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clockwise
rotation,
which
Indicates
an abnormal con-
dition, turn off the
power and
recheck
the amplifier
wir-
ing
and components*
b)
SETTING
BIAS
ADJ,
control
(BIAS
VOLTAGE
AD-
JUSTMENT):
Use
either
a
VOMof
at
least
2Q,000Q
per
volt
sensitivity
and
±3%
accuracy on dc voltage measure^
ment
or
a
VTVM.
Set the Instrument at the
minus
or
neg™
otlve
DC
volts functions
and
a
range
of not
less
than
50
volts
or
more
than
150
volts (the closer
the point
on
the
scale at
which
the
reading
Is
made
is
to
^ull
scale, the
more
accurate
it is).
Rest the amplifier
on
either short
side
and remove
the
bottom
plate.
Locot#
the
arm
(center
contact
lug)
of the
BIAS
ADJ,
control
and connect
the
"hot"
meter
lead
to
It,
Touch
the
common
or
ground mater
lead
to
any
unpaInted point
on
the
chassis
(ground)
and
read
the
negative dc voltage
on
the meter.
Adjust
the
BIAS
ADJ,
control
for
areadingof
"47dc
volts
(negative).
Disconnect
the
meter
leads
when
this
Is
completed,
c)
SETTING
BALANCE
ADJ,
CONTROL:
Set
the
VOM
or
VTVM
at either the plus or
minus
DC
Voltage function
and
select the lowest
DC
voltage range.
Connect
the
meter
leads
to
the
two
METER
pins jacks
on
the rear chassis
apron*
If
the
meter
pointer deflects
to
the
left
of zero,
reverse the leads.
Adjust
the
BALANCE
ADJ,
control
for
a zero
or
minimum
reading.
This
completes
the
balance
adjustment,
whereupon
the
meter
leads
can be removed
from the
METER
pin jacks,
d) Set the
VOM
or
VTVM
at the plus
DC
voltage function
and
select the lowest
DC
voltage range
(not
higher than
3
volts
full
scale).
Insert
the "hot"
meter
lead
Into either
one
of the
METER
pin jacks
and
touch
the
common
or
ground
meter
lead
to
any
unpainted
point
on
the chassis (ground).
Readjust the
BIAS
ADJ.
control
for
a
meter
reading
of
0,65
volt,
e)
Repeat
step c
f)
Repeat
step
d
TROUBLE
SHOOTING
and
OPERATING NOTES
Your
amplifier should require
little
service
except
for
nor^
mal tube replacement.
We
recommend
no
substitutions
for
the
tube types used
in this
amplifier
except
as stated.
The EL34 and
GZ34
types are distributed nationally
by
the
Amperex
Electronic
Corporation (230 Duffy
Ave,,
HIcksvIlle, L.l,,
N,Y,)
and Mullard
Ltd, (International
Electronics
Corp.,
81
Spring
St*,
N,Y,
12,
N.Y.)
If
necessary,
replacements
can
be
obtained
directly
from
EICO.
Itshould
be noted
thatsllght red coloring of the
EL34 out-
put tube
plates
In
operation
Is
not
abnormal
and
does not
indicate that the amplifier
Is
operating Improperly,
The
HF'"52
Is
Intended
for
operotion
at
a
line
voltage of
117
VAC.
To
afford
conservative operation of
the unit
In
areas of high
line
voltage, both
117Vand
125Vtaps have
been
provided
on
the
primary of
the
power
transformer.
The
normal connection
in
both
kit
and wired
units
is
the
117V
tap.
The
amplifier
components
will
be
operating
within
their ratings
with
the
117
V
tap so long as the
line
voltage does not
exceed 124V.
If
the
line
voltage
In
your
location
exceeds 124
V,
it
will
be
necessary
to
rewire the
power
transformer
primary connections
for
125
V
operation.
To
do
this,
It
will
be
necessary
to
remove
the
bottom
plate
and connect
the
black-green
lead (125
V
power
transformer
primary
tap)
to
the
fuse post
terminal
XFl"!
instead of the
black-red
lead
(117V
primary
tap).
If
you have
built the
kit
according
to Instructions
or
purchased
a
wired
unit,
you
will find
the
black-green
lead strapped
back on
the
black-
red lead.
Of
course
you must remove
the
line
cord plug
from the outlet before rewiring.
The
rewiring
procedure
is
as
follows;
1,
Unsolder
the
black-red
lead from fuse post terminal
XF1""1 (terminal at
end
of the
post),
2,
Remove
electrical
tape holding black-green lead
to
biock^^red lead.
3,
Strip
1/2"
insulation
from
end
of
black-green
lead,
4,
Cut
off the stripped
end
of the
black-red
lead.
Bend
the
and
of
this
lead
back on
Itself
(about
an inch)and
tape
It
very
carefully
to
the
black-green
lead
so that the
and
of
the
black-red
lead
Is
entirely Insulated
and can
not
short
out against the
chassis.
This
1$
very
Important.
5,
Connect and
solder the
black-green
lead
to fuse
post
terminal
XFI^l
To
facilitate
servicing,
remedial
and
trouble-shooting pro-
cedures
have been
provfded
in
the
TROUBLE
SHOOTING
CHART
that follows.
A VOLTAGE
AND
RESISTANCE
CHART
Is
also
provided
as
an
aid
in
locating defective
components.
DC
operating voltages are given both
at
no
signal
and
a
signal
developing
50
watts output
as
we!!
as
the
corresponding
1
dc
signal
voltages.
TROUBLE-SHOOTING
PROCEDURES
Connect
a
phonograph and
speaker
to
the amplifier
as
de-
scribed
In
"Electrical
Connections"
and
set controls for
phono
listening.
Play a
known
high quality LP recording
on
the
phonograph.
If
there
is
no
output
to
the
speaker
or
If
the
output
is
low
or
audibly
distorted,
precede
to
the
checks
for
those
symptoms.
If
there
is
excessive
hum
In
the
output, disconnect
the
phono
Input
cable from
the
amplifier
and
short
the
phono
input jack
to
chassis
.
If
the
hum
disappears, the trouble
is
not
in
the amplifier but
in
the
phonograph
or
in
the
connection
to
the amplifier.
The cause
of
phonograph
hum
maybe
a
metal
pick-up arm
not
grounded
to
the
cable
shield
(try
a
good
single
ground
connection
to
the
cable
shield
from
turntable
frame, pick-
up arm,
and
cartridge case), direct
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 vacinity
(try
moving
phonograph
away
from suspected source).
Check
also that
the
phono
input
cable
shielding
is
grounded
to
the
ampli-
fier
chassis
atone
point
only through
the
skirt
of the Input
connector
where
it
plugs
into
the amplifier.
Finally,
try
7
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