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Soldering question....strain relief

Discussion in 'Electronic Repair' started by Borrall Wonnell, Oct 20, 2004.

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  1. Hi all,

    I am trying to add a surface mount phono (RCA) jack to an existing 12V
    line. Unfortunately, the connection needs to handle some mechanical
    stresses. I have switched the line from solid core wire to stranded
    in an effort to reduce the stress, but the solder connection still
    fatigues after a few mechanical cycles.

    Has anyone else dealt with a similar situation for strain relief? I
    have a limited amount of space to work with (perhaps 0.5"). Will
    simple heat-shrink tubing help here? Will I need something more
    robust (a thicker plastic sleeve perhaps)? Should I practice my
    soldering technique?

    FWIW, the wire I am using is 18 gauge.
    Constructive comments will be appreciated!

  2. Solder is not glue!!! :)

    You have to use something else to provide the mechanical support.
    The wire should not be pulling on the solder.

    Not being able to see what you are dealing with is a problem but the wire
    will have to be anchored somehow (wrapped around a peg, cable clamped,
    embedded in hot-melt glue, etc. Then, adding some heat shrink or plastic
    tubing to distribute the bending stress over a larger area.

    We may need to also look at your soldering technique.....

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  3. Thanks for the response.

    To answer some questions, the RCA jack I am using has pass-through
    holes at the +ve/-ve terminals. Effectively, each terminal consists
    of a thin plate of metal with a hole in it.

    To give you an idea...

    You can see one terminal on the right with an oval hole. The other
    terminal can be (partially) seen at the back of the picture...this
    would also have a hole. I tried simply looping wire through these
    holes and compressing (solid-core wire) or twisting (stranded wire).
    Using either method, the resulting connection is 'loose'....kind of
    similar to a link in a chain.

    When soldering, I tried holding it steady, but was not terribly
    successful doing this with my two hands (no clamp). My soldering
    technique would be ok, but I have a crappy iron which translates into
    frustrating work (I have better tools, but I was just using what was
    available at the time).

    The 'chain link' effect makes for a weak solder join. Any suggestions
    on what could improve the join prior to soldering?

  4. Bianca

    Bianca Guest

    Hm, you try to film and make steady shots, standing at one leg in a heavy thunderstorm and wonder why it don't succeed... ;o)

    Seems that the flux is already gone before the soldering is done. Then, work faster (to prevent the flux is evaporated), use a clamp
    or thirdhand-thingie, or add some acid free flux and be sure to keep whole thing steady untill the solder is hard again.

    Such parts as the RCA connector is normally easy to do, up, under, in, around the hole of the mass ring or in, against or wrapped
    around the signal pen, if good soldered; you can hang easily 2 kg on the soldered wire (if chassis part is some quality, you could
    pull the signal pen out of it).

    A quick overview here might be helpfull.

    If still not working, try to make a picture of your result.
    A picture can tell more than 1000 words. ;o)
  5. Try to clamp the device in a small vise or a "helping hands" type of holder. The
    idea of soldering is to heat both the wire and the lug enough to allow the
    solder to flow freely; the part melts the solder, not the iron. Also, some of
    the lower cost RCA jacks and the like have a plated surface that resists
    soldering. Sometimes it's necessary to file or scrape the surface to down to
    good metal. Just takes a little practice. Good luck.

    Alan Harriman
  6. 2nd attempt...

    Well, it looks like the equipment I was using was the limiting factor.
    The 2nd time around, I used a 'shop quality' soldering station and
    some grips (helpinbg hands). I cleaned off the terminals with some
    abrasive to get rid of the gold plating...the solder didn't seem to
    like sticking to this very much. Also, I tried a smaller diameter
    solder, which seemed to work well.

    The result (after applying heat-shrink tubing) was excellent. Bending
    the wires seems to put little stress on the join; it looks like the
    heat shrink is doing what I intended.

    Thanks for everyone's advice!

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