Technical information

[]
@
RADIO
RETAITING'S
"Squie
A.K. 3r7,
337, 637
No broadcast
reception
check
voltage
on oscillator
section
of 6A,8.
This
should be
approxinratcly
185
volts.
If lorver
replace
30,000
ohm
platc
dropping resistor.
AK
.tl6-{.f&l16
Intermittent
or
weak
. .
. shorted
.l
mfd. condenxr
(marked
No. 102)
be-
tween 6F6
cathode
and .1 meg.
resistor,
replace.
A.K.
a35
Dead,
constant hunr. Check for
open
.05
mfd.
bypass in
6K7
i.f.
grid
circuit. This
condenser is
C5
in
schematic.
A.K.
435
Internrittent
noise
reol:rce
20,000
ohrn
2
n
att c:u'bulr
r.iisro,
supplying
scleens
of
6.\7 and
6K7.
AK
46sQ.
Distortion.
sounds
like
speaker
out
of
adjustment
Caused
by
an
open
8 mike
electrolytic
connected
from
B-plus
at
speaker
cord
to
ground.
This_open
also
causes
howling
at
times
and
is
almost
always
diagnosed
at first
as
speaker
trouble.
AK
,t6t
Distortion,
weak
on low
frequency
ctrd or
fadcs out
replace
.00145
mfd. fixed
padder
located
under
osc.
coil with .001 and
a small trimmer
and
tune same
as regular low
frcquency
trimmer;
I.F. 130
K.C.
ATWATER
KENT 480
Dead
on lorv frequency
end
check bypass
in
plate
circuit
of 58 r.f.
Ior
leakaee.
AK 5IIW
TUN-O.MATIC.
Auto-
A-K
612.
Distortion
on low
volume,
clear
on high
volunre
Due
to an
open
volrrme
control
in nrost
cases.
Ex-
ces:iive
sensitivity
(sorne
people
object
to interference
fronr
"honkv-tonk"
dx)
.
Substitute
an
80 for
thl
83 feeding
r.f.
stagcs.
Lowering
of
voltages
in
thii
nrallner
does
not
affect
locals.
ARVIN 5I8
Iixcessive
hum
.
ground
lug
on
6QZG
tube socket
is fastened
to chassis
by rivet
that
holds socket.
Bend lug
over
and solder
clilect to chassis. Be
surc
a
goocl
solder conncction is nradc..
AK 665.
Oscillation
See
that
screen
grid
stage control
lead
spring,
which serves
as a shield,
is kept
away
from
the 2A5.
ATWATER
KENT
667
Heavy
bass Inrplove
tone bv
replacirrg
C.l2
.02
nri<I.
on 2A-; to
.006
or.01 nrfd.
A.K.8r0
Ilotorlxr:rting
arrcl
autlio ho*'l
check
]
rvatt
carbon resistors,
connectetl
{ronr plates
of 6F6
tubes
tlrrough
.01
rrftl
condensers
to
ground.
Open l0
rufd
electrolytic
condenser
across bias
has
caused
excessive
a.c.
to pass
through
these
resistors,
causing
thenr
to heat
and
change
value. Replace
resistors
rvith I rvatt
10,000
ohnr
units,
con-
denser
is l0
nrfd
at 200
volts.
A.K.
8
12
ljlratic trlreration, rr.risc,
irrterntit-
tent. Broken
or loose connection
to
thc .00145 mf<l condenser
located
inside
osi:illator coil
shitlcl.
AK 8f2.
Bad
tone
and
blocking when
volume
is turned
up . 500,000 ohm
potentiometer
connected
to
diode
plate
2
of
second
detector
has changed
value
to
about
I megohm.
Shunt with fixed
resistor
to restore value
to normal.
Balancing double-spot
tuning trimmer,
fourth
on
5
gang
unit
Set
for'
minimum
signal with oscillator
running
at 1400
and set dial at 1240.
AK 825
Fluur. cspecially rvitlt
:rdvance<l vol-
unre control
leakagc between orre
se-ctior.r
of filter block and case.
Re-
yrlace.
u-ith
triple 8
nrfd
200 r'olt.
