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CIRCUIT DESCRIPTION
Half Tone Pin (40)
This pin is responsible for controlling the background transparency of the Main Menu. When the customer
calls up the Main Menu, they can select the CUSTOM section. Within the CUSTOM section is MENU
BACKGROUND. There are three selections for this, GRAY, SHADED, and CLEAR.
CLEAR:
Selection turns off any background for the Menu and video is clearly seen behind the Menu.
SHADED:
Selection adds a transparent background, which makes the Menu and some of the video
behind the Menu easier to see.
GRAY:
Selection generates a GRAY background for the MENU blocking video behind the Menu.
This is accomplished by outputting any one of three different pulses from pin (40) of the Microprocessor.
This signal is then routed through the PSZ1 connector pin (20) to the Rainforest IC IX01 pin (47) as YM
signal which does the following:
CLEAR:
No output during the display of the Menu.
SHADED:
1/2 Vcc pulse equal to the timing of the Menu background.
GRAY:
Full Vcc equal to the timing of the Menu background.
OSD Blanking Pin (51)
This pin is responsible for muting the video behind each character produced by the Microprocessor. This
pulse is in exact time with the character, however it is slightly longer. In other words, just before any
character is produced, this pin goes high and just after any character turns off, this pin turns off. This clears
up the video behind the OSD character to make it easier to read. OSD Blk is produced from pin (51) of the
Microprocessor. This signal is then routed through Q013, then through Q007, through the PSZ1 connector
pin (19) to the Rainforest IC IX01 pin (36) as YS1 signal which mutes the video.
P Blk Picture Blanking Pin (56)
This pin is responsible for muting the video when the Microprocessor deems it necessary. This would be
during power up or power off, child lock, channel change, or selecting a video input with no video input
available. P Blk is produced from pin (56) of the Microprocessor. This signal is then routed through Q007,
through the PSZ1 connector pin (19) to the Rainforest IC IX01 pin (36) as YS1 signal which mutes the
video.
Closed Caption Display From The Microprossessor Source
The Microprocessor is also responsible for stripping the Closed Caption Display (CCD) from within the
Vertical Sync on horizontal line 21. It receives the composite video signal at pin (28). This signal is tapped
off the main video path before it arrives at I005 pin (5). See Video Path Circuit Diagram and Explanation
for Details. The tapped video is routed through Q021 to the Microprocessor at pin (28). See Sync Signal
Path Circuit Diagram and Explanation for Details.
DCU As The Source
The DCU (Digital Convergence Unit) generates its own OSD patterns and text. The DCU generates these
characters in the same fashion as the Microprocessor. The DCU generates Digital Red from pin (11), Digital
Green from pin (12) and Digital Blue from pin (10) output from the PDG and then through (QK06 Dig Red,
QK07 Dig Green and QK08 Dig Blue). The DCU characters are then routed through the PSD1 connector
pins (2 Red, 4 Green and 6 Blue). These are then routed through (QX01 Red, QX02 Green and QX03
Blue) and sent to the Rainforest IC IX01 pins (35 Analog Red In, 34 Analog Green In and 33 Analog Blue
In) as Digital Convergence graphic signals. When the DCU is activated by pressing the Service Only switch
on the Deflection PWB, the DCU outputs a BUSY signal. This signal does two things.