Technical information

O
RADIO RETAILING'S
,,,
a,uhe
ll
o
STEWART
WARNER RI8OA
fnsensitive,
dial off calibration, im-
possible
to align
at lorv end
of dial
.
. . . add .0025 nrid.
conclenser
to the
.0054
unit which is
alreadv
across tlre
padder.
STEWART-WARNER R301,
R3OIA,
R30lB, R30lE.
Inoperative,
especially
on high frequency
. .
. . Check voltage
of
27
oscillator. If less
than 100 con-
verter is
probably
cutting
out.
If
series
resistor,
usually 17,500
ohms, is
used
in
series with red
plate
lead, remove
this
resistor
entirely
or
substitute
one of
lower
value to
suppty 100 volts
to
plate.
While chassis
is
open
resolder
connec-
tions to
coils and
other high
frequency
connections.
Slipping
dial mechanism
.
Twist
thin rubber
band around
each rubber pulley.
Also
check for
leaky
2-mfd.
plate,
by-pass
condcnser,
even
though
it functions
ok. Leak of
appro4imately
150,ffi0
ohms
indicates
unit
will
soon
break
down.
Condenser
is cased
and
connected
between
25.000-
ohm,
l-watt
plate
supply
resistors
and
ground.
STEWART
WARNER
9OO
Interrnittent
faclinq
chcck
tl-rc
.25
mfd
r.f.
bypass
iondcrrser.
l'his is
the
green
leacl
on
the conrlenser
block.
STEWART
WARNER
9OO
Serious
intt,rntiltent
ia<linr
irr
this
rrtotlel
is usrralll'
cads.<l
lr1.
the .?5
:rrid
rf.
cathcxle
bypass
conclt'nser.
Thi,
is
tlrt'
grcen
lr:arl
iri
the t.,rtrdenscr
lrlrrck.
STEWART-WARNER
950.
Set
dead
or
no
pep
with excessivc
hum
.
.
.
Check
I
mfd,
condcnser
in
cathode
cir-
cuit
of detector,
speaker
6eld
resistor
and filter
condenscrs.
STEWART-WARNER.95O
SERIES.
Burned
out volume
control.
Measure
voltage
across
control and if in excess
of 70 replace 20,000 ohrn,
threc
watt
resistor with
new unit.
STEWART-WARNER
950. Oscilla-
tion at
low
frequencies. Clean
variable
condenscr
contact clips
and bend
them
to lncreasc
pressurc.
Oscillation
at high
frequencies.
Look
for open
'25
mfd,
r.f. by-pass condenser
located
close
to
r.f. coils.
Tone
distorted, set
oscillates.
Try riplacing
.25 mtd.
r.f.
grid
by-pass
condcnser,
If
set
oscillates
when
quick-
heatcr
tubcs arc used
replace .25
mfd.
screen-grid
by-pass with
,5
mfds.
or
morc.
STEWART-WARNER
95O,
RIOO.
Poor sensitivity and
low volume. Check
red resistor
(6,326
for low value
or char-
ring. This resistqr shunts
r.f.
plates
to
minimize effect of
variation
in
plate
current when
difterent
tubes
arc uged
and if low
increases
load and
reduces
screen
voltagcs.
STEWART-WARNER
1171.
To
reducc brilliancy of
pilot
light
.
.
. Re-
place
15 ohm
pitot
light resistor with
35
.ohms.'
60
STEWART.WARNER
II2I, 1122.
To
increase volume
and
improve
tone
. .
. Disconnect
B-plus
(yellow
and
red
lead) from side
of output
transformer
from screen
grid
terminal
of output
tube
and
connect
it
to the
high
voltage side
of the
combination
relay and
6lter
choke.
The most convenient
point
to
connect is the
cathode terminal of
the
rectifer
tube.
This
raisea
plate
poten-
tial
about
40
volts. Change
the
grid
rcsistor
of
the 4l
from
510,000
ohms
to
250,000. It is inclosed
in a
piece
of
large
cpaghetti
and
,is
connected
from
the 4l
grid
to
ground.
Change
the
per-
manent tone
control
condenser
which
is
connected to the
plate
of
the output
tube
from
.01 to .006,
600 volts. It
may
bc neccssary
to
readjust the spring
of thc relay aB output tube
plate
current
no longcr
passes
through it.
Reduce
the
tgnsion of
the
relay spring, which
t€nds
to
kepp
the contacts closed,
by
stretching it slightly.
STEWART-WARNER
tl8l, ttEz,
1183.
Won't
play
unlers local
switch
is clicked on
and off . .
.
Change 50,-
000
ohm
resistor on 6A7 sockct to
60,fi)0
ohms. If
set
goes
into
oscillation
put
a
.25
mike condcnser
from cathode to
ground
on the 6A7.
