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to. the other end
of the Fast solenoid via
Q907 and flashing current flows through the
solenoid via path (1) for 220 msec. This cur-
rent causes the solenoid to operate.
e. In 220 msec, the output of the controller at
P10 falls to L-level, thereby turning off tran-
sistor 0906. As Q906 is off, Q907 turns off
and stops delivering the high voltage develop-
ing at its emitter to the solenoid.
f. The terminal of the solenoid which connects
to Q907 is also connected to the power line
of approx.
13 V via diode D910 and current
continues
to flow to the solenoid
via the
diode and path (2). This current maintains the
current state of the solenoid.
Thus varying voltages (currents) are supplied to
the solenoid for driving and holding it. The large
drive current produces a large mechanical power
in the solenoid to secure operation. The small
holding current protects the solenoid from heat-
ing up. We call the circuit that controls supply
voltage of the solenoid in this way the 'flashing
circuit''
and the !arge drive current "flashing
current".
When REW mode is selected, controller 1(C U913
outputs an H-level signal which turns on transis-
tor Q911 in the same manner as in F.FWD mode.
Operation of the flashing circuit is the same as
in F.EWD mode but that the flashing current be-
gins to flow with a delay of approx. 65 msec.
When the Fast mode has been released (for ex-
ample, the STOP button has been depressed dur-
ing F.FWD or REW mode), operation proceeds
as follows.
CONTROLLER
g. The
controller
outputs
L-level
at pin
13
(F.FWD) or at pin 5 (REW).
.
h. With the base current cut off, transistor Q911
turns off. Now the solenoid is cut off from
the circuit and, because holding current flows
no longer, it gets released.
3-8-2. Head base solenoid drive circuit
See Fig. 3-15.
.
This solenoid operates during PLAY,
PAUSE,
REC/PLAY,
and REC/PAUSE. The controller
generates signals which
control the head base
solenoid during these modes (see Fig. 3-8). The
timing diagram (Fig. 3-8) shows that, even in a
certain operating mode (REC/PLAY, for exam-
ple), the controller provides head base control
pulse at varying timing depending on whether
REC/PLAY
mode
is entered initially or 'trans-
ferred from PLAY mode. The same thing occ!'rs
"with ftashing controt pulse. The-reason-for~
is as follows. To change REW mode to PLAY
mode, it is required to raise the head base after
the tape has stopped and, therefore, to delay the
head
base control pulse for the time interval
which the tape takes to stop traveling. For this
reason, head base solenoid operation should be
-explainedseparately "for each mode: for -exact-
ness. However, it is described here only for when
PLAY
mode is entered from STOP mode. You
may refer to the timing diagram for information
of delay.
a. When the PLAY
button has been depressed,
controller IC U913 outputs a flashing circuit
-control-signal-4H-level) at-pin-10.and-a head
+36V
Fig. 3-15.
Head base solenoid drive circuit
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