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This is something that happened recently.

I was casually using my laptop with the laptop placed on a table, charging and my feet on the marble floor below. Only one of my feet was in contact with the floor and that too was not completely in contact with it. Only my toes were actually in contact with the floor.

So, I accidentally touched the metallic case of the in-built speaker and it gave me a very hard electric shock. I think it's worth mentioning that my finger's still hurting from it. I also felt like the current was alternating. I felt a very fast vibration in my hand and that is how I assumed that.

I have experienced this earlier a few times as well, whenever I'm barefoot and my feet are in contact with the ground. We went to a repair shop and the employee there said that it's normal for the metallic parts to shock you and it's just 12 volts DC, so it won't be fatal.

Is it normal or something is seriously wrong?

vu2nan
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Rajdeep Sindhu
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3 Answers3

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This subject pops up regularly. One reason is the rf filtering at the AC mains input of the power supply. The filtering tries to prevent the power supply polluting the electricity with high frequency switching pulses. The filter has often capacitors connected to the protective ground wire from both hot and neutral AC wires. The protective ground is directly or capacitively connected to the ground side of the DC output.

If you don't have AC outlet with proper protective ground - it can be nonexistent or have a voltage to your stone floor - you get an AC voltage between the DC output and the stone floor. If the protective GND is missing it's half of the mains AC voltage. It can be more if there's voltage between the protective ground and your floor.

I have seen how people destroy valuable electronics by using equipment which need grounded AC input without the protective ground. Sometimes they have tried to avoid ground loops which collect noise to their inter-device signals.

Finally there can be a fault. It can even be intentional. I guess you have a good possibility to get fake electronic devices if you happen to live in a place where businessmen can do what they want as long as local authorities and mobs get their part of the money. Or if you order something from a foreign webshop.

Stop using the system and let a proper electrician test your AC outlets and the device. Use only a person that you know he understands the problem and wants to solve it. He doesn't start "it's only the low voltage DC".

  • AC outlet without proper protective ground or what in germany is called "classic earthing" [short circuit N with PE], may course problems as described. If you know what you are doing or ask a electrican, you might buy a multiplug and add a wire from the PE Pins. Then you can connect this wire to e.g. a metal water pipe or a metal heating pipe - which at least in germany are normaly connected with PE. But again: this is hazardous voltages: only skilled personal should build things like this! I also want to agree: It might be a fault in your devices. a hot candidate is the power supply. – schnedan Aug 23 '20 at 09:43
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If the shock was hard causing you a finger hurt then it is not a 12 V shock but much higher. (Be assured, anyway, that no one can understand if it's DC or AC simply by judging from the shock sensation). Being the plug a 3-pin plug and assuming it is original then your laptop is experiencing an insulation fault. A live part near the case of the speaker is having an insulation fault and that live part is coming into contact with the case. Moreover I assume that where you using your laptop there is no electric protection device equipped with a differential relay otherwise it would have prevented the shock with an emergency shut off. Now you should avoid using it (at least, avoid touching the metallic parts), until you go back to the repair shop (maybe a new one) and tell them to find the fault and repair it, or at least insulate the case. If you buy a test screwdriver you can check that that case is now a live part.

trying
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  • I think it's important to let you know that the speaker case isn't the only part. I have the 's' key off and the 'pins' in it also shocks with a similar intensity. – Rajdeep Sindhu Aug 22 '20 at 20:32
  • How did you manage to type 's' characters? are you now using an other device? place some insulating tape to close holes on the keyboard. But again, please, do not use it until you get it repaired. – trying Aug 22 '20 at 22:21
  • I'm using a different device now. I used a spare keyboard for typing from that laptop when the key was out but occasionally touched the 'pins' from the key and got shocked sometimes.. – Rajdeep Sindhu Aug 23 '20 at 04:24
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Best recommendation: Replace the obviously defective powersupply for that particular laptop. Not against some chinese ripoff cheapo crap. But by an original device from the respective manufacturer, made and intended for the actual laptop.

Bernd
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  • It is possible to get an electric shock from a properly functioning class 2 power supply because the output floats at about half the mains voltage due to a filter capacitor between the DC output and the AC input. A class 1 power supply connected to a correctly wired 3-pin socket would eliminate the problem because that filter capacitor is connected to the mains ground (earth) wire. – Andrew Morton Aug 23 '20 at 14:26