Studio Technologies IFB Plus 2007 - Manual (Page 27)

Model 2 User Guide Issue 9, January 2006
Studio Technologies, Inc. Page 27
should find relatively equal audio levels. Use
the audio level meter, connected to IFB chan-
nel 1’s line output, to “tweak” the trim pots.
If you don’t have an audio level meter handy,
or if you’re not concerned about exact cali-
bration, use one of the LED level meters on
the front panel to set the trim pots. Actually,
if your ears are pretty good use them, and
no meters, to set the trim pots to get equal
levels—that’s what we would do if we were in
the field! Confirm your subjective adjustment
with the LED meter and you should be set.
Setting the Line-level Trim Pot on the
Model 22 and Model 24 Access Stations
The Model 22 and Model 24’s line input
circuitry allows balanced and unbalanced
signals with a nominal level of –15 to +10
dBu to be correctly interfaced. The system
is designed to have an access station send
interrupt signals at a signal level of –10 dBu
to the Model 2 Central Controller. A level
adjustment trim pot on the Model 22 and
Model 24 allows the various signal levels
to be adjusted to give the desired signal
strength. Set the trim pot only after installing
the entire IFB system. Start by connecting an
audio level meter across the two test points,
labeled COM and AUDIO, on the Model 22 or
Model 24’s circuit board. Then, while speak-
ing into the microphone, headset, or other
device that produces the line-level signal,
adjust the trim pot to give an average level
of approximately –10 dBu on the meter. Peak
signals should fall in the –5 to 0 dBu range.
This setting should result in a clean, clear
interrupt signal, without excess compressing
by the Model 2’s circuitry.
Model 32A and Model 33 Output Level
By design, the output level on the Model 32A
and Model 33 Talent Amplifiers cannot be set
to fully “off.” While the output level can be
substantially attenuated, it never can be set
for full attenuation. This was to ensure that
talent personnel could never accidentally
be fully “isolated” from their program or IFB
source. There may be special cases where
full attenuation is desired. This might be es-
pecially true with the Model 33 Talent Ampli-
fier, where a mix of the two IFB channels can
be achieved. Referring to the Model 32A or
Model 33 schematic diagram, observe that a
resistor is connected between circuit com-
mon and the counterclockwise connection
of each potentiometer. This resistor prevents
full attenuation. By replacing this resistor
with a “0 ohm” resistor or jumper strap, full
attenuation can be achieved.
Troubleshooting
Troubleshooting the Model 2 and related
components is to be performed only by a
qualified technician. Operating the Model
2 with the cover removed exposes you to
hazardous voltages.
Block diagrams are located at the end of
this guide. Schematic diagrams are avail-
able upon request. These documents pro-
vide assistance during maintenance and
repair. Understanding the schematics and
block diagrams will lead to much better
understanding of the individual circuits and
how they work together (or, in case of trou-
ble, how they don’t work together!)
Model 2 Central Controller
The Model 2 consists of many relatively
simple circuits. Detailed troubleshooting
procedures are difficult to describe because
there are few specific circuits that are prone
to failure. The following paragraphs may
give a few helpful hints if problems do arise.
In all cases, you are welcome to contact
Studio Technologies for technical support.