JBL gto 75 4, GTO-75.4II Service Manual
GTO Series
75.4
75.4II
4 CHANNEL POWER AMPLIFIER
SERVICE MANUAL
JBL Consumer Products
250 Crossways Park Dr.
Woodbury, New York 11797 R
ev3vvv10/2005
Power Amplifier GTO 75.4/75.4II
1
- CONTENTS -
SPECIFICATIONS ………………………………….……..1
FEATURES/TEST CONDITIONS……..…………………2
INSTALLATION………………….……...……..…...…...…3
CONNECTIONS………………….……...……..…...…..…4
SET-UP/CONTROLS ……..………………..…….….…...5
INSTALLING NEON TUBES..…….…….………………..5
BASIC TROUBLESHOOTING..…….…….………………7
TYPICAL SYSTEM WIRING..…….…….……………..…8
EXPLODED VIEW/PARTS LIST…….….….…………....9
MECHANICAL PARTS LIST..…….…….…………….....10
AMPLIFIER BLOCK DIAGRAM…………………….……11
P.C.B. DRAWINGS….……………………………….…….12
ELECTRICAL PARTS LIST ..……….……….…….….…16
VERSION II ELECTRICAL PARTS LIST ADDENDUM….……….19
IC/TRANSISTOR PINOUTS..……..….…….….….….…..20
GTO 75.4 SCHEMATICS………..………………..……...23
GTO 75.4II SCHEMATICS………..……………………...26
PACKING……..…………………………………………....29
GTO 75.4/75.4II Specifications
Output Power: 104W RMS x 4 channels @ 4 ohms; ≤1% THD + N
(14.4V supply) 142W RMS x 4 channels @ 2 ohms; ≤1% THD + N
284W RMS x 2 channels @ 4 ohms; ≤1% THD + N
Signal-to-noise ratio: 80dBA (reference 1W into 4 ohms)
Dynamic power: 163W @ 2 ohms
Effective damping factor: 6.38 @ 4 ohms
Frequency response: 10Hz – 83kHz (–3dB)
Maximum input signal: 5.8V
Maximum sensitivity: GTO 75.4 - 230mV
GTO 75.4II - 75mV
DC Offset <50Mv (-50%)
Output regulation: .069dB @ 4 ohms
Idle Current 1.3A
Input Impedance 22kΩ
Max Current Draw 52A @ 4 ohms
83A @ 2 ohms
Dimensions: 15 1/8 x 12 5/16 x 2 3/8” (L x W x D)
(384mm x 313mm x 60mm)
Fuses: 30A x 2
JBL continually strives to update and improve existing products, as well as create new ones. The specifications and details in
this and related JBL publications are therefore subject to change without notice.
GTO 75.4/75.4II
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INSTALLATION
3
GTO 75.4/75.4II
WARNING: Playing loud music in an
automobile can hinder your ability to hear
traffic and permanently damage your
hearing. We recommend listening at low or
moderate levels while driving your car. JBL
accepts no liability for hearing loss, bodily
injury or property damage resulting from
the use or misuse of this product.
IMPORTANT: To get the best
performance from your JBL Grand Touring
Series amplifiers, we strongly recommend
that installation be entrusted to a qualified
professional. Although these instructions
explain how to install GTO amplifiers in a
general sense, they do not show specific
installation methods that may be required
for your particular vehicle. If you do not
have the necessary tools or experience,
do not attempt the installation yourself.
Instead, please ask your authorized JBL
car audio dealer about professional
installation.
INSTALLATION
WARNINGS AND TIPS
• Always wear protective eyewear when
using tools.
•Turn off the audio system and other
electrical devices before you start.
Disconnect the (–) negative lead from
your vehicle’s battery.
• Check clearances on both sides of
a planned mounting surface before
drilling any holes or installing any
screws. Remember that the screws
can extend behind the surface.
• At the installation sites, locate and
make a note of all fuel lines, hydraulic
brake lines, vacuum lines and electrical
wiring. Use extreme caution when cutting or drilling in and around these areas.
• Before drilling or cutting holes, use a
utility knife to remove unwanted fabric
or vinyl to keep material from snagging
in a drill bit.
• When routing cables, keep input-signal
cables away from power cables and
speaker wires.
•When making connections, make
certain they are secure and properly
®
insulated.
• If the amplifier’s fuse must be replaced,
use only the same type and rating as
that of the original. Do not substitute
another kind.