ATWATER
KENT 944
\\reak,
sensitivit_v
contlol has
no
clTect
. look
for
open l rnegohm
resistor
connected
irom
the
4
mfd. 6lter
to the
gligl
oi
57
tube.
AK.
Noisy
wire
wound
volume
con-
trols.
Clean
contact
arm
and winding
with
alcohol.
Using
No, I soft lead
pencil,
fill
in
spaces
between
windings
at contact
edge until
surface
appcars
level
and
smooth.
A.K.
Flat ribbon
drives
can be
replaced
with phosphor
bronze
dial cable. Solder
cable to
pin
on
pulley
that
originally
rvent
through
belt.
ATWATER KENT
MODEL
Q
.\rrdio
lrou
l
shrrnt th(,
:rc('n(lal'\'
,,i
thc
fir'-t:r.f.
tllrrr.fr,rrrrtr
rritlr ltX).(}{li)
t'ltttts.
also
tlrt' :tcortrlarl
ott tlrt:
prt.h-
pull
inprrt rr itlr l5O.(l{X) olrnrs.
AK.
I'olunrc
controls
zc,hich
beeome
ttoisy
ttccL!
not
alu,oJ,.e
bc replaced.
Rcnttz,c
thcm
lronr
the
clnssis,
sumb
thc
u,indingt
with a rloth
saturated
with
alcohol,
bcnd
thc
slidr oiln
so tha.t
it
nutkes
firuer
contact aith
the
zyinding.
and
also
tighten
it
ogainst
lha tension
sl>rnq.
AUTOMATIC
AUTOMATIC
MODEL
B
Oscilletior-r
rvith
volunre
set
:rt
ntid_
point
Coltrol grid
leacl
of
6Q7G
too
close
to 25t,6G
AUTOCRAT
AUTOCRAT
80
Low
voluure
lcakagc
betn-een
scction
of
dual
electrolytic
filter
con-
denser shorting
speakcr-
6eld.
BEL}IONT
BELMONT
7IC
Birdies
all
over
dial
check
56
oscillator grid
leak
for
increase
irr
value causing
oscillator
to super-rc-
generatc.
BELMONT
7lC.
Audio
trequency
nrodulation
of
oscillator,
audible
all
over
rlial
Replace
56
grid
leak
with
proper
size. It
has
probablf
increasetl
irr
value.
BELMONT
IOI
Distortion,
two
spot
tunirrg
L'heck
leakage
.05
condenser
in
avc
lead
of r.f.
stage. Also
.05 cathode
to
ground
condenser
on
same
tube.
BELMONT
7778
Inrproved
tone :rn<l
perfornrance
can
be had lrv
rcplacing
180
ohnr
c:rthode
lesistor
on
6D6 trrbes rvith
3t)0 ohnrs.
BELMONT
778.
SERIES
B
Interntittent
or cleatl
on low {re-
quency
end
suspect
bakelite
con-
denser across
terrninal
of low frequency
trimnrer for
open.
matic feature
won't
shut
off,
tuning con-
densers
swing
to 1,600
kc.
ok, but line
is
not cut
. . . Look
at
nine
point
normal,
oft,
and
automatic
switch
at right
on
front
panel.
Switching
blades are
a littte
too
wide
and
sometimes
contact
two
points
at
once,
preventing
opening
of the
circuit.
File
blades
down
a little or re-
place
with
later
type
switch
available
from
factory.
No reception
Look
for leads
soldered
to
tone control
switch
touching
housing
of volume
control
and
grounding
out.
These
two are mounted
so close
together
on
front
panel
that
sometimes
the rubber
insulated
pieces
on
the
tone control
leads
slip
oft from
vibration.
Slide
them
back in
place
or
bend
leads
back.
Hum
not due
to cir-
cuit faults
. , .
May
be
due to
reversal
of
antenna
and
ground.
523 rectifier
and
2A3
tubes also
seem
critical.
Change
them
when looking
for
hum.
AK
559
\Iotorboating
and
distor:tion as lol-
ume
is increased
reDlace
output
filter
condenser.
If
2A5s
do not
match
in
er-r-tission there
rvill
also be
nrotorboating.
l3