JBL 6230 - 2.10 SECURITY COVERS

would
present a
shock
hazard.
In
addition, a
good
quality
ground
on the
chassis
provides
shielding
from
external
fields
and
minim-
izes
radiation
of internal
fields to
the
outside
world.
To comply
with
safety
regulations
in many
localities
and to
protect our
customers,
we
provide
this
product
with a
ground
connection
through
the
3-wire electrical
cord.
In many
situations
this
will present
no
problem. But
there are
instances
where a
hum
or
buzz
will
be
noticed
in
the
amplifier output
due to a
phenomenon
known as a
ground loop.
This
results
when there
is a
significant
potential
between
the
audio ground
from
the
previous
piece
of
equipment
and
the
mechanical
ground to
which
the
amplifier
has
been
connected.
If
this is
the case,
the
first
attempt
at a
solution
should
be
to
remove the
strap on
the rear
panel
barrier
strip
which
conn-
ects
audio
ground
and chassis.
Audio
ground
will
then be
refer-
enced
from the
signal
source
and the
chassis
ground
will be
separate
and
still
connected
to
mechanical
ground.
In
some
instances,
the voltage
difference
between
the
grounds
will be
so
great
that a
direct
connection to
mechanical
ground is
not
possible
without
hum in the
amplifier
output.
Check
for
this
using a
3
prong to
2
prong
AC
adaptor
between
the
power
cord and
the
power
outlet,
temporarily
ungrounding
the
amplifier.
Try the
amplifier
both with
and
without the
ground
strap on the
barrier
strip.
Determine
which
connection
works
best.
Remember,
however,
that
for
safety
you must
still
have
a
connection
to
chassis
ground.
This is
normally made
through a
properly
grounded
third
pin
connection.
2.10
SECURITY
COVERS
In
some
installations
it may
be
necessary
to
safeguard
the
amplifier
gain control
settings
from
deliberate
or
accidental
mis-
adjustment.
For
this
purpose
the
Model
6200SC
Security
Cover
is
made
available.
The
6200SC
contains
enough
individual
covers
for
six
amplifiers.
Installation
is
simple;
1)
Remove the
two
Level
control
knobs.
If
they are
on too
tight
to
be
removed by
fingers,
use a
pair of
long
nose
pliers
to
grasp
the bar
on
the
knob and
pull
outwards. Wrap
the
jaws
of
the
pliers
with
masking tape
to
prevent
scratching
of the
knob.
2)
If
necessary,
adjust
the
gain
controls
using a
small
screw-
driver.
3)
Press each
of
the
security
covers
into place to
cover
the
holes
in the
front
panel.
Make sure
they snap
firmly
into
place.
To
remove
the cover,
slip
your
fingernail
under
the edge
of
the
cover
and
pry
it up
and
off.
Alternately, a
small
screwdriver
or
knife
blade
may be
used,
giving
due
care not
to scratch
the
front
panel.
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