Bh Board - Sony BVM-1911 Operation And Maintenance Manual

3-3. BH BOARD
3-3-1. Switching Circuit Between Y (Luminance) Signal,
Color Difference Signal and RGB Signal, AGC Pulse
Insertion, Y-C Matrix
Switching Circuit of Y Signal, Crosshatch Signal and SET UP
Signal, Buffer
Y signal, crosshatch signal and SET UP signal are selected by the
switcher (IC! (1/3) (2/3)) and selected signal is output via buffer
QI.
Switching Circuit of R-Y Signal, Red Signal and SET UP Signal
!Same as B-Y, G-Y Signal)
R-Y signal, Red signal. SET UP signal are selected by IC2 (1/3, 2/3)
and selected signal is output via buffer Q4.
Y Signal Screening (Same as R-Y. B-Y, and G-Y Signals)
The signal is performed SAMPLE and HOLD (S/H) at the back
porch of signal by transistor Q2 and JCS (2/2). Y screening is per-
formed by replacing S/H output signal, by the original signal.
For color difference signals screening is made at the Horizontal
Sync portion.
Red Matrix, Blue Only SW, Buffer !Same as Green and Blue)
Red is obtained by Y-C matrix circuit composed of resistor net-
work CP9 from color difference signals.
AGC pulse from pulse generator is inserted into Red signal for
contrast control.
IC7 activates by the Blue only SW on the front panel. Blue only
SW is used for the display of blue signal as a monochrome picture.
3-3-2. Contrast Control, Brightness Control, Peak L imitter
Red Contrast, and Brightness Control Amplifier !Same as Green and
Blue)
This is a variable gain control amplifier composed of variable resistor
element ICI0I and transistor Q!02 and Ql03. By controlling the
voltage at pin
©
of IC! 01. contrast control is performed. and
brightness control is done by controlling the bias voltage of tran-
sistor Ql02.
Red limitter (Same as Green and Blue)
When excess input signal comes in . amplitude is limitted by the
limitter composed of transistors Ql 04 and QI 05.
Red Contrast Control
AGC pulse inserted in Red siirnal is clamped by transistor QI 07
and sampled by transistor QJ08.
Amplitude of above
AGC
pulse is compared with the reference
1oltage applied from CONTRAST control on the front panel in
1(102
(2/2)
Contrast control is performed by controlling the gain of Red con-
trast brightness control amplifier so that these voltages may match.
Red Brightness Control !Same as Green and Blue)
The black level of Red signal is performed SAMPLE and HOLD
(S/H) by transistor QI 06. This S/H voltage is compared with the
reference voltage applied from Brightness control on the front
panel in ICI02 (1/2). Brightness control is performed by controlling
the bias of Red contrast Brightness corrtrol amplifier so that these
voltages may match.
3.5
BLOCK DIAGRAM OF BH BOARD
-
~
"""'"'·"
05 6 IC2(3/3)511/2)
I
R • Y/R/SETUP
R-Y /R
SW S
SCREENING I
BUFF
i
t
IC311/3 2/3) 07
05 9 IC3(3/3) 6(2/21
0
G-Y/G/SETUP
~
~
G -Y /G
I
SW a
SCREENING
r
BUFF
i
L
_J
t
~"""·"" ,o,o
QI I, 12, IC4(3/3),6U/21
H
B-Y/8
I
8 -Y/8/SETUP
~
SW &
SCREEN I NG
I
BUFF
T
L
_J
i
IClll/3,2/31 QI 02 3 IC 1(3/3),5\2/21
~Y/CROSS HA:,-
H
~
y
SET UP SW
SCREENING
T
L
i
-
-
CP9, IC?, 013
ICIOI 0101 ~ 103
0107 108 iCI0212/2)
l
R MATRIX,
R .CONT/8RT
~y
R CONTRAST
--I
8
.o.sw,
CONTROL AMP
CONTROL
BUFF
i t
I
CP 12 ICB 014
IC201 020 I -203
0207 208, IC202(2/2)
I G MATRIX,
t
H
G.CONT/BRT
~y
G CONTRAST
LJ
8.0. SW,
BUFF
CONTROL AMP CONTROL
-
t
i
I
CPI5,015
I C301, 0301"-303
0307 308 IC302(2/21
~y
I
5 MATRIX,
~y
8.CONT/ BRT
8 CONTRAST
.J
BUFF CONTROL AMP
CONTROL
-
T
i I
IC9,IC10(1/3J
l
l I
016, 17
H
I
I
CONTRAST, BRIGHNESS,
-
1-1
AG(, PULSE GEN
ttt
~
S2
0
l
S!
RVI
RV2 RV3
OIRE 75 I RE IOOIRE
-
-
0104 105 0106 ICI0211/2)
Al GND
y
R LI MITTER~YR/BRIGHTNESS Bl GND
CONTROL
A2 C.H. IN
I
t
82
D. Y. IN
I I
A3
R. IN
I
83 S.S.N
A4 RGB. SW
84
O.R-Y. IN
r
A5
G. IN
85 S. U. SW
A6 W. SW
86
D.G-Y.IN
0204 205
0206, IC2021I/21
A7
B. IN
~y
G/BRIGHTNESS I
G LIMITTER
CONTROL
I
87 C.H. SW
-
AB
S.U. VR
I
i B8
D.B - Y IN
A':J
GND
1
B9
GND
AIC
C,CL. P
~
BIC
Y .CL. P
All C.BLK.P
811 8.0.SW
~Al2 CHAR. BLK
I 812
Y. BLK .P
0304 305
0306, IC303(1/21
Al3
8.P
B LIMITTER~y 8/BRIGHTNESS
813
AFC. P
CONTROL
Al4 DL.SW
I
i
BI4
Al5
BRT. VR
I
~
815 R.OUT
Al6 B. CL P
816 CHAR. IN
Al? CONT. VR
I
817 G.OUT
Al8 W.CL.P
BIE GND
I ICIOi3/31, 11, 12, 13, 14, CPI?, 33
Al"
81-;: B. OUT
CONTROL, PULSE GEN
AZ.
+
I2V
I l ' l
t
B2( ~ I2V
A21
-I2V
B21
-12 V
AZ GND
'
BZ, GND
( YI COLOR DI FF ER ENCE/ RG 8
)
BH SIGNAL SW ITCH ING,
Y/C MATRIX, CONTRAST/
B~GHTNESS CONTROL
-
3-6