USB plug is zapping me, sparking when touching metal

MrAl

Joined Jun 17, 2014
11,389
The thing is, if there were constant sparks then there must be something wrong with the wall wart also unless there are also two separate circuits in the room where the wall wart is plugged into one and the computer is plugged into the other and the two outlets are wired to different line phases.

Wall warts that have the right isolation rating and work normally will not spark no matter how a single outlet is wired. That's because the output is electrically isolated from the input.

If you dont agree then try to show how an outlet can be wired to make a normally functioning wall wart cause a spark on the output when the output ground touches anther ground.
 

MisterBill2

Joined Jan 23, 2018
18,167
The thing is, if there were constant sparks then there must be something wrong with the wall wart also unless there are also two separate circuits in the room where the wall wart is plugged into one and the computer is plugged into the other and the two outlets are wired to different line phases.

Wall warts that have the right isolation rating and work normally will not spark no matter how a single outlet is wired. That's because the output is electrically isolated from the input.

If you dont agree then try to show how an outlet can be wired to make a normally functioning wall wart cause a spark on the output when the output ground touches anther ground.
Certainly MrAl is correct for all 2-pin wall warts. If the package has a third pin, the ground pin, then the situation is different, because for some reason a ground connection is carried through to what is supposed to be an isolated output circuit.
But it was mentioned that this supply has a two pin connection, without any ground pin, so that is not the case here. There is no intentional ground connection. The output is SUPPOSED TO BE TOTALLY ISOLATED. Clearly it is not.

Of course the key words are "Right Isolation", which is different from "the cheapest possible way to do it" isolation. Mister Al is totally correct on that point!

What is funny is that right now I am using a "portable" HP computer that has a 3-wire grounding plug on the power cord for the little power supply. But this computer does not need a ground connection for any aspect of it's operation, it works quite well running from the battery pack. So just exactly what was the motivation to demand operation from a grounded outlet? Probably the same motivation that added the feature that I can only use the $99 HP original power pack instead of some other one.
 
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Thread Starter

Domarius

Joined Sep 1, 2013
46
Based on the inspection results now you need to replace the power socket, unless you are renting, in which case the remntal manager needs to get it replaced. The really hard part is purchasing the replacement. If the TS is in 220 volt territory then it is a good idea to switch off the circuit feeding that power outlet. And if in 120 volt territory it may still be handy to switch it off, although I seldom do.Make certain that the feeding wires are corrdctly connected at both ends, that could be part of the problem.
The outlet that fed this equipment should be replaced immediately and the wiring checked for a ground condition. The wiring needs to be isolated and checked for a high impedance ground. You have a dangerous situation that needs to be fully checked and fixed before a fire happens. If this high impedance ground changes to a low impedance ground you will have a fire.
Thank you for the concern guys. Well obviously I'm not using the broken one (which was the culprit), so hopefully that avoids the risk. Also the Energex guys job is to make sure everything is safe, which included all of those checks I assume - they had a long blue wire running in from the grounding pipe outside, into a device that they plugged into the wall socket, while doing their tests. Apparently a few years ago there was a little girl that died simply by touching a metal plumbing pipe and it was the fault of Energex supplying power wrong somehow. So now they are super responsive coming out and testing shock risks for free. They came within a couple hours of my call. They left saying absolutely everything was safe as far as they were concerned, the only thing they noticed was the socket was working and then it wasn't. I've put in a repair request with our property manager, they said they would be chasing it up with the owner. Though he's slow...

The thing is, if there were constant sparks then there must be something wrong with the wall wart also unless there are also two separate circuits in the room where the wall wart is plugged into one and the computer is plugged into the other and the two outlets are wired to different line phases.

Wall warts that have the right isolation rating and work normally will not spark no matter how a single outlet is wired. That's because the output is electrically isolated from the input.

If you dont agree then try to show how an outlet can be wired to make a normally functioning wall wart cause a spark on the output when the output ground touches anther ground.
Certainly MrAl is correct for all 2-pin wall warts. If the package has a third pin, the ground pin, then the situation is different, because for some reason a ground connection is carried through to what is supposed to be an isolated output circuit.
But it was mentioned that this supply has a two pin connection, without any ground pin, so that is not the case here. There is no intentional ground connection. The output is SUPPOSED TO BE TOTALLY ISOLATED. Clearly it is not.

Of course the key words are "Right Isolation", which is different from "the cheapest possible way to do it" isolation. Mister Al is totally correct on that point!

What is funny is that right now I am using a "portable" HP computer that has a 3-wire grounding plug on the power cord for the little power supply. But this computer does not need a ground connection for any aspect of it's operation, it works quite well running from the battery pack. So just exactly what was the motivation to demand operation from a grounded outlet? Probably the same motivation that added the feature that I can only use the $99 HP original power pack instead of some other one.
MisterBill2, you're right about the hdd power plug - it has only 2 prongs. Not 3 like my PC power cord.

MrAI, if there should be no sparks at all, then that may be concerning. I can reproduce tiny blue sparks upstairs in a completetly different environment - different computer, usb hdd, and different wall sockets. The only similarity is they're in the same house. But the Energex guys said everything here was fine, so... I guess I have to assume the tiny blue sparks are normal? Because there was a difference with issue that started the thread - the USB plug actually stung when touched, and caused much larger sparks (in the video I posted) and that wall socket is now dead.

So I don't know how all this works, but I'm currently assuming it was the one (now dead) socket that was causing painful sparks, and the other tiny blue sparks are normal...
 

