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Morduant Short Avant 309i Active Subwoofer

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    #1

    Morduant Short Avant 309i Active Subwoofer

    Got given the above because it "works sometimes and not others".
    Connected it up and it works for a short period then sound breaks up even at low volume.
    Opening it up I see lots of brown glue that has gone off and two 10uf 100v bipolar electrolytic caps that have bulged and leaked.
    Removing the caps was relatively easy after unscrewing the large aluminium heatsink - refitting looks as though it will be difficult given the proximity of the blue filter cap. surprisingly 10uf NP caps are difficult to find in the UK, HiFi collective turned out to be the most affordable even with the £4 postage for the two caps!
    Will post back results when they arrive and are fitted.
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    #2
    Re: Morduant Short Avant 309i Active Subwoofer

    very impressive, someone did their homework! but did you check for bad solder joints aswell?
    Things I've fixed: anything from semis to crappy Chinese $2 radios, and now an IoT Dildo....

    "Dude, this is Wyoming, i hopped on and sent 'er. No fucking around." -- Me

    Excuse me while i do something dangerous


    You must have a sad, sad boring life if you hate on people harmlessly enjoying life with an animal costume.

    Sometimes you need to break shit to fix it.... Thats why my lawnmower doesn't have a deadman switch or engine brake anymore

    Follow the white rabbit.

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      #3
      Re: Morduant Short Avant 309i Active Subwoofer


      Let me guess - those 10uF NP caps are part of the output filter in a Class-D amp? Can't see much point for the huge coils over there otherwise.

      I swear, people who decide to go down that design route oughtta be hung, drawn & quartered

      *sigh*
      Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

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        #4
        Re: Morduant Short Avant 309i Active Subwoofer

        It does appear to be a digital amplifier and the caps have arrived and been fitted - but in the process the 2sc1845 screwed to the heatsink and attached to the circuit board by an 8 inch flying lead lost it's legs so waiting for a replacement for that ;-(
        I did hear the Sub working at it's previous owners house, a long time ago, and it was (hopefully) not set up properly as it made my head ache with the one note overblown bass.
        I examined as much of the board as possible for bad joints and found none.
        It will be Friday at the earliest before the trannies arrive.

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          #5
          Re: Morduant Short Avant 309i Active Subwoofer

          Got the replacement 2sc1815 and fitted it. re-assembled sub and it works - for about 2 minutes then back to what it was doing before:-(
          Any ideas?

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            #6
            Re: Morduant Short Avant 309i Active Subwoofer

            Going to try some new output transistors pick em up from rs on Tuesday.
            Seen other reports of the two caps already replaced being associated with damaged output transistors.

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              #7
              Re: Morduant Short Avant 309i Active Subwoofer

              Output transistors replaced - still doesn't work.
              Measured voltage on large filter caps as +62 and -62v - stuck now.

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