Reference Series
7520a
2 CHANNEL POWER AMPLIFIER
SERVICE MANUAL
Infinity Systems, Inc. |
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250 Crossways Park Dr. |
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Woodbury, New York 11797 |
Rev0 5/2004 |
Power Amplifier |
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Reference 7520a |
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- CONTENTS -
SPECIFICATIONS ………………………………….……..1
FEATURES/TEST CONDITIONS……..…………………2
CONTROLS/CONNECTIONS………….……..…...…..…3
INSTALLATION………………….……...……..…...…...…5
BASIC TROUBLESHOOTING..…….…….………………6
TYPICAL SYSTEM WIRING..…….…….……………..…7
EXPLODED VIEW/PARTS LIST…….….….…………....8
MECHANICAL PARTS LIST……………..…………........9
AMPLIFIER BLOCK DIAGRAM…………………………10
P.C.B. DRAWINGS….…………………………………….11
ELECTRICAL PARTS LIST ……………………………. 14
IC/TRANSISTOR PINOUTS..……………………….. …..17
SCHEMATICS………..……………………….…………...19
PACKING……..…………………………………………....21
Reference 7520a Specifications
Output Power: |
97W RMS x 2 channels @ 4 ohms; ≤1% THD + N |
(14.4V supply) |
142W RMS x 2 channels @ 2 ohms; ≤1% THD + N |
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283W RMS x 1 channels @ 4 ohms; ≤1% THD + N |
Signal-to-noise ratio: |
83dBA (reference 1W into 4 ohms) |
Dynamic power: |
190W @ 2 ohms |
Effective damping factor: |
6.389 @ 4 ohms |
Frequency response: |
10Hz – 69kHz (–3dB) |
Maximum input signal: |
5.5V |
Maximum sensitivity: |
240mV |
DC Offset |
<50mV (-50%) |
Output regulation: |
.078dB @ 4 ohms |
Idle Current |
900mA |
Input Impedance |
22kΩ |
Max Current Draw |
22A @ 4 ohms |
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37A @ 2 ohms |
Dimensions: |
12 x 11 7/16 x 2 11/16” (L x W x D) |
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(305mm x 290mm x 68mm) |
Fuse: |
30A |
Infinity 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.
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Reference 7520a |
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POWER CONNECTIONS |
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The Reference amplifiers are capable of delivering high power levels, and require a 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. Sand away any paint from this location; use a star-type-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. Do not
install the fuse at 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 metal. Failure to adequately protect the positive wire from potential damage may result in a vehicle fire. When you are done routing and connecting this wire to the battery and to the amplifier, you may install the fuse at the battery. The
fuse value should be selected based on total amplifier-current draw; see chart at right.
REMOTE CONNECTION
Connect the amplifier’s Remote (REMOTE) terminal to the source unit’s Remote Turn-On lead using a minimum of 18-gauge wire. If your source unit does not have a remote turn-on connection, connect the amplifier’s (REMOTE) terminal to the vehicle’s accessory circuit.
WIRE-GAUGE CHART |
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Amplifier |
Maximum |
Minimum |
Model |
Current Draw |
Wire Gauge |
7520a |
34A |
#8 AWG |
7540a |
85A |
#8 AWG |
5760a |
87A |
#8 AWG |
310a |
40A |
#8 AWG |
610a |
69A |
#6 AWG |
1210a |
115A |
#4 AWG |
These recommendations assume 7' – 10' wire runs. If your installation differs markedly, you will need to adjust the wire gauge accordingly.
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 7520a, 7540a and 5760a 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 310a, 610a and 1210a amplifiers are not equipped with high-level inputs.
NOTE: When using the low-level or high-level inputs, the AUX outputs can be used to pass a full-range line-level signal to another amplifier.
Figure 2. Speaker-level connector.
GRAY/B
Figure 1.Terminal-connection end plate.
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APPLICATIONS – 7520a
The 7520a amplifier can be set up for stereo or bridged-mono operation, as shown in Figures 5 and 6.
NOTE: For simplicity, Figures 5 and 6 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.
