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Technics SA-5460

Technics SA-5460
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M
SERVICE
AID
®
FM
soft
muting
When
moving
the
tuning
point
away
from
the
point
of
maximum
output
(optimum
tuning)
the
signal
output
gradually
decreases
until
it
reaches
zero
output.
(between
stations.)
In
conventional
muting
circuits
a
sharp
‘’popping’’
noise
is
heard
when
tuning,
due
to
the
sudden
(switch-like)
action
of
the
muting
circuit
from
zero
signal
to
full
output.
This
“Soft
muting”
circuit
lets
the
sound
fade
more
gradually,
making
it
more
natural
and
pleasant
to
listen
to.
Muting
point
AF
output
Muting
point
AF
output
AF
output
Noise
FM
input
FM
input
FM
input
Without
muting
:
Conventional
muting
Soft
muting
®
Circuitry
principles
This
circuit
makes
use
of
the
VBE
characteristics
of
TR102
(2SC828).
(Refer
to
fig.
1.)
The
detected
voltage
from
the
FM
IF
input
signal
is
applied
to
the
base
of
TR102.
When
the
FM
input
signal
increases
this
voltage
increases,
causing
the
emitter
current,
to
increase,
which,
in
turn,
decreases
the
collector
voltage
of
TR102,
making
the
collector
voltage
approache
ground
potential.
Because
the
collector
of
TR102
is
connected
to
the
1C101
IF
amplifier
through
the
muting
switch,
a
change
in
the
collector
voltage
will
control
the
output
of
the
1C101
IF
amplifier.
When
the
FM
input
signal
increases
to
the
point
that
the
base
voltage
of
TR102
reaches
its
operating
point
(about
0.6V),
the
output
of
1C101
reaches
maximum.
R111
DliO
hae
FM
IF
IN
PUT
AF
QUT
PUT
G)
Operation
a
j
=
IC
101
IE
Pos
e)
(
SVILA1230
)
FM
IF
AMP
23
DET
(312)
TO
SIGNAL
METER
FM
signal
input
VB
0.6V
FM
input
vs.
AF
output
curve
O
oC
oe
VBE
curve
of
TR102
Fig.
2
Fig.
1.
HM
FM
RF
ALIGNMENT
INSTRUCTIONS
.....
Only
Set
for
Germany
ABGLEICHANWEISUNGEN.........
VOR
DEM
ABGLEICH
SORGFALTIG
DURCHLESEN
MESSENDER
SKALENZEIGER-
EINSTELLUNG
DES
SCHALTUNG
FREQUENZ
|
EMPFANGERS
[ABSTAND]
FM
HF-ABGLEICH
87.5MHz
Output
meter
Uber
Lautsprecher-
[{Omm]
schwingspule
anschlieRen.
90
MHz
90MHz
(
»
)
(17.2mm)
106
MHz
106
MHz
creed
(174.1mm)
ANGEIGE
(ROHRENVOLTMETER
ODER
OSZILLOGRAPH)
ABGLEICH
BEMERKUNGEN
Anschluf§
an
den
FM
Antennenanschluf&
Uber
die
ktinstliche.
FM
Antenne
(Vgl.
Abb.
1)
87.5MHz
(100%
Mod
bel
400
Hz)
Auf
max.
Ausgang
abgleichen
L5
(Oszillatorspule)
L3
(Zwischenkreis)
L2
(Antennenspule)
CT3
(OSZ.
Trimmer)
CT2
(DET.
Trimmer)
CT1
(ANT.
Trimmer)

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