(5-7-5. CD-17 Board)
6. Drum Rotation Detection
Based on the DRUM FG A and B signals which are converted
to the TTL level in the drum
drum rotational
direction,
speed and drum PG phase are detected, and this
information is sent to the CPU in the form of data indicating the
drum status.
Rotational
Direction
Detection
Rotation Prevention)
The drum rotational direction is detected by
0-
type
IC4M-I3 which is set "High" when the drum is rotating in the
clockwise direction
and set ..Low" when it is
in the
counterclockwise
direction.
TP12 TTL
FG A
ccw
~
~
TP13 TTL FG B
IC4M-13
"L"--------
Rotational
Speed Detection
The drum rotational
speed is detected by IC3 F.
The 0.4 microseconds
clock
is used for
amount equivalent to 19 cycles of the DRUM FG B signal and
this information
is sent to the CPU as the data indicating the
drum's rotational
speed
7. Drum PG Delay
The drum PG
from the drum motor is output
the
timing before 9.S±2H
from the negative-going
edge of the
vertical equalizing
pulse, and its level is 0.3 to 1.3
This DRUM PG signal is input into pin I2A of the CD board
via the DA board, and converted
into the TTL level by IC26
with the point crossing with 0 volt serving as the reference. Since
the drum phase differs by V/3 with playback by the PLAY head
and playback by the RIP head, the drum FG signal and 0.4
microseconds
clock pulses are used to delay the drum PG signal
by ICS K (CTC) in accordance
with whether the RIP head or
PLAY head is used The
drum PG
output from
pin 2SB(PG PULSE)
to the LG board and it is used as a
reference for the switching position. Furthermore,
the delayed
drum PG signal is also used for the drum phase and skew
detectors.
DRUM PG DELAY
12A:
DRUM
PG
IC26-7
TP15
IC5F-9
TP23
258 : PG PULSE
BV H-2000( U/C) IPS/PM
BVH-2180(U/C)/PS/PM
8. PG Phase Detection
The gate pulse corresponding
from the positive-going
edge of
the
V
from
to the neaauve-zomz
of the PG pulse is generated by IC3 B and at ICSF the gate time
is measured
by the 0.4 microseconds
clock pulse.
this measurement
ICI C-4 is
(PG PHASE
ACK)" which advises the CPU that measurement
is being
conducted
The gate pulse corresponding
to the phase difference between
the REF V signal input to pin 32B and the PB V signal input to
20A is
by
V PHASE
and
IC3F
the gate time is measured by the 0.4 microseconds
clock pulse
which
timed by ICS-O.
PG PHASE DET
328:
l
r
REF
v
Z
IC4C-14
:
0
PG PHASE REO
~
<l
a:
IC1C-4:
--.J
w
PG PHASE ACK
a..
0
I.L
PHASE GATE
0
>-
a:
0
PB
DET
w
I
I-
328:
l
r
REF
v
20A:
PG PULSE
IC2C-9 :
PB
v
PHASE DET
Results of PG phase measurement
is used for control of drum
Results of PB V measurement
is used for control of the
AUTO PG during normal playback of the RIP head
9. Skew Detection
The time extending from the PB H at the end of the video track
to the PB H at the start of the next video track is measured and
the skew is detected
ICS K (CTC) measures the width of the gate pulse generated by
and ICSN
a 0.4 microseconds
clock
and this
information
is sent to the CPU as the skew data.
P8
SYNC
RF
SW
----
--------------
------.
VIDEO
I
SYNC
I.....,;".;.;;..;;;.;~_
VIDEO
208: PB H
IC5F-1O:
DELAYED
PG
IC4L-6
~------
-------------
-----....,
5-7-1
SERVO SYSTEM
Содержание BVH-2000
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