Specifications
connection
to the
cable
shield
from
turntable
frame,
pick-
up
arm,
and
cartridge
case),
dired
hum
pick-up
by the
magnetic
cartridge
from
the
record
player
motor (try using
a rubber mat on the
turntable
to
Increase
the
separation
of
the
pick-up
from
the
motor), or
pick-up
from a power
trans-
former
or
other
magnetic
field
in
the
vicinity
(try moving
phonograph
away
from suspected
source).
Check
also
that
the
phono
input
cable
shielding
Is grounded to
the
ampli-
fier chassis
at
one
point
only
through
the
skirt
of
the
Input
connector
where
it plugs Into
the
amplifier.
Finally,
try
a good
building
ground such as a
connection
from a
cold
water
pipe
terminated
under
speaker
terminal II Gil on
the
amplifi
er.
Do not
connect
such a ground
wire
to
other
components In the system.
Excessive hum on
other
inputs may be
checked
in a
similar
manner.
Disconnect
the
Input
cable
In question and short
the
particular
input
jack
to
the
chassis. If
the
hum
dis-
appears,
the
trouble is
extemal
to
the
amplifier.
Note
that
on all inputs,
the
braid
of
the
Input
cable
should
con-
nect
to
the
amplifier
only
through
the
skirt of
the
Input
connector.
The
cause
and
remedies for
the
following symp-
toms
are
then based on
the
assumption
that
checks
made in
the manner
described
above
have
eliminated
the possibll ity
of
the
trouble
being
external
to
the
amplifier.
If the
trouble
is no
output
or low
output,
checkAC
signal
voltages
and
DC
operating
voltages
starting
at
the
input
and working
step-by-step
toward
the
output.
Set
the
VOLUME control to maximum (10),
and
the
BASS
and
TREBLE
controls to
their
mid-points
(0). Use a 1000
eye
Ie
sinewave
signal,
such as supplied by the EICO
377
Sine &
Square
Wave
Audio
Generator.
In
addition,
use a
pre-
cision
100:
I
attenuator
to permit
obtaining
a level of
0.01
volt
fedintoMAG.
PHONOfrom
an
audio
generator
output
of 1
.0
vol
t,
which
can
easily
be measured on
the
lowest
ACvolts
range
of yourVTYM(also improves signal
to hum from
generator).
Use a high
input
Impedance
VTYM
for
allAC
signal
voltage
measurements (such as the EICO
232,249,221,
or
214)
and aVTYM
or20,000n/voltVOM
for DC
voltage
measurements.
If the troubl e is an
excessively
distorted
output,
try tube
replacement,
signal
tracing,
or
procede
directly
to vol
tage
and
resistance
measurements.
When the
defective
stage
is
localized,
precede
to a
resist-
ance
and
vol
tage
check
of the
stage,
using the
data
In the
VOLTAGEand RESISTANCE
chart.
Disconnect
the
ampll-
-fler
from
the
power
line
and
discharge
capacitors
prior to
making
any
resistance
check
and prior to removing
either
or both of the
EL84
output
tubes V4
and
V5.
Do not turn
the
amplifier
on with
either
of the
output
tubes
removed.
6
TROUBLE-SHOOTING A TYPICAL
TUBE
STAGE
1.
Check
tube.
2.
Check
plate
and
cathode
resistors.
3.
Check
coupling
capacitors
for
leakage
or short.
4.
For
output
stage,
check
de
resistance
of transformer
windings.
5.
Check
grid
leak
resistor for
open.
6.
Check
cathode
by-pass
capacitors
for short.
7.
If no or low
B+
voltage
on
tube,
check
decoupling
path for
open
or
defective
R18, R31, R32, R33 and
filter
capacitor
C17
or
C18.
8.
If wiring and
circuit
components
including
the
tube
check
O . K. and
B+
voltage
is
excessive,
check
the
de-
coupling
path
for short or
defective
R18, R31, R32, R33.
Suspected
trouble
in
the
equalization,
tone,
and
volume
controls
and
networks should
lead
to
specific
resistance
and
capacitance
checks
to
localize
the
trouble.
In
gen-
eral,
if
the
user suspects poor
frequency
response,
defec-
tive
equal
ization,
or
defective
operation
of the tone
con-
trols,
the
amplifier
should be
tested
thoroughly with
audio
generator,
vtvm,
and
scope.
SERVICE
If trouble
develops
in your instrument
which
you ccn
not
remedy yourself,
write
to our
service
department
listing
all possible
indications
that
might be
helpful.
Note
num-
ber
appeari
ng in red under
the
word"
ManuaP'
on
the
front
cover. If
there
is no number,
state
this. If desired, you
may return
the
instrument to our
factory
where
it wi II be
placed
in
operating
condition
for
$7.50
plus
the
cost of
parts
replaced
due
to
their
being
damaged
in the
course
of
construction.
NOTE: Before returning this
unit,
be
sure all parts
are
securely
mounted.
Attach
a
tag
to
the
instrument,
giving
your home address and
the
trouble
with
theunit
. Pack
very
carefully
in a rugged
container,
using
sufficient
packing
material
(cotton,
shredded newspaper,
or
excelsior),
to make
the
lonitcompletely
immovable
within
the
container.
The
original
shipping carton is
sat-
isfactory, providing
the
original
inserts
are
usedor
suffi-
cient
packing
material
is
inserted
to
keep
the instrument
immovable.
Shipby
prepaid
Railway Express, if possible,
to
Electronic
Instrument
Co.,
Inc.,
33-00
Northern Blvd. ,
Long Island
City
1,
N.
Y. Return shipment will be
made
by express
collect.
Note
that
a
carrier
cannot
be
held
liable
for damages in transit if
packing
IN HIS OPIN
ION,
is
insufficient.