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AR-15 VOLTAGE REGULATOR / POWER CONDITIONER
unit from the rack. This breaker will trip if the
unit’s 15 amp capacity is exceeded at any
time.
2. A fast-blow 1/4 amp fuse is located inside
the unit. This fuse will blow if the unit has
been connected to a voltage that is above
the range of the Extreme Voltage Shut-
down circuitry. To replace it, the unit must
be completely disconnected from all power
and removed from its rack. The six hex head
screws and two Phillips head screws holding
the top cover must be removed. The internal
fuse is located in a holder on the printed circuit
board. Replace the fuse only with the exact
same type (1/4 fast blow).
INPUT VOLTAGE MONITORING
The row of ten LED’s at the left of the front
panel make up a meter that indicates INPUT
VOLTAGE. Only one LED will light up at a time.
There are two red LED’s at the endpoints. When
lit, they indicate that the input voltage may
be above or below the point where it can be
restored to the selected nominal output volt-
age (though it may still be restored to a usable
level) but is not high or low enough to cause an
extreme voltage shutdown.
OUTPUT VOLTAGE MONITORING
A green LED labelled OUTPUT IN REGULATION
indicates proper function (i.e., that the output volt-
age is within ±5V of the selected output voltage).
Your equipment will always work normally when
this light is on, and often will work satisfactorily
even when it is off.
The AR-15 offers a 10-LED bargraph line voltage
meter to monitor the incoming line (the Voltage
Regulator output).
INSTALLATION
Because of their toroidal transformer design,
Furman Voltage Regulators may be posi-
tioned near most other equipment without fear
that the other equipment will be disrupted by
leakage of a strong 50/60 Hz magnetic eld.
Nevertheless, suggested rack locations would
be either at the top or bottom.
As with any rackmount equipment, be sure to
use 10-32 machine screws for mounting in the
rack’s tapped holes (this is not a metric size).
In particular, beware of 10-24 screws, which
may t if forced but which will strip the threads.
To avoid marring the front panel nish, use
plastic washers under the screw heads.
DESIGN
The AR-Series uses a design based on an
eight-tap toroidal autoformer. The toroidal de-
sign assures minimal leakage of stray magnetic
elds, and, because of its high efciency, a very
compact size for its rating. The Voltage Regula-
tor’s circuitry monitors the incoming line voltage
with each cycle, comparing it to an extremely
precise voltage reference, accurate to ±0.15%.
If a voltage uctuation requires that a different
tap be selected, the new tap is electronically
switched exactly at the zero-crossing, to avoid
distorting the AC waveform. If necessary, it can
switch taps as often as once each cycle. Most
commercial voltage regulators using multiple-
tapped transformers switch taps at uncontrolled
times, thereby creating voltage spikes and
clicks that can leak into the audio! Hysteresis in
the switching circuits avoids “chatter” or unnec-
essary switching back and forth between adja-
cent taps. Unlike those voltage regulators that
employ ferro-resonant transformers, Furman
Voltage Regulators are not sensitive to small
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