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Problems soldering 2.1 mm DC line socket

Discussion in 'Electronic Repair' started by Christopher Tidy, Nov 13, 2006.

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  1. Hi all,

    I recently bought a 2.1 mm DC line socket from Maplin (part no. JK11M)
    so I could power a project using a plug-in power adaptor (wall wart).
    Soldering a lead to the outer coaxial contact was no problem, but when
    I tried to solder a lead to the inner contact, the plastic insulation
    melted!

    I'm not a novice to soldering and I wasn't using an inappropriately
    large iron. The iron I was using is an Antex rated at 18 watts,
    although it isn't a regulated iron. I didn't touch the plastic
    insulation with the iron. The joint clearly didn't get hot enough to
    melt the solder, so I reckon the plastic must have melted at less than
    180 deg. C.

    The Maplin socket design is bad in two ways. Firstly the insulator is
    made from a thermoplastic, and secondly the solder bucket for the inner
    contact is right next to the plastic insulator.

    So I have a few questions. Are all 2.1 mm line sockets like this or are
    there better designs out there? If there are better ones available,
    where can I get one from? And how are you supposed to solder these
    sockets with thermoplastic insulators?

    Suggestions would be appreciated.

    Best wishes,

    Chris Tidy
     
  2. That's the problem. You need a 60 W iron and you need to work FAST! Anything
    you can do to make the solder stick faster will help.
     
  3. Arfa Daily

    Arfa Daily Guest

    The trick to soldering any of these small connectors - DC power, audio or
    RF - is to fit a mating plug or socket to the item you are trying to solder.
    Then, with it all held still in a small vise or helping hand, tin the
    connections. Even if the centre insulation does soften, the pin / socket
    will be held in place by the mating connector that you've fitted. After
    tinning the contacts, tin the wire ends, then solder the wires to the
    contacts as 'touch' joints. Although the conventional soldering wisdom is
    that a good mechanical joint should be made, before applying solder, in the
    case of small connectors, a touch joint is good enough, as the plug's strain
    relief will normally supply enough mechanical stability to the joints.

    Arfa
     
  4. I have a 40 W iron and a 75 W iron too. The 75 W is far too unwieldy,
    so I'll try the 40 W next time.
    I thought of this just a few minutes ago while I was looking at the
    melted plug. Neat idea. I wish I had thought of it earlier!

    By the way, does anyone know of any 2.1 mm line sockets made from heat
    resistant plastic?

    Thanks for the help.

    Best wishes,

    Chris
     
  5. No reason they aren't made but if you can buy the original connectors,
    someone somewhere is soldering them OK.
     
  6. 3T39

    3T39 Guest

    Hello, Christopher!
    You wrote on 13 Nov 2006 09:32:48 -0800:

    CT> I recently bought a 2.1 mm DC line socket from Maplin (part no. JK11M)
    CT> so I could power a project using a plug-in power adaptor (wall wart).
    CT> Soldering a lead to the outer coaxial contact was no problem, but when
    CT> I tried to solder a lead to the inner contact, the plastic insulation
    CT> melted!

    CT> I'm not a novice to soldering and I wasn't using an inappropriately
    CT> large iron. The iron I was using is an Antex rated at 18 watts,
    CT> although it isn't a regulated iron. I didn't touch the plastic
    CT> insulation with the iron. The joint clearly didn't get hot enough to
    CT> melt the solder, so I reckon the plastic must have melted at less than
    CT> 180 deg. C.

    CT> The Maplin socket design is bad in two ways. Firstly the insulator is
    CT> made from a thermoplastic, and secondly the solder bucket for the inner
    CT> contact is right next to the plastic insulator.

    CT> So I have a few questions. Are all 2.1 mm line sockets like this or are
    CT> there better designs out there? If there are better ones available,
    CT> where can I get one from? And how are you supposed to solder these
    CT> sockets with thermoplastic insulators?

    CT> Suggestions would be appreciated.

    CT> Best wishes,

    If you have space, use of a small crock clip positioned just a little
    downstream of the intended soldering point, can act as a heat sink and carry
    some of the heat away, give yourself just enough free metal to make a quick
    joint.

    With best regards, 3T39. E-mail:
     
  7. Jim Land

    Jim Land Guest

    Yes, a heat sink is a good idea, but as Christopher originally stated,
    the point he is trying to solder is right next to the plastic that melts,
    so there's no room for a clip.

    The idea of inserting the mating connector probably provides a little
    heat sink. If you want a larger one, try suspending the connector
    (solder connection up) in a cup of water, so the water covers the
    plastic, but the solder connection is out of the water. That should keep
    the plastic cool while you solder. Just dry out the connector before you
    use it.
     
  8. I bought two more sockets from a different supplier and tried again.
    This time I used a 40 W soldering iron and a mating plug as a heatsink.
    The results were acceptable, but only just. These sockets also use
    thermoplastic insulators, and both suffered a little damage. Because
    the solder bucket is right next to the insulator, it seems that the
    insulator will inevitably be softened, and that the mating plug is
    essential to hold the central pin in place. For anyone trying to solve
    the same problem in future, the mating plug is the key.

    It's a pretty pitiful piece of design really. An extra 5 mm between the
    solder bucket and insulator or a change to a heat resistant plastic
    would make all the difference.

    Thanks for the help.

    Best wishes,

    Chris
     
  9. Baron

    Baron Guest

    Turned, solid brass pins, used as a plug will help ! Mine are 2" long
    and provide a good heatsink for the centre pin ! It also helps that
    you can clamp the brass pin into a vice to hold the assembly steady.

    But I do agree, a better plastic would help. I also get this softening
    on SO239 connectors that do not use teflon or similar, as the
    insulator.
     
  10. quietguy

    quietguy Guest

    I have recently made up 6 leads using these connectors and have not run
    into any problems - a hot iron, tin the tags and the wire first, and add
    just enough heat to sweat the wire to the tags. If I was worried about
    too much heat I would just hit the joints with some cotton wool dipped in
    metho to get a rapid cooldown

    My connectors come from DSE/Tandy - nothing special

    David
     
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