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7-5. ATF METHOD
For 8 mm video, an ATF (Automatic Track Finding) method
has been adopted for tracking.
In this method, four types of pilot signals are recorded onto
the tape, and these signals are processed during playback
to detect the tracing position of the head for tracking.
(For the principles of ATF, refer to one of the previous
Service Manuals.)
7-5-1 . Actual Circuit Operation
ATF processing is carried out by XR-1 082 (IC371 ) .
The circuit diagram is shown in Fig. 7 - 6.
IC371 is divided into the recording pilot signal generation
block (REC pilot), the playback reference pilot signal
generation block and the error detection block.
REC
PILOT
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IC371
XR1 082
CP1 BOARD
Fig. 7-6. ATF Circuit
[ Recording]
The four pilot signals are generated by dividing the 1 1 .8
MHz output from the crystal oscillator (X3501 ) . The division
ratio is selected by the 2-bit select signals SEL 1 and SEL2
(Pins ® and @) ). SEL 1 and SEL2 are output from Pins ®
and @ of CXP80724 respectively.
(Refer to Fig. 7-6.)
The recording pilot signal is recorded together with the YC
(video) and A (audio) signals.
[ Playback]
The signal from the playback amplifier is input to Pin @ of
the IC. It passes through the mixer, BPF and comparator,
etc. , and is finally output from Pin @ as the ATF error
signal.
The ATF error signal is input to Pin !@ of CXP80724 and
AD converted inside the IC, after which it is added to the
motor speed data. The ATF data is used instead of the
mode phase data during recording. ( Refer to Fig. 7-6.)
Tracking is carried out by the same servo control operation
as in recording mode.
IC351
CXP80724
CD
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