Philco 410 Manual

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PHILCO
RADIO MODEL
4IO
Circuit Description
Philco Model 410
is a
portable four-tube
suPer-
heterodyne
providing reception
on
the
standard-
broadcait
baird.
A
high-impedance
loop
within
the
cabinet normally
prov:ides
-adeqtrate
si$nal
pickup.
However, provisions
have
been made
for
connectine
an external aerial,
if
required.
The aerial circtrit rttotks directly
into a lR5
con-
verter, where the incoming signal is
converted
to
the
460-kc.
intermediate frequency.
A lT4
is used
in
.t
single high-gain stage of
-i-f
amplification, r,r'hich em-
ploys
neutrilization to
suppress
oscillation.
A
3-mmt.
^condenser,
C304,
feed paits
of the i-f
voltage,
of
the
proper
phase,
back
to tire
lT4
grid through the tube-
socket capacitance.
A
lU5
diode-pentode
is
used
in
the detector, a'v-c'
and
first
audio
-circuits. Then pentode section is
re-
sistance-coupled
to
a
3V4
Pentocte
otrtptrt amplifier,
which works
into
a p-m
speaker.
The
operating
voltages are
obtained from
a
battery
pack,
Philco type
P-361.
Philco TROUBLE-SHOOTING Procedure
For rapid trouble
shooting,
the radio circuit
is
divided
into
four
sections,
with test points
specified
for
each section; these sections
and
test Points
arc
indicated
in
the
schematic
diagram.
The
trouble-
shooting procedure given
for
each
section includes
a
simolfied
test
chart and a bottom view of the
chassis
shoining
the locations
of
the
test
points and the
com-
ponenta
of
that
section.
In
each
chart, the
first step is a
master
check for
determining whether trouble exists
in
that
section,
without going through the entire chart.
Failure to obtain the
"NORMAL INDICATION"
in
any
given
step
indicates trouble
within the circuit
under
test.
After
isolating
the trouble
to
a
single stage,
the
defect
is
located
by:
first, testing the tube;
secontl.
measuring tube electrode voltagcs;
third,
rneasuring
circuit
resistances;
fourth, substituting
condensers.
T'he trouble
revealed
should be corrected
before
test-
ing
further.
Preliminery
Checks
To
avoid possible damage
to
the radio, the follow-
ing preliminary
checks
should be made before turn-
ing on the
power:
l.
Inspect
both the top and the bottom
of
the
chassis.
Make sure
that
all
ttrlles are secure
in
the
proper
sockets, ancl
look for
anv broken
or
shorted
ionnections, burned
resistors,
or other
obvious
sources
of
trouble.
2. Check
the total
filament
resistance,
with
the
power switch turned on, and the battery plug
discon-
nected
from
the
battery.
If
the
resistance
between the
Af
and
A-
pins
on the battery Plug is higher than
100 ohms,
one
of the tube filaments is
probably
oPen.
Note:
If
the
3V4
filament
is open,
check
conden'
ser
C203B before
replacing the
tube.
3.
Measure
the
resistance
between
the
Bf
and
B-
pins on the
battery
plug.
If
thc reading is lower
than
5000 ohms, check condenser C203A
for
leakage
or
a
short.
The
resistance
value
above,
which
is much
lower
than normal,
does
not
represent
a quality
check of
this condenser;
it
is the lowest
value which
will
permit
the voltage
checks
of
Section
I
(power
supply)
to
be
performed
without
excessive
battery drain.
MODEL 4IO
SPECIFICATIONS
CABINET
........Molded Polystyrene
(maroort,
Four-tube
superheterodyne
CIRCUIT
..........
tan,
ivory,
or
green)
FREQUENCY
RANGE
......
540-1600
kc.
AUDIO
OUTPUT
160 milliwatts
OPERATING
VOLTAGES ......................"8"; 90
volts;
"4",
f.5 volts
POWER
CONSUI\{PTION
"B",
13
ma.
at
90
volts; "A",
50
ma.
at
7.5 volts.
AERIAL Built-in
high-impedance loop;
terminal also provided
for
ex'
ternal
aerial
INTERMEDIATE
TREQUENCY
460
kc.
PHILCO TUBES
(4) lR5, lT4, lU5,
3V4
BATTERY
TYPE
Philco
P-361
rp_4523
Gopyright
194E,
Phllco corporanon
ot
Ganat!
Ltrr.