Harman JBL GTO-751EZ, Service Manual

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TROUBLESHOOTING
If your amplifier isn’t performing the way you think it should, check to see if the problem is covered in this section
before calling your dealer or contacting JBL customer service.
PROBLEM CAUSES AND SOLUTIONS
No sound (the amplifier’s
Power/ Protection LED is off): • Check that the amplifier’s +12V and GND connections have been properly
made.
• Check if the fuse on the +12V wire located near the battery is blown; if so,
replace it with an identical fuse.
• Check all amplifier fuses; if any are blown, replace them with identical fuses.
• If you are using the amplifier’s REM connection for turn-on, check that the
wire is properly connected to the audio system’s remote turn-on wire or to the
vehicle’s ACC power terminal.
• If you are using the amplifier’s Auto Turn-On circuit for turn-on, check that the
amplifier’s Auto Turn-On switch (on the amplifier’s bottom panel) is set in the
“On” position.
No sound (the amplifier’s
Power/ Protection LED is
orange): • Check that all amplifier input and speaker connections have been properly
made.
• Check that the amplifier’s Gain control is not turned all the way down.
• Check that the vehicle audio system’s source unit’s volume control is not
turned all the way down.
• If you have connected an optional Remote Bass Control (sold separately)
to the amplifier, check that it is not turned all the way down (fully
counterclockwise).
No sound (the amplifier’s
Power/ Protection LED is red): • Confirm that the vehicle’s electrical system is supplying between 9V and 16V
DC to the amplifier. If the supply voltage is outside of this range, correct the
condition before attempting to use the amplifier.
• If the amplifier has overheated, wait until it has cooled down before attempting
to use it again.
• Disconnect all speakers from the amplifier and attempt to turn it on again:
– If the amplifier turns on (the Power/Protect LED is orange), there is a short
circuit in one or more of the speaker wires. Correct all short circuits before
reconnecting the speakers to the amplifier.
– If the amplifier does not turn on (the Power/Protect LED is still red), contact
your authorized JBL dealer for assistance.
• If the optional Sub Channel Level control is connected to the amplifier, check
that it is not turned all the way down (fully counterclockwise).
Sound is too quiet, even with the
vehicle audio system’s head unit
volume turned all the way up: • Check the amplifier’s Input Level switch. If it is set to “Hi1,” turn the amplifier’s
Gain controls all the way down and re-set the Input Level switch to “Low.”
Then perform the
Set the Gain procedure, on page 7, again.
Sound in the subwoofer is
distorted: • If the Input Level switch is set in the “Low” position, change the setting to “Hi1”
and perform the Set the Gain procedure, on page 7, again for those channels.
• While listening to bass-heavy music, turn the Bass Boost control all the way
down, and then gradually increase it until the distortion begins to return.
Reduce the Bass Boost control setting slightly to eliminate the distortion and
leave it set there.
• Check that the distortion is not originating from the vehicle audio system’s
source unit.
The amplifier’s Gain LEDs
constantly illuminate red while
the amplifier is operating: • Set the amplifier’s Gain LEDs switch in the “Off” position.
GTO-751EZ
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