POWER LED not illuminated
:
Check that the power (
O
/
I
) switch is toggled to the ON (
I
) position.
A 20mm fuse is incorporated in the AC POWER socket. It is necessary to
remove the power cord before extracting the fuse holder. Test the continuity
of the fuse using a multimeter. A spare fuse is provided in the fuse holder.
Any replacement fuse
must
be of the same fuse rating and type as
printed on the rear panel of the unit.
POWER LED flashing continuously
:
Amplifier has failed self test and is in safe mode. No signal will be fed into
the loop. Switch the unit OFF, remove all connections except the loop and
power connections, turn all front panel controls to minimum and switch back
ON. If the problem persists, contact Ampetronic for advice.
COMPRESSION LEDs not illuminating
:
Check input connections.
Ensure that the appropriate front panel control (Mic / Line) is turned up.
Check that there is sufficient signal level for the required input.
CURRENT LEDs not illuminating
:
Check that the COMPRESSION LEDs are illuminating.
Check that the LOOP CURRENT control is turned up sufficiently.
Check that the LOOP ERROR, or OVERHEAT LEDs are not illuminated.
Ensure the POWER LED is illuminated and not flashing.
Remove any connection to the SLAVE I/O socket.
Check that the loop cable is connected, terminated correctly and inserted
into the LOOP OUTPUT socket.
Check the loop cable is not open circuit, short circuit, or connected to earth
(see Instability or high frequency noise section of Troubleshooting).
Note: You can listen to the actual loop signal by using a pair of headphones
plugged into the loop monitor socket.
OVERLOAD LED illuminated
:
Indicates that too much current is being delivered into the loop.
Check that the COMPRESSION LEDs are illuminating.
Remove any connection to the SLAVE I/O socket.
Turn the LOOP CURRENT control down to avoid running too much current
into the loop.
TROUBLESHOOTING
Check the loop cable is not open circuit, short circuit, or connected to earth
(see Instability or high frequency noise section of
Troubleshooting
).
OVERHEAT LED illuminated:
Indicates that the internal heatsink is too hot. Loop current is not delivered.
Ensure that the unit is installed in a location with sufficient ventilation.
Check the loop cable is not open circuit, short circuit, or connected to earth
(see Instability or high frequency noise section of Troubleshooting).
LOOP ERROR LED illuminated:
Indicates that the loop cable connected to the unit is outside specification.
Check that the loop cable is connected, terminated correctly and inserted
into the LOOP OUTPUT socket. Ensure the DC resistance is acceptable.
Low magnetic field strength:
Due to insufficient LOOP CURRENT or excessive metal loss.
May require a special loop design to achieve acceptable performance,
contact Ampetronic for advice.
Instability or high frequency noise
1) It is possible for the loop cable to become grounded under fault
conditions, resulting in instability which may sound like high frequency
noise, buzz or whistling. The results of this type of fault are unpredictable
and may appear as any combination of the front panel indication errors.
This fault is easy to determine: simply unplug the loop cable from the
amplifier and test with a resistance meter between either of the loop wires
and a good earth point such as a metal radiator. There should be an
infinitely high reading i.e. no connection at all. Any reading indicates a
failure of the loop cable insulation and you will need to either repair or
replace the loop cable.
2)
Instability can be caused by using poor quality signal cables, long
unbalanced (2-wire) signal runs to the inputs, or by running input cables in
close proximity with the loop wire over any appreciable distance. Loop
amplifiers are capable of delivering high currents at audio frequencies. If
the loop cable is run close to sensitive signal cables it may be possible to
induce a signal back into the input of the amplifier causing feedback. Cable
runs and loop wires should be kept well apart from each other. To avoid
interference a proximity of 300mm should only be run for a few meters.
Always used balanced (3-wire) circuits where possible.
