of the Extreme Voltage Shutdown circuitry (approximately 200 VAC for AR-1215 and AR- 1215J; approximately 400 VAC for AR-2306). To replace it, the unit must be completely discon- nected from all power and removed from its rack. The six hex head screws and one Phillips head screw 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 voltage (though it may still be restored to a us- able level) but is not high or low enough to cause an extreme voltage shutdown.
The AR-1215J and AR-2306, which have switchable output voltages, also have multiple scales on the Input Voltage meter corresponding to the selected voltage. On the AR-2306, there are three scales, with the top for 220V, the middle for 230V, and the bottom for 240V.
OUTPUT VOLTAGE MONITORING
A green LED labelled OUTPUT IN REGULATION indicates proper function (i.e., that the output voltage is within ±5V [±10V] 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.
If you wish to monitor your AR-1215’s output volt- age more precisely, you may want to use a Furman PL-PLUS Power Conditioner and Light Module
in conjunction with it [use model PL-PLUS-E with model AR-2306].
The PL-PLUS is the perfect complement to a Furman Voltage Regulator to assist in rack power distribution.
It offers a 20-LED bargraph line voltage meter to moni- tor the incoming line (the Voltage Regulator output), twin slide-out, swiveling lights with a dimmer control for equipment illumination, and eight [ten] additional outlets with their own spike and surge protection and RFI / EMI fi ltering.
INSTALLATION
Because of their toroidal transformer design, Fur- man Voltage Regulators may be positioned near most other equipment without fear that the other equipment will be disrupted by leakage of a strong 50/60 Hz magnetic fi 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 fi t if forced but which will strip the threads. To avoid marring the front panel fi nish, use plastic washers under the screw heads.
DESIGN
The AR-Series uses a design based on an eight-tap toroidal autoformer. The toroidal design assures minimal leakage of stray magnetic fi elds, and, be- cause of its high effi ciency, a very compact size for its rating. The Voltage Regulator’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 fl uctuation requires that a different tap be selected, the new tap is electronically switched exactly at the zero-crossing, to avoid dis- torting the AC waveform. If necessary, it can switch taps as often as once each cycle. Most commercial voltage regulators using multiple-tapped trans- formers 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 unnecessary switching back and forth be- tween adjacent taps. Unlike those voltage regulators that employ ferro-resonant transformers, Furman Voltage Regulators are not sensitive to small errors
