JL Audio MHD600/4-24V Owner's Manual page 16

"status" led / Protection circuitrY
There is a single multi-color LED on the
control panel of the amplifier to indicate the
amplifier's operating status. This LED's behavior
is as follows:
1) Flashing Green: amplifier is powering up,
audio output is muted.
2) Constant Green: amplifier is on and
functioning normally, audio output is active.
3) Constant Red: lights to indicate that the
amplifier has exceeded its safe operating
temperature, putting the amplifier into a
self-protection mode, which reduces the
peak power output of the amplifier. The red
light will turn green and the amplifier will
return to full-power operating mode when its
temperature returns to a safe level.
3) Constant Amber (yellow): lights to indicate
that the impedance of the speaker load
connected to the amplifier is lower than
the optimum load impedance range for the
amplifier. When this light is on, a protection
circuit engages and reduces the power output
of the "Front" or the "Rear" channels,
depending on which channel is experiencing
the problem. The amber indicator will also
light when a short-circuit is detected in the
speaker wiring (this can be a short between the
positive and negative speaker wires or between
either speaker wire and the vessel chassis). This
can be used to diagnose a short-circuit by only
connecting one of the amplifier sections at a
time ("Front" or "Rear" channels). The amber
LED will light when you connect the section
that is experiencing the problem and turn the
volume up.
16 | JL Audio - MHD600/4-24V Owner's Manual
4) Alternating Red and Green: lights to indicate
that the amplifier is experiencing a fault that
may require service of the amplifier, its wiring
or the vessel's charging system. Audio is muted
when this fault occurs. The most likely cause
of this fault is a low supply voltage condition.
If battery voltage drops below 17 volts at any
point, the amplifier (except for the "Status"
LED) will shut itself off to protect itself and the
vessel's charging system. If the Remote Turn-
On voltage drops below 12 volts, the "Status"
LED will also turn off.
The amplifier will turn back on automatically
when voltage climbs back above 18 volts. This
shut-down and turn-on behavior may happen
in a rapid cycle when bass-heavy program
material causes a weak charging system to
momentarily dip too low. If this is happening
in your system, have your charging system
inspected to make sure it is working properly.
If no problem is found with the supply voltage
to the amplifier and you are still seeing
alternating Red and Green on the "Status"
LED, check that there are no short-circuits to
chassis ground in any of the speaker wiring
in the vessel. Disconnect speaker connectors
from the amplifier one-by-one to check.
If no problem is found with the supply or
remote voltage, disconnect everything except
power/ground/remote. If the amplifier is then
turned on and displays an alternating red-
green, the amplifier needs service.
For more information on troubleshooting this
amplifier, refer to Appendix D (pages 20, 21)