Thursday, 23 February 2017

Beware - Cheap Soldering Guns

As my regular readers will know (ha! how cocky am I to think I have regular readers?), I get a lot of small parts from the Far East. On the whole, I have few problems, other than the odd small packet getting lost in the post. But recently one purchase has proved to be very disappointing.

Having a need to solder some rather hefty cables and connections, and for jointing boxes made from PCB material, I took a chance on a low cost soldering gun. Now, a soldering gun is little more than a switch, a hefty transformer with a very high current, low voltage secondary winding, and a high resistance but otherwise short circuit loop forming the soldering tip. Not exactly hard to make. This particular one was rated 175W and cost a little over  a tenner (you can see where im taking a chance - compare with a similar Weller machine!), now I never for a moment thought i'd get 175W from it! But did think it would maybe run around 125-130W.

The first thing to note is that what arrived is not even marked as 175W! -

wrong rating - not a good start!
But worse was to come. It is supplied with a two pin plug, which is a pain, but not a big problem. Well, I tried to use it. I thought it was a bit off how it took quite a few seconds until it would actually melt solder! But the real problem came when trying to actually make a soldered joint - you cant!

Put the tip to anything bigger than solder wire, and it loses all its heat and the solder solidifies. Even after well over  a minute in contact with a 2inch square of PCB material the solder still wouldnt melt, let alone flow. The damn thing has just NO heat capacity!

As it happens, I have a 230v mains energy meter. Running at a measly 500mA current draw and a power factor of around 0.6, it became very clear that this is simply not up to the job. The picture below shows my energy meter in Watts mode, with the soldering gun active

Thats 71W its reading there! The peak reading feature of the meter showed at no time did the soldering gun consume above 75W!

So, I have started the necessary case for a refund. No doubt the seller will try and argue for it to be sent back. What? to Hong Kong? 'ave a day 'orf! Sending it back will cost more than it did. I will push for a refund, then this one will eventually end up in the WEEE skip!

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