Bg Board - Sony BVM-1911 Operation And Maintenance Manual

3-2. BG BOARD
3-2-1. Luminance Signal Circuit
Filter SW
!CI works as a selector switch of composite video signal or
luminance signal derived from Y /C separation circuit. This IC
activates by either FILTER-SW in right side drawer or killer signal.
Aperture Control
Aperture control circuit is composed of DLl (delay line), transistors
Q5, 7, 8 and IC2. IC2 operates as a variable resistor. Resistance
value between Pin(DandG)is controlled by the potential between
pin
0
and pin
© ,
also pin (D and pin© .
Input signal: eTo,
Delayed signal by delay line:
eT
1
Second delayed signal: e72
See Figure 4
e1 (at base of transistor Q5) is obtained as below due to the com-
bination of direct wave and reflected wave by
DLI.
+Vee +Vee
eo
e-ro
05
-Vee -Vee
Figure 4
e1 = (ero +
e72)/2
Therefore eo is
eo
= -(m
+1[
(eT1 -{ (eTO + e72 )})
1st term 2nd term
K:
variable constant
In the above equation, 1st term shows waveform A in Figure 5 and
2nd term shows waveform B. When K is variable,amount of pre·
shoot and overshoot can be varied.
Switch S1 is used for selection of boost frequency.
3-3
-Ii
I '
-{Ji-
' I
I
I I
t-
Figure 5
Y Delay, Y Buffer Amplifier
A
B
-eo
Y/C delay time can be matched by delay line DL2 and Y signal
is amplified and fed to the next stage.
3-2-2. Color Gain Control Circuit
In this section (R-Y) signal processing is described as below, but
(8-Y) signal is processed by the same way as (R-Y) signal.
R-Y Amplifier and Clamping
The R-Y color difference signal from the decoder board is amplified
at the amplifier composed of transistors 021 and 022 and clamped
at the Horizontal Sync by transistors Q23, Q24 and IC3.
R-Y Gain Control Amplifiter
This is a variable gain control amplifier composed of variable resistor
element of IC4 and transistors 025-027. Gain of this amplifier can
be controlled by the color gain control voltage at the pin@ of
IC4.
AGC Pulse Generator
Generates the reference pulse for AGC (Automatic Gain Control)
of color gain control circuit.
Gain Control Amplifier for AGC Pulse
Circuit is the same as R-Y GAIN CONTROL AMPLll·IER. Gain of
this amplifier is controlled by the voltage at pin® of IC4.
Color Gain Control
AGC pulse, which is output signal of Gain control amplifier for
AGC pulse, is clamped by IC6 ( 2/3) and is made sampling by 1C6
(3/3). Amplitude of AGC pulse and DC voltage supplied from
CHROMA control on the front panel are compared and mach-
ed
by IC7 (
1/2)
with controlling the above gain control amplifier.
This control voltage is supplied to the control terminals of R-Y and
8-Y gain control amplifiers and controls color gain.
3-2-3. G-Y MATRIX amplifier
G-Y signal is obtained by matrixing R-Y signal and 8-Y signal with
the amplifier composed of transistors Q44 and Q45.
3-2-4. NTSC MATRIX SW
NTSC MATRIX mode operation is obtained by the matrix circuit
composed of resistor networks CPI4-CP19, transistor 029, 030,
Q39, Q40, Q49, QSO and IC5. CP14-CP19 perform matrixing and
!CS works as a switch.
I
3-2-5. Vector Output Circuit
3-2-6. COMPONENT R-Y Amplifier and Delay Circuit
R-Y Vector Output Gain Switcher
Vector output levels are compensated for each color standards,
NTSC, PAL and SECAM.
R-Y signal of COMPONENT signal is compensated with amplitude,
porality and delay time to match the R-Y signal of decoder output.
R-Y Vector Output Amplifier and Clamping
Vector output signal is amplified by IC9 (2/2) and transistor Q54
and clamped by IC8 and transistor Q55 for the suitable operation.
BLOCK DIAGRAM OF BG BOARD
-
-
01 ,01
~
4 .5MHi
S1 FREQ SELECT
05, 7,8, 1(2 DL 2, 09
6~
~ l
COMPOS1Tf
I
APERTURE
y
Y OEL.il.Y
v10fo eurr
r1LTER SW
r;;;
Tc,, l CONTROL
I -~
DL
COMP cv,
f f f
LV'
FILTER
DL COMP
~REO
SW l<.iLLfR
'¥2
APT PRESET
4 """"·"'~'"""·'""'"
025-28,1(411/3) 051-5.3
COMPONENT R-Y R-Y R Y
~ 1
R-Y GAIN CONTROL
r--~
R.
y
VECTOR
our
AMP & OE~AY AMD a (LAMP
,.P
GAIN SELECT SW
~
t,,
~::,~t
.t tJ
I
GA1N
PAL GAIN GAIN
~
l j
041-.43,1(4131.31 044,45
R·Y
AGC PLUS£
~
-H
COLOR GA1N
I
G-r MATRIX G·Y
'
SE
GAIN CONTROL AMP (QNrnOL
A"P
8·\
r
•c612/3,3/3l
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RV4
t
}RVS
RATIO GAIN
1(4(2/31
""""°"~
Q3J.,..34,IC3t2/2l 035~ 38 056 --58
1
COMPONENT 8·Y 8-Y 8·Y
8-Y GAIN CONTROL
~
-Y
8 • Y VECTOR OUT
AMP
&
DELAY AMP & (._AMP ••P GAIN SELECT SW
;(.vzz
L
:~,,~t
t
i
Rv,~J
GAIN
SECA
-
010 ... 12
Al GND
y
Y AMP BUH
9, GNO
I
L.
42 O.Y.OUT
f.vJ
-~
~ 82 IAPT.VR
A3 l<ILLER
I
GAIN
83 FILTER SW
A4
-
84 COMP IN
-
"
C.CL.P
BS GNO
A6
--
86
Y,IN
054, 55, 1(8(2121, 9(2/2)
~ A7 B.CL P
R-Y VECTOR OUT
r-r=: -
t- 87
ss.c
AMP .8. (LAMP AB CL.P.SW
88 W CL.
r
A9 C.R-Y. IN
89 RGB. SW
"
+
R~
8. p .,,
C.8-Y.IN
8,i
I COLOR VR
029,30,39, 40, 49,50
D76, 77
812 R-Y tN
,cs
D15-17 _..._
I S.S.N
1HSC
COMPONENT
~-
-
813
ss.P
MATRIX SW
SELECT
--
·~
S.S S
CONTROL
t
-
-~·
B·Y IN
Al C R·Y. OUT
81 MATRIX SW
Ai6
GNO
I V R·Y. OUT
17 D G Y. QIJT
81 GNO
A, GNO
1(811/2),9!1/2)
T
'"
'r.
8-\. OUT
059,60 " D
e~v
OUT
8-Y VE(TOR OIJT
81 GNO
AMP Ii, C.LAMP
"' tl2V
"" +-1cv
A21
-12v
"' -12v
"' GNO
L
r
GAIN PAL GAIN GAIN
~
GNO
Be
(COLOR GAIN CONTROL, COMPONENT R-Y AMP
8:
DELAYY
APERUTURE CONTROL,Y DELAY,VECTOR OUT
-
-
-
3-4