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Thread: Sub Woes

  1. #1
    Join Date: Jan 2014

    Location: london se6

    Posts: 697
    I'm AndyElectroNumpty.

    Default Sub Woes

    Well my sub has started making a buzzing sound when switched on , starts faint and then gets louder as it's used . Even when there is no signal going into it. So in the spirit of numptyness I decided to open it up to see if there was anything obvious wrong with it
    and found the following culprit (possible)
    At the cutting edge of Numptyness!

  2. #2
    Join Date: Jan 2014

    Location: london se6

    Posts: 697
    I'm AndyElectroNumpty.

    Default

    Bulging cap so just replace and see what happens I guess . I looked at the large power supply caps and they are slightly curved but its hard to tell as there is a cover on them so I might just change them anyway. Anything else I should look out for ? Thanks





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  3. #3
    Join Date: Jan 2014

    Location: london se6

    Posts: 697
    I'm AndyElectroNumpty.

    Default

    Power caps




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  4. #4
    Join Date: Apr 2012

    Location: London

    Posts: 546
    I'm James.

    Default

    That tall cap looks ready to blow! The others are not obviously knackered, but for the price of them it might be worth while changing them anyway?

    The pcb does appear to be somewhat discoloured, though there's no obvious culprit, maybe its the lighting, maybe some component on the other side of the pcb? Worth a look.

    Hope this helps a little - is it a BK sub?

    Edit, actually one of the main reservoir caps looks a little swollen as well, the one with the sticker on it, but could be eyes/phone/pic...

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  5. #5
    Join Date: Dec 2018

    Location: London

    Posts: 28
    I'm Greg.

    Default

    You could reflow all the solder points (or at least the ones which look suspicious). It saved my aura va80se when it was attacked by gremlins.

  6. #6
    Join Date: Jan 2014

    Location: london se6

    Posts: 697
    I'm AndyElectroNumpty.

    Default

    Quote Originally Posted by Jazid View Post
    That tall cap looks ready to blow! The others are not obviously knackered, but for the price of them it might be worth while changing them anyway?

    The pcb does appear to be somewhat discoloured, though there's no obvious culprit, maybe its the lighting, maybe some component on the other side of the pcb? Worth a look.

    Hope this helps a little - is it a BK sub?

    Edit, actually one of the main reservoir caps looks a little swollen as well, the one with the sticker on it, but could be eyes/phone/pic...

    Sent from my BLA-L09 using Tapatalk
    Hi thanks , it's MJ acoustics reference 100 sub , about 15 years old now from new so probably needs some tlc. Think ill replace the large power caps as you suggest. The pcb is ok , its the light on the board and copper that makes it look funny. Ill have a look at the other components as you suggest though.

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  7. #7
    Join Date: Jan 2014

    Location: london se6

    Posts: 697
    I'm AndyElectroNumpty.

    Default

    Quote Originally Posted by Gregje View Post
    You could reflow all the solder points (or at least the ones which look suspicious). It saved my aura va80se when it was attacked by gremlins.
    Good point didn't think of that, cheers

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  8. #8
    Join Date: Jan 2014

    Location: london se6

    Posts: 697
    I'm AndyElectroNumpty.

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    Ok so took the power caps of , lots of glue on them. Cleaned the board with isopropyl and it came up ok but took ages. the board is discoloured, there are 2 long (ceramic?) resistors under there, they both measure ok but should I replace anyway? Opinions welcome.

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  9. #9
    Join Date: Jan 2014

    Location: london se6

    Posts: 697
    I'm AndyElectroNumpty.

    Default

    oh and the bulging cap was replaced by an Elnic on the right , the red one. A panasonic has replace the cap that was on the extreme left of the picture.

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  10. #10
    Join Date: May 2008

    Location: Surrey

    Posts: 6,258
    I'm Rob.

    Default

    The main chips under the black clip type heat sinks look like they could be LM3886's from their shape which are pretty robust. However it would depend on the rail voltages as to how stressed they are and how much heatsinking they should have.
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