It's been a while since I have soldered, so I bought a cheap unbranded soldering iron to use while I re-familiarised myself with the skill. After a few weeks of use, I turned it on just now and it popped with a blue spark. Now it appears to be dead. Did I do something wrong, or is that simply what happens sometimes when you buy a cheap soldering iron? I'm curious to find out what could have happened.

Ironically, just before the magic smoke escaped from the cheap one, I actually bought a new soldering station (Hakko FX-888D) earlier today, as I had a feeling it was time to get better equipment. Spooky. I guess the cheap one got upset and self-destructed.

Out of curiosity, I dismantled the dead soldering iron and took a photo of the board inside.

Dead soldering iron PCB

With my limited knowledge of electronics, my intuition tells me that an arc occurred between the AC wires. If so, is this bad luck, bad soldering, or user error?

Close up of the burnt AC wires

The insulation appears burned, but also the core of the wires seems to be a bit frayed. Was this as a result of the arc, or low quality manufacturing?

Bonus question: I wasn't touching the button at the time the iron popped, but if I was, would I have received an electric shock? Would it have been life threatening or painful?

Edit: I am in the UK (230VAC).

  • 11
    \$\begingroup\$ It's very probably not your fault--those cheap soldering irons aren't worth even the tiny amount they cost. You seem to have purchased exactly the iron I would recommend to replace it, so good choice! \$\endgroup\$
    – Hearth
    Jul 3, 2021 at 21:55
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    \$\begingroup\$ People don't destroy soldering irons. They destroy the tips, and the soldering iron destroys the work. \$\endgroup\$
    – DKNguyen
    Jul 3, 2021 at 22:37
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    \$\begingroup\$ were you soldering on live wire/circuitry? if so, it is your fault. otherwise its likely someone manufactured the soldering iron's heating coils poorly. \$\endgroup\$
    – Abel
    Jul 4, 2021 at 0:44
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    \$\begingroup\$ Also, if getting cheap gear go for simple- like an iron with no temperature setting (or power button) for example. KISS helps reduce manufacturing screwups that make it to store shelves. \$\endgroup\$
    – Abel
    Jul 4, 2021 at 0:51
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    \$\begingroup\$ @NickBolton If you re-make those connections when your nice new iron arrives, you might have a working iron that you can use for messy jobs like melting plastic. \$\endgroup\$ Jul 4, 2021 at 16:39

4 Answers 4


That thing was not UL Listed

and should never have been plugged into AC power. It violated the safety codes of lots of countries.

Never plug anything into AC power that isn't UL Listed.*

enter image description here

Buy from reputable vendors in the future. Note that on Amazon, many third party (eBay crud tier) items ship from Amazon warehouses with Prime. Make sure the seller and shipper are both Amazon, and you have a chance of getting a better quality product. Amazon seems to follow the "bricks and mortar retail" quality laws on their own stuff.

The safer option is to buy from actual bricks and mortar vendors (even if you mail order from them), such as Home Depot, Galco, Grainger, Radio Shack (though watch out these days) etc. Sorry, there's slim pickings these days for electronics bricks and mortar. Mouser and Digi-Key and McMaster-Carr have been reliable IME.

* Or if you want to get into the gory details...

Listings from other NRTLs are generally acceptable. That is because the other NRTLs duplicate UL's high level of independent third-party scrutiny. Off the top of my head, British BSI, German TUV, a dozen others. UL and the other NRTLs are extremely aggressive about defending their mark, and as a result, UL, CSA, BSI and TUV marks are almost never seen faked.

Who the heck is USA OSHA to decide who is an NRTL? I don't know, but somebody has to do it, and they do a good job, and many agencies in many countries simply defer to that list rather than try to administer their own list.

The CE mark is universally faked, mockingly, on a "catch me if you can" basis by pretty much every manufacturer who keeps their assets outside the reach of EU authorities. The only way to count on that mark is to buy at a competent, trustworthy bricks-and-mortar shop physically inside the EU whose assets are inside the EU. Walk into Wickes and you're fine. With mail-order, all bets are off. It only works if you have a responsbile in-EU seller, such as Wickes.co.uk or Mouser. But many warehouses, such as Amazon's, do drop-shipping for many third-party sellers. Amazon is not responsible for regulatory compliance for third-party items, even those sold on its site. So effectively, ordering a third party item on Amazon (or other website where Amazon or a like-minded shipper is the drop-shipper) is the same as direct ordering overseas - there are no consequences for faking the CE mark, so it most likely is faked on a product whose distinctive feature is that it is a bargain.

Pretty much the same for the CCC mark. The manufacturer may be in the jurisdiction of the mark issuer, but the government turns a blind eye if the item is only for export.

I have researched these companies. As an example, I found one who claimed to be a 100-year-old famous German electronics firm which had merged with a four-year-old American LLC. Their USA address was an apartment block in Sunnyvale. Their German address was a drop box in downtown Dortmund. Their China address was a massive industrial park. Nothing within the reach of EU authorities. They had bought the corporate shell of the defunct electronics company.

