Technical information

T-
.O
RADIO
RETAITING'S
ff,
ehun@
RCA 281
l)istortion on
locals
ntake sut'e
76 and
6D6 tubes
ir.r
special
a.v.c.
circuit
are
O.K.
I{um check
42 output
tubes
for
plate
current bal-
ance.
RCA
321.
Phonograph
PlaYs
but
not the
radio
.
.
. Check
for
short in
condenser
having
blue lead
to terminal
near oscillator
padding
condenser.
Whcn
replacing
be
sure
to include
30,000 ohm
resistor
in original
position'
Use
4 mike
unit
with
500
volt
rating.
RCA 330. 33r
(G.
E. K-78,
K-79)
Oscillation
blanl<ets
reception
rvltcu
volume control
is adjustcd
near
ntaxi-
nrunr sctting
suspect
open
ir-r
'1
nrfd. corrdcnscr,
comporlcnt of
a
10.4
mfd.
clectrolytic
block
located untler
oo\\'ef t1-ansrof
1'llcl'.
RCA 331
Strong
buzzing
.
connect a
.001
nrfrl
conrlenser from
centcr
terminal
of
volunre
control
to
thc
side
lug of con-
trol
that connects
to
60,0d) ohm
re-
sistor.
'I'his
will
bypass
excess r.f. cur-
rents.
RCA
DUO 3E0HR.
To
test
neon level
indicating lamps
. Connect suspected
lamp, in series with
200,000 ohm
fixed
resistor, across source
of a.c. voltage.
This
may be the
regular ll0 volt supply
line shunted by
a suitable
voltage drop-
ping potentiometer.
Connect
high
re-
oistance
a.c.
voltmeter
across output of
potentiometer
and
riary this adjustment.
The
lamp
should.not
light before
52
volts
is applied and
must not require
more than
64, If otherwise
thcy
arc
defective.
RCA 381
Inlerrritt,.nt
crackiing noise
le-
placc
both
6.3 volt
dial
light as the
origirals are arcing
in
the filament wire.
RCA sIOK
Weak
reception
check
:tntentta
coil
ior
opell or band switch
for
poor
contact.
RCA
8II K
Dead,
no
voltage
on
plates
of 6N7
phase
ir.rverter . Check
1100 ohm
section
of candohm
resistor.
RCA 8il
K, 8t2
K, 816
K
A.f.c.
pulls-in
on
one
side of
reso-
uance ouly,
canltot
be adjusted
nor-
nrally
Rcplace
22,000 ohm
bleeder
{rorn cattdohu-t
fesistor
to
cathode
of
oscillator control
tube
100,000 or
150,000 ohms.
Realign
r.f.
circuits
after this
is done.
RCA 8I3K
Noisy on automatic tuning
clean contacts on muter su,itch
r'vhich
operates
by
end-torque
of niotor.
RCA
VICTOR
867
Dead on
rli:tl trrnirtg,
tlper:rtive
otr
push-button turrirrg
lcrok
for'
shorted
stator
tttt
,tscill:ttot'
tuttittg
sec-
tion
o{
gang
ctttttlcttser
RCA 9I IK
Candohm
resistor
burned,' sirock
*'hen
chassis
is
touched a.c. line
Llscs
one
spare
terminal of the 5T4
socket. Sockct leaks to
ground,
re
pl:Lr:e
sockct.
RCA I939
AUTOMATIC
TUNING
MODELS
Dial
rocks
back and forth when
buttons are depressed
Insert
srnall
spring
behind the flywheel be-
tween
nlotor and washer
so that
mo-
tor
will disengage when current
is
renroved.
RCA I939 AUTOMATIC
PHONO
Will
not
complete recorcl
after
playing
several
.
.
. bend
plutch
pres-
sure
fingers
out
slightly.
See that
cabinet
is
level.
RCA
t939
ELECTRIC TUNERS
If
station
inrlic:ttor
rvon't cotrte
to
stop
but kecps
ntc'rvitrg
l-racl< arrtl
folth
tighten set
screw olr
rrrotor
flyrr'hcel.
