Studio Technologies IFB Plus 2005 - Manual (Page 21)

Model 2 User Guide Issue 8, December 2005
Studio Technologies, Inc. Page 21
audio scene where most equipment has a
low output source impedance, and a high
input impedance.
Revising Mains Voltage
The Model 2 can operate from mains power
of either nominal 120 or 220/240 V. Internal
“straps” select the operating voltage. Follow
this section if a change of operating voltage
is required.
The following procedures must be per-
formed by a qualified technician. Operating
the Model 2 with the cover removed ex-
poses the technician to points in the power
input section with hazardous voltages.
1) Ensure that the mains power cord is
removed from the Model 2’s power connec-
tor on the back panel.
2) Remove the top cover via the four 6-32
button-head cap screws.
3) Locate the power supply jumper straps.
They are directly adjacent to the power
transformers on the right side of the circuit
board. The circuit board legend shows the
designated locations for the two operating
voltages. From the factory, 0 ohm “resis-
tors” are used for the straps. These resistors
are really just encapsulated jumper wires.
For 120 V operation, two “0 ohm” jumper
straps are installed for each of the three
power transformers (total of six straps). For
220/240 V operation one strap is associated
with each transformer.
4) Review the present configuration. If a
change is required, use a soldering iron and
appropriate tools to revise the straps. With
care, the changes can be made without
removing the circuit board from the chassis.
Removing the circuit board from the chas-
sis is a painful and time-consuming experi-
ence. The voltage selection straps can be
removed and installed from the component
(top) side of the circuit board. Ensure that
the ends of the straps do not extend below
the circuit board so as to touch, or even
come near the bottom of the chassis. Failure
to heed this warning can result in safety, reli-
ability, and operational problems. Confirm
that the required straps have been installed
for all three transformers.
5) If the mains voltage was changed,
replace the fuse with the correct value:
0.500 A for 120 V, 0.250 A for 220/240 V.
The fuse is a 5 x 20 mm fast-acting type.
6) Replace the top cover and secure it
using the screws.
7) Before reconnecting mains power, use
an ohm meter to ensure that none of the
straps leads have shorted to metal chassis
below the circuit board.
8) Reconnect the mains power and check
the Model 2 for correct operation.
Dim/Mute Function
From the factory, program audio is set
to mute upon interrupt. If level “dimming”
rather than full muting is desired, a simple
modification can be performed by a quali-
fied technician. Schematic diagrams
should be obtained prior to performing
any revisions.
The following procedures must be
performed by a qualified technician. Operat-
ing the Model 2 with the cover removed
exposes the technician to points in the pow-
er input section with hazardous voltages.
1) Ensure that the mains power cord is re-
moved from the Model 2’s power connector
on the back panel.
2) Remove the top cover via the four 6-32
button-head cap screws.