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7.
The
bias oscillator
is
made
by
push-pull
circuit
of
transistors
Q7 and Q8. The
bias
oscillator
output
current
is
fed
to
the
erase
head
(E.H.)
to
erase
the
signal
recorded
on
the
tape.
At
the
same
time,
it
is
supplied
to
the
recording head (R.P.H.) through
the
switch
(S
t -s
)
for
recording
bias.
SWITCHING CIRCUIT
1.
With the
POWER SWITCH
(S
t
z)
turned
"ON",
30V and 24Y
appear
on the
two
secondary
winding
of the
power
trans-
former.
2.
The 24
volts AC
rectified
by
the
SILICON
DIODE (Dl
)
passes
through
the
RELAY
CONTACT
(RLt-+)
and
lights
the
DIREC-
TION PILOT lamp (F)
indicating
the
for-
ward
tape
direction.
3.
With
the
contact
of
the
"REV."
side
of
the
DIRECTION SELECTOR SWITCH
(Sa)
closed,
current
flows
through the
relay
and
the
resistor
(Ro+
),
causing
the
relay
to
operate.
The relay is
held
operated
by
the
contact RLt-+.
4.
The
current
operates the
PLUNGER through
contact
RLr-s
and
the switch interlocked
to
it
switches
the
input to
the amplifier
circuit
and the ouput from the
H.F.
oscillator
circuit.
5. When
the
PLUNGER
starts
PLUNGER
SWITCH
(Se
)
shortcircuits
the
resistor
Roo
permitting more current
to flow,
increasing
the
magnetic
attraction.
After
the starting
operation
of the
PLUNGER
releases the
switch Ss, allowing
the
current
to
flow
through
R6
6
,
and the
PLUNGER
is
held
without
big
heat.
T-EiCioo
6.
When the
contact of
the
"FWD"
side
of
the
switch
(Ss)
is closed,
both
ends
of
the relay
coil
are
shorted
causing
the relay
to
release.
7.
Since
the contact
point
is
inserted
in
parallel
into the
switch
(Sa),
the
same
operation
as
in
3 and
6
above
will
be
performed when
the
contact
point
is
shorted
by
the
sensing
foil
affixed
on
the
tape.
8.
When the AUTOMATIC
REVERSE
SWITCH
(Sr
+
) is
set
to
the "OFF",
the
shorting
of
the contact
point
does
not
affect
the
relay operation.
9.
The switch
St
is
connected
in
series
with
the
switch
(Sa).
.When
the FUNCTION
LEVER
is set to the "FAST"
position,
this
switch
releases
DIRECTION
SELECTOR
switch
and
the contact point to
prevent
an
auto-
matic
reversal
of
the
tape.
MOTOR CIRCUIT
1.
When
the
tape
is
threaded
SHUT
OFF
SWITCH
(St
t
)
is
pushed
on by
tape. With
the FUNCTION LEVER
set
to
the
"PLAY"
or "FAST"
position, MOTOR
SWITCH
(St
o) turns
on.
2.
When the
POWER
SWITCH S12, the
SHUT
OFF
SWITCH
Sr
1,&nd
the MOTOR
SWITCH
516
are
closed,
100V
will
be
supplied
to
the
motor.
3. With
the contact
of
the
"REV"
side
of
the
DIRECTION
SELECTOR
SWITCH
(Ss
)
is
closed,
relay
will
operate.
The
STARTING
COIL(L)
of
the
motor
changes
by
the
opera-
tion of the
relay
contacts
(RLr-r,
RLr-z),
causing the
revolution of
the
motor
to
reverse.
Fig.2
6
CONTACT
POINT
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