Remote Turn-On Connections; Operating Procedure; Servicing; Output Tube Bias Adjustment - Audio Research VS55 Owner's Manual

5Model VS115

Remote Turn-on Connections

The VS55 has a built-in 12VDC remote turn-on/off circuit
for operation by a master control system in a home theater
or large audio system. Use a 3.5mm (.140") diameter mono
mini plug to connect to the +12V IN jack on the rear of the
VS55. Two identical paralleled jacks are provided to
allow chaining connections to control two or more VS55s
or other equipment.
The +12V IN jack should be connected to the +12VDC
output of the master control system, using a continuous
+12VDC signal at 20mA per VS55 for the duration of am-
plifier on-time. Do not use a momentary or data pulse con-
trol signal.
The front power rocker switch on the VS55 must be off to
use the remote turn-on. The front power rocker switch may
still be used when the remote turn-on is connected, but the
remote will not turn the VS55 off if the front power rocker
switch is left on. The front power rocker switch will not
turn the VS55 off if the remote system is on.
The +12VDC remote jacks have polarity protection, so they
will not operate if a -12VDC signal is accidentally connect-
ed, or if the control wires are reversed. The 12V remote
relay in the VS55 has click suppression to protect circuits
in the master control system.

Operating Procedure

1. Make sure you have read and complied with the IN-
STALLATION AND CONNECTION instructions prior to
attempting operation.
2. Make sure your VS55 is properly connected to a high-
current power receptacle via the attached power cord
(see AC POWER CONNECTIONS).
3. Your preamplifier should be "on" and muted and/or set at
minimum gain.
4. Turn the Power switch from "Off " to "On." The green
power LED indicator should glow immediately. Note: If
the power indicator LED fails to light, turn the Power
switch to "Off" and check the appropriate fuse for possi-
ble failure.An extra fuse for A. C. power is included with
your VS55.
5. Your VS55 should now operate satisfactorily. However, a
full stabilization or warm-up time of approximately one
hour is recommended for best sonic performance.

Servicing

Because of its careful design and exacting standards of
manufacture, your VS55 amplifier should normally require
only minimal service to maintain its high level of perfor-
mance.
CAUTION: The VS55 amplifier contains sufficient levels of
voltage and current to be l e t h a l . Do not tamper with a
component or part inside the unit. Even with the power
turned off, a charge remains in the energy storage capaci-
tors for some time. Refer any needed service to your autho-
rized Audio Research dealer or other qualified technician.
Replacement vacuum tubes may be obtained through your
authorized retailer or directly from Audio Research Cus-
tomer Service. For best performance, the 6550 output tubes
should be matched pairs.
Additional questions regarding the operation, maintenance
or servicing of your amplifier may be referred to Audio
Research Customer Service at (763)-577-9700.

Output Tube Bias Adjustment

As shipped from the factory, the output "bias"
adjustments are set for a nominal 65mA per 6550 tube.
Under these idle conditions the tubes are each dissipating
approximately 27 watts of their 48 watt rating (42
watt plate, 6 watt screen). This point of operation provides
"enriched" Class AB 1, and will satisfy the most critical
listener.
For best results, operate and adjust the VS55 at 120VAC.
Adjustment must be made under zero-signal conditions
after at least 15-20 minutes of uninterrupted stabilization
time.
A digital voltmeter capable of accurate measurements with
0.lmVDC resolution is preferred for accurate adjustment
(must have 3 1 / digit display). Use the plastic alignment
2
tool provided to make the adjustment. The measurement
points are banana test jacks at the rear of the VS55. Adjust
the "bias" for an average voltage reading of 65mVDC (.065
Volt DC) between test jacks.

Cleaning

To maintain the new appearance of this unit, occasionally
wipe the front panel and top cover with a soft, damp (not
wet) cloth to remove dust. A mild, non-alkaline soap solu-
tion or dilute isopropyl alcohol may be used to remove
fingerprints or similar smudges. Cleaners containing abra-
sives should not be used as they will damage the anodized
finish of the front panel. A small, soft paint brush is effec-
tive in removing dust from bevels, the recessed nameplate
and other features of the front panel.
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