Question about JBL SCS125A System

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Subwoofer "thumping" w. no audio feed

My sub is making a "heartbeat" noise even with no audio feed. It is plugged in to a surge protector (I tried two different strips that are working with other components). The audio feed is unplugged and it makes a thump-thump on a regular interval. Any idea? Blown fuse?

Thanks,
B

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  • Anonymous May 15, 2008

    It's not a matter of the RCA not being plugged in all the way.
    As previously stated, the Sub thumps even when not receiving any signal.


  • jbl_issues Jul 14, 2008

    I'm having the exact same issue after several months of use... Every time I turn on my sub, there is a loud Thump, Thump, Thump, Thump which stays at a constant volume, regardless of the volume knob level in the back. Sounds exactly like someone tapping on a loud microphone in perfect timing. I disconnected my audio signal cable completely from the sub and it does it as well... tried different electrical outlets, and different switch positions on the back... auto or not, it still makes the "heartbeat" sound. It does this for about 10 seconds and then goes silent... when everything is connected to the receiver, it will play perfectly for a while and then at random times will break back into the Thump, Thump, Thump.... It drives me crazy... any solutions? Looks like a quality issue.

  • blankensh830 Oct 15, 2008

    i just moved into a house and my jbl amp is making the same sound
    checked the fuse it was fine and voltage out of the socket it was fine
    any ideas

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You need to check your ground connection. If there is a bad ground there will be feedback to the amp and it will just sit there and loop back with the Thump, Thump, Thump sound. I had to wire my amp's ground all the way back to the negative battery terminal. It was a pain but I have never had a problem since :)

Posted on May 24, 2011

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I have Bose sound bar that is thump thump thump it's really annoying any one know why
I've checked all connections
I'm running it through the aux to headphone jack
As the optical cable won't give any decent volume

Posted on Oct 08, 2016

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Any idea if its doing this from lack of full power

Posted on Aug 26, 2013

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I moved into a new house and my sub is making the same sounds checked the fuse ok and the voltage in the outlet all fine and ideas g

Posted on Oct 15, 2008

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I'm having the exact same issue after several months of use... Every time I turn on my sub, there is a loud Thump, Thump, Thump, Thump which stays at a constant volume, regardless of the volume knob level in the back. Sounds exactly like someone tapping on a loud microphone in perfect timing. I disconnected my audio signal cable completely from the sub and it does it as well... tried different electrical outlets, and different switch positions on the back... auto or not, it still makes the "heartbeat" sound. It does this for about 10 seconds and then goes silent... when everything is connected to the receiver, it will play perfectly for a while and then at random times will break back into the Thump, Thump, Thump.... It drives me crazy... any solutions? Looks like a quality issue.

Posted on Jul 14, 2008

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There is some live wire touching the negitive point check the complete wiring once again. if possible disconnect all wires and then connect them again

Posted on Oct 28, 2008

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Jacks not pluged in all way re defult sound drivers

Posted on Feb 12, 2008

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