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posted by Blackmoore on Friday November 14 2014, @06:30PM   Printer-friendly
from the stone-knives-and-bearskins dept.

via Hack A Day Extreme Repair of a Burnt PCB, xsdb had a catastrophic failure of a printed circuit board in a commercial product and he restored the unit to operation. Burned FR4 is conductive, so any repair requires cutting out that bit. Replacing that void is quite the trick, requiring great patience.

[xsdb] had a real problem. His JBL L8400P 600 watt subwoofer went up in flames – literally. Four of the large capacitors on the board had bulged and leaked. The electrolyte then caused a short in the mains AC section of the board, resulting in a flare up. Thankfully the flames were contained to the amplifier board. [xsdb's] house, possessions, and subwoofer enclosure were all safe. The amplifier board however, had seen better days. Most of us would have cut our losses and bought a new setup. Not [xsdb] he took on the most extreme PCB repair we’ve seen in a long time.

If you ever have a gadget with a similar failure, built by a company that is out of business or otherwise not easily irreplaceable, this guy's effort is worth bookmarking.

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  • (Score: 0) by Anonymous Coward on Friday November 14 2014, @07:07PM

    by Anonymous Coward on Friday November 14 2014, @07:07PM (#116016)

    I've had to use a microscope to find a smaller than hairline bridge in a defective PCB. Its all fun.

  • (Score: 1) by BananaPhone on Friday November 14 2014, @07:34PM

    by BananaPhone (2488) on Friday November 14 2014, @07:34PM (#116022)

    Regardless,

    Very cool to see that partial PCB replacement is doable.

    • (Score: 1) by Ethanol-fueled on Friday November 14 2014, @07:57PM

      by Ethanol-fueled (2792) on Friday November 14 2014, @07:57PM (#116028) Homepage

      Yeah, there's only a top layer and a bottom-layer. He could have just wired it point-to-point or made a daughterboard out of a piece of protoboard or something and took like an hour or two to perform the repair from start to finish.

      Sure, it's precise, but so also is a tweeker organizing the sock drawer during a meth binge.

      Your average SMT PCB Microscope rework tech does more remarkable things in much shorter amounts of time, and all on a daily basis.

      • (Score: 3, Interesting) by Hairyfeet on Friday November 14 2014, @08:41PM

        by Hairyfeet (75) <reversethis-{moc ... {8691tsaebssab}> on Friday November 14 2014, @08:41PM (#116037) Journal

        Sadly most of the burnt stuff that crosses my workbench is multilayer so all I can do is pop out the good chips and throw the burnt board on the pile :-(

        And man you are speaking truth about the tweakers, used to have a tweaker that would come by and buy the old junkers in the back to tweak on. One day he brought one back to have me show him what he was doing wrong on an OS install and when i popped out the side door to see why the DVD wasn't reading....holy shit! The inside of that old thing was so fucking clean and shiny it looked like it had been wrapped in plastic at the factory and kept that way until today. When I asked him how in the hell he had gotten those grungy insides THAT clean and sparkly? He sat there with a fricking makeup brush and toothbrush and scrubbed every single inch of the entire system!

        Still its nice in this day and age of "throw away everything" to see somebody fix something instead of tossing, although I wonder how much of the new "throw it away" attitude is caused by the shitastic new solder, but still a hearty two thumbs up for TFA.

        --
        ACs are never seen so don't bother. Always ready to show SJWs for the racists they are.
      • (Score: 2) by Grishnakh on Friday November 14 2014, @10:31PM

        by Grishnakh (2831) on Friday November 14 2014, @10:31PM (#116059)

        Yeah, there's only a top layer and a bottom-layer. He could have just wired it point-to-point or made a daughterboard out of a piece of protoboard or something and took like an hour or two to perform the repair from start to finish.

        Wrong.

        Point-to-point wiring doesn't give you any shielding. This board had some large copper fills, which are used not just for high current, but also some EMI shielding (though granted, not as much as you get with a 4-layer board that has power and ground planes). It's quite likely a point-to-point replacement would have had noise problems or even not worked at all, if it uses a SMPS. SMPS designs are notoriously sensitive to PCB design.

        • (Score: 1) by Ethanol-fueled on Friday November 14 2014, @11:27PM

          by Ethanol-fueled (2792) on Friday November 14 2014, @11:27PM (#116071) Homepage

          Okay, then make a daughterboard and encase the sensitive components or the whole thing in an off-the-shelf EMI shield like one in this [google.com] picture, ground the EMI shield, problem still solved in a much quicker and less tweeker way.

          • (Score: 2) by Grishnakh on Saturday November 15 2014, @07:08AM

            by Grishnakh (2831) on Saturday November 15 2014, @07:08AM (#116145)

            There's more to it than that. The trace lengths, trace widths, etc. all affect a SMPS design hugely.

  • (Score: 0) by Anonymous Coward on Friday November 14 2014, @08:21PM

    by Anonymous Coward on Friday November 14 2014, @08:21PM (#116034)

    'capacitors on the board had bulged and leaked. The electrolyte then caused a short in the mains AC section of the board, resulting in a flare up.'

    So what did he breath in, PCBs? :P

    • (Score: 2) by Ellis D. Tripp on Friday November 14 2014, @09:35PM

      by Ellis D. Tripp (3416) on Friday November 14 2014, @09:35PM (#116046)

      PCBs haven't been used in electrical gear since long before that craptastic amplifier was made.

      --
      "Society is like stew. If you don't keep it stirred up, you end up with a lot of scum on the top!"--Edward Abbey
      • (Score: 0) by Anonymous Coward on Saturday November 15 2014, @12:45AM

        by Anonymous Coward on Saturday November 15 2014, @12:45AM (#116088)

        We had a cap blow out in an old teletype machine, it created a fog low to the ground. It was the size of a pringles can.