Sony BVH-2000, Operation And Maintenance Manual

Page: 289 / 505

(5-4-4. DM-25 Board)
4. Sync Separator (ICIE,2F,3F)
The demodulated video signal is amplified approximately 3-
times by the initial-stage operational amplifier IC3F.
In order to ensure accurate sync separation, any level below the
sync tip produced
in the single- head playback mode is DC-
shifted by the next-stage operational amplifier IC3F using the
dropout-I signal from the EQ board, thus resulting in the
elimination of any level below the sync tip.
D2 to 5 are analog switcher. The sync tip is sampled, its voltage
is held in C24, this voltage is fed back to the drive voltage of the
analog
switcher with video signal whose pedestal level is
fluctuating, and fluctuation is tracked.
Video signal in which the sync tip is clamped at OV is produced
at TP3, and it is only the sync portion of the video signal which
is converted to the TTL level by the next-stage comparator
ICI E
and output
z
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5. Burst Level
:SUt)DrE~SSC)r
(IC4E,5E,QI2)
The burst level which was amplified 2-times by the MD board
during recording is now returned to its regular level in the
playback mode by this circuit
PB V / PB H SEPARATOR
TP6
OEMOO VIDEO
TP12
P8 SYNC
IC40- 5(0)
IC4E- 6
IC40-13(0)
IC58-11
IC58- 6
IC48-13(0)
IC4A-5(0)
TP9 P8 V
IC4C-5(0)
TP10 PB H
VIDEO SIGNAL SYSTEM
6. RF Switching Noise Suppressor (QI3,14,ICIB,3B,14)
This circuit reduces the dropouts contained in the video signals
which is played back from the tape and also the switching noise
which is generated when the video/sync
heads are switched
7.
White Marker Generator (IC2B,2D,2E,3A3B,3C,4B)
When the WHITE REF switch SWI on the DM board has been
set to ON and the VTR enters the EE mode, one of the
frequencies
below corresponding to the white peak in the RF
signal can be inserted into 2 lines of the vertical blanking
period
10 MHz for NTSC/PAL-M
8.9 MHz for PAL/SECAM
The insertion line can be designated using insertion line
selector switch SW2A.
8. PB H, PB V Detector (ICIAID,3B,3C,4A,4B,4C,4D,5A,5B)
The PB Hand PB V signals are detected from the EE RF or PB
RF demodulated video signals. The PB V signal is output with a
width of 250 usee from the position of the third equalizing
pulse.
Level Detector
(Q7,8,IC7,8,9,3D,5C,5D)
This circuit detects the envelope of the demodulated video
signal's subcarrier component and samples the portion corre-
sponding to its burst level. The sampling pulse is provided from
the H SYNC signal produced
from the PB SYNC signal.
The sampled voltage is held in C95 and is output as the burst
level signal to the auto chroma equalizer on the EQ board The
playback RF characteristics
is controlled here so that the burst
level during playback is constant
5-4-8 BVH-2000(U/C)/PS/PM
BVH-2180(U/C)/PS/PM