REMLER
REMLER 40
Noisy, fade
s
inte
rmittentll'
replace
R1-1. a
-100
olrur
1 ivatt
bias
resistor
on
the
4l;
also
C9, a .1 rnicl.
bypass
across this
resistor.
Check
(R17)
the 15,000
ohm 5
watt
carbon
screen
dropping
resistor
for
6A7
anrl
ot
/.
REMLER
60
Loss
of volutttc
lrfter
a
few' nlintttes
opcratiorr.
Check
for
irrtclnal
short ir.r
positive legs
of Cl4
and C15
filtcr cottrlct.tscLs.
'-l'his
shorts
crttt
sueal<er
ficlcl.
REMLER
62
Cuts off u'ith vghistlr:
on rcsoltance
ivith
strong
sigrral.
.
.
. Chccl< for
baclly
leaking .1
nrfd.
6F6
bias
bvpass.
SEARS ROEBUCK
SEARS.ROEBUCK
4585
Distortion
shortecl
second de-
tector
plate
bypass condenser.
SCOTT
SCOTT
CUSTOM
BUILT
Sonre
of
these use neon
trrlres as
voltage
regu'lator
rvhich
tend
to oscil-
late
under
certain
conclitiorrs.
Shunt
.5 nrfd
condcnser
front high
voltage
lead
of neon
to
glountl.
SENTINEL
SENTINEL
AC-DC 560. No
signal
. . . Check
for open
8 mike
section
in
8-8-4
block connected
as follows: Black,
common
negative.
8 mike
positive
to
one side
of filter choke.
8 mike
positive
to other
side of
choke.
4 mike
positive
to
cathodes
of
2525. All
negative
con-
n€ctions are,
incidentally,
independent
of chassis.
SENTINEL 90 B 167 S
Flerluettc,r'
jumps
scveral kc.
anrl
returns
rcplace oscillator
cnil,
purt
3-129.
SILVER
SILVER
30. Dial belt will not
stay in
groove
Chip
"V"
deep enough
to
allow cable to come flush with
surface
of
pulley,
wrap
fine
wire around ends of
cable, then tin. Also tin
the
"V"
cut in
pulley,
then
sotder
cable
tq ends of
"V."
SILVER.MARSHALL
SILVER MARSHALL 30
Weak or no reception check
400-ohm
resistors in cathode circuits
ol
21s in rf
stages for opens.
Intermittent v-shaped
springs
on socket
prongs
corrode and rvork
loose
or break causing shorts with
adjacent
prongs.
Springs
are designed
to
keep
prongs
fronr spreading, but
really
are
not needed: remove them
all from set
when
the trouble de,r'elops.
SI'LVER MARSHALL
36A. Breaks
into
oscillation
after
operating
satisfac-
torily
for
a short time, insertion
of
analyzer
cable
in
any socket
clears up
trouble and makes test. difficult
. .
Trouble is
defective
r.f. choke in series
with first i.f. amplifier tube's
cathode.
SILVER MARSHALL 37,38,39, 782.
Distortion at low volume level on
local
signals Replace second 24
from
front of
set with 35 or 51, change
minimum resistor
to 100
ohms
(on
Bake-
lite
strip with one end
grounded
and
other
to volume control)
and connect
a
25.000 ohnr resistor
betwen screen of 35
and high
voltage side of volume control.
SILVER MARSHALL 60
Distortion replace
bias
cell
on
61i5. ,\lso clt;tnge
I trtcgohnt
gr-irl
re-
turn rcsistor on
6Ii5
to 2-i0,00{l
ohnrs
to
prcvent glid
fr,rrrr
goirrg po.itive
on
:rrrdio
peaks.
SILVER MARSHALL MODEL R
Insensitive, especially
on
lorv
fre-
quency
end
of
broadcast band
re-
placc
R8,
80,000 ohm
cathode resistor
on cletector.
Also
R7, 3500
ohm cathode
l'cslstor.
SILVER
MARSHALL
Dead
.
Replace
6500
ohm resistor
in
56
tube
circuit
(fourth
tube to
right
looking
from rear).
53