Pioneer tuning fork Service Manual page 51

Tape
Head
Pilot signal
shifts here
(a) When tape is slow.
RFSWP
A c h
Bch
Reference pilot to be added
d. Flying-erase-head
In the (3 and V H S systems one frame erasing is impossible
because the fixed Full-erase-head erases the signal across
the full tape width. This produces noise signal when edit­
ing. In 8mm VCR an Erase-head installed between the two
Full-erase head
•Tape
Erased
area
(a) Full erase
Video
PCM
Center pilot is neglected.
( / 1 + / 2 + / 3 )
LPF
+
(A)
Pilot OSC
CO Tracking Servo Circuit
Fig. 3 9 Automatic Track Finding(ATF)
Head
Fig. 4 0 Erasing Methods
2 /
H
46.145kHz
46.259kHz
16.407kHz
f X integer
/ -102.544kHz-(378/
H
1
/ -118.951kHz-(378/
2
/ =165.210kHz-(378/
3
/ =148.689kHz-(378/
4
l / l - - 1 4 d B
P c
(b) Pilot frequency (NTSC)
( / 1 ~ / )
4
Too slow
46kHz BPF
Tracking error
16kHz BPF
Too fast
(/ ~ / )
3 4
Video-heads on the Drum can erase signals frame by frame
with the help of the A T F system. This makes noise-free
editing possible.
Flying-erase head
(b) Flying erase
A / « / „
A
A / - 3 /
B H
16.521kHz
)/58«-CH1
H
)/50-CH2
H
)/36 - CH3
H
)/40 - CH4
H
(375/ in PAL)
H
Capstan motor
49