Marantz 2215 - FM Tuner Troubleshooting Guide; Troubleshooting: No FM Reception; Troubleshooting: No Stereo Separation; Phono and Pre-amplifier Section

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
tuning
meter.
If
the
meter
deflect
at
several
frequencies
received,
the
circuits
preceding
the
IF
amplifier
H204
may
have
no
failure.
When
no
reading
is
obtained
in
the
meter,
check
FM
local
oscillator
circuit,
using
a
RF
VTVM.
The
normal
local
oscillator
voltage
is
one
or
two
volts
(rms)
at
the
tuning
capacitor,
depending
on
the
tuning
capacitor
position.
If
the
local
oscillator
voltage
is
normal,
next
check
all
voltage
distributions
in
the
FM
circuits
and
compare
them
with
those
shown
in
the
circuit
diagram.
When
the
tuning
meter
deflects
but
no
sound
is
obtained,
check
audio
circuits,
using
a
high
sensitive
oscilloscope.
3.3.2
Symptom:
No
Stereo
Separation
First
check
the
“MONO”
switch
is
in
normal
out
position.
Connect
a
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
tuner
and
AUX
jacks
are
applied
to
the
selector
switch.
Signals
from
the
PHONO
jacks
are
applied
to
the
phono-amplifier
consisting
of
transistor
r'901,
H903
and
H905.
The
gain
of
the
amplifier
is
40
dB.
The
amplified
and
equalized
phono-signals
are,
then,
fed
to
other
section
of
the
selector
switch
which,
in
turn,
applies
output
signals
from
the
tuner,
phono-amplifier
and
AUX
jacks
to
the
TAPE
MONITOR
switch
and
TAPE
OUT
jacks.
The
TAPE
MONITOR
switch
applies
the
signals
to
the
balance
and
volume
controls.
The
controlled
signals
are
fed
to
the
pre-amplifier
consisting
of
H501,
H503
and
H505.
Frequency
response
of
the
amplifier
can
be
varied
by
BASS
and
TREBLE
controls.
The
controlled
output
are
then
led
to
the
main
amplifier
through
high
and
low
pass
filter
push-switches.
5. Main Amplifier
Transistor
H701
is
a
pre-driver
coupled
to
the
transistor
H703
through
capacitor
C711.
Transistor
H703
drives
the
inverter
transistors
H709
and
H710
which,
in
turn,
drive
the
power
stage
consisting
of
HOO1
and
HOO2.
Transistors
H705
and
H709
are
current
limitters
and
operate
as
power
protecting
circuits.
Excessive
currents
flowing
into
the
power
stage
are
detected
by
the
resistors
R741
and
R745
and
the
resultant
variations
are
applied
to
the
transistors
H705
and
H707
and
make
them
turned
on.
This
decreases
the
current
flowing
into
the
H709
and
H710.
In
this
way
the
currents
flowing
in
the
power
stage
(HOO1
and
HO02)
are
restricted
within
a
safe
value.