Figure 5. 7520a amplifier set up for stereo operation.
Figure 6. 7520a amplifier set up for bridged-mono operation.
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INSTALLATION AND SETUP |
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SETTING THE CROSSOVER(S)
Determine your system plans and set the crossover-mode switch accordingly. If your system design does not include a subwoofer, set the crossover mode to FLAT and skip to “Setting Input Sensitivity.”
MODE SWITCH
Flat: Allows a full-range signal through to the speakers; can be used with larger full-range speakers such as 6" x 9"s.
HP: Allows a high-pass signal through to the speakers; should be used with most loudspeakers (can protect your full-range speakers from being overdriven with low frequencies, one cause of speaker damage).
LP: Allows bass to pass through to the speakers; should be selected when powering subwoofers.
SETTING INPUT SENSITIVITY
1.Initially turn the INPUT LEVEL control(s) to minimum (counterclockwise).
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, blue 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 page 7.
AUX OUTPUT
Reference amplifiers (except 5760a) are equipped with full-range outputs that can be used to connect additional amplifiers.
NOTE: When using the lowor high-level inputs, the AUX outputs can be used to pass a full-range line-level signal to another amplifier.
Figure 13. Control end panel.
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 7520a or 7540a to drive a subwoofer(s), set the crossover mode to LP (low pass).
NOTE: The 310a, 610a, 1210a and the subwoofer output of the 5760a are low-pass only and do not have a crossover-mode switch.
REMOTE LEVEL CONTROL (OPTIONAL)
All three Reference subwoofer amplifiers and the 5760a amplifier have inputs for an optional remote level control (100rc).This will allow the subwoofer level to be adjusted from the listening position. Connect the optional remote level control using the RJ-11 jack on the side of the amplifier. Install the control module in the front of the vehicle within easy reach of the driver. Both the underside of the dash and the center console are suitable locations. Refer to the mounting instructions accompanying the 100rc.
SETTING THE BASS BOOST
The 7520a, 7540a and 5760a are all equipped with a bass-boost control. This allows you to enhance the bass output of your system at 50Hz up to 12dB.
NOTE: Only rear channels of the 7540a are affected by the bass boost control.
7520a
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TROUBLESHOOTING |
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•PROBLEM:
No audio (POWER LED is off).
CAUSE and SOLUTION:
No voltage at BATT+ and/or REM terminals, or bad or no ground connection. Check voltages at amplifier terminals with VOM.
•PROBLEM:
No audio (PROTECT LED flashes every 4 seconds).
CAUSE and SOLUTION:
DC voltage on amplifier output. Amplifier may need service; see enclosed warranty card for service information.
•PROBLEM:
No audio (PROTECT LED is on).
CAUSE and SOLUTION:
Amplifier is overheated. Make sure amplifier cooling is not blocked at mounting location; verify that speaker-system impedance is within specified limits.
•PROBLEM:
No audio (PROTECT and POWER LEDs flash).
CAUSE and SOLUTION:
Voltage less than 9V on BATT+ connection.
Check vehicle charging system.
•PROBLEM:
No audio (PROTECT LED is on).
CAUSE and SOLUTION:
Voltage greater than 16V or less than 8.5V on BATT+ connection. Check vehicle charging system.
•PROBLEM:
Distorted audio.
CAUSE and SOLUTION:
Input sensitivity is not set properly, or amplifier or source unit is defective. Check INPUT LEVEL setting, or check speaker wires for shorts or grounds.
•PROBLEM:
Distorted audio (PROTECT LED flashes).
CAUSE and SOLUTION:
Short circuit in speaker or wire. Remove speaker leads one at a time to locate shorted speaker or wire, then repair.
•PROBLEM:
Music lacks “punch”.
CAUSE and SOLUTION:
Speakers are not connected properly. Check speaker connections for proper polarity.
STATUS LEDs
Clip: Indicates the amplifier is being overdriven, and your speakers may be in danger. This should blink only on musical peaks, and not be on constantly.
Power: Indicates the amplifier is on.
Protection: Refer to “Troubleshooting” for specific indications.
Figure 15. LED status.
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