Sony BVH-2000, Operation And Maintenance Manual

Page: 288 / 505

5-4-4. DM..25 Board
1. Outline
The PB RF signal from the EQ board and the EE RF signal
from the MD board the demodulator on this
board, and one of these is selected by the EE/TAPE
signal from the LG board
set to ON and the VTR is in the EE mode, a frequency (10 MHz
for NTSC/PAL, 8.9 MHz for PAL/SECAM) corresponding to
lines
period in accordance with the setting of the insertion line
SW2A.
The demodulator operates with, the pulse count system.
After demodulation, the the burst level
su ppressor by way circuit and video
amplifier, and the burst level, amplified to double what it was
The head switching noise in the output is reduced by the
suppressor and the output itself passes the low-
which is output VM board and to the
AD board on the plug-in time base corrector.
aucnnon
to
with a white reference marker generator, a pedestal clarnper, an
AGC circuit for keeping the video level constant in the shuttle
EE
WHITE REF SW
2. FM Demodulator
(Q3 to 6,15,ICl to 6)
The PB RF or the EE RF signal, supplied at the ECL level, is
converted
a TTL by IC6 and, after selector
IC5, it input to the pulse count system FM demodulator.
The demodulator output is de-emphasized by R66 and C60, it
(4.5 MHz for NTSC/PAL-M, 5.5 MHz for PAL/SECAM) and it
is to the video and sync separator.
The fluctuations in level occur
frequency varies due to speed changes in the shuttle mode is
in
pedestal after demodulation and by feeding back these changes
with AGC circuit IC3.
BVH-2180(U/C)/PS/PM
3. Pedestal Clamper (QI0 to 12,ICII,IA,3C,3D,5D)
Feedback is applied to video amplifier ICl2 and ICI3 so that
the
DC level the is
made OV and the pedestal of the IC13 video output is kept
constant
signal from the sync
C01111l2:UI'e a and switcher and
back porch of the demodulated video signal is sampled
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