USB plug is zapping me, sparking when touching metal

RobNevada

Joined Jul 29, 2019
66
Meter the power supply. If the power supply is rated for DC output then check on the AC side. If you are getting a voltage on the AC side your power supply is failing. Replace it ASAP so it doesn't damage your computer. If it is a AC transformer then it is feeding a bridge rectifier and a voltage regulator and that should be checked to verify that it is not failing. Somewhere you are getting AC voltage if you are seeing a spark to ground.
 

Thread Starter

Domarius

Joined Sep 1, 2013
46
I have some new information. I have gone around the house testing other devices on other power outlets. Actually I can reproduce the little blue sparks from any powered USB device whether it's a USB hub or external hard drive, on a completely different computer upstairs. Also I do read an AC voltage from all of them as well when testing in the same manner as in the video.

But the important difference regarding the hard drive I'm concerned about, is the Sparks are much more spectacular, they are larger and sometimes Orange. Also the voltage is higher. From the hard drive in question it shows 88v AC and -10v DC, whereas all the other devices show 86v AC and -8v DC.

The main thing is - the USB plug coming from that hard drive actually hurts! No other USB plug me and my partner have touched today have any effect on us. When we were testing all this on my computer earlier, she sat down and her thigh accidentally touched the USB hub from this hard drive without her realising, and she recoiled away and said "ow!" That is not normal.

Update: I can't hurt myself on it as badly anymore, at least, right now. After unplugging it and trying some things, it's plugged back into the same powerboard and everything when it was causing a problem. I definitely felt something but it wasn't as painful... I dunno, maybe it takes a while to build up...

It could be that all these readings and sparking is kinda normal and this one device just does it slightly worse... feel like I'm chasing ghosts now...

OK, and after seeing the video and those meter readings it is clear that something is not at all right. So the first thing that I suggest is checking the desktop computer unplugged and verifying good continuity between the computer frame and the line cord ground pin. Then you will be able to know where the fault does NOT lie. Also check between each of the computer line power pins and the computer frame, switch ON, cord unplugged. Those should show open. Then a similar test with your external hard drive and power supply, if it has a ground pin, and also the line pins. And last, check the connections inside the powerboard, with it unplugged but switched on. What is obvious is that it is a real problem just as you describe. If those checks do not reveal the cause then it is time to investigate a bit farther. I have a guess but nothing solid to back it up with yet.
Everything checks out as you describe. Although I wasn't quite sure what to do with the power brick for the external hard drive because it does not have a ground pin on the power plug. But I can confirm that there is no continuity between either of its pins and what should be the ground metal area surrounding it's USB 3 socket.

And actually I skipped checking the power board because I simply removed it from the equation by plugging the external hard drives power plug straight into a wall socket and plugging the computers power cord straight into the wall socket next to it before doing the above tests. Edit: at the time I did the tests, I was still able to reproduce the painful Zap and spectacular orange Sparks with it plugged into the wall.

Meter the power supply. If the power supply is rated for DC output then check on the AC side. If you are getting a voltage on the AC side your power supply is failing. Replace it ASAP so it doesn't damage your computer. If it is a AC transformer then it is feeding a bridge rectifier and a voltage regulator and that should be checked to verify that it is not failing. Somewhere you are getting AC voltage if you are seeing a spark to ground.
I'm not exactly sure how to test what you're asking but I wouldn't like to suspect the PC's power supply is the problem, because firstly the problem is solely with the external hard drive itself- having it plugged into the wall socket and then touching it's USB plug zaps you rather painfully. The computer is not involved in that process. Secondly the power supply for that PC is very new and of good quality. It's an Antec EDG550.
 

DickCappels

Joined Aug 21, 2008
10,153
If you have a resistor around 1K you can ground your USB through that resistor then measure the leakage current that produces an AC voltage drop across that resistor. More than 1 or 2 milliamps would have me thinking about replacing the fault piece of equipment. Over 10 ma and I would definitely not use it.
 

Tonyr1084

Joined Sep 24, 2015
7,852
How much of a zap you FEEL depends on a lot of factors. Largest factor is how dry your skin is, followed by how well hydrated you are. Oily skin will give you a stronger sensation of shock than dry skin. Ambient humidity may also play a factor. The salinity of your skin is another.

Like Dick Cappels said, be cautious of how much current is flowing through your body when getting shocked. It doesn't take much to stop your heart. At worst, keep your left hand in your pocket, meaning only touch (if you must) both units in question with one hand. At BEST - don't touch it at all. That way you're not passing current through your chest, and potentially your heart.
 

