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Harman Kardon HK3400 - Page 6

Harman Kardon HK3400
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CIRCUIT
DESCRIPTION
@IFM
TUNER
SECTION
The
FM
signal
which
has
entered
through
the
antenna
is
high-frequency
amplified
in
the
front
end.
Then
it
is
mixed
with
the
output
of
the
local
oscillators
and
converted
into
the
10.7MHz
intermediate-frequency.
The
10.7MHz
signal
is
amplified
in
the
intermediate
frequency
amplifying
section
which
consists
of
CF201,
Q201,
CF202,
Q202
and
CF203
and
fed
to
pin
1
of
1C201.
In
1C201,
the
signal
is
sent
through
the
IF
amplifier
and
after
being
detected
in
the
quadrature,
it
is
sent
through
the
post
amplifier
to
pin
12
and
then
input
to
pin
2
of
|C301.
In
IC301,
the
pilot
signal
is
detected
out
of
the
signal
which
has
been
fed
and
38kHz
signal
is
produced.
Then
by
this
signal,
stereo
signal
is
demodulated,
output
from
pin
4
for
the
left
channel
and
from
pin
7
for
the
right
channel
and
transmitted
to
the
input
selector
section.
MAM
TUNER
SECTION
The
AM
signal
which
has
entered
through
the
antenna
passes
through
the
tuning
circuit
consisting
of
CB251
and
is
inputted
to
pin
21
of
1C201.
In
IC201,
it
undergoes
radio-frequency
amplification
and
local
oscillation
and
is
output
from
pin
20,
and
passed
through
the
transformer
(T251)
and
ceramic
filter
(CF252)
and
enters
pin
18
of
IC201.
It
is
then
passed
through
the
IF
amplification
and
detection
and
is
output
from
pin
15.
This
signal
is
fed
to
1C301.
MAUDIO
AMPLIFIER
SECTION
The
signal
which
has
entered
from
each
input
terminal
is
selected
by
the
input
selector,
passes
through
the
balance
circuit,
volume
and
loudness
circuit
and
is
fed
into
the
pre-amplifier.
Then
it
is
fed
into
the
power
amplifier
through
the
tone
control
circuit,
power
is
amplified
and
transmitted
to
the
speaker
terminal.
The
power
amplifier
has
an
over-output
protective
circuit.
if
current
exceeding
the
specification
flows
to
0419,
Q421
(L
ch),
Q420,
Q422
(R
ch),
it
is
detected
at
Q27
(L
ch)
and
Q28
(R
ch)
and
the
protective
circuit
consisting
of
Q22
and
Q24
draws
in
Q23
and
Q29,
and
thus
the
input
signal
is
cut
to
protect
the
circuit.
MMUTING
CIRCUIT
lf
FM
or
AM
is
received
out
of
tuning
or
in
a
very
weak
field
intensity,
pin
31
of
|1C701
becomes
high
level.
This
is
fed
to
the
base
of
0707,
whose
collector
then
becomes
low
level
and
the
collector
of
Q708
high
level.
As
a
result,
Q301
(L
ch)
and
0302
(R
ch)
are
conducted
to
mute
the
output.
IESYNTHESIZER
SECTION
@FM
The
local
oscillation
output
at
the
front
end
is
fed
to
pin
21
of
the
prescaler
IC702
and
after
being
frequency
divided
into
30
or
32,
control
output
signal
if
fed
from
!C701,
compared
with
the
divided
local
oscillation
output
and
output
to
pin
16.
This
voltage
is
level
converted
at
0701
and
Q702,
and
fed
to
the
front
end.
eAM
The
local
oscillation
output
is
fed
from
pin
24
of
IC201
to
pin
19
of
10702.
In
IC702,
control
output
signal
is
fed
from
iIC701,
compared
with
the
local
oscillation
output
and
output
to
pin
16.
This
voltage
is
level
converted
at
Q701
and
Q702,
and
fed
to
the
AM
local
oscillation
section.
HINDICATOR
SECTION
@
Frequency
display
The
indicator
tube
is
turned
ON
by
the
output
decoded
in
IC701.
@
Tuning
When
broadcast
is
received,
Q711
turns
ON
by
the
control
signal
in
1C301
and
“Tuned”
of
the
indicator
tube
is
turned
ON.
When
FM
or
stereo
broadcast
is
received,
pin
9
of
1C301
becomes
low
level,
Q712
turns
ON
and
“Stereo”
of
the
indicator
tube
is
turned
ON.

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