4
...
-. ..
a.--•~
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
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 distribution in the
FM
Front
End
and
IF amplifier
unit
and
compare them
with
those
shown
in
the circuit diagram.
When
signal
strength meter deflects
but
no sound
is
obtained,
check audio circuits, using 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
19KHz
pilot
signal
and
38KHz
switching signal, using
an
oscilloscope.
4.
PHONO
AND
PRE-AMPLIFIER
Signals from the PHONO jacks
are
applied
to
the phono amplifier mounted on P700. The
amplified
and
RIAA
equalized phono
signals
and
signals
from the tuner section
and
the TAPE,
AUX1, AUX2, jacks
are
applied
to
the selector switch which, in turn,
leads
the selected signals
to
the TAPE OUT jacks
and
mode switch.
Applied
to
the other section
of
the TAPE MON switch
are
signals
from the TAPE IN jacks.
The TAPE MON switch selects the
signals
from the mode switch or those from the TAPE IN
jacks
and
the selected
signals
go
to
the pre-amplifier.
Signals
are
then mode
processed
by the
mode switch
and
its associated circuit and applied
to
the tone control amplifier through the
volume control. The
bass
and
treble controlled
signals
from the tone control amplifier
pass
through the balance control section
and
the hi-filter before they
reach
the main amplifier.
4.1 Mode Switch
Mode switch S005
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
+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 corresponding
channel.
In the
VARI-MATRIX
position, 2-channel stereo input
signals
are
converted
into
quadra-
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.
Dimension Control Setting
LR
Output
RR
Output
Minimum
(FCCW)
LF
+RF
RF+
LF
Center
LF
RF
Maximum (FCW)
j_
LF-
RF
RF-
LF
When
the dimension control
is
set
to
the minimum position the LR
and
RR
channel
signals
-
To Next Page
Loading...
