Technical information

O
RADIO
RETAILING'S
,,.
a,ui@
AK
55
(Early).
lntermrtrenr
opera-
tion after
a
few
minutes
of use,
recep-
tion
gradually
fading
out
completely
with
a buzz
. . Open sccondary
in
second
r.f.
transformer.
Plate lead,
of.24
comes
through
this coil
and as fault is
intermittent
it
is usually
difficult
to hit
the open
period
when checking
socket
voltages. Application
of
heat from a
60 watt lamp
will hasten
the opening
if
this condition
exists.
A-K 55.
O""0,
or almost inaudible.
Check detector
coupling resistor,
which
frequently
fails.
Replace with 25,000
ohm
unit. Value not
critical.
AK 55, 60.
Fading can often be
traced
to loose
rivets on wire-wourd
resiitors.
In
most
cases
re-clamping
them with
pliers
effects
a
repair.
Check
particularly
bleeder
No.
l, r.f.
-bias
and lst
a.f.
bias
ur.rits, as
these
work loos-e nrore of ten than
other
units
at the rivets.
lf SS,
OO.
Aligning condensers .
When
pulleys
are
completely discon-
nected from shaft and condensers
aligned
replacenrent
of
pulleys generally
throws the
job
out again.
fo overcome
this
loosen
one
screw completely and
then
loosen the other very slightly,
just
enough to
allow the condenser shaft
to
turn when the
pulley
is held in
place.
AK
55
TO 67
F'ading,
intermittent
recelrtion
Of.ten due to
poor
connectious at
vari-
ous tubular
condensers.
Also,
resistors
are
mounted
on insulating strips,
the
connecting lugs being integral
parts
of
these
strips.
Resistors of
,metallized
variety with solde
r
ends are soldered
to
rather gingerly
by factory
to
avoid
melting
and
poor
connections
frequently
develop.
Test all
resistpr conncctions
mechanically
and
electrically, moving
them
while
ohmmeter
is
attached. Con-
nect ohmmeter
prods
to lugs r.ather
than to resistors.
AK
E0. ll/her
z,olume coilrols
become
noisy
raise the
end
ol
thc
contact uith
long-nosed
pliers
ond
betd h toumrd
thc
winding
slightly,
then
clean the
str;p
urith
alcohol.
AK 80 Series.
Hurrr and distortion
not due to condensers or
resistors' .
Replace
grid
resistor in
47
input, also
coupling condenser to
detector
plate.
AK
80.
Intermittent operation
Rub
pencil
eraser around top of tube
sockets before looking elsewhere
for
trouble. Twisting of tubes
on
socket in
order to
find
the correct
positi,rn
re-
nloves enough solder
fr,.'rrr
thr trrbe
prongs
to make a high
rrsistanc.i
.'hi,rt
between
socket hole- aryl this
i:
frc-
quently
enough to kiil tlrc r,',:r,iatr,:
tube.
AK 80, 82, 83,
E4,
85.
Interrrritt,:nt
whistle
near 700 kc. .
.
. Rclriace resistor
from
grid
of 27
oscillator
to
grourrd
wilh
50,000 ohrns.
t2
AK
E2. Very
poor
reception,
oscil-
lation,
cutting in
and
out of signals
. . .
Check
mica
of i.f.
stage
plate
trimmer.
It
sometimes
either rots
or
carbonizes
and leaks badly,
later
shorting
and then
opening.
The condenser
is one
of two
trimmers
on top
of the
i.f. transformer,
completely inclosed
in
shield can.
AK
82.
Oscillation
Try reptac-
ing
a.v.c.
plate
by-pass
with a new
I
or
I
mfd.
unit. Intermittent
reception
Replace
screen
by-pass
condenser.
AK
E3, 85. Poor
tone, low
votume and
little response
with tone
control turned
to bass.
Look for
open r.f. choke in
pentode
control
grid
circuit.
Analyzers
miss
this one.
A.K. 84
Oscillation
check
60,000
ohm
grid
resistor
on
27 oscillator
for
change
in value.
Ak
84
Ille:tks
into oscilllrtion
:rfter. oDerilt-
ittg
tL slr,rlt
lirrrt: r'c1,I:rce
60,tX)t)
olrrr
resistor
in thc
grirl
cirCuit of
the
)7
r,.cillrLtor'.
AK
E4.
Weak reception
on
strong
locals,
voltages
and current
ok . .
.
