Capacitor leakage.

Discussion in 'The Projects Forum' started by Brandon$B, Dec 19, 2013.

  1. Brandon$B

    Thread Starter New Member

    Dec 12, 2013
    Hi I have a Marantz NR1501 Amplifier 7.1 with a Jamo 5 channel speaker system.

    For the past week of so I've been getting a crackling popping sound randomly coming from all speakers including the subwoofer, so I checked on another home theatre forum and I found several similar problems one of which being blown capacitors due to surges this could be the problem, because I leave my amp on when I leave home(not any more).

    So I opened it up to check if any of the caps are bulged or opened or if there is any visible fluid at the base, I came across this (Addendum A) not sure if it's dielectric or some sort of adhesive.

    Addendum A:


    Another reason for this as suggested by one of the posts on that forum was that the speaker wires are too close to the AC/power cable which stands for grounds of mutual inductance right?

    This is a really expensive system and I just realised I had it connected incorrectly for 3 years I had the surround speakers(High signal) connected to the Subwoofer(Low signal) could this have damaged the amplifier due to poor impedance matching? If so can I take it to my local repair man to let him sort it out?
  2. Sensacell

    Senior Member

    Jun 19, 2012
    The white stuff is adhesive used to hold the caps in place. If it worked for 3 years, you probably did no harm, it's just come to it's planned obsolescence.
    Brandon$B likes this.
  3. crutschow


    Mar 14, 2008
    If the speaker wires are too close to the AC power cable it could conceivably cause some hum but not likely a crackling sound.

    There should be no problem caused by connecting the speaker output to the sub input. Solid state amps are not affected by a high impedance (or no) load.

    It does sound like you have either a bad electrolytic or a bad connection somewhere in the amp.
    Brandon$B likes this.
  4. Brandon$B

    Thread Starter New Member

    Dec 12, 2013
    Thank you for replying to post guys, really appreciate it.
  5. #12


    Nov 30, 2010
    I have found random crackling/popping noises coming from a bad bipolar transistor in 1972 and a jfet in 1998. Both of them were in low level audio stages. Finding the difference between something loose and a semiconductor going bad is where experience can be very valuable. Good luck finding the noise.
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    If the random popping sound is in all speakers it might be a PSU fault.

    I agree with Sensacell that the white stuff looks to be glue, although personally I would pull that cap out and have a look at it anyway.

    Re the popping, a common fault is a damaged regulator on the pre-amp rails, check if there is a pair of 15v regulators ie; 7815 7915. If so resolder their legs and any nearby resistors etc that look like they got hot. Even replacing the regulators can be a good idea, they only cost about a buck each.

    Tapping around the PCB with an insulated probe or plastic stick can help track down the noise. The handle end of a plastic toothbrush works good, and you can use the brush end to clean off all that dust and crud of your expensive PCB. :)