Hitachi DV-P250U Service Manual page 15

4. D/A CONVERTER (DAC)SECTOR
Constituted of 10bit DAC, it transforms DIGITAL VIDEO DATA to ANALOG VIDEO DATA for output. Under
control of output voltage by DAC pins (22, 23, 36, 37, 38 pins), it output 3 kinds of ANALOG VIDEO
SIGNALS:
a. ANALOG COMPOSITE VIDEO SIGNALS (CVBS/35 pin), output voltage 1.0Vpp.
b. ANALOG INTENSITY SIGNALS (Y/33 pin), output voltage 1.0Vpp.
c. ANALOG CHROMA SIGNALS (C/29 pin), BURST part output voltage 286mVpp.
d. ANALOG COMPONENT YP
S2 Processing Circuit (only for Japan)
S2 is a standard used in wide television sets possessing screen size switching function in NTSC mode. By
inputting VIDEO signals formed by superposing DC voltage on C signal at S input terminal, it switches
automatically to TV display size. The DC voltage superposed on C signal varies according to the ASPECT
RATIO of VIDEO SIGNALS.
1. Case of SQUEEZE SIGNAL (*1)
H-level voltage is input in SQUEEZE INPUT; Q2202 and Q2201 are powered and +4V DC voltage is superposed
on C signal output line.
2. Case of LETTER BOX SIGNAL (*2)
H-level voltage is input in LETTER INPUT; Q2205, Q2204, and Q2203 are powered and +1.8V DC voltage is
superposed on C signal output line.
1. *1: It is a laterally shrunk image information with 525 lines and an aspect ratio of 16:9 carried by the
standard TV signal format of 525 lines and an aspect ratio of 4:3. When viewing on a 4:3 TV set, the image
appears vertically oblong.
2. *2: It is a wide screen signal in the standard TV signal format of 525 lines and an aspect ratio of 4:3 with
coexistence of upper and lower blank areas of 525 lines and an aspect ratio of 4:3 screen and the
principal image area of 4:3 aspect ratio (line 53~232/316~495). When viewing on a 4:3 TV set, one sees
black areas at the top and bottom of the screen.
12
P /RGB.
B R
Chapter 1