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1 . 9
A U T O B L E C I R C U I T
Auto BLE provides the function of setting bias,
recording level and equalization to obtain the ideal
recording characteristics exhibited by the various
type formulations. Operation is fully automatic.
When the AUTO key is pressed, a signal is trans-
mitted from PD4010 to control IC PD6006 in
initiating mechanism operation and coarse-adjust
recording level. It then shifts to bias adjustment.
Bias is set by detecting the ideal current, deter-
mined by subjecting the lkHz tone oscillator signal
to record/playback at 16 step levels of intensity
and selecting which of the 16 bias strengths is best.
The resistance of the bias circuit is set accordingly.
This adjustment cycle may be repeated up to
four times. Then after equalization has been set,
S I G N A L
P A T H
} I E A D
the tape is rewound to the starting position. The
complete adjustment process requires from 10 to
20 seconds.
In case one of the adjustments is impossible for
AUTO BLE to make, it is automatically disabled.
The tape is then rewound and standard values are
set.
The detection
method used for each value
adjustment consists of passing the record/playbaek
signal through the Lch and Rch rectifier circuits
and comparing them (with comparators) with an
analog voltage obtained from a CPU digital sgnal
passed through the D/A converter. These circuits
are contained in PM9001.
M E C H A N I S M P A T H
C L E A R
L I N E
O U T P U T
1 7
C O N T R O L P A T H
P M 9 0 0 I
n .
o s c
F i g . ' l - 2 7 B . L . E . c i r c u i t b l o c k d i a g r a m
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