Technical information

O
RADIO RETAILING'S
",
enuie
FORD PHILCO I937
Ignition interference
Male
end
of
antenna
lead making
poor
contact
in set socket.
Solder short heavy braid
to shield on
male
cap and fasten securely
under edge of
junction
box
after
6rst
cleaning off
paint.
If
some noise still
persists,
bond
the
middle
screw on set
cover
to dash. also
junction
box
to emergency brake bracket
screw.
FORD V-8 NOISE ELIMINATION
Ignition
interference
insert r.f.
choke,
made
by winding 12
to
14
turns
of 14 d.c.c.
wire on
l
in.
form,
directly
at the fuse terminal
with other
end
direct
to leacl
to set. This
"Hot
A"
lead should
be as s/rorl as
possible
and
shielded right down
to the set,
grounded
only
at
the set end. Try
several
small
mica
condensers from 50 to 250
mmf.
betwcerr
r.f.c.
and
open errd of shield.
FREED
FREEO MB9.9O
Fading.
.
.
replace .02 coupling
con-
denser between 55 and
56. Vibration
or tapping will cause this condenser
to
short.
GENERAL
ELECTRIC
GE, RCA. In avc
equipped
models
locals
sometimes
snap
in and
out
as they
are
tuned-through.
Substitute a new
35
for
those
in RF
and IF stages
until
the trouble
is found.
GE
Cf4. Operates at low
volume
on
long
antenna and will not
play
ut all on
regular
car type, volume
control
has no
effect .
Check
for
open .02
(Cl6
on
diagram)
mfd. condenser
connecting
diode section
of 687
through variable
arm
of
control
to
grid
of triode
section
of same tube.
GE H3l, H5l. Intermittent recep-
tion
.
. .
Check
primary
of
i.f.
trans-
formers.
Trouble is usually in the
second. Distortion at low volume set-
tings of the volume control on
locals
, , , Usually caused by drop in value of
110,000
ohm unit on
resistor
strip.
GE 40. Noise alter
standard suppres-
sion has been installed.
Ground rubber-
mounted
triangular
plate
of
tuning
con-
trol
sheath to side of chassis.
GE 40B
(RCA).
Loud roar
after
set
warms
up .-.
.
Check for
arcing at vi-
brator
points.
If
found, connect
500,000
ohm resistor
across transformet
sec-
ondary,
the terminats
of which are
brought out
to two insulated
screws.
Connect
two .01 mfd.
condensers across
secondary,
in
series,
grounding
midpoint
between
them. Use
600
volt capacitors.
GE B.+O
(RCA
M30). Fuses
blow
immediately
upon being
installed
Most
often caused
by shorted .03 mfd.
condensers
in vibrator
base.
G. E. K.1OA
No
volume
. .
worn
insulation on
ante?na lead where
it
passes
through
chassis.
6E
&r0. RCA Ml4
Hash,
difficult to
rernove
even
rvith
all
condensers
replaced and
vibrator
points
functioning
properly
Be
sure screws holding vibrator
in
place
are
tight,
shielding of
cable to control
head
is ok and securely
soldered
to base
of
vibrator. Shield ends of two
screws
holding red and
green
wires coming
out of
vibrator
base. lVlake this
extra
shield in
form
of box
rvithout lid,
soldering to chassis
at end
of
terminal
board
over
screws.
Depth
of
box
should be
sufficient
to
clear the
screws
nicely
as
thev
are at
high
potential.
GE K|OA. Weak
and distorted re-
ception .
.
.
Most
common cause
is ex-
cessive
leakage or total shorting of
doubtc
4 mike electrolytic condensers.
The
most
troublesome unit is
the
one
connected in the
2525 circuit, the next
best bet
the
one
in the 77 or'78
cathode
circuits. Sometimes the
set does
not
opcratc after
these condensers
are re-
placed.
If
this trouble
is encountered,
try changing the
2525
tube
even though
it shows up
ok in a checker,
If
the
rectifier
is
causing
trouble usually
the
38's
plate
current will be
abnormally
low while other
voltages
seem to be
about right.
