 0 1 /p in 3 I C in p u t 3 . 6 V
I C 9 0 0 1 /p in 8 I C o u t p u t 1 4 4 V
I C 9 0 0 1 /p in 5 I K o u tp u t 9 . 0 5 V
The red video signal from the video processor is input to the C board and
buffered by Q9009. The output is applied to the video output IC. This
voltage amplifies the input to drive the picture tube.
IK Output Circuitry
The picture tube’s cathode current flows through the video output ICs. A
sample of that current is output from each IC at pin 5. The three IC outputs
(one for each color) are connected in parallel. This way all three IK signals
can be returned to the video processor on one input at CN9001/pin 8.
The three IK pulses are located in the vertical blanking area just before the
first scanning lines at lines 17, 18 and 19. It is difficult to determine if all
three pulses are present at CN9001/pin 8 because they are so small. You
can see them with an oscilloscope if you trigger to the larger IK drive pulse
from the R, G or B output at CN9001/pins 1, 3 or 5. They are located in the
vertical blanking area of the waveform after the vertical sync pulse,