Hitachi 46W500 Training page 33

DP-3X MICROPROCESSOR NTSC SYNC INPUT CIRCUIT EXPLANATION
NTSC SYNC CIRCUIT DIAGRAM.
(See NTSC Sync Circuit Diagram for Details)
The Microprocessor I001 must have Sync inputs from the Chassis to Lock it's generation of OSD, Closed Cap-
tion, Customer's Menu, Service Menu, etc.....
The Chassis feeds back this information in the form of Blanking pulses and Sync from the Video. The following
describes the types of feedback sync signals. The following describes the pins on the Microprocessor.
(62) H BLK (Horizontal Blanking):
•
H Blk is input to the Microprocessor at Pin 62. H Blk is generated from the Deflection Transformer pulse
off pin 7 of T701, wave shaped by Q706. Then routed out the PPD3 connector pin 8 to the Power Supply.
Then out the PPS3 connector pin 8 to the Signal PWB. From here it is sent to the base of Q025 where it
gets level shifted and inverted and into pin 62 of the Microprocessor.
(64) V BLK (Vertical Blanking):
•
V Blk is input to the Microprocessor at Pin 64. V Blk is generated from the Vertical Output IC I601 pin
11. Then routed out the PPD3 connector pin 12 to the Power Supply. Then out the PPS3 connector pin 12
to the Signal PWB. From here it is sent to the base of Q026 where it gets level shifted and inverted and
into pin 64 of the Microprocessor.
(93) MAIN AFC (Automatic Frequency Control):
•
Main AFC is input to the Microprocessor at Pin 93. Main AFC is generated from the Main Tuner U301
pin 16. Then routed to Q041 and Q042. Then into pin 93 of the Microprocessor.
The Microprocessor uses this input signal to align or adjust the precise Oscillator and Programmable divider
settings within the Main Tuner for proper Reception.
(92) SUB AFC (Automatic Frequency Control for PinP Tuner):
•
Sub AFC is input to the Microprocessor at Pin 92. Sub AFC is generated from the Sub Tuner U302 pin
16. Then routed to Q035 and Q036. Then into pin 92 of the Microprocessor.
The Microprocessor uses this input signal to align or adjust the precise Oscillator and Programmable divider
settings within the PinP Tuner for proper Reception.
(100) MAIN CCD IN:
•
The Microprocessor receives Main Sync information and strips the Closed Caption Data from line 21.
This composite sync signal is supplied to the Microprocessor from I008 pin 14. It uses this same input for
stripping V Chip Data.
•
When an NTSC component input is supplied to Input 2, this is called 480i. This must also be monitored
for Closed Caption data and for V. Chip Data. If Input 2 is selected and it is 480i (NTSC), then the Micro-
processor outputs a Main CCD Select signal from pin 73 to I008 pin 11 to select 480i input at pin 13.
•
NOTE: Component inputs other than 480i (NTSC) are not able to display Closed Caption Data.
(97) Sub CCD IN:
•
The Microprocessor receives Sub Sync information and strips the V Chip Data. This composite sync sig-
nal is supplied to the Microprocessor from I008 pin 15.
•
When an NTSC component input is supplied to Input 2, this is called 480i. This must also be monitored
for V. Chip Data. If Input 2 is selected as PinP source and it is 480i (NTSC), then the Microprocessor out-
puts a Sub CCD Select signal from pin 74 to I008 pin 10 to select 480i input at pin 1.
(23) M/S Sync Det (Main / Sub Sync Detection):
•
The composite sync signal from either Main or PinP (Sub) is supplied to the Microprocessor from I008
pin 4. The Microprocessor uses the Sync signal to activate the AFC loop, and for Auto Programming.
When the channels are changed for the PinP Tuner, the Microprocessor outputs a short control signal from
pin 25 (SD Sel) to I008 pin 9. I009 then outputs the Sub composite sync signal input on pin 5. Normally
this IC outputs the Main composite sync signal input on pin 3.
PAGE 02-09