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The other day, my soldering iron tip accidentally touched a plastic cable, so I quickly tried to remove the plastic stuck to my tip using a tester lying nearby. I Soon discovered that the tip was live as the bulb in the tester glowed. I then disconnected the power supply and then check the connectivity of each of the plug to the tip, there was no short between the plug and the tip. I tried to touch the tip when it was on and I couldn't feel anything. I tried hooking up a multi-meter as well which showed about 9V between the tip and ground. Should I be worried about using my soldering iron? Is it safe to use it?

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  • \$\begingroup\$ 9 Volts AC or DC? \$\endgroup\$
    – Jeroen3
    Jun 19, 2017 at 14:18
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    \$\begingroup\$ "I tried to touch the tip when it was on and I couldn't feel anything." yep, that's the proper way to check if anything is connected to live mains... \$\endgroup\$
    – PlasmaHH
    Jun 19, 2017 at 15:30

4 Answers 4

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The glow in the tester might be due to a lot of reasons. The heat in the soldering iron might have led to thermal conduction in the tester. The testers usually have very low resistance of their own, so a small current could have led to the glow in the LED. Also, there might be some static charge on the tip of soldering iron which might have led to the glow. Some Leakage current can be another reason. I could think of these reasons based on your description.

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Think about it for a minute, if your soldering a component with an absolute maximum rating of 8V (or 5V) and the source of the voltage on your soldering iron is low impedance (it can source a reasonable amount of current like more than 10mA) then there is a possibility that you could burn out components electrically while you solder.

In all of the soldering irons that I've taken apart, there is a heating coil that is electrically insulated with ceramic from the tip. So you either have a short somewhere or its a bad design (from a cheap chinese soldering iron). I'd look at getting a new one if your soldering sensitive components.

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Please make sure your search if your question has been asked earlier.

I think you should be from this post.

A potential of 10V though might not be harmful for you, can be harmful for the circuit components. Also in due course of time this potential can increase which can be dangerous to you as well.

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  • \$\begingroup\$ If the question is a duplicate, you should really flag it as such rather than adding a link to the duplicate in your answer. \$\endgroup\$ Jun 20, 2017 at 6:49
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If you only have a 2 pin connection to the AC power then the voltage you see is AC and probably due to the capacitance between the heating element and the metal shaft and tip of the iron. It will be at very low current.

Often (but not always) a soldering iron will have a 3-wire plug with ground in which case the tip will be grounded.

It is a potential hazard but I have never had any damage caused by such coupling. If the AC plug is symmetric you could rotating its position in the socket and see if it changes the voltage seen.

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