Video Signal Amplification Section; Controls - NEC MultiSync FP1370 Service Manual

2) Video Signal Amplification Section

The video signal amplification section basically consists of the input section circuit and the amplification circuit.
Each Red(R), Green(G) and Blue(B) video signal circuit is identical to each other, the G circuit being described
below.
The video signal through the input selection circuit is input the amplification circuit. The amplification circuit
is constructed with IC711(Pre-amp), Q711G(buffer), IC721(Output amp).
IC711 controls CONTRAST and R/G/B GAIN with I
external DC voltage. IC711 is possible to change gain, it is approx.4.3 after the video adjustment.
The output of IC711 is buffered by Q711G and fed to IC721(Output amp).IC721's gain is fixed approx.15.
Rs and Cs connected IC721 pin 13 form emitter peaking. On American version, emitter peaking effect
changes 4 levels by Q721G, Q722G and Q723G. On European version, that changes 2 levels by Q721G.
R736G
From
Input
Selection
Circuit
IC801
CLAMP PULSE
C712G
11
C711G
IC711
M52742ASP
2
I C BUS
15 23
ABL
CPU
(Fig 1.2) Video Amplification Circuit
2
C BUS by CPU. Only ABL function is controlled by
+12V
R717G
29
26
R716G
R718G
25
24
SHARPNESS1
SHARPNESS2
SHARPNESS3
8-4
Q711G
C729G
R719G
IC721
12 14
VPS16
13
C72AG C723G
R724G
R725G
Q721G
C72EG
R723G
R727G
R72HG
Q722G
R726G
Q723G
R72KG
Only American version
To
CRTCathode
C722G
R722G