You’re not going crazy – your soldering iron IS cold (and yet another failure)

Recently, I thought my soldering abilities were degenerating. – I should have known better, and realised yet ANOTHER failure was incoming.

Normally, soldering is a non-issue as I’ve been doing it for so long, and I use proper kit, a Weller Magnastat. These things just work.

But, recent jobs just weren’t going as expected, with random instances of poor wetting, and solder flow. At times, it even seemed as if the iron wasn’t on – but whenever I specifically checked, everything seemed to be fine, hence suspicions that I was somehow at fault.

As noted in the recent post about the dead fan on my modified 12 V cool box, things came to a head when I was exonerated, and the soldering iron stopped working altogether – right in the middle of this job. At least I have plenty of spares, and they warm up fast :-)

What went wrong?

Yet another damned failure to investigate – at least these things are not complicated, being a Magnastat as opposed to electronic temperature control.

Even so, it put up a little fight.

The power supply was obviously OK, since the replacement iron was fine.

All the part in the handle checked out OK as well – it’s not unknown for the contacts in the ‘Power Switch’ to fail, but not this time.

My last failure, years ago, was related to that, when the link between the magnet and switch broke, due to corrosion, which had just eaten through it, and it separated. Not this time though.

I was scratching my head for a moment, then realised I hadn’t checked the cable!

Sure enough, one of the wires inside that cable was open circuit. Yes, my kit uses those cute little 3-pin plugs.

It had probably been failing for a while, hence the past intermittent issues I’d been experiencing – at least this confirmed not imagination, or going nuts.

But, where IS the break?

The only problem was finding out WHERE the break was. Not obvious since I don’t own one of those neat RF system that can now be attached to suspect wires, and have a small handheld unit to sniff out where the signal stops along the cable. Nor do I have a TDR (look it up).

I resorted to a method demonstrated by an expert – grip the cable firmly a short distance from the end, then grab the end of each wire in turn, and PULL.

Do it carefully (this is NOT a method for the ham-fisted that break everything they touch), and the broken wire will stretch as the ends move apart, unlike the undamaged wires, which will not move.

This actually worked, and showed the wire had broken just past the black tail seen at the right-hand end of the body, in the pic above, No great surprise.

The only problem with this is the length of cable that has to be cut off to make a new end to connect to the iron – as can be seen below, the length of the earth wire means a lot of waste in the power wire, especially in this case, since the broken wire was blue in my case, but that’s the old colour, and the pic shows a new cable, so it’s the black one.

This cable is short to begin with, and it’s now even shorter, but at (currently) £25 just for this short piece of cable – it’s heat-resistant silicone, so a hot soldering iron won’t damage it – it could get much shorter if anything else breaks.

Problem? Of course there was a problem

This SHOULD have been straightforward once I’d cut off the dead section, and terminated the new end as shown above.

However, referring to the earlier Magnastat diagram, note the small board above the words ‘Power Supply’, where these wires are attached to eyelets that provide mounting points for the wiring to the ‘Power Switch’ and element.

While this may be great for the factory – drop in the wire, blob on some solder, and the job is done.

That board is actually a thermoplastic moulding which supports all the internal parts, and acts as a cable grip.

That plastic is one that begins to melt almost as soon as it is threatened with a hot soldering iron, and the eyelets will just come out of the plastic as soon as they are heated to remove the original wiring!

Instead of a few moments work to remove the old wires soldered into them, and solder in the new ends, I had to set up TWO mini-vices, one to hold the board with the eyelets, and one to hold the wire ends in place.

Without this, the eyelets would just have fallen out of that plastic as soon as it melted, and that was BEFORE the solder had melted, and allowed the old wire ends to be removed.

Maybe fine for production, but a terrible choice of material, from a repair/service viewpoint at least, making the job almost impossible. I’m lodging this one deeply in my ‘Bad Design’ category.

To end on a positive note – at least this iron now seems to be working the way it should. Something I don’t was true for some time.

Irritating failed Weller soldering iron tip – it was almost a ‘secret’

 

I haven’t had to do a great deal of soldering in recent months, and to be fair, most of what I have had to do has needed different soldering irons than my usual favourite, a Weller Magnastat. A lot of work had involved various types of surface mount devices, or similarly small components.

Some people seem to hate the Magnastat, but I suspect they’re just jealous that this ancient technology just works, and needs no electronics, microprocessors, or microcontrollers to do its job – it just works. In our workshop, these irons were turned on at the benches in the morning, ran all day, and got turned off at night – no dramas, puffs of smoke, or endless repairing/replacing/fixing. The only sin seen on anything like a regular basis was the erosion of the electrical contacts in the actual magnastat in the handle. They could stick together as there wasn’t much actuating force, but that was quickly sorted by cleaning/resurfacing the contacts, or replacement if they were really burnt.

For those not familiar with the magnastat temperature controlled soldering iron, the temperature is set by the replaceable tip (various temperatures are available) which contains a magnet. This magnet attracts a magnetic core in the centre of the hollow element, and when its Curie Point is reached (the temperature at which a magnet stops being a magnet), the core is released, causing the contacts to open, thereby switching the element off. As the temperature falls, the Curie Point is passed, the magnet become a magnet once more, the tip attracts the core, and the element is switched on – and that process repeats to maintain the tip temperature. By tailoring the magnetic in the tip, different switching temperature can be achieved.

In short, I’d been having a terrible time soldering recently. Most non-SMD work seemed to go very badly, and the solder didn’t seem to want to flow, or ‘take’ to the materials, components, wires, or leads being soldered. I’d even started using separate flux on everything – normally only needed for ‘special’ jobs

Since soldering is fairly simple, I thought it was me, or more likely, the presence of lead-free solder, which has become pervasive these days, and some people absolutely hate, as it is demonstrably inferior to the original tin/lead type.

Although ambivalent about the stuff, I was beginning to think I was finally suffering the lead-free solder effect too.

I wasn’t.

The culprit finally revealed itself as failure of the tip as seen in the pic.

These are iron-coated for longevity – plain copper tips soon begin to erode in use, and slowly disappear. Iron coating resists this process, while the copper core still provides good heat conduction. But, the thermal stresses take their toll, and even the iron coating fails in time.

The failure is usually obvious as the tip generally falls apart as the copper erodes in use once the protective iron coating has gone. – but not this time.

Somehow, the iron coating held its shape as the copper disappeared beneath, leaving no visible clues that the tip had failed. With no copper behind it, there was, of course, no real flow of heat to the tip – just what could get along the iron coating.

I only discovered this when arguing with a particularly awkward piece of solid core wire sticking through a PCB – it got caught in the tip and peeled it back like a tiny hinged trapdoor, revealing the tiny void beneath. – at least this finally explained why all the jobs I’d done up to this point had been so reluctant to melt and flow in the way I was used to. And it wasn’t down to lead free solder either!

I’m pleased to report that a nice shiny new tip was fitted, and normal service was restored in minutes, with fast melting and easy flowing solder returning to my sad little world.

I still can’t quite believe how perfect that failed tip looked though, and visually at least gave me no reason to suspect there was anything wrong with it.