7
seated by reversing the removal process. This fuse also serves as a
front-panel emergency power disconnect.
Mains Voltage
Selector
Unless specifically ordered for export shipment, the 261 is set at the
factory for operation from 115V, 50/60Hz AC mains. This can be
confirmed by checking the designation beneath the mains connector
on the rear panel. The
inappropriate
voltage and fuse value will
have been crossed out at the factory with an indelible felt marker.
To change the mains voltage, first remove the top cover of the unit.
A clearly marked slide switch is directly behind the AC mains con-
nector on the circuit board.
With power disconnected
, use a small
screwdriver to set the switch for
115VAC
or
230VAC
operation.
Be sure to install the appropriate fuse listed on the rear panel. You
can remove the factory strikethrough with lacquer thinner or nail
polish remover and then cross out the inappropriate marking with
an indelible felt pen.
Power Cord
The detachable IEC-type power cord supplied with the 261 is fitted
with a North-American-standard male plug. The individual cord
conductors may be color-coded in either of two ways, regardless of
the shipping destination:
1) In accordance with US standards:
BLACK = AC HOT
WHITE = AC NEUTRAL
GREEN = EARTH GROUND
2) To European CEE standards:
BROWN = AC HOT
BLUE = AC NEUTRAL
GRN/YEL = EARTH GROUND
RADIO FREQUENCY INTERFERENCE (R F I)
Location
Although the Model 261 is expected to be installed in the vicinity of
high-power radio or TV transmitters, please practice reasonable care
and common sense in locating the unit away from
abnormally
high
RF fields.
Ground Loops
Because the active-balanced analog inputs and outputs of the 261
are not truly floating, but are referenced to chassis ground, a mains
frequency or RF ground loop could be formed between output cable
shield ground and the AC power cord ground. A ground-lifting AC
adapter may well remedy such a situation, although the chassis
somehow must be returned to earth ground for safety. Generally,
being screwed-down in the equipment rack will satisfy the safety re-
quirement.