122
is
muted. Since the bias oscillator
is
work-
ing at this time, the tape runs
with
no
signal recorded on it.
d.
On the other hand, when
0610
turns on,
base
current flows through
0612,
turning
it
on (0611
is
off
during record mode).
When
0612
turns on, the REC
MUTE
LED
lights.
The R EC/MUTE mode
is
released by
re-
setting the
REC
MUTE
flip-flop.
There are
three ways this
can
be
done
as
below.
i)
Depress
the
PLAY
button.
An L-Ievel reset signal
will
be
applied
to
the
base
of
0609
via path
CD
.
ii)
Depress
the PAUSE
button.
When
the PAUSE
button
has
been
de-
pressed,
the deck changes
from
the
re-
cord/reproduce (mute) mode
to
the
re-
cord/pause mode. Therefore,
pin
12
of
U601 changes
from
H level
to
L, apply-
ings
L level signal
to
the
base
of
0609
via path ® .
iii)
Depress
any
of
the STOP, F.FWD, and
R
EW
buttons.
The record/reproduce (mute) mode
will
be
released and pins 12 and 10
of
U601
drop
to
L level.
As
a
resu
I t, a reset
signal
will
,
be
appli
ed
to
the
base
of
0609
via path ®
or
@.
When
an
L-Ievel reset signal
has
been
appli-
ed
to
the
base
of
0609,
0609
turns
off
as
its
base
current
is
cut
off.
Since the collec-
tor
of
0609
rises
to
H level,
base
cu
rrent
flows through
0608
and
it
turns on reset-
ting the REC MUTE
flip-flop.
When
0609
is
off,
0610
turns
off
as
i,ts
base
current
is
cut
off.
(Note: ,In this
case,
the
base
cur-
rent
of
0608
flows via path @ . The volt-
age
drop
across
R647
caused
by this cur-
rent (the emitter-base voltage
of
0610)
is
approximately 0.16 V
so
0610
cannot
turn on.) When
0610
has
turned
off,
01
111,
0110,
and
011a
turn
off
in sequence
to
release
the record amplifier
from
muting.
Note that, when the STOP,
F.
FWD,
or
REW
button
is
depressed during REC/
MUTE
mode
(case
(jii)l,
the record mode
will
be
released. In this
case,
when pin
10
of
U601 drops
to
L level,
0604
turns
off
as
its
base
current
is
cut
off,
while
0611
turns
on
as
base
current
is
applied
to
it.
Therefore,
even
if
0609
turns
off
with
the
REC
MUTE
flip-flop
reset,
0610
remains
on
because
its
base
current flows via R648
and
0611.
This
means
that
the record
amplifier
is
not
released
from
muting.
30
AMPLIFIER
SECTION
3-11,. REPRODUCE
CIRCUIT
See
Fig. 3-26.
a.
The signal picked up
by
the reproduce
head
is
amplified
by
reproduce equalizer amplifier
transistors
0101
and
0102.
The reproduce
equalizer
amplifier
negative feedback loop
determines the compensation characteristic
(time constants)
for
reproduction
as
given in
Table 1. The compensation curve at high fre-
quencies
is
determined by the composite
resistance
of
R301-R304,
the combination
of
which
is
determined
by
the settings
of
SPEED switches S4-10 and S4-8 and EO
switch S5-2, and the capacity
of
Cl04.
Table
2 summarizes the composite resistances in
relation
to
the settings
of
the SPEED and
EO
switches.
Table 1
Compensation characteristic
for
reproduction
~
EQ
STANDARD
HIGH
METAL
3180
+
70
3180+
35
Co
(Cr02)
3180
+
70
3180+
35
NORMAL
3180+120
3180+50
(unit:
,usec)
Table 2 Composite resistance
~
EQ
STANDARD
HIGH
METAL
R30Z
=
S.2k.
R301
IIR302
~3.1
k
Co
(Cr021
R302
=
S.2k
R301
//R302
~3.1
k
NORMAL
R302
+
R304
~10
.
9k.
R30111R302
~
+
R30311R304
~4.2k
("II"
represents
parallel
connection
of
resistors.
unit:
ohms)
b.
Capacitor
Cl07
and coil
L1
01
connected in
series
are a bias trap
with
a resonance fre-
quency
of
100 kHz.
c.
Semi-fixed resistor R
11
adjusts reproduction
level.
d. Capacitor
Cl08
and semi-fixed resistor
Rl0
compensate
for
characteristics at high fre-
quencies.
e.
Thermistor
RT10
compensates
for
variations
in the sensitivity
of
the reproduce
head
due
to
temperature changes.
The standard resistance
of
RT10
is
10k
ohms at room temperature (25°C). The
resistance
decreases
(increases) when the
temperature
rises
(falls). On
the
other
hand,
the sensitivity
of
the reproduce
head
rises
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