CHOOSING A LOCATION
AND MOUNTING THE
AMPLIFIER
Choose a mounting location in the trunk
or cargo area where the amplifier will not
be damaged by shifting cargo. Amplifier
cooling is essential for proper amplifier
operation. If the amplifier is to be installed
in an enclosed space, make sure there is
sufficient air circulation for the amplifier
to cool itself.
When mounting the amplifier under a
seat, ensure that it is clear of all moving
seat parts and does not affect the seat
adjustments. Mount the amplifier so it
is not damaged by the feet of backseat
passengers. Make sure that the amplifier
is mounted securely using nuts and bolts
or the supplied mounting screws.
Mount the amplifier so that it remains
dry – never mount an amplifier outside
the vehicle or in the engine compartment.
Figure 1. Terminal connection end plate.
POWER CONNECTIONS
The GTO amplifiers are capable of
delivering extremely high power levels,
and require a heavy-duty and reliable
connection to the vehicle’s electrical system
in order to perform optimally. See Figure 1
for connection location. Please adhere to
the following instructions carefully:
Ground Connection
Connect the amplifier’s Ground (GND)
terminal to a solid point on the vehicle’s
metal chassis, as close to the amplifier
as possible. Refer to the chart below to
determine minimum wire-gauge size. Scrape
away any paint from this location; use a startype lock washer to secure the connection.
Power Connection
Connect a wire (see chart at right for
appropriate gauge) directly to the vehicle’s
positive battery terminal, and install an
appropriate fuse holder within 18" of the
battery terminal.
this time. Route the wire to the amplifier’s
location, and connect it to the amplifier’s
Positive (+12V) terminal. Be sure to use
appropriate grommets whenever routing
wires through the firewall or other sheet
Failure to adequately protect the
metal.
positive wire from potential damage may
result in a vehicle fire.
routing and connecting this wire, you may
install the fuse at the battery.
Remote Connection
Connect the amplifier’s Remote (REM)
terminal to the source unit’s Remote TurnOn lead using a minimum of 18-gauge wire.
NOTE: When using the speaker level
inputs, connect the remote (REM) terminal
to the source unit. If your source unit does
not have a remote turn-on connection,
connect the amplifier’s (REM) terminal to
the vehicle’s accessory circuit.
Do not install the fuse at
When you are done
Speaker Connections
Refer to the application guides on the
pages that follow. Speaker connections
should be made using a minimum of
16-gauge wire.
High-Level Input Connections
The GTO75.4 and GTO75.4II
amplifiers are equipped with speaker-level
inputs that allow you to add an amplifier
to head units that do not have RCA line
outputs. The speaker outputs for the
source unit should be connected to the
amplifier using the supplied connector
(square four-wire plug). Remember to
check for proper polarity. The GTO301.1,
GTO601.1 and GTO1201.1 amplifiers are
not equipped with high-level inputs.
NOTE: When using the high-level inputs,
the AUX outputs can be used to pass a
line-level signal to another amplifier.
Wire Gauge Chart
Amplifier Maximum Minimum
Model Current Draw Wire Gauge
GTO75.4 85A #8 AWG
G
AWG
AWG
These recommendations assume 7' – 10'
wire runs. If your installation differs markedly, you will need to adjust the wire
gauge accordingly.
IMPORTANT NOTE: If you are planning
to use optional neon tubes, install them
before making any electrical connections
to the amplifier (refer to“Installing Neon
Tubes” on page 5).
CONNECTIONS – GTO 75.4/75.4II
NOTE: For simplicity, Figures 6 through
8 do not show power, remote and input
connections.
NOTE: Minimum speaker impedance
for stereo operation is 2 ohms.
Minimum speaker impedance for
bridged operation is 4 ohms.
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
4
The GTO 75.4/75.4II can be set up for stereo
4-channel, 3-channel or bridged
2-channel operation, as shown in
Figures 6 through 8.
Figure 6.GTO 75.4/75.4II amplifier in 4-channel (stereo) operation to drive front and rear full-range speakers.
GTO 75.4/75.4II
Figure 7.GTO 75.4/75.4II is set up for 3-channel operation to drive a set of full-range speakers and a subwoofer.
Figure 8.GTO 75.4/75.4II used in bridged 2-channel mode to drive a set of components or subwoofers.
INSTALLATION AND SETUP
SETTING THE
CROSSOVER(S)
SETTING INPUT
SENSITIVITY
1. Initially turn the INPUT LEVEL control(s)
to minimum (counter clockwise).