I realize many readers want to believe those oh-so-cheap items on Amazon are legal and safe. I'm sorry to burst your bubble.

Note that even when CE is working as intended, by an EU company with EU assets selling inside EU watched by EU regulators, the CE mark is still a self-certification, which is weak tea compared to a third party NRTL certification and followup examination. EU used to agree; that is why BSI and TUV were formed in the first place.

  • \$\begingroup\$ Good answer. Could you tell me more about how to check if something is UL listed? How did you find out that the product wasn’t UL listed? \$\endgroup\$ Jul 5, 2021 at 23:26
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    \$\begingroup\$ Look for the distinctive UL in circle mark, along with a 6-9 digit "file number". I can tell the product wasn't UL listed because I pay a lot of attention to certain supply channels, and also, that build quality lol... note that UL is not the only NRTL; others will suffice but CE isn't one. \$\endgroup\$ Jul 5, 2021 at 23:34
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    \$\begingroup\$ Good luck finding small 230V-only appliances with a UL listing in the UK. CE has been deemed good enough by the appropriate authorities, so that's what you get, regardless of issues caused by dodgy self-certification (or outright fakery) \$\endgroup\$
    – Chris H
    Jul 6, 2021 at 7:56
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    \$\begingroup\$ UL is an American certification company, UL Listed only means that the product was tested following guidelines issued by that particular company. There are other certification bodies and standard and it varies widely across the globe (IEC, CE, CSA, CCC, etc...). Usually only product sold in north America are UL tested. \$\endgroup\$
    – Damien
    Jul 6, 2021 at 8:58
  • \$\begingroup\$ CE is the European Union's certification scheme. Over the course of this year Britain is introducing its own scheme, UKCA. gov.uk/guidance/using-the-ukca-marking \$\endgroup\$
    – padd13ear
    Jul 6, 2021 at 10:48

Just looking at how these wires are soldered to the PCB indicates a low quality product. I would not blame you but the product instead.

  • 1
    \$\begingroup\$ Could the way that AC wires are soldered to a PCB cause cause an arc? \$\endgroup\$ Jul 3, 2021 at 23:00
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    \$\begingroup\$ And, would I have gotten an electric shock if I was touching the power button? The power button is right next to the AC solder connections. \$\endgroup\$ Jul 3, 2021 at 23:00
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    \$\begingroup\$ If the one strand of wire snaps it could end up bridging live to neutral or to ground. and to me that looks like what happened. \$\endgroup\$ Jul 4, 2021 at 3:11
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    \$\begingroup\$ At best you'd get a big scare, at worst this product can be lethal. I'd request a full refund and flag/mark/review it as a dangerous product where you purchased it. And finally congrats with your new Hakko iron, it is a nice step-up :) \$\endgroup\$ Jul 4, 2021 at 11:14
  • \$\begingroup\$ You'd have to look at the wires/joints before they burned to crisp. It does look like bad wetting, but it is hard to judge the quality of the soldering as it stands. Not using an isolated connector instead is rather the main remark here, but that's related to the PCB design. \$\endgroup\$
    – Lundin
    Jul 6, 2021 at 7:30

This soldering iron is garbage. The PCB has been soldered by machine and is likely ok. The power cable looks like it hasn't even be soldered on in a factory but by home workers with bad equipment and bad skills. It starts by the cables not being properly deinsulated (you can see a number of torn copper strands) and then not being properly twisted and presoldered (you can see lots of blank copper) and then not being properly shortened: there are far too long open strands off the solder pads. The solder joints look more baked on rather than thoroughly heated, particularly the right one. Also it appears like there has too much been cut from both outer insulation and wire insulation to have any pull protection measure work reliably.

I would expect the ground wire to easily sprout a copper wire over where it may touch the live wire.

But it doesn't even look like that is what happened: one can see in the upper picture that tracks leading to the switch have burnt off, so the short wasn't even in the awful cable soldering (where the damage would have been contained nearby while blowing the fuse) but was somewhere higher.

In addition, the PCB design does not appear to accommodate any significant amount of cross section for the ground tracks, so the amount of security provided by them is limited: you might get a flash and a bang and the thing continues "working" after having rid itself of the ground track. And might even work for the next user after having killed you.


It looks like the mains cord was not fully soldered to the board.

You can see a stray whisker of the ground still. There were probably also loose strands on the current-carying conductors. They probably flexed enough to touch when you were handling the cord, and when you plugged it in, they bridged a rush of current through and vaporized. POP!

I'm kind of surprised that it broke the iron. It shouldn't have. But whatever. I've been using $10 irons all my life and they work okay for me without any circuit board inside them. But that hakko is super great too, so enjoy it.

  • 1
    \$\begingroup\$ Perhaps it blew a fuse. Nick could check whether the plug or cord has a fuse (doubt it unless they live in the UK) \$\endgroup\$ Jul 5, 2021 at 13:12

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