I had this question in my mind for many days.

The main question came to my mind from times ago when I was working on some electronic devices and at that time I had an ac adapter that it had some keys on it which let me to choose voltages from 1.5 to 12 (It was not advanced like those power sources that are used on electronics labs, it was at the size of a laptops power adapter) it had open wires at the end and I used to twist the wire ends of my circuits to the adapter's ones.

In the middle of my work and when I was building the circuit to connect and test with the adapter, suddenly the adapter blown (boom!) I had no idea of what caused this, why would an adapter blow? I had no idea, I just plugged it out of wall fast to prevent further mess.

I now have made my own power source, I had an old samsung phone (which is dead now - rip) it had a charger which had an output of 4.2V and 650mA and I cut the end that connects to the phone and that gave me two open wire for using in my projects.

What Im saying is that:

1. If I unconciously touched the open wires of the old adapter (which blown) could I have got out alive or I was going to R.I.P like my samsung phone?

Im saying that does a blown ac adapter conduct out electricity or they have machanism for these situations (they stop conducting out electricity)

If they dont, Is it true to say that every mobile phone charger that we carry is a killing machine???

2. Is what Im doing right? (working with open ends of ac adapters and just twist them to every circuit I make?)


closed as unclear what you're asking by Voltage Spike, uint128_t, Enric Blanco, Marcus Müller, Andrew May 18 '17 at 12:02

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  • \$\begingroup\$ Its is better to rig your own connector to the tail end of charger so that you won't accidentally short the outputs causing it to boom (some chargers might have short circuit protection, some not). Regarding blown out adapter, anything might have gone bad and it is definitely not safe now to use it, unless you debug it before hand. \$\endgroup\$ – Umar Mar 4 '17 at 13:33
  • 1
    \$\begingroup\$ I think you mean you are using the DC end of an isolated AC-DC converter and the DC side is blown from short circuit or something. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 4 '17 at 15:50
  • \$\begingroup\$ @TonyStewart.EEsince'75 Im using the DC end but, you might have seen inside phone chargers that they have some kind of coil inside them, this coil blown in my old charger, it just melted (if it is DC side from what you saying) so there is no coil in between the circuit, and does this mean that the AC current hits the end tails? \$\endgroup\$ – AmirHossein Mar 6 '17 at 18:22
  • \$\begingroup\$ a broken supply does whatever it was designed to do if it fails, otherwise anything is possible \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 7 '17 at 5:21
  • \$\begingroup\$ If you mean conduct from the AC side to the DC side, then extremely unlikely if the adapter was UL/CE tested and approved. All isolation barriers within it must survive any failure mode up to a certain overvoltage level. What you are left with is direct or almost direct lightning strikes which may break down your isolation and can cause harm when plugged in. \$\endgroup\$ – winny May 17 '17 at 22:03

Q1: It depends on HOW it failed. It could be open circuit or it could be a short to the input. Or it could catch fire if you plug it in again. It is impossible to tell without debugging it. THROW IT AWAY.

Q2: If you are using these adapters for powering hobby projects, do yourself a favor and go out and buy yourself a proper bench supply. One that you can adjust the voltage and more importantly monitor and limit the current like the one shown below. There are also multi channel varieties.

It might seem expensive, but it will save you large dollars in blown components and circuitry. Or add it to your Santa list.

enter image description here

  • \$\begingroup\$ I just thrown it away the day after :) it is just dangerous in simple thought so I did what I thought was best that time. So do you mean, if my new phone's charger - android phone - just blows (for whatever reason) can this cause to killing my phone which is charging or perhaps killing me if I was using it or suddenly touched the micro-USB end? \$\endgroup\$ – AmirHossein Mar 6 '17 at 18:29
  • \$\begingroup\$ With the recent flood of exploding and combusting phone videos on u-tube I would be extremely wary of using any suspect adapter to charge ANY phone. The batteries in phones hold A LOT of energy. \$\endgroup\$ – Trevor_G Mar 7 '17 at 13:40

I do understand the reason for the question: what if I could have been electrocuted? I still remember an old TV set I was diagnosing, it has been unpluged for many hours, but I accidently touched the HV wire... zap!

Obviously if it is dead and you cannot repair it, dispose off properly.

But any blown device has the potential to conduct electricity across because of capacitors, carbon deposits, exploded components making shorts, dirt/corrosion between copper traces, etc. Also, every circuit has some part of it with energy, just before the fuse or whatever, so it may be possible to get a shock even if it is not working.


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