13
Owner’
s Manual
In Case of Difficulty
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
identical ones. If the new fuses blow
immediately, check all the wiring
connections. If the source of the problem
cannot be determined, consult your JBL
dealer.
• Remote-on wire between the head unit and
the amplifier is disconnected or defective;
check for
+
12 volts between amplifier's
remote-on input terminal and the ground
wire with the head unit on.
Power light is on, but no sound is heard
from some or all of the speakers
• Incorrect switch settings; make sure 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.
Power light is on, but no sound is heard
from some or all of the speakers
• Defective head unit or signal processor;
check each component for proper wiring and
operation.
• Defective GTQ amplifier; if there is audio
signal present at the inputs of the amplifier
and there is no output, the GTQ amplifier
may be defective.
Alternator whine through the audio system
with the engine running
• Ground loops; follow the wiring sugges-
tions in the section called “Solving Noise
Problems.” Also, verify that the chassis
grounding point you have chosen is true
ground by checking for continuity between
the chassis ground point and battery ground.
Bass output from speakers too low
• Speaker wired out of phase; check for
proper polarity on all speaker wiring (
+
amp
terminal to
+
speaker terminal and – amp
terminal to – speaker terminal).
Power light is blinking and no sound is
heard
• Incorrectly connected or shorted speaker
wires; check for shorts in wiring.
• Defective GTQ amplifier; if there is no short
on the speaker outputs, the GTQ amplifier
may be broken. Consult your JBL dealer.
If you want to talk to us about any problems,
call JBL Customer Service at 1-800-336-4JBL
between 9AM and 5PM Eastern time.
Solving Noise Problems
System Noise
System noise, generally appearing as
hiss, is usually the result of improper
input gain (sensitivity) adjustment. With
the proper setting, your JBL amplifier will
not create this noise, but will amplify any
noise generated ahead of it as part of the
signal. Refer to “Adjusting the Gain”
section on page 11 for instructions on
how to minimize this noise.
Vehicle Noise
Every vehicle has some electrical noise
that is generated by the ignition system,
the alternator, the accessories, and their
wiring. High-performance audio
equipment is more likely to pick up such
noise than conventional equipment
because it has wide-frequency bandwidth
and high-gain (amplification) circuits.
GTQ amplifiers have two built-in power
supply filters to help prevent noise
problems. If noise occurs it is probably
the result of improper installation. The
following suggestions will help you
eliminate most noise problems.
Source Noise –
Often noise in a system
is picked up by the signal source. Before
attempting to eliminate noise from the
amp, be sure it is not being picked up by
the signal source and then passed on to
other components. To do this, connect
the signal source output to an external
amplifier which has no other connection
to the vehicle except for the audio signal
leads. A battery-powered amplified
portable speaker, such as those sold for
use with com-puters or Walkman-type
portables, works well for this. Listen to
see if the noise is present in the signal
from the source unit. If so, consult the
manufacturer of the source unit, or your
JBL dealer, for help in reducing this
noise. If there is no noise in this signal, it
can be eliminated as the source of your
problems.
Ground Loops –
The vast major-ity of
noise problems are caused by
inadequate or improper grounding. The
head unit, the amplifier, and any other
components must be grounded to a
major metal member of the vehicle’s
frame. Make sure to choose a solid metal
ground point, as some new vehicles
contain structural elements made of
plastic.
Most often the noise level in the system
will be lower if amplifiers and signal
processors that do not have isolated
supplies are all grounded to the same
point on the chassis. Amplifiers, such as
the GTQs, which internally isolate the
signal ground connection from the power
ground connection, generally do not
benefit from this. Usually the head unit
does not need to be grounded to the
same point as the rest of the system, but
in some instances, depending on the
design of the signal processors involved,
grounding signal processors to the same
point as the head unit will also help. If
this does not adequately reduce the
noise level, try another ground point on
the car frame. Because of current flow
patterns within the vehicle chassis, some
ground points are noisier than others. As
a general rule, try to keep grounds away
from the main flow of current between
GTQ 190 - English 06/03/98 11:50 Side 13
