Issue 2, December 2013
Model 42A User Guide
Page 16
Studio Technologies, Inc.
It’s important to note that during the 10-
second off period no voltage monitoring
takes places. Removing the fault condition
will not result in the output voltage imme-
diately turning on again; the 10-second
shut-down period must first elapse.
Operating Parameters
As expected with professional equipment,
whenever AC mains power is discon-
nected from the Model 42A, the present
operating state will be stored in nonvolatile
memory. Specifically, the IFB output chan-
nel selected for audio monitoring and the
status of the auto scan function will be
saved. This ensures that upon subsequent
power up the unit will return to its previous
operating state. If, for example, the auto
scan function was active when the Model
42A was powered down, auto scan will
begin once AC mains power is again
connected.
Troubleshooting
If you’re having trouble getting the Model
42A 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 42A Doesn’t
Function At All
A source of AC mains power must be
connected to the Model 42A. The unit is
a “universal input” type so that applying
power in the range of 100 to 240 volts,
50/60 Hz is acceptable. Whenever AC
mains power is connected the front-panel
LEDs should go through their power-up
routine, lighting in a processor-controlled
sequence. If this does not occur confirm
that AC mains power is active (“hot”) and
that the cord is securely mated with the
inlet connector on the Model 42A’s back
panel.
In all foreseeable situations, both normal
and abnormal, the status and meter LEDs
should go through their normal power-up
routine. However, it’s possible that if all
four IFB outputs are being presented
with a short-circuit condition, the internal
36 volt power supply may enter its protec-
tion mode and shut down. In this case
no LEDs will light. If this scenario occurs,
even after confirming that AC mains power
is correctly being applied, try removing the
loads from the IFB outputs. The easiest
way to do this is to remove the 3-pin
female XLR connectors that are plugged
into the Model 42A’s back panel. If normal
operation then begins, carefully check the
IFB output wiring for fault conditions.
If the front-panel LEDs still don’t go
through their power-up routine, even
after confirming that AC mains power is
present and that the IFB outputs are not
shorted, it’s likely that the unit requires
factory service. For safety in the event of
a major internal failure, the internal 36 volt
power supply contains a fuse in series
with the incoming AC mains power. This
fuse will open (“blow”) only if a serious
failure occurs inside the unit. The fuse is
not field-replaceable. The Model 42A must
be returned to the factory or an authorized
service location for review and repair.
Maintaining Correct Input
Signal Levels
The Model 42A’s four 2-channel audio
inputs are designed for nominal signal
levels of +4 dBu. Applying signal levels
significantly lower than +4 dBu will