See if
excess
wax from
field
coil has
worked
into
armature, freezing
voice
coil.
ATWATER
KENT
8,f
Inoperative
shorted
oscillator
plate
tuning
condenser
at right
of
chas-
sis.
AK 84. Poor volume,
or
intermittent
normal
and
low volume
. . .
If
all volt-
ages
are nornral check for
an
open in
the i.f. stopping
choke.
The
leads
fre-
quently
break under the
protective
wax
where they are
soldered
to
lugs.
ATWATER KENT
84
I)t'rLd
. . .
shorted
oscillator
plate
tun-
irrg
q1r11dgns6r
at
light
of
chassis
look-
ing frorn front. Nlotorboating
.
. -:ui-
pect
scii,ttrl <lctcctor lrilr:
and
screcn rc-
.:i
stot'.
AK
89
\lot,rrlro;rtittg
lu
()ull(l
()00
to 1,.5(Jt)
Iic. t'lrlck
all chokt's irr
r-.f.
S('cli{)lt fot-
slt0r-t
r,t'
0|tt,rt.
AK
96, 99, Set dead,
neon
tuning
in-
dicator
inoperative,
180 volts on i,f. tube
grid.
Remove coil shield, i.f. shield,
and look at
the
snrall
grid
resistor
tucked
in
near
the
first detector
plate
coil.
Its
insrrlation frequently
breaks
down,
perrrritting
a
short. Wrap
it in card-
boartl or fibre.
AK
99.
IIifTh
potential
on
one control
grii'l
cap.
Ilrrnove i.f.
cans, insulate rc-
si!t{)r's which touch
coil
forms. Troublc
csirirjs
ncon light
to be inoperative
and
krll,r
all
signals.
AK l'15
Audio squeal, unaffeoted
by
touching
2A7
or
58
grid
caps
but
aggravatd
by
touching
2A6
grid
cap
Un-
solder,
remwe
and
throw
away
metal
clamp around 2A6
grid lead at
point
of
ground.ing.
Solder
the
wire
twisted
around
the
grid
lead
to the
point
at
which
clamp
was soldered.
It
is
impos-
sible
to
dotect
this trouble
with
instru-
ments.
A.K. t55
Weak, distortion
.
.
. .
replace .5 meg
metalized
grid
return resistor
from
4?
grid
to
ground.
AK
155. Hum and
distortion in
these
a.c.-d.c.
midgets . . .
Check
dual
and triple filter condensers
for bad leak-
agc and if it is
found
replace
with 8
mike sections. Also
see
if volume con-
trol has
changed
value from
normal
i
megohm.
Before delivering to
customer
adjust trimmer
betwecn
tuning con-
dcnscrs and speaker, at top
front of
chassis, to loudeet
point.
A.K. t65
Weak, oscillation,
crosstalk.
Look
for open
bias resistor
ort 5z-
mixer.
This
is
a
rvircrvound
pigtail
type.
ATWATER
KENT
I65,
I85,525
Oscillation
rvhen volunrc
is
turuccl on
full
.
,
replace
doublc 25O
mrnf
con-
<lcnser
rvith tr.r'o sitrgle bakclitc
rrnits.
'l'lris
condens('r c()ullects
frorn the
plate
of 5.9 i.f.
to the
trvo diorlc
platcs
of
the
l.\
6.
AK 206
Oscillation
fronr
l9 to 20 nreters
. . . . this nray
be cot'rectcrl
lx'
ruoving
lcatl
to control
grid
of 2;\7
tos;rrcl
the iront
of set.
AK
246.
Bad
audio
howl
as
volume
control
is
advanced
with
tone
control
in-low position...
Generally
due to
dcfective
votume
control.
Riplace.
AK 2+6.
Set
stops
playing
sud-
denly
Check
for
poor
contact
on
filter
choke,
whcre
it connects to
plate
of
first
detector 58. The brads that
hold
the connection
on both sides of the
coil
loosen
and corrode,
A.K. 276
Bad
hum Connect a lead from
common
ground point
to
chassis. ThiS
set
does
not
use the
chassis
as
a
ground
return, consequently stray currents
picked
up
in the shields and chassis
are carried
around
to all
parts
of the
circuit.
AIWATER
KENT 3I7. 337
Irrternrittent
and
u'cak orr l,nv fre-
(pency
end of dial.
Chcck
plate
r(.sistor
in
oscillator
circuit oi 64'8.
Ii defective
replace
s-ith
30,0()0 ohnr
unit.
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