Video System; (3-L) Video Signal Amplifier - NEC MultiSync 4FGe Service Manual

3. Video System

Video signal amplifier
3-1.
The three video circuits are the same for the each R/G/B color. Threfore only the Green video circuit will be
explained here. The Green video signal input is fed to the pin @of IC701 through the Q701G. The video signal is
attenuated by IC701 ,and the attenuation level is controlled by the user contrast control. The output signal of IC701
is supplied to IC702. The output signal of IC702 pin @I is supplied to IC703. IC702 is preamplifier, and the gain is
adjustable by the GAIN VR702. IC703 is output amplifier.
CN-IN @
Video input
G GAIN
VR702
CN-C
(Fig 3-l-l) BLOCK DIAGRAM of Video signal amplifier
52
clamp
ABL
Blanking
Pulse
Video Mute
User
Contrast
Control