2. Reconnect the (–) negative lead to the
vehicle’s battery. Apply power to the
audio system and play a dynamic music
track.
3. On the source unit, increase the volume
control to 3/4 volume. Slowly increase
the INPUT LEVEL control(s) toward three
o’clock until you hear slight distortion
in the music. Then reduce the INPUT
LEVEL slightly until distortion is no
longer heard.
NOTE: After the source unit is on, red LEDs
(on the top panel) will light, indicating the
amplifier is on. If not, check the wiring,
especially the remote connection from the
source unit. Also refer to “Troubleshooting”
on the next page.
AUX OUTPUT
NOTE: When using the high-level inputs,
the AUX outputs can be used to pass a
line-level signal to another amplifier.
INSTALLING NEON TUBES
(OPTIONAL)
1. Using a Phillips screwdriver, remove all
screws on the amplifier’s output/power
end panel and set them aside.
2. Using a 3⁄ 32-inch Allen wrench, remove
only the screws on the amplifier’s (top)
clear cover and set them aside.
3. Remove the end panel and slide the
cover off. Set both parts aside.
4. Locate the enclosed hardware bag and
remove the four clips. Each clip has a
square end and a larger round end.
Using a round end, press two clips onto
each neon tube (e.g., Street Glow AN9
or equivalent), as shown in
Figure 13.
5. For each tube, align both clips so the
square ends slide onto an exposed
extrusion edge, as shown in Figure 9.
Do not cover any screw holes. When
installed correctly, each neon tube will
sit under an extrusion and not be visible
when viewed from directly above.
6. Route each neon tube’s power cable
through its respective NEON hole on the
end panel (see
Figure 13).
7. Slide the cover back into place and reinstall its screws. Then, replace the end
panel and reinstall its screws.
8. Finish the installation of the neon tubes
as instructed in their owner’s manual.
Figure 12.
5
GTO 75.4/75.4II
Determine your system plans and set the
crossover mode switch accordingly. If you
plan to use the GTO 75.4/75.4II to drive
full-range speakers, set the crossover
mode to FLAT and skip to “Setting Input
Sensitivity.”
Initially set the crossover frequency
control midway. While listening to music,
adjust the crossover for the least
perceived distortion from the speakers,
allowing them to reproduce as much
bass as possible.
Systems using a separate subwoofer set
the crossover mode to HP (high pass) for
your full-range speakers. Adjust the
crossover frequency to limit bass and
provide increased system volume with
less distortion.
For subwoofers, choose the highest
frequency that removes vocal information
from the sound of the subwoofer.
If using the GTO 75.4/75.4II to drive a
subwoofer(s), set the crossover mode to
LP (low pass).
GTO 75.4/75.4II amplifiers are
equipped with full-range outputs that can
be used to connect additional amplifiers.
GTO 75.4/75.4II
6
INSTALLATION AND SETUP
To Neon
Power
Supply
To Neon
Power
Supply
7
Figure 13. Installing neon tubes in a JBL GTO amplifier.
TROUBLESHOOTING
GTO 75.4/75.4II
SYMPTOM LIKELY CAUSE SOLUTION
No audio No voltage at BATT+ Check voltages at
(POWER LED or REM terminals, amplifier terminals
is off) or bad or no ground with VOM
connection
No audio DC voltage on Amplifier may need
(PROTECT LED amplifier output service; see enclosed
flashes every warranty card for
4 seconds) service information
No audio Amplifier is Make sure amplifier
(PROTECT overheated cooling is not blocked
LED is on) at mounting location;
verify speaker system
impedance is within
specified limits (see
“Specifications” on
the next page)
No audio Voltage less than 9V on Check vehicle
(PROTECT BATT+ connection charging system for
and POWER defective voltage
LEDs flash) regulator
SYMPTOM LIKELY CAUSE SOLUTION
No audio Voltage more than 16V Check vehicle
(PROTECT or less than 8.5V on charging system for
LED is on) BATT+ connection defective voltage
Distorted audio Input sensitivity is Check INPUT
Distorted audio Short circuit in Remove speaker leads
and PROTECT speaker or wire one at a time to locate
LED flashes shorted speaker or
Music lacks Speakers are not Check speaker
“punch” connected properly connections for
regulator
not set properly, or LEVEL setting; or
amplifier or source check speaker wires
unit is defective for shorts or grounds
wire, then repair
proper polarity
GTO 75.4/75.4II
8
Grand TouringGrand Touring
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