Advice for transplanting surface mounted capacitors between laptop boards?

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  • StardustTinker
    New Member
    • Oct 2022
    • 2
    • Australia

    #1

    Advice for transplanting surface mounted capacitors between laptop boards?

    I am attempting to repair a Dell Latitude E6440 laptop that was damaged when an end user shoved something into a USB port so hard that it destroyed the port and sheared off a surface mounted capacitor located behind the USB port; effectively preventing the laptop from powering up.
    The capacitor is round approx. 5mm diameter by 5mm height with a plastic 'foot' and two small soldered pads visible (can't recall the specs printed on the top).

    In order to repair it, I'm thinking of replacing the capacitor by transplanting a similarly marked capacitor from a donor board taken from a disused laptop.

    Can I get some advice if this is possible and if so - what's best practice to transplant the capacitor? I've only seen advice about demounting old surface mounted capacitors using pliers or knives (which would destroy them, I think?) - and then soldering brand new capacitors into place.

    I only have an amateur combination hot air and soldering station with abysmal temperature control - not good shop tools.
  • corrize
    Badcaps Veteran
    • Apr 2021
    • 268
    • France

    #2
    Re: Advice for transplanting surface mounted capacitors between laptop boards?

    There is no problem to replace capacitor by same one from donor board. Juste see if it’s the same size and value. Capacitors are not marked (if you see something like C108 ; it’s not the value). If you have a basic multimeter, you could have a button with « uF » (look). You can measure values.
    If you don’t can’t measure value, you can find or deduce it with schematics.
    For solder, if you have hot air, it’s good (desolder, solder). Not knife pls. But if it’s your first time, that could be horrific, you absolute need training before on donor bord : try to remove and remplace one.
    You MUST have a good tweezers. (And flux).
    With the twezzers, you don’t just have to catch the component, you have to catch it at half of thickness, else the component will turn on itself. Without dedicated tweezers, you can’t do anything and get crazy.

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    • todenkopf
      Member
      • Oct 2014
      • 49
      • UA

      #3
      Re: Advice for transplanting surface mounted capacitors between laptop boards?

      Best way to solder/desolder smd electrolytic capacitors is to heat positive terminal (!) with good (70w+) soldering iron, while applying gentle force to capacitor itself. Trick is to rock capacitor to lift its positive terminal off the board, negative one usually have a huge polygon connected thus its way harder to melt solder on it.

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      • corrize
        Badcaps Veteran
        • Apr 2021
        • 268
        • France

        #4
        Re: Advice for transplanting surface mounted capacitors between laptop boards?

        Sorry, I don’t saw it’s chemical capacitor, in this case, avoid hot air as possible as. Use solder iron yes. You can use low melt solder for help if needed.

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