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4.
AC
POWER
5.
MOUNTING RACK
REQUIREMENTS
The power
transformer can
be
connected
for
115-volt or
230-volt, 50
or
6QHz
AC
operation.
If
a 230-volt option
was
specified
when
the
unit
was
ordered,
a
tag on the
power
cord warns
of
the modification.
The two primary
windings
of the
power
transformer
are
connected
in
parallel for
115-
volt
operation and
in
series for
230-volt operation. (See the
Schematic
Diagram
in
Appendix
E.)
To
strap the
power transformer
for
a
different voltage,
remove
the top cover.
Strapping
instructions are
found on
the insulating fishpaper
around
the
power
transformer.
It
is
not necessary
to
rearrange
the
heavy
insulated wiring;
all
strapping
can be
performed
with bare
jumper
wire.
Take
care not
to
burn
the
insulation.
The power
cord
is
ordinarily
terminated
in
a
"U-Ground"
plug to
USA
standards.
The
green/yellow wire (which
is
connected
to
the long prong)
is
connected
directly to
the
275A
chassis.
Circuit
ground
is
connected
to
the chassis
ground by
means
of a single
green wire adjacent
to
the
power
transformer.
If
it
becomes
necessary
to
isolate
the
audio
ground from
the chassis
to
eliminate
hum
due
to
ground
loops,
this
wire
may
be
disconnected.
WARNING!
If
the
chassis
ground
itself
is
defeated, certain
ground
fault
conditions
in
the
unit or
in
the
system
to
which
it
is
connected can
result
in
appearance
of
full
line
voltage
between
chassis
and
earth ground. Such voltage
is
capable
of
causing
electrical
shock,
possibly resulting
in
severe
injury or
death.
CONDUCTOR
WIRE
COLOR
Normal
Alt
L
LINE
BROWN
BLACK
N
NEUTRAL
BLUE
WHITE
E
EARTH
GND
GREEN-YELLOW
GREEN
Fig.
2-4
:
AC
Line
Cord
Color Coding
Vertical
space
of
one standard rack
unit
(1
3/4"/4.5cm)
is
required
for
the
275A
or
the
275A/RC Remote
Control Panel.
It
is
expected
that either the
main
chassis or the optional
Remote
Control Panel would
be located
at
Master
Control.
2-5
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