I found a Weller D550 pistol grip type solder gun that I have forgotten I even had. What little work I do is better done with a pen solder iron. Come to think of it I don't even see it in the hardware and electronics stores anymore where once they were quite ubiquitous. Is this the trend that they are not popular anymore? If so what is the reason?
My next question is how do they work? I see a coil and it is described as an induction type tool. This implies there is an air gap between the coil and the heat generating component. How does it generate heat quickly and locally at the solder tip?
They are still quite available if you shop in the right places.
Lowes has 'em:
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As does Home Cheepo.
Probably you see less of them in DIY hardware stores because less people do things requiring soldering heavy stuff, what with electronics shrinking to where I can't see the components anymore.
I still have a 200 watt Weller and a couple of smaller ones too. I used the big one just last week to solder a lug onto a piece of BMF stranded cable young son was stringing through the body of his car so he could power a 1000 watt subwoofer amp in the trunk.
The operating principle is that of a transformer. That big thick "U" with the tip connected across its "open" end is the one turn secondary of that transformer.
There's a multiturn coil of small sized magnet wire wound around the "inside" leg of the "U". Think of it being shaped like a spool of thread slipped onto that leg.
When you pull the trigger 120 volts ac is connected to that multiturn coil. The heat comes from many amperes of ac current flowing in the "short" across the secondary created by the tip. Because the tip is much thinner than the "U" its resistance per unit length is much higher, so most of the heating energy gets concentrated there.
Weller still makes them and they haven't changed much. I think the main reason they are not as popular as they were 25 years ago is that todays electronic gadgets don't have components big enough for them to be used on.
They work by being a step down transformer that takes 120V and turns it into low voltage, high current that passes through the tip and heats it.
Speaking of which... has anyone tried the cold solder pen type tool now advertised on TV? Requires no electric wire and the tip is cold immediately open removing the tip from the work (the guy solders a wire and then immediately pinches the tip between his fingers). It seems to be only for soldering circuit boards wires and connections, at least, that is all they show it doing.
Yeah, that's just a version of the old "two carbons" resistance soldering system. The tip has two tiny points of carbon or stainless steel. When both points contact the metal part you want to solder current flows from the batteries and makes the tips get hot and they xfer their heat to the work.
Like this:
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I wouldn't expect to get too many joints out of one set (or charging) of batteries on the unit they are pushing on TV. For a "portable" iron where there's no line voltage available I think I'd rather have one of the little butane heated irons and a can of cigarette lighter gas to refill it with. (Then I wouldn't have to worry about whether the batteries wer still charged or not.)
Haven't you noticed that the skin on your thumb and forefinger is remarkable resistant to heat (for a short time)compared to skin elsewhere on your person? I can whisk the dross off a small hot soldering pencil with my fingertips as long as I do it fast enough.
Thanks. It's not that I need one of them (I leave that electronics stuff to qualified people). I will tell you that I was trained as a metalsmith in the Navy. I could gas and electric weld, solder (using the large iron heated in a flame), forge, temper, case harden, and anneal steel, and fabricate sheet metal. Alas, except for the occasional soldering, all that knowledge has been fragmented and hidden by 48 years of other acquired knowledge.
I have a couple of Wellers, and they are great. You do have to watch to make sure the screws that connect the tip are tight.
A few weeks ago I was soldering a few connections in lampcord, the first few heated up hot and quick, then the gun just seemed to die. The tip would get warm, but not hot enough to melt solder. Checked the screws.....yup, tight. Sanded down the tip to clean it up--no good. Finally I took the tip off, and there was quite a dent in the tip where the attachment screws clamp into the tip. I thought "hmmnh..." and turned the tip over so the screws dig into fresh metal, and voila--hot and quick again.
Some of the guns have dual wattage. 1st click, low wattage; 2nd click, high wattage.
I haven't looked at one for a long time -- and I may be wrong here -- but I think that it's basically just a step-down transformer, stepping the 115 volt line voltage down to some very low voltage (maybe 1 volt or so) which is applied to the copper "load" element. The load is of such low resistance that, even at the low voltage involved, a high current flows in this load. This heavy current then causes localized heating in the relatively high resistance "pinched" area of this load where the actual soldering is done. I hope this explanation is not too far from the truth.
I forgot to mention that soldering guns are also handy for demagnetizing small things like screwdriver blades and drill bits, so steel chips don't stick to them.
Just pull the trigger and stick the thing to be demagnetized through the "hole" formed by the tip. Twist it a little and withdraw it. Don't release the trigger until the object is a few inches away.
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