20 Most Recent Infinity 7540A Car Audio Amplifier Questions & Answers


I have a infinity interlude

Hi and welcome to FixYa,

Initially, the description "...smelling like smoke..." as it would indicate that indeed something did burned.

Offhand, replacing the 4A fuse restored power temporarily and either burned itself again or allowed further damage to the sub woofer. As you have done, repairs involve opening the unit for a look and see.

Options then are:
  • consider a DIY (do-it-yourself) repair if and only if very familiar with electronic components & circuitry, use of a DVM/VOM, a soldering iron/station and safe working practices with electrically powered devices. Access to a Service Manual or at the very least, a schematic diagram would be a necessity;
  • should you be uncomfortable with a DIY, perhaps your best bet would then be to seek the services of an authorized Service Center (specially if still under some form of extended warranty) or a qualified professional.
If a DIY is being considered, suggestions and technical details to consider when repairing an Infinity Interlude Series IL120s Subwoofer :
  • the power supply used in this model is a switch mode type;
  • the sub's amp is a 500W class A-B;
  • remove the power supply unit (PSU) PCB (printed circuit board) from main chassis by squeezing the heads of the plastic standoffs with a long-nose pliers;
  • bench test the PSU;
  • tests components Q501, Q502, both are IRF740 MOSFETS;
  • tests components R506, R503, both are 22 ohms 0.6 watts;
  • tests components R505, R502, both are 422 ohms 1/4 watts.
Reference below component / board layout.


Good luck and thank you for asking FixYa.
12/18/2018 8:32:22 PM • Infinity 7540A... • Answered on Dec 18, 2018

Is there somewere i can

Go to harmonkardon.com
5/11/2011 10:19:51 PM • Infinity 7540A... • Answered on May 11, 2011

Is it possible to hook

yes it is however the hookup for it requires something a bit unorthodox

you have 4 outputs (bridgeable)

channel 1 and 2 must be bridged (to lower the ohms) then connected to the 2 6X9 in Parallel..
this must then be set to the high pass frequency (eliminates bass)
lower all the settings as low as possible then turn them up slightly to increase volume to a level where its the hardest and clean sounding..lower volume after

this eliminates the bass and keeps the 6x9 pushing your mid range and high range frequency

now you have 2 channels remaining,, set 3 and 4 to low pass and connect each 12" to an individual channel. (this keeps the bass and ohms high so you will get a clean bass to match with mids and high's. Dont set or bridge for a low bass as it will jam out the 6x9 and your music will sound terrible.

so there u have a simple hookup that will work and keep you sounding clean. remember not to raise the volume on the 6X9 too much as you will blow them..
3/29/2011 1:15:37 AM • Infinity 7540A... • Answered on Mar 29, 2011

The power cuts off when i hit the bump, after

The wiring my not be getting a good connection to where you got them connected. Check the ground where and make sure there is a good strong connection
4/25/2010 3:37:29 AM • Infinity 7540A... • Answered on Apr 25, 2010

It is on protect and clip mode it stopped working

Hi most of the time protect mode comes on when there is a wiring problem check your earth and wiring to subs speakers etc some thing has come loose i bet
10/18/2009 6:54:15 AM • Infinity 7540A... • Answered on Oct 18, 2009

The lights blink 1 2 3 just as his....

hook up power to power and ground to ground, and remote wire to power amp or anttenea on radio
6/11/2009 8:50:53 PM • Infinity 7540A... • Answered on Jun 11, 2009

Protect light comes on, no power

Hello patrick_h_mi,

You'll also need a remote turn-on source for the amp to operate. Normally, this is a blue or blue/white wire from your head unit, but for test purposes, you just need 12V to the "remote" terminal on the amp. The amp should power up without speaker inputs or speaker connections, but it is not recommended.

Hope this helps.
5/30/2009 4:32:50 AM • Infinity 7540A... • Answered on May 30, 2009

Infinity Interlude IL120s Powered Subwoofer (home) will not power

Some of these Infinity Amps have an Internal Glass Fuse. Open the Case and Check for this Fuse. Please Rate My Response! Thanks!
3/28/2009 10:27:58 PM • Infinity 7540A... • Answered on Mar 28, 2009

Clip light

A shorted speaker, a pinched speaker wire or a short in the amp, itself. Try to disconnect the speaker wire from the amp. Did the clip light go out? No?? Ok take out the amp and send it to the service center as unless your a tech, there are no user serviceable parts inside as its all solid state. Good Luck
12/23/2008 12:14:32 AM • Infinity 7540A... • Answered on Dec 23, 2008

On and off

Are any lights on?
12/3/2008 2:42:49 AM • Infinity 7540A... • Answered on Dec 03, 2008

On and off

Take the input leads out of the amplifier for a start, but leave the power and remote cables connected.
See if it still turns on and off. If still faulty, you have probably blown a power transistor inside and the amp is shutting down when the output rises each time. It will almost certainly need looking at. Also make sure you are running into the correct impedance load. If you have hooked up too many speakers you will cause damage.

10/25/2008 4:45:04 AM • Infinity 7540A... • Answered on Oct 25, 2008

Help with my infinity 7540a

It probably has shorted output transistors. Read through the following page to eliminate other possible causes. Let me know if you have any other questions.

Amp in Protect Mode - Troubleshooting
10/21/2008 4:38:55 PM • Infinity 7540A... • Answered on Oct 21, 2008

Can you help me with Infinity REF-5760A

ok positve on amp straight to battery
negitive to ground on car or battery
remote wire to back of head unit
and rcas in head unit to amp
9/5/2008 5:06:29 PM • Infinity 7540A... • Answered on Sep 05, 2008

No sound

I would try it without the slot for the additional amp. However, there is a chance that it is fried. When its powering up I would check the voltages with a multimeter to make sure everything there is in order.
7/2/2006 9:20:15 PM • Infinity 7540A... • Answered on Jul 02, 2006

Amp cuts out with loud volume

From what you describe it could be that its not getting enough power when the car is fully running. Its been a long time since I have had to deal with car audio problems. Does it happen when the vehicle is running but in park? If so it could be a short (Not likely though, it would be happening more often). Or it could be a loose connection somewhere that the vibrations of the vehicle are shaking. That would also be a problem if it happens when it moves. If it is still a problem, I would take it to a Checkers Auto. A lot of them offer free electrical testing.
7/2/2006 9:17:12 PM • Infinity 7540A... • Answered on Jul 02, 2006
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