STEWART-WARNER
1181,
11E2.
Belllike
rattle . . .
Traceable to
tubu-
lar
condensers.
inside
power
transformer
covcr. These
units break oft and
strike
against
cover.
Remove
four scrcws,
pry
ofi
covcr, resolder
and tape
condensers
to transformer
and replacc
cover. Set
inoperative except
for faint response on
powerfirl
locals . . .
Look for broken
lead on coupling
condenser
connected
to
movabte arm
of volume
control.
Mount-
ing hint .
.
,
Sets are equipped
so that
speakcr
may be
pointed
outward but
troublc
will be experienccd
in
this
posi-
tion duc
to the
horizontal
position
of the
vibrator and tubes. Use
gide
or end
mounting with
speaker downward.
STEWART
WARNER
I235.8
Oscillation .
replace
4
mfd filter
condenser
in
can
v"'ith
audio
bypass
with
higher
voltage
type.
STEWART
WARNER
I25I TO 1259
No reception
.
cause
is
often
0.006
mfd., 600 volt tubular conden-
ser; connected
between
plate
of
41
tube and chassis.
Part No.
83,706.
Use
1,000 volt
replacement.
Noise
.
lrg on 0.02
mfd., 1,000
volt,
metal-cased condenser,
connected
bctween
line
and
chassis.
is
often
pulled
loose
by
line
cold. Replace
condenser
and
adjust knot
in
cord
to
prevent
pull
on new
unit.
Noise
accompanied
by suclden
vol-
ume
changes
. rotor
wipers on
band-changing
switch
have lost
their
extension
and
making poor
contact
with
stator
points.
Hum
this trouble
also
caused
by
open in line
filter
condenser.
STEWART
WARNER
R.I252A
Dead, exccpt for huru.
The .25
nrfrl
condenser connectcd to the third tao
fronr left
of cirnclohnr resistor antl
bracket
has
low
resistance
leak.
Re-
place
with
sinrilar
urrit.
STEWART
WARNER
I26I
Weak
on shorts;rves
r':ri.t
us-
cillator
plate
voltage
by shorting
10,000
ohm droppirrg
resistor
irr plrte
lead.
STEWART.WARNER
I845
TO I869
Motor
lrurns
lrut
rioe.
n(_)r
rulr
leversllrg
conta.cts
on
lrack
,*u
itclr
not
clo5lng;
l,rrv
lirrc
r,,ltege,)r.
ilrrpl,,p(.1.
llrre
Irc(luenc\'.
Internrittent
oltcratiotr
of
urrrtor
trnd
lights.
itrsuflicient
conritcr
Drrs:ure
or
dirty
c.ttl;rcts
,rn
lr;rrk
ur
si,le
switch.
Set
tunes.hroadll.
afc
contacts on
side
switch
not
closing.
Sliglrt
lrurrr
uhcn lrrrttrrrr
is rlct,resrr,l.
Irot
lreard
wl)cn
lruil,'tr
i.
relelr.ed
.
poor
or
defective
discriminator
ttrlre.
Signals
are heard
r.vhen
tuning fronr
()lre
station
to
arrother
autorrritic:rllv
.
muting
contaction
back
su.itcit not
clrsing
or utakine'
poor
contact.
Set
noisy
electricalll'
tvhen
star-ting
;ind
stol;ping
during
autonratic
tuning
.
lnsu..clent
:Intenlla
or
ntute
col-t_
t:rcts
oll
back
sri itch
clo-.iug
too late
lincl openilg
too
soolt.
STEWART.WARNER,
3040.3049
Oscillation
rvhen
tuned
to weak
sta-
tions
or between
stations
can be re-
moved
by connecting
a
ground
to the
recerver.
If
a
ground
is not
available
oscilla-
tion
can
be
prevented
by
connecting
a
.01
mfd.
buffer condenser
from
one
side
of
the
power
line
to chassis.
In
connecting
the
condenser,
first
solder
one
side
to the
chassis.
Touch
the other
lead
to
one
terminal
of the
line cord
and
note
whether
the
hum increases.
If
the
hum
increases
touch
tlre con-
denser
to
the
other
line cord
terminal.
This
will
usually
be
the line
cord ter-
minal
which
connects to
the off-on
switch.
Solder
the
condenser
in
this
position.
STEWART-WARNER
Converter.
No reception
. Remove
both
tubes
and clean
prongs
thoroughly
with
saud-
paper.
Also
see
that 27
oscillator
shieltl
is
not
touching
condenser gaug.
Cross-
talk from
broadcast
band while
listening
to
shortwaves
See
that broadcast
receiver
dial
is Set
just
above
1,000
kc.
and make
the
connecting
wire
from
orrt-
put
of converter
to antenna
post
of
bc
job
as short as
possible.