Sony D98 chassis Operation Manual page 22

DDC2Bi
Rear
Input
DDC2B
Front
input
DDC2Bi to N Board
VIDEO "A" BOARD ELECTRICAL CIRCUIT
The main function of the A Board is to receive incoming video signals and process them into the RGB video drives necessary
for the CRT cathodes. Video signals can be received from two sources: One is the conventional 15 D-sub connector and the
second is an additional input located at the front of the monitor consis ing of the female portion of the 15 D-sub. The purpose
of this second input is to allow easy hookup to a laptop computer with the aid of an additional video cable (provided).
The A board circuitry also buffers the Sync timing signals, and provides On Screen Display (OSD) video. The timing
analysis for the Auto Size Center function as well as the Analog to Digital conversion for the Color Restoration functions are
processed on the A-board also. Additional functionality's include: the Display Data Channel information functions to the
DDC equipped host computer and all the CRT cathodes operating voltages such as the heater, G2 and focus are either
processed or passed to the CRT socket (J001).
A Board Functions
The A Board functions are divided into four operational sections which are described as follows.
1) Video Select and RGB Process Functions
- Video input selecting is controlled by Microprocessor.
- Sync Timing Buffering.
- RGB video signal amplification and adjustment according to white balance requirements, contrast and
brightness settings.
- On Screen Display mixing.
- D/A conversion for RGB CRT cathode cutoff G2 levels control.
2) On Screen Display Generator, Timing Analysis and A/D Conversion
- OSD RGB video pattern generation.
- Timing analysis for Auto Size Center function.
- Analog to Digital Conversion for Color Restoration function.
Heater and Focus Voltages
from D Board
Rear Input
Front Input
Syncs to N Board
2
I C Communication
H Sync,V Sync and H fly
DDC
19 D98 Chassis A board Block Diagram
RGB Cathode Drv
Video
Select,RGB
Process
D/A Level
D/A Conv
Active
Video
for ASC
OSD Generation
Timing Analysis
Beam
A/D Conv
Current
Feedback
- 22 -
CRT
Cuttoff
Voltage
G2 Voltage
G2,Cutoff
and Beam
Current
Feedback