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VAC VOICE ALARM SYSTEM
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VAC Installation and Maintenance Manual • Approved Document No. DAU0000402 Rev 6 • Page 29
BGM (background music) input.
Adjust the BGM input level so that it can be heard but is not annoying. If it is too loud, the
amplifier will cut off intermittently.
Walk the circuit listening to each loudspeaker in turn and assessing whether it is working and
if it is set to the correct level.
(3) There may be one or more bad connections on the loudspeaker circuit.
A loudspeaker may be off, intermittent or crackly
A loose contact/wire adds impendence to the circuit causing the EOL to be less effective.
(4) One or more loudspeakers may be mis-connected
A loudspeaker may appear to be connected but it doesn’t work
1
00 volt loudspeakers have transformers with tappings and it is possible to connect them
incorrectly. When the circuit is tested with an impedance meter, the reading is more than 167
ohms, which appears to be acceptable, but the load monitoring system will still detect the
problem.
Apply the rule of halves.
Remove the end of line, split the circuit at the middle, connect the EOLD and attempt to recal-
ibrate. If it does not r
ecalibrate, split the line in half again and repeat. If it does recalibrate
reconnect the line and split again at the three-quarter point.
Continue until the mis-connected loudspeaker is identified.
(5) One or more of the loudspeakers may be damaged or faulty
As section (4), look for uninsulated cores, water damage and physical damage.
Earth faults
Earth fault indications only apply to loudspeaker circuits and are indicated on the front of the
AVAC as speaker faults. (Note that the Speaker Fault A and Speaker Fault B indicators will also
illuminate for open and/or short circuit faults). To ascertain if there is an earth fault, open the
AVAC and check to see if the Speaker Earth Fault A or B indicators on the main PCB are lit.
Amplifier faults occur on the system but when reset they do not reoccur for some con-
siderable time.
An audio input which is not currently running may be set incorrectly, intermittently overdriv-
ing the amplifiers. See section (2) above.
If paging is installed has there been any feedback? Check for loudspeakers near telephones or
microphones and move the equipment further apart.
The load may be changing due to bad connections – see section (4) above.
The emergency mic shows a fault.
The last Master AVAC panel connected to the emergency microphone should have its
Master/Phantom PLK2 link fitted. Check that no Local Fault links are fitted on any Master AVACs
The emer
gency mic that has been used is not compatible – you must use the V
A405.
There is no emergency mic fitted and the EOL resistor has been omitted - see page 19.
Connecting some input sources causes noise.
Use volt free switch contacts on the paging input.
Avoid multiple screen and multiple 0 V connections as circulating currents cause excessive
noise. If a source is unbalanced and connected to signal + or - and 0 V try connecting across
signal + and Signal - inputs instead.
Master to slave faults
Are all AVAC masters and slaves Rev 4? If not, contact your distributor/technical support for advice.
Ensure all PLK2 Local Fault links are removed from Slave AVACs before calibration takes place
and that the links are refitted AFTER calibration.
Is the PLK2 Master/Phantom link fitted at the last slave AVAC?
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