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Thread: low or super low ESR + impedance caps

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  1. #1
    Xtreme Member
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    Jul 2004
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    271
    Quote Originally Posted by sluggo

    ..Try vertical bus-bars to get additional caps in without adding inductance.

    i dont get it. "Vertical bus-bars" ??? Maybe its my bad english but could you be more specific about this? Thanks.
    All*AIr

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  2. #2
    Registered User
    Join Date
    Jun 2005
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    Quote Originally Posted by sang
    i dont get it. "Vertical bus-bars" ??? Maybe its my bad english but could you be more specific about this? Thanks.
    I wish I had some drawing skill to show what I mean, but I'll try to describe it. If you take a cap out of a board you are left with two holes drilled through the board. You can insert in each of these holes a stiff wire of appropriate length (2-3 inches). You can then solder several caps to these wires in a parallel arrangement. Install the package onto the board in the original two holes and you have multiple paralleled caps where before you had only one.

    What I've done as a quick and dirty setup is to take a couple of paper clips and straighten them out (they don't have to be perfectly straight). Solder the caps to the paper clips and bond the caps together with some RTV silicone adhesive. Trim all excess wire, but leave a couple inches of paper clip exposed from one end. Now insert the paper clip ends into the board (observing polarity), solder, and trim the excess wire on the other side of the circuit board.

    You'll want to mechanically secure the capacitor bundle in some way, because if they vibrate they will flex the wire and eventually the wire will fatigue and break away at the circuit board. A simple bracket mounted to one of the motherboard screw mounts and attached to the cap bundle with a nylon strap or some RTV works fine.

    If paper clips are too big for the holes you have you can use any solid wire of the right diameter.

    I like to put caps on both sides of the wire for balance and aesthetics, if there's room. The nice thing about this is you can twist the two wires up to 90 degrees to make room for whatever sort of capacitor arrangement you have and whatever sort of space you have above the motherboard.

    Obviously, it's much easier to do all the cap soldering first and then solder the package onto the motherboard.

    sluggo

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