Capacitor leakage.

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

  1. Brandon$B

    Thread Starter New Member

    Dec 12, 2013
    8
    0
    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:

    [​IMG]

    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

    Well-Known Member

    Jun 19, 2012
    1,127
    266
    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.
     
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  3. crutschow

    Expert

    Mar 14, 2008
    12,986
    3,226
    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.
     
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  4. Brandon$B

    Thread Starter New Member

    Dec 12, 2013
    8
    0
    Thank you for replying to post guys, really appreciate it.
     
  5. #12

    Expert

    Nov 30, 2010
    16,252
    6,751
    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
    5,435
    1,305
    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. :)
     
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