Marantz 4230 - Service Notes; AM Tuner; Suggestions for AM Tuner Trouble Shooting

INTRODUCTION
This
service
manual
was
prepared
for
use
by
Authorized
Warranty
Stations
and
contains
service
information
for
Marantz
Mode!
4230
Stereo
2
+
Quadradial
4
Receiver.
Servicing
information
and
voltage
data
included
in
this
manual
are
intended
for
use
by
the
knowledgeable
and
experienced
technician
only.
All
instruction
should
be
read
carefully.
No
attempt
should
be
made
to
proceed
without
a
good
understanding
of
the
operation
in
the
receiver.
The
parts
list
furnish
information
by
which
replacement
part
may
be
ordered
from
the
Marantz
Company.
A
simple
description
is
included
for
parts
which
can
be
usually
be
obtained
through
local
suppliers.
1. SERVICE NOTES
As
can
be
seen
from
the
circuit
diagram,
the
chassis
of
Model
4230
consists
of
following
units.
Each
unit
mounted
on
a
printed
circuit
board
is
described
within
the
square
enclosed
by
a
bold
dotted
line
on
the
circuit
diagram.
1.
FM
and
AM
Tuner.
.........
00
cee
eee
eee
tenes
mounted
on.P.W.
Board,
P100
2.
Phono
Amplifier
.......
0.00.0
eee
eee
eee
mounted
on
P.W.
Board,
P400
3.
Vari-Matrix
Unit
2.0.2.0...
ccc
ee
eee
mounted
on
P.W.
Board,
P500
40.
Dolby
URit
case
ech
eee
kai
eee
tA
ot
bac
andaa
sa
et
mounted
on
P.W.
Board,
P600
5.
Power
Amplifier
.........
0.
cece
eee
ee
tenes
mounted
on
P.W.
Board,
P700
6.
Power
Supply
.......
00.
cece
e
eee
eee
eee
ene
eee
mounted
on
P.W.
Board,
P800
7.
FM
De-emphasis
Switch
Unit.
.......
2.0...
ee
eee
ee
eee
mounted
on
P.W.
Board,
PCQ1
8.
Buffer
Amplifier
..
0.0.0...
0c
cece
eee
eee
mounted
on
P.W.
Board,
PDO1
9.
Tone
Amplifier
..
0.0.0.0...
0
ee
eee
eee
mounted
on
P.W.
Board,
PEO1
10.
ToneControl
Unit...
cc
eens
mounted
on
P.W.
Board,
PFO1
11.
Balance
Control
Unit...
0.0.0.
ee
eens
mounted
on
P.W.
Board,
PGO1
12,
400Hz
Oscillator
and
Meter
Driver...............25005-
mounted
on
P.W.
Board,
PLO1
13.
Loudness,
Hi
Filter,
Speaker
and
Power
Switch
Unit.......
mounted
on
P.W.
Board,
PSO1
14.
Tape
Monitor
Switch
Unit.......
0.0...
2c
eee eee
eee
eee
mounted
on
P.W.
Board,
PTO1
-15.
Indicator
Lamps
.........
2.00
cece
eee
eee
eee
eens
mounted
on
P.W.
Board,
PYO1
16.
Dial
Lamps
....
0...
cee
e
ee
eee
cece
renee
eee
enees
mounted
on
P.W.
Board,
PZ01
2. AM TUNER
All
components
except
ferrite
bar
antenna
are
mounted
on
a
printed
circuit
board
P100.
The
AM
signals
induced
in
a
ferrite
bar
antenna
are
applied
to
the
base
of
converter
transistor
H113
through
a
capacitor
of
C171,
while
the
local
oscillator
voltage
is
injected
to
the
emitter
of
H113
through
a
capacitor
C172.
Both
AM
signals
and
oscillating
voltage
are
mixed
at
the
base-emitter
junction
and
converted
into
455KHz
intermediate
frequency.
The
resulting
IF
signal
is
applied
to
the
first
IF
transformer
L116
consisting
of
one
ceramic
filter
and
two
tuned
circuits.
The
output
of
L116
is
led
to
the
transistor
H104
which
in
turn
apply
its
output
to
the
transistor
of
next
stage
H105.
The
fully
amplified
IF
output
is
then
applied
to
the
diode
H
123
to
detect
audible
signal
through
the
detector
transformer
L117.
The
detected
audio
signal
is
filtered
and
the
final
audio
output
is
obtained
from
pin
terminal
J118
and
applied
to
the
audio
amplifier
section
through
the
SELECTOR
switch.
The
DC
component
of
the
detected
IF
signal
is
used
as
a
AGC
voltage
to
control
emitter
current
of
H104
through
the
resistor
R185.
A
part
of
IF
signal
output
is
also
applied
to
the
diode
H124
through
a
capacitor
C180
and
rectified
to
obtain
DC
current
for
energizing
the
SIGNAL
STRENGTH
meter
M004.
_ 2.1 Suggestions for AM Tuner Trouble Shooting
Check
for
broken
AM
bar
antenna,
next
try
to
tune
station
by
rotating
fly-wheel
tuning
knob