GTH 400 (serv.man2) - JBL Car Audio User Guide / Operation Manual. Page 22

21

Power-on light does not come on

• Head unit not on; turn the head unit on.

• Ground wire is disconnected or

defective; check for continuity with an
ohmmeter between the amplifier’s
ground terminal and a known chassis
ground point.

• Battery wire is disconnected or

defective; check for approximately +12
volts between the amplifier’s battery and
ground terminals.

• Blown fuse; check amplifier’s fuses 

located on the end panel near the power
connector. If they are blown, replace 
them with an identical one. If the new
fuses blow immediately, then check all
the wiring connections. If no fault is
found, consult your JBL dealer.

• Remote-on wire between the head unit

and the amplifiers is disconnected or
defective; check for +12 volts between
amplifiers remote-on input terminal and
the ground wire with the head unit on.

Power light is on, but no sound is heard 

• Incorrect switch settings; make sure 

from some or all of the speakers

that all switches (mode, input  and
crossover) are in their correct positions
for your system configuration.

• Incorrectly connected or shorted

speaker wires; check for shorts in
wiring.

• Defective or disconnected audio cables;

check for continuity and replace if 
necessary.

• Incorrect gain adjustment; verify that the

amplifier gain controls are not turned
completely down. If they are, sound
output level may be very low and may
give the impression that the system (or
part of the system) is dead.

GTH400-20107  06/03/98 15:50  Side 21