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How do solder guns work?

Discussion in 'Misc Electronics' started by Dave, Jul 17, 2004.

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  1. Dave

    Dave Guest

    I have two different solder guns (a 100W Radio Shack and a 325W
    some-other-brand) with the same problem, low heat output. The big one will
    work properly if held at just the right (fairly verticle) angle, and you can
    feel something shifting inside as this is attempted. Looks like it has a
    couple of transformers in it, one of which (standard coil of wire through
    which the AC current controlled by the switch runs) induces a current in the
    other (roll of sheet metal electrically connected to the heating element).
    At least that's what I *think* is happening. Can anyone give a better
    description of how a solder gun works? I would like to fix them rather than
    buying new, as I am on disability. I got them each to work briefly for the
    original projects they were purchased for, but then they each decided they
    didn't like me


  2. Boris Mohar

    Boris Mohar Guest

    Resistive heating of the soldering tip. The current flow is impeded by the
    lousy connection. Tighten well the two bolts the hold the tip.


    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs
  3. John Miller

    John Miller Guest

    I second that motion. Because you're trying to break through the corrosion
    at the tip connectors, it's helpful to loosen first, then retighten. It's
    kind of routine for soldering gun operation.
  4. The Al Bundy

    The Al Bundy Guest

    Well a solder gun works with a transformer. A large primary coil for the
    mains and a very thick wire or metal pin going outside where the soldering
    tip is connected between. The tip heats up by the large current flowing
    through it. When there is a bad or no electrical contact at all the tip wont
    heat up. Cleaning the contacts helps allot. Those solder guns are very
    robust, if you maintain them of course.

    Some tip for the tip:) If you don't want to buy those expensive soldering
    tips just get some copper wire, as thick as possible, and shape it like such
    solder tip. It works as good as an original one:)

    If you would like to know the current that flows through the tip you can
    measure it with some current transformer around a connection for the solder
    tip. Once I tried it and measured some 100-150A, no wonder you must make
    sure that everything makes a good electrical contact.

  5. DaveC

    DaveC Guest

    You might try removing those two nuts that hold the tip to the gun. Clean the
    copper tip's ends and re-insert and tighten *with feeling*.

    It's a regular maintenance thing. With solder guns, way more frequently than
    I like. That's one reason I bought a traditional iron.

    Good luck,
    Please, no Google links. I wouldn't ask a
    question here if I hadn't done that already.


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  6. CWatters

    CWatters Guest

    They have a transformer that steps the volts down and current up. The
    secondary winding has very few turns - perhaps only one.

    The tips have a low thermal mass (eg not much metal) so thay they heat up

    They don't work well on larger jobs because the tip does not have enough
    thermal mass (eg the work piece cools down the iron).

    The solution is to use a conventional iron with the right size tip (physical
    size and thermal mass size).
  7. Dave

    Dave Guest

    Wow. Thanks to each of you. I'll clean the contact points for the tips. I
    originally thought it was a bad switch, and replaced same, but got no
    improvement. Suspected it was a microfracture in the wire leading to the
    primary transformer, caused by the movement of the same shifting slightly
    with motion. Was about to unwrap a couple of turns ansd resolder. Mayby
    not necessary after all.

    RE soldering tips having low thermal mass: before I got the 100W model I
    tried soldering several resistors together for an antenna dummy load, but
    realized this was hopeless with the 27W iron I was using when the tip FROZE
    to the project under construction. Eight or ten resistor leads sucked all
    the heat out of the molten solder as well as the tip it was on. Was I ever
    disgusted. And that was the final step I needed to complete before screwing
    the cover down.

    Thanks again to all of you for your help.

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