MisterBill2

Joined Jan 23, 2018
18,167
Thank you for the concern guys. Well obviously I'm not using the broken one (which was the culprit), so hopefully that avoids the risk. Also the Energex guys job is to make sure everything is safe, which included all of those checks I assume - they had a long blue wire running in from the grounding pipe outside, into a device that they plugged into the wall socket, while doing their tests. Apparently a few years ago there was a little girl that died simply by touching a metal plumbing pipe and it was the fault of Energex supplying power wrong somehow. So now they are super responsive coming out and testing shock risks for free. They came within a couple hours of my call. They left saying absolutely everything was safe as far as they were concerned, the only thing they noticed was the socket was working and then it wasn't. I've put in a repair request with our property manager, they said they would be chasing it up with the owner. Though he's slow...



MisterBill2, you're right about the hdd power plug - it has only 2 prongs. Not 3 like my PC power cord.

MrAI, if there should be no sparks at all, then that may be concerning. I can reproduce tiny blue sparks upstairs in a completetly different environment - different computer, usb hdd, and different wall sockets. The only similarity is they're in the same house. But the Energex guys said everything here was fine, so... I guess I have to assume the tiny blue sparks are normal? Because there was a difference with issue that started the thread - the USB plug actually stung when touched, and caused much larger sparks (in the video I posted) and that wall socket is now dead.

So I don't know how all this works, but I'm currently assuming it was the one (now dead) socket that was causing painful sparks, and the other tiny blue sparks are normal...
NO!!! Sparks from a device that is supposed to be completely isolated are not normal and are an indication that something is big time wrong.Power supplies are supposed to be completely isolated, meaning NO VOLTAGE between any supply input connection and any output connection. So if there is such a voltage then there is a defect. If you can open the case of that supply without destroying the supply it might become clear what has failed, or possibly not. An easy fix, not a repair, and probably not cheap, would be an isolation transformer on the supply side. That should stop the sparks and end the shocks, but it will not fix the supply, it will only solve the one problem.
 

MrAl

Joined Jun 17, 2014
11,389
Thank you for the concern guys. Well obviously I'm not using the broken one (which was the culprit), so hopefully that avoids the risk. Also the Energex guys job is to make sure everything is safe, which included all of those checks I assume - they had a long blue wire running in from the grounding pipe outside, into a device that they plugged into the wall socket, while doing their tests. Apparently a few years ago there was a little girl that died simply by touching a metal plumbing pipe and it was the fault of Energex supplying power wrong somehow. So now they are super responsive coming out and testing shock risks for free. They came within a couple hours of my call. They left saying absolutely everything was safe as far as they were concerned, the only thing they noticed was the socket was working and then it wasn't. I've put in a repair request with our property manager, they said they would be chasing it up with the owner. Though he's slow...



MisterBill2, you're right about the hdd power plug - it has only 2 prongs. Not 3 like my PC power cord.

MrAI, if there should be no sparks at all, then that may be concerning. I can reproduce tiny blue sparks upstairs in a completetly different environment - different computer, usb hdd, and different wall sockets. The only similarity is they're in the same house. But the Energex guys said everything here was fine, so... I guess I have to assume the tiny blue sparks are normal? Because there was a difference with issue that started the thread - the USB plug actually stung when touched, and caused much larger sparks (in the video I posted) and that wall socket is now dead.

So I don't know how all this works, but I'm currently assuming it was the one (now dead) socket that was causing painful sparks, and the other tiny blue sparks are normal...
Something is seriously wrong somewhere. As MisterBill says there should be no sparks unless something is not isolated.

To put it another way, i have never in my life seen any sparks small or large with any USB device i have every used. I've used a USB hard drive enclosure and USB oscilloscope for example and if there was going to be any isolation issues i would see it with the USB hard drive enclosure because it has its own power supply.

I have however measured significant voltages in places you would not normally expect to see them, but that was with devices that are not isolated.

From what you are saying it sounds like there is a small capacitor charging somewhere in one of your devices so maybe they are using capacitors to develop some sort of artificial ground. This would require taking the unit(s) apart or doing some careful measurements to find out for sure.
Apart from that, i am out of ideas.
 

MisterBill2

Joined Jan 23, 2018
18,167
It will be interesting to see what is wrong when that failed outlet is replaced, or possibly the problem is fixed. I have a number of interesting tales about wiring problems but this thread is not the place for them. perhaps there is a portion of this site where tales can be told, that others may be aware of the fixes for interesting problems. Certainly we have read about them in comments in other threads. And the thread about the house with 24 volts on the ground wire seems to have disappeared. I was really wondering how that one turned out.
 

MrAl

Joined Jun 17, 2014
11,389
It will be interesting to see what is wrong when that failed outlet is replaced, or possibly the problem is fixed. I have a number of interesting tales about wiring problems but this thread is not the place for them. perhaps there is a portion of this site where tales can be told, that others may be aware of the fixes for interesting problems. Certainly we have read about them in comments in other threads. And the thread about the house with 24 volts on the ground wire seems to have disappeared. I was really wondering how that one turned out.
How about using the Off-Topic section?
 

MisterBill2

Joined Jan 23, 2018
18,167
If the socket was bad then perhaps it caused damage to the wall wart.
That is probably not possible. Consider just what conditions would be needed to cause the output of a correctly isolated power supply to become connected to the supply mains side. To cause a breakdown would require quite a bit more voltage than is normally available in normal home wiring.
 
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