Fault Diagnosis
5-3
Revision 2 - 20 March, 1997
HP SERIES DIMMER
OPERATING MANUAL
dimmer working again.
5.4
DMX faults
The HP Dimmers feature a Last Hold facility that remembers the last received DMX
message. In the event of a DMX signal cable being unplugged or severed, the
dimmers will to “hold” the DMX levels until a new DMX message is provided, or a
Snapshot, Scene or Chase function is selected.
The
DMX IN
LED will light when there is a DMX signal.
5.5
Phase fault indication
The three green
PHASE
LEDs will light when all three power input phases are
present.
WARNING
IF ONE OR MORE PHASE LEDS IS OFF,
IMMEDIATELY
DISCONNECT
POWER TO THE DIMMER AND CHECK THE MAINS SUPPLIES AND
WIRING BEFORE RE-CONNECTING POWER.
5.6
Cold lamp filaments
Cold lamp filaments consume considerably more power than warm filaments. This
means that when a lamp is flashed to full, the surge current can be much greater than
the rated current for the lamp.
The cold surge current to large lamps may be enough to trip the output circuit
breakers. If such nuisance-tripping of the circuit breakers is a problem, the filament
Preheat facility may be utilised. See section 4.1.4.4 for instructions on enabling the
Preheat facility.
Preheat turns on the selected channels a very small amount (around 1%) which heats
the lamp filaments and increases their electrical resistance. When the lamp is then
turned on full, the surge current is much less and the circuit breaker is less likely to
trip.
Other advantages of using Preheat are an increase in lamp life (due to the reduction of
thermal shock to the filaments), and a reduction of lamp heat up time (the lamps will
flash to full slightly faster).
When Preheat is on, the lamp filaments may show a barely perceptible dull red glow.
5.7
Output Loads
The HP12-TR will correctly control all resistive and mains-voltage incandescent loads
from 2500 watts down to 10 watts, and transformer-driven incandescent lamps (eg.
pinspots and low voltage halogen lamps) down to 20 watts. The HP12-TR will also
control the speed of most "universal" motors.
In addition to those loads controllable from an HP12-TR, the HP12-SC will control
more "difficult" loads, such as fluorescent and discharge lamps, due to the use of DC-
fired SCRs within the dimmer.
