Redback A 1937 User manual

www.altronics.com.au
Operating Manual
A 1937 250W 100V Amplier Module
This module is designed for use in emergency evacuation
systems and is powered by an external 24V DC source. It
accepts a line level audio input and produces a 100V line
output via a transformer. It also features short circuit,
overload and thermal cutout protection, and is constructed
on a steel chassis. Designed with reliability and robust
performance in mind, it is the ideal audio power source for
evacuation systems, or any application which requires a DC
powered 100V line amplier.
FEATURES
• Powered by nominal 24V DC
• 100V line audio output
• Line level audio input - 600mV
• Short circuit, overload, and thermal cutout protection
• Bolt-in chassis construction
• Australian designed and assembled
INSTALLATION
Connecting the Audio Source
The input connector for the audio source is the 3 way screw
terminal block labelled “INPUT”, (see gure 1 for the PCB
location and pinouts). This input may be used with balanced
(3 wire) or unbalanced (2 wire) audio sources. When
connecting an unbalanced (2 wire) source, jumper the GND
and -ve connections on the terminal connector (See g 1
inset).
The amp module’s input is suitable for impedances between
600Ω and 10kΩ. The high impedance of 10kΩ enables
multiple amplier units to be paralleled together when
driven from a low impedance source ie 600Ω.
An output connector (LOOP OUT), feeds the input audio
directly out and has been provided for easy connection of
multiple modules feeding off the same input source.
Connecting Power
Connect 24-28V DC to the power supply input (24V DC IN)
terminal as per g.1.
Ensure that the power supply is capable of providing the
necessary current (see specications).
A 24V DC output has been provided with a maximum current
draw of 1 amp to provide power to external devices.
Connecting the speaker load
Connect the output load to the (SPEAKER OUTPUT) terminals
shown in g.1. Speakers fitted with 100V line transformers
may be connected. Always ensure the total load of the fitted
speakers does not exceed the rated output of the amplifier
otherwise damage may result. When fitting speakers with
line transformers the impedance of the load cannot be
measured using a standard multimeter. An impedance
meter is required. Fig 2 lists the impedance at certain loads
of speakers fitted with 100V line transformers. So for a
total load of 250 watts using 100V line transformer fitted
speakers the impedance of the speaker load should be 40Ω.
LED INDICATORS
Power
This indicates that the unit has power.
Signal Present
This indicates that an audio signal has been detected at the
audio input terminals.
Fault
The Fault LED indicates the unit has a fault condition. Check
the other indicators for further diagnosis.
Temp
The Temp LED will illuminate when the unit shuts down due
to excessive temperature rise.
Overload
The overload LED will illuminate when the unit’s output is
limited due to excessive load on the speaker outputs.
Limit
This LED indicates that the amplier has reached it’s maximum
output level.
Protect
This LED indicates that the unit has gone into protection
mode due to internal failure
User manual revision number 1.0 21/12/2016

www.altronics.com.au
Redback® Proudly Made In Australia
2
* Specications subject to change without notice.
Distributed by Altronic Distributors Pty. Ltd. Perth. Western Australia. Phone: [phone] Fax: [phone]
SPECIFICATIONS
Output Power: ...................................................250W RMS
Current Draw: .............................................17A at full load
................................................................360mA Quiescent
Freq. Response: .............................................40Hz - 13kHz
Distortion: ...............................................................< 0.6%
Signal to Noise Ratio:................................................. -91dB
Sensitivity: .......................................................600mV RMS
Fuse Rating and Type: .........................................20A Blade
Dimensions (mm): ...............................300W x 240D x 95H
TROUBLESHOOTING
Fuse blows: Check speaker loads and replace fuse with 20
Amp blade fuse.
Fuse continually blows: Disconnect load, apply power. If
fuse blows again, refer unit to authorised service centre.
Overload LED illuminates: Check speaker types and
ratings to ensure the amplier is not overloaded, and that
there are no shorts on the speaker line.
Temp LED illuminates: In this condition check the unit for
adequate ventilation. Check also speaker types and ratings
to ensure the amplier is not overloaded, and that there are
no shorts on the speaker line.
20A
OUTPUT TRANSFORMER
HEATSINK
FAN
DC FUSE
(20 Amp)
+ -
24V DC
IN
+ -
24V DC
OUT
(1A MAX)
+ -
SPEAKER
OUT
(100V)
+ GND -
INPUT
+ GND -
LOOP OUT
PROTECT LIMIT OVERLOAD TEMP FAULT POWER
LED INDICATORS
AUDIO INPUT
POWER INPUT
SPEAKER
OUTPUT
VOLUME
SIGNAL
SIGNAL PRESENT INDICATOR
LINK GND & -VE INPUTS FOR
AN UNBALANCED
INPUT
+ GND -
i
Wiring speakers in parallel for 70/100V line: Where several speakers are to
be used at one time, on one circuit, it becomes necessary to use speakers tted
with line-matching transformers. This is to overcome the effects of connecting
speakers in parallel and cable losses. The amplier generally has an output
voltage of 100 volts (70 volts is typically used in North America, however
operation is similar). In this conguration the total wattage load on the amplier
is derived from adding all the line transformer primary tap ratings together. For
example, 70 one watt speakers will have a total speaker load of 70 watts. Or
alternatively, it is conceivable to connect 100 one watt speakers to a 100 watt,
100 volt line amplier.
Measuring 70/100V Line Speaker Impedance: To measure amplier system
load, you must use an impedance meter in order to measure the ac resistance
of the connected speaker network. Impedance cannot be measured with a
standard multimeter, as this measures the dc resistance. Use the Altronics
Q 2001 or similar impedance meter.
About 70V & 100V Line Speaker Systems
Load 70V 100V
0.5W 9.4kΩ 20kΩ
0.66W 7.12kΩ 15kΩ
1W 4.7kΩ 10kΩ
1.25W 3.76kΩ 8kΩ
2W 2.35kΩ 5kΩ
2.5W 1.88kΩ 4kΩ
3W 1.56kΩ 3.3kΩ
5W 940Ω 2kΩ
7.5W 626Ω 1.3kΩ
10W 470Ω 1kΩ
15W 313Ω 666Ω
20W 235Ω 500Ω
30W 156Ω 333Ω
40W 117Ω 250Ω
60W 78Ω 166Ω
100W 47Ω 100Ω
125W 37Ω 80Ω
250W 19Ω 40Ω
500W 9.4Ω 20Ω
Fig 2
Fig 1