Marantz 4230 - Suggestion for Trouble Shooting of FM Tuner; Phono and Pre-Amplifier; Mode Switch

Pin
@
on
the
MPX
IC
H114
is
connected
through
R163
to
the
collector
of
the
autostereo
switch
transistor
H112,
which
turns
on
or
off
according
to
the
incoming
FM
signal
strength,
thereby
automatically
switching
between
the
stereophonic
and
monaural
operations.
The
H112
turns
on
or
off
in
accordance
with
whether
the
FM
signal
strength
is
more
or
less
than
approximately
25uV.
3.3
Suggestion
for
Trouble
Shooting
of
FM
Tuner
3.3.1
Symptom:
No
FM
Reception
First
turn
on
the
POWER
switch
and
try
to
tune
FM
stations.
Rotate
the
fly-wheel
tuning
knob
slowly.and
observe
the
FM
SIGNAL
STRENGTH
meter.
If
the
SIGNAL
STRENGTH
meter
deflect
at
several
frequencies
received,
the
tuner
circuits
preceding
the
discriminator
circuit
may
have
no
failure.
When
no
reading
is
obtained
in
the
meter,
check
FM
local
oscillator
circuit,
using
a
RFE
VTVM.
The
normal
local
oscillator
voltage
is
one
or
two
volts
(rms)
at
the
tuning
capacitor,
depending
on
the
tuning
capacitor
position.
When
SIGNAL
STRENGTH
meter
deflects
but
no
sound
is
obtained,
check
audio
circuits,
using
high
sensitive
oscilloscope.
3.3.2
Symptom:
No
Stereo
Separation
Connect
an
FM
RF
signal
generator
output
modulated
by
a
stereo
modulator
to
the
rear
FM
ANTENNA
terminals,
and
check
the
stereo
beacon
is
turned
on
or
not.
If
not
turned
on,
check
for
19
KHz
pilot
signal
and
38
KHz
switching
signal,
using
an
oscilloscope.
4.
PHONO
AND
PRE-AMPLIFIER
Signals
from
the
PHONO
jacks
are
applied
to
the
phono-amplifier
mounted
on
P400.
The
amplified
and
RIAA
equalized
phono
signals
and
signals
from
the
tuner
section,
CD-4/AUX
and
TAPE
MONITOR
IN
jacks
are
applied
to
the
SELECTOR
switch
which,
in
turn,
leads
the
selected
signals
to
the
TAPE
MON.
switch
and
TAPE
MONITOR
OUT
jacks.
Applied
to
the
other
section
of
the
TAPE
MON.
switch
are
signals
from
the
TAPE
MONITOR
IN
jacks.
The
TAPE
MON.
switch
selects
the
signals
from
the
SELECTOR
switch
or
those
from
the
TAPE
MONITOR
IN
jacks
and
the
selected
signals
go
to
the
DOLBY
and
MODE
switches.
Signals
are
then
mode
processed
by
the
MODE
switch
and
its
associated
circuit
and
applied
to
the
tone
control
amplifier
“through
the
buffer
amplifier
and
BALANCE
and
VOLUME
controls.
The
bass
and
treble
control-
led
signals
from
the
tone
control
amplifier
pass
through
the
hi
filter
before
they
reach
the
main
amplifier.
4.1 Mode Switch
MODE
switch
S002
has
positions
of
MONO,
2
CH,
DISCRETE,
VARI-MATRIX,
and
SQ
DECODER.
In
the
MONO
position,
all
input
signals
are
mixed
together
and
delivered
to
all
four
channels.
In
the
2
CH
position,
each
pair
of
input
signals
right-front
(RF)
and
right-rear
(RR),
and
left-front
(LF)
and
left-rear
(LR)
are
mixed
together.
The
resultant
signals
(RF
+
RR)
and
(LF
+t
LR)
are
delivered
to
the
pairs
of
RF
and
RR,
and
LF
and
LR
channels,
respectively.
In
the
DISCRETE
position,
each
channel
signal
is
separately
routed
to
the
correspondirg
channel.
In
the
VARI-MATRIX
position,
2-channel
streo
input
signals
are
converted
into
quadré
phonic
signals
through
the
vari-matrix
circuit;
the
input
right
and
left
channel
signals
are
fed
directly
to
the
LF
and
RF
channels,
while
the
signals
to
the
LR
and
RR
channels
are
synthesized
from
the
2-channel
input
signals
under
the
control
of
the
DIMENSION
control.
The
LR
and
RR
channel
signal
components
are
controlled
by
the
DIMENSION
control
as
shown
below.