Studio Technologies 43 - Manual (Page 9)

Issue 1, July 2004 Model 43 User Guide
Page 10 Studio Technologies, Inc.
In the event that a very long cable run is
required, the resistance of the cable can
impact the DC power supplied by the
Model 43. There’s no way to get around the
fact that some DC voltage will be dropped
by the interconnecting cable. A simple
ohms law calculation will tell you the impact
a specific cable run will have. You’ll need
to know the current draw of the connected
device(s), the minimum voltage required by
the connected device(s), and the resistance
of the cable’s conductors. This is generally
stated as ohms per 1000 feet. Make sure
that you account for the resistance in both
the pin 1 and pin 2 legs! In general, if there
is the potential for a cable-length problem,
moving to a more substantial cable gauge,
such as 20, 18, or 16 can be effective.
24 Volt DC Power
An external source of 24 volts DC nominal
is required for Model 43 operation. (In real-
ity, correct operation will take place with
any source that is in the range of 20 to 32
volts.) The unit requires 450 milliamperes
(0.45 amperes) maximum for correct op-
eration. The power source is connected by
way of a 2.1 x 5.0 mm coaxial power jack
that is located on one side of the Model
43’s enclosure, adjacent to IFB circuit’s
connector. The center pin of the jack is
the positive (+) connection.
A 24 volt DC external power supply is
included with each Model 43. The power
supply’s DC output cable is terminated
with a compatible but non-locking power
plug. For special applications, a provision
has been made to support a positive “lock”
between the external source and the Model
43’s jack. An installer can terminate the
cable associated with the external source
using a Switchcraft® S760K “locking” plug.
Using its threaded bushing, this plug can
be secured onto the Model 43 power entry
jack. As soon as 24 volts DC is applied,
the Model 43’s power present LED will
light. The unit is now fully functional.
Operation
There are no switches, potentiometers,
or user controls associated with the Model
43. It’s designed for continuous operation
with no adjustment or maintenance re-
quired. Proper operation will take place
as long as attention is paid to the level
presented on the audio inputs and the
loading placed on the IFB circuit.
Troubleshooting
If you’re having trouble getting the Model
43 up and running, this section may help.
If you haven’t read the previous sections
of this guide, you should do so before
proceeding.
If the Model 43 Doesn’t Work
At All
A source of nominal 24 volt DC power
must be connected to the Model 43. The
unit is fairly forgiving of the power that is
applied; generally anything between 20
and 32 volts DC is acceptable. Whenever
power is connected the power present
LED should be lit. This LED is powered by
the 30 volts DC that is provided on pin 2
of the IFB circuit output connector. If the
LED is not lit confirm that external 24 volt
DC power source is active and that its
connector is securely mated with the inlet
connector. Also ensure that an acceptable
load is being place on the IFB circuit.