Deo Output Stage - Tatung OMNISCAN SERIES Service Manual

TEST
CONDITION
Fh=31KHz
V1
TEST
POINT
V1
V2
V3
V4
V5
V6
0.8 Vpp
TEST POINT NAME
RINPUT
BUFFER OUTPUT
CLAMP INPUT
FEEDBACK INPUT
VIDEO OUTPUT
BUFFER OUTPUT
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3.40 VIDEO OUTPUT STAGE
(Refer to circuit diagram Fig-40)
The output signal to the cathode is provided by
cascade amplifier 0003-0006. The gain of this stage
is approximates to 16. L001 and L002 are peaking
coils for high frequency video response. C022 and
R042 are emitter peakings.
Though a circuit is complicated, it is possible to
choose kinds of CRT to set arbitrary DC voltage, thus
C015 is used to make the output circuit be a AC
coupling system.
The cathode is DC clamped by network 0004-0005-
0004-C028-R053-R048-R051-R052. The DC
clamping or CUTOFF1 level at the cathode is set by
potentiometer R058 (R118, R178 for green and blue).
The B
+
of the potentiometer is provided by
+
12V.
Network 0009-R057-R054-R056-R058, along with
Green and Blue channel equivalents, enable the color
point of the monitor to optimized during set up.
The potentiometers R058-R 118-R 178 (CUTOFF1) and
R 119-R 179 (CUTOFF2), enable the background of the
monitor to be adjusted during set up.
=
3-33
=