SMART EXM556, Installation And Service Manual

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INSTALLATION & OPERATION
impedance headphones will not be as loud as the low
impedance type.
EXCITER SUPPLIES
The MN556 is a monitor only unit, and has no exciter
supply. The EXM556 contains two exciter supplies.
The main supply is a fully regulated switching type
supply that sets new standards for tightness of regula-
tion for line voltages from 109 VAC to 130 VAC. The
output of the supply will not vary more than 1/10 of
1% within the specified AC operating range. Because
the supply switches at 25,000 times a second, hum and
noise are above the audio range. DC output is continu-
ously variable from 4.5 VDC to 10 VDC and is installer
adjusted from the rear of the EXM556. The supply
runs very cool under continuous service and, unlike
conventional “brute force” regulated supplies, does
not contribute a lot of heat to the system. Field
replacement of the regulated supply is easy. The
5100A module may be removed from the back of the
EXM556 without taking the monitor/exciter out of the
rack. Four phillips screws hold the module to the main
chassis. A heavy, high current connector will discon-
nect the module from the main power source in the
EXM556.
The second exciter supply in the EXM556 is the DC
backup supply. This supply is unregulated. The HI
and LO DC output voltages are selectable by the
installer. The LO setting will produce about 5 volts
and is used with European type exciter bulbs. The HI
setting is used with domestic bulbs. The factory sets
the emergency DC supply to the Hi setting before
shipping unless the product is intended for export and
has a 220/240 power transformer.
The exclusive “Auto Sense” circuit in the EXM556
monitors the output of the regulated main supply. In
the event of a failure of the main supply, or if the sup-
ply is removed, the “Auto Sense” comparator will
automatically switch the exciter lamp to the internal
backup DC supply. The operator LED indicator on the
front panel will switch from the NORMAL position to
the BACKUP mode and begin blinking. This indica-
tion tells the operator that the exciter is in emergency
backup and the sound engineer should be notified.
Even though both supplies are built of heavy duty
components, the exciter supplies have been designed
for one exciter lamp. The load should not exceed more
than 5 amperes (at any voltage). If two projectors are
used in the booth a relay or switch should be added to
switch between one exciter lamp and the other. Often
this can be a spare set of contacts on the controlling
device that performs other changeover functions.
Make sure the switch or relay contacts can handle the
required exciter lamp current.
KILL CIRCUIT. Another deluxe feature of the 5100A
module is the “kill circuit” that drops the regulated
output exciter voltage to about one volt when the
show is in intermission. This bulb saver feature allows
the bulb to stay in a pre-warmed condition. Bulbs that
are turned on and off during the day will possibly
have a shorter life due to the shock of the high inrush
current into a cold filament. The kill circuit extends
bulb life and is part of the turn-on soft start design of
the 5100A module.
INSTALLATION
INSTRUCTIONS
AMPLIFIER OUTPUTS
The stage speakers may use conventional broadband
power amplifiers with a crossover network at the
loudspeakers, or they may use a biamplified scheme
where there is no crossover at the speaker, but a sepa-
rate power amplifier feeds the high frequency driver
and another feeds the bass speakers directly. An elec-
tronic crossover divides the audio spectrum into two
parts to feed the inputs of the power amplifiers. If you
are using conventional amplifiers, connect each ampli-
fier output to the appropriate input terminals on the
monitor labeled “FROM AMPLIFIER OUTPUTS.” BE
CAREFUL! Most solid state power amplifiers tie the
low output to amplifier ground. Connecting the HOT
terminal to the monitor ground could “fry” the ampli-
fier or monitor input.
Connect conventional amplifiers only to the LF inputs
on the back of the monitor. Even though these inputs
are labeled LF for biamplified systems, they are actual-
ly broadband, full range inputs. When connecting a
biamplifier to the monitor inputs, the HF (high fre-
quency) amplifier outputs are connected to the appro-
priate channel HF inputs on the MN/EXM556 moni-
tor. The LF (low frequency) amplifier outputs are con-
nected to the LF inputs of the monitor. The signals
from the HF and LF amplifiers are summed at a 1:3
ratio inside the monitor so that the proper balance of
HF and LF sound is heard in the monitor speaker and
through the headphone jack. When listening to the
monitor you can determine if a section of the biampli-
fied signal has failed. If the monitor sounds bassy, the
HF amplifier is not producing the HF sounds. If the
monitor sounds shrill, the bass amplifier may have
failed.