€E
S.t2l
(RCA
R.r3)
Distortion
at high volume
. . . a few
shorted turns
on one sidi
of
primary
of input transforner
(No.7265).
Check by inserting milliammeter in
each of
p.p.
plate
leads and compare
current
peaks
on
loud
signal.
Any
marked difference indicates defective
transformer; replace.
cE K43.
A.c. hum,
especially
noticeable
on
sta-
tions, in
early
models
. . . Connect 500
ohm resistor
from
set side
of .01 antenna
condenser
to chassis. Later models
came
through
with an
r.f. choke
in this
position.
GE S42.
Noisy, or cuts
out when
jarred
.
Before removing chassis
try
removing 35 i.f. tube
and 24 first de-
tector and
tightening bolt between them.
It works loose
quite
often
and inasmuch
as
it holds
the
oscillator coil
in
place
and
provides
a
ground
for this coil
trouble may be
this
alone.
GEK43
RCA
100, 101 Xtodulation
hum
Connect 50,000
ohm
non-inductive
resistor
from
antenna
post
to
ground.
GE
K50P, Ks{P,
K60P,
K65P.
Shortwave switch
does
not fall in
ptace
when knob
is turned
. Due
to falt-
ing
out of clip
which
fits into
slot on
shaft,
holding
the
shaft in
place.
Leave
out clip
and, instead,
cut
a slot in
the
end of
the
shaft so that
a
floor
nail
can
be
fitted into the
slot.
Solder the nail
to
the shaft.
When the switch
is
turned
the nail will fall
against
either one
side
or the
other sitle of the
protruding
bake-
lite
wall, holding
the switch in
place
in
either
position.
G.E. L-50
Dead,
low
B voltage
. .
. open
8
mfd
tubular
voltage doubling'conderser
mounted under
chassis.
GE 5r, RCA il8,
2tl
Intermittent
hunr
.
.
replace .05
mfd
condenset coupling 687
grid
to volume
control.
G.E. 852
Weak
Check
control
grid
of
6B7 f.or short to
ground.
This lead
enters
the
i.f.
shield
can at the
bottom
and often the
insulation
gets
cut.
GENERAL ELECTRIC
K52
Volunre
tlecleases
a short tirire
after'
set
is tulnecl on.
Espe
cialll'
troub,le-
soure
when ne$. set
of tubes
ure
in-
stalled.
Replace
27 A
V tl tube
(
centcr
rear
oi cluissis
) l
itlr
.56.
GENERAL
ETECTRIC A54,
Oscillation
or distortion
at
low
fre-
quency
end of broadcast
band when
tone
control is in high,
counter-clock-
wise,
position
and not when
it is in
low
. . . May
be due to open
in capaci-
tor
C27 or high resistance
solder
joint
to this condenser.
GE
C5O
Some of tlre:e auto sets
have leads
brought
out to
lile
lugs
on the an-
tenna coil. one
is
unused.
If
antenna
trimmer has no effect
and noise level
is
high,
cormect
gritl
lead
from variable
condenser to
vacant
lug instead
of orig-
inal
connecti()n
:o tllat all
of the sec-
ondarf is use<l-
GE 6IM. RCA I29
"B"
band dead
. hold
soldering
iron
close to.
but ,rot
touching
coil
rvintling
until u'ax rlelts
and
flows.
Re-
touch
all lugs
orr
cojl r.r,ith
soldering
tip. Allou'
to cool
an<l realign.
€E
K62, RCA
Rrl
Motorboating
Connect a .l
across
the
resistor
mounted inside
the
antenna
coil.
e.E. 63, 65
Intermittent
on one band
only.
Small insulating ceramic
bushing
on
band
switch
broken. These
bushings
are held into
switch by
pressure
and
may
be
replaced
easily.
GENERAL EIECTR,IC
A63,
A65.
Distortion
Open
or
partly
open
6F5
plate
resistor, R8
in
diagram,
250,-
000 ohms.
G.E. A63,
A6s
Distortion
and
low
volur.ne
shorted or
leakr'.03
tone
control
con-
qenser.
23