Akai VS-2EGN - Page 53

3-4 QUASI-VERTICAL SYNCHRONIZATION PULSE GENERATOR CIRCUIT
R130 10K
220K
R26
R25
21 390P e62_1/50
SERVO I2v
st
oF
R129 100K 2 ~
Mt
ee
ald]
[ou
SERVO S8; 1 ee
RVO BS anes >
; pean)
REVIEW L
R126 220K
SERVO l2V
- QUASI- VERTICAL,
PUL!
SE OUT
22, 00068 R29 33K
R27 100)
TRI9
Be RI40 220K
CUE or REVIEW: H
R138 220K
Fig. 7-55 Quasi-Vertical Synchronization Pulse Generator Circuit
During the trick-play of CUE, REVIEW, PLAY, PAUSE,
etc. it sometimes occurs that a noise bar occurs during
the vertical blanking period, or that the TV picture
sways vertically or rolls.
3-4-1 CUE MODE
When CUE mode CUE/REVIEW @® terminal goes to
HIGH, TR18 and TR19 are turned on while R31 and
R27 are grounded.
SERVO l2v
To prevent such trouble, a quasi-vertical synchronization
pulse is generated during trick-play modes, and it is add-
ed to the PB signal (squelch circuit of video circuit) to
achieve TV synchronization.
x
8
8
SWITCHING, RIZA 100K & ~
° ~
PULSE ics
AN6914
-
mee
9 QUASI-VERTICAL
PULSE OUT
62 1/51
22 0.068 TRIT
Fig. 7-56 Quasi-Vertical Synchronization Pulse Generator Circuit (CUE mode)
The quasi V-pulse is delayed 480 us from Switching
Pulse CH-1 and CH-2 with the pulse width being 300
sec.
@ The delay is determined by the time constant of
R129 and C64 and the reference potential which is
determined by the comparator’s inverse inputs R28
and R31. (See Fig. 7-57(@).)
| __ fevice Manual VS-2EGN
50
@®The pulse width is determined by the threshold
potential, as determined by R29 and R30, and by the
time constant (CH-2, C21, R25 and R26 or CH-1, C22
and R27) that differentiates delayed Switching Pulse.
(See Fig. 7-574) ,©@.)
©C62 (1/50) is employed to prevent disturbance
of the picture caused by the video power source taken
into the servo due to timing lag between servo power
source (SERVO 12 V) OFF and video power source
AL 12V.