Technical information

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RADIO RETAILING'S
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PHTLCO
80
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PHILCO
80
Insensitive
replace
240,000
ohnr
pla,te
resistor.
This
unit has
greatly
in-
creased
value.
PHILCO 80. Volume control does
not cut
down smoothly
on strong
locals
and on some stations will not attenuate
to
zero
, . . Change volur;re control cir-
cuit,
using
No. 3793B
part.
Original
control had one terminal to
ground,
the
other to the
antenna
post
and the vari-
able arm to the antenna coil.
Using
new
part
place
one end to the antenna
post
and also to
the
antenna coil, the
other to the
i.f.
grid
return and the vari-
able arm to
ground.
The
j.f.
grid
re-
turn errd
goes
to the
2nd
detector,
anchored
on
cased condenser lug to
one
side of chassis. Remove
lead from
con-
denser.
PHTLCO
80
Loose
rotor
on condenser
gang
Remove
assembly and take
off
rear
bearing
plate.
Center
punch
the depres-
sion on this
plate
so
that it
protrudes
further against
shaft.
If
plates
are out
of
line
when the
unit is
assembled
thiy
can be realigned by
loosening
set
screws
holding them to shaft.
PHILCO 80 AC. Noise Plate
lead fronr
i.f . transf
ormer to first 36
rubs
coil base and insulation is
punc-
tured.
Or,
grid
resistor number 26 for
42
tube, lying close to socket, shorts to
proug.
PHTLCO 8t
Fading
Usually
caused
by fait-
ure of one
of the condenseis
in the
a.c.
line
or in the
center-tap
of
the
power
transformer.
Opens
are the most com-
mon failure.
Usually
attended
by a
hum
or
squeal,
depending upon which
con-
denser
opens.
PHILCO
JR
81.
Oscillatron of
rn-
termittent nature .
.
Replace
condenser
3793R,
which
acts as
bypass
for
42 out-
put
tube and also bypasses
one side of
the a.c. line.
PHTLCO
8.f
Sudden drop in
volume.
.
.
dual con-
denser
bypassing
screens
of. 77 tubes
shorting:
replace.
PHILCO
848
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to
oscill:rtor
coil.
This is
part
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carr
be inrplovctl
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f,lre
green
tcr-
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PHILCO 8,t
Oscillation .
.
connect .05 mfd.
fron:
high voltage to
ground.
PHILCO
84
Loud
hunr
check
rivet
that
holds
42
socket,
lug from
42
cathode ground-
ing
on rivet.
PHTLCO
84
Impossible to turll volume
off on
lo-
cals
. shield first detector
tube.
If
still
troublesonre
shield
grid
lead.
PHILCO
86. Low hissing
which
per-
sists even with known-to-be-good
tubes
.
.
.
Often caused
by defective
first
audio
transformer. Don't
relv
on
tests.
Substitute new
unit.
PHTLCO
86
Dead
Check for
a
shorted
.l
rrfd
condenser
sealed in
cylindrical
can
along
with the
plate
resistor.
Dis-
connect the condenser
lead
and
sub-
stitute
a 600 volt unit.
PHTLCO
87
Crackling,
ohm section
ohm and
750
noisy
replace 3785
of R8 with
20 rvatt
3000
ohm units
in
series.
PHTLCO
87
Ffum
control ineffective
. shorted
twin .25
mfd.
condensers
across
li
volt
filament.
Replace
condensers,
set
hum
control.
Condensers
are in long
can
on front
of
chassis.
PHILCO
E7.
Instability,
will
not
neutralize
. .
. The
first,
second
and
third r.f.
plate
circuits
include
resistors
wound
directly
on
.l mfd.
condensers.
The
.l
mike
units
are
connected
fe-
tween
the
resistors
and
the r.f,
primaries.
Usually
the 6rst
one
is
open,
causing
excessive
oscillation.
Check
all
three.
PHILCO
87.
Low
volume
or
fading
.
. . Look
at
r.f. trimmers. Metal
eye-
lets
in insulators
supporting these may
have temporary
short to trimmer
stators.
Remove
screws through eyelets and slip
thin
piece
of insulation
under them. Re-
move
adjusti4g nuts and
give
trimmer
stators
an upward
bend. This tension
will hold them in
place.
PHILCO
89
Continuous
crackling
look
at
second i.f.
primary
for
partial
open.
PHILCO
E9.
Voltages
check ok but
set
refuses
to
operate
over entire
dial
.-.
:
T:V
reve-rsing primary
leads of the
nrst
t.t.
transtormer.
PHILCO
898
Poor tone, intermittant
reception
section
of
part
No
7 in 75 detector
plate
leaky or bad.
PHILCO 898
I.ow
volunre
and noisy
de-
fcctive
seconrl I.F.
transfornrer. This
unit
will check o.k.
on
voltage
test.
PHTLCO
90
Noisy.
Check
for loose
oscil-
lator coil
shield.
Crimp edge
to
make
tisht
fit or solder to
chassis.
PHTLCO 90
Dead on
high frequency
end
of dial
.
connect 10,000
ohm resistor
across oscillator cathode resistor.
PHILCO 90. Fading,
periodic program
interruption. Replace all three 3903
(L.M.R)
condensers extending
one be-
hind
the other
from tone control
to
speaker
plug
for
permanent
repair.
PHTLCO
90
(With
one
-17
output) Weak,
sta-
tions do not track with dial settings
.
. .
althought
the
i.f.
peak
is
given
as
260 kc.
by the
manufacturer
some
rvere built to align
at
175
kc.
PHil-cO
90.
Microphonic
howl, stops if
oscillator
or i.f.
coil cans are
pressed
or squeczed
. .
Remove
coil assemblies
and
melt
paraffin
over the
forms
to
hold
leads
solidly
in
place.
Paper
around the coils
frequently
becomes loose,
vibrates and
moves
leads sufficiently
to cause trouble.
PHILCO
90. Intermittent
reception
.
Generally
due to trouble in
coupling
condensers
between
first
and
second'27's
or between
second
and third 27's,
or be-
tween
third 27
and 47 final
amolifier.
The
first
one is hard
to test
and it is
best
to insert
a
new
one and trv the
receiver.
PHILCO
90.
Oscillation
between
1,100
and
1,500
kc.
when trimmers
are
adjusted
to resonance.
Shunt
a 0.1
mfd.,
200-volt
condenser
across
first r.f.
(24)
and
oscillator
(27)
5,000-ohm
cathode
resistors.
PHILCO
90.
Audio
howl
not
due
to
microphonic
tubes . . .
Check for
con-
trol shafts
or
chassis touching
front
of
cabinet,
and
also
for
correct
functioning
of
rubber
cushions.
Vibration
fre-
quently
causes
oscillator
plates
to
vibrate,
causing
tuning
change and
howl.
PHTLCO
90,
90A
No
reception,
set snrokes
filter
choke
coil
shorts
to core
due
to ab-
sence
of
paper
insulation
betlveen
two
conlponents.
As short
usually
dam-
ages
coil
badly,
install
ner.v
choke
having
needed
insulation.
PHTLCO 90, 90A
No
reception
27
oscillator
pe-
riodically
goes
dead
despite
norr.nal cir-
cuit corrditions.
PHILCO
91. Gradual
widening out of
the shadow tuning
indicator after
ten
or
fifteen minutes of
operation . .
. Re-
placc
two
44 a.f. and
i.f.
tubes
They
may tcst ok but
due to
gas gradually
draw
higher and
highcr
plate
current,
evcntually burning out
thc indicator
through
which this
current flows.
43