Sony D8MM-01, Training Manual

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33
Three extra bit patterns are used to create three different signals during
playback. These are called F0, F1 and F2. The F0 tracks do not contain
a pilot signal. F1 contains a 465 kHz pilot and F2 contains a 697.5kHz
pilot.
The system works similar to that in analog 8mm. The head is wider than
the actual track that is being played back. Therefore signals from the
adjacent tracks are read from the tape at the same time the main track is
read. If we look at the drawing below, we can see that anytime the heads
are on an F0 track, we can obtain different pilot signals from the adjacent
tracks. These signals are level compared and an ATF error is generated.
This ATF error controls the phase of the capstan motor. Whenever a F1
or F2 track is read, no ATF error is generated because the adjacent tracks
are both F0 tracks. Even though the ATF circuit is only operational on
every other track, it still maintains the phase of the capstan motor.
Mech Initialization
One of the following sequences will occur when a tape is inserted and the
door closed:
§
The mech will attempt to reverse play the tape in the analog 8mm
mode. This attempt is aborted when the clear leader is seen.
§
The tape will then turn forward until the clear leader is not detected
and stop.
Determination of the type of recording is not done in this mode. After play
is pressed, the unit will start in the digital mode. If it determines that tape
being used is not digital, the unit will stop, adjust the servos and playback
in the analog mode.
If the tape is not rewound
§
The mechanism will pull the tape out of the cassette until it is in the
fully loaded position.
§
The mech reverse plays the tape in the analog 8mm mode for ap-
proximately one second.
§
The mech plays the tape in the analog 8mm mode for approximately
one second.
§
The mech reverse plays the tape in digital mode for approximately
one second.
§
The mech plays the tape in digital mode for approximately one sec-
ond.
In this mode, a determination of what type of recording is on the tape is
made during the initialization period. When play is pressed, the camcorder
immediately enters the right mode.
Determining Recording Type
The determination of a D8 recording is done by recognition of the digital
RF signal and the presence of system data. If an RF signal and system
data are not detected, IC401 DV Mecha Control will go into high imped-
ance state and IC902 8mm Mecha Control will take control of the mecha-
nism.
The presence of the RF signal and the ATF pilot signals are used to deter-
mine if an analog tape is being used. If an analog recording is detected,
then IC902 8mm Mecha Control will continue to operate the mechanism.
If neither type of tape is detected, the unit will stay in analog mode. There-
fore if a blank tape is inserted, the unit will default to analog mode.
See the troubleshooting section for instances when a recording type can-
not be determined.
If the tape is completely rewound to the beginning
§
The mech will pull the tape out of the cassette until it is in the fully
loaded position.
D8 ATF