Thread Starter

Domarius

Joined Sep 1, 2013
46
The zapping is well and truly back. Since this is the only device that does this, I think the simplest thing is to just replace it with a non-powered external HDD. It is pretty old anyway. And I can de-case it and re-use the actual HDD inside my PC.

What you could do is try to reverse the connection to the power supply AC input by turning the plug upside down. If that helps, then you have a bad wall wart.

Another possibility is that you have the PC plugged into one outlet and the Drive plugged into another outlet and they are on separate circuits which also happen to be on opposite sides of the AC transformer/line that feeds your house or office. In that case make sure they are both plugged into the same outlet.
Hey I missed this first time around. I'm in Australia so reversing the socket is not possible. Also I can reproduce this problem with the HDD plugged into any outlet or powerboard - the USB plug zaps me. The PC isn't involved in that process.

If you have a resistor around 1K you can ground your USB through that resistor then measure the leakage current that produces an AC voltage drop across that resistor. More than 1 or 2 milliamps would have me thinking about replacing the fault piece of equipment. Over 10 ma and I would definitely not use it.
I don't have a resistor but I know they're cheap, so I'm tempted to look into this.

How much of a zap you FEEL depends on a lot of factors. Largest factor is how dry your skin is, followed by how well hydrated you are. Oily skin will give you a stronger sensation of shock than dry skin. Ambient humidity may also play a factor. The salinity of your skin is another.

Like Dick Cappels said, be cautious of how much current is flowing through your body when getting shocked. It doesn't take much to stop your heart. At worst, keep your left hand in your pocket, meaning only touch (if you must) both units in question with one hand. At BEST - don't touch it at all. That way you're not passing current through your chest, and potentially your heart.
Thank you, well the zapping is back. It's sharp and unpleasent, but I never felt it was enough to be a serious risk to me, just my PC!

Get the equivalent of one of these, but for your country, and test the outlets in your house. Quick easy first step that will allow you to eliminate improper wiring from your list of possible causes:

https://www.amazon.com/Sperry-Instr...ster&qid=1575812310&smid=ATVPDKIKX0DER&sr=8-4
I would like to do that actually. On eBay the Australian ones look to be around $20, I think I will get one if I start suspecting the house wiring. Right now it's just this one device that does it.
 

MisterBill2

Joined Jan 23, 2018
18,169
Now I am suspecting a problem with your PC power supply. Did you verify that the ground pin on the PC power cord is connected to the frame of that PC?
But putting that HDD inside the computer with a direct connection is the one safe way to avoid the problem. Not to fix it, but to avoid it.
And now I am wondering if it is something else connected to that PC that has the problem, such as a modem or monitor or printer.
But still, my instinct is pointing towards the power supply of the external HDD package.
 

TeeKay6

Joined Apr 20, 2019
573
Now I am suspecting a problem with your PC power supply. Did you verify that the ground pin on the PC power cord is connected to the frame of that PC?
But putting that HDD inside the computer with a direct connection is the one safe way to avoid the problem. Not to fix it, but to avoid it.
And now I am wondering if it is something else connected to that PC that has the problem, such as a modem or monitor or printer.
But still, my instinct is pointing towards the power supply of the external HDD package.
@MisterBill2
In his last few posts @Domarius has stressed that no PC is needed for him to sense a shock or see a spark. He needs only the external HDD and its wall-wart. It's hard for me to believe the problem is anything other than a leaky wall-wart.
 

MisterBill2

Joined Jan 23, 2018
18,169
@MisterBill2
In his last few posts @Domarius has stressed that no PC is needed for him to sense a shock or see a spark. He needs only the external HDD and its wall-wart. It's hard for me to believe the problem is anything other than a leaky wall-wart.
Well, YES! I was rather tired when I gave that response. Certainly a wall wart with inadequate isolation will cause problems. And it may be a tabletop supply that has an inadequate isolation barrier. A non-isolated switchmode supply can certainly function but have an intrinsic lack of isolation because of the circuit. But probably it would cost less to produce. And for some companies nothing else matters other than cost reductions.
 

Tonyr1084

Joined Sep 24, 2015
7,852
@MaxHeadRoom My wife and I have external HDD's. Both units are independently powered. My modem is also independently powered. I have a DVD drive that plugs in via USB and it is powered from the PC. I have a scanner that is battery powered (for travel). It can be powered from a wall wart or just four AA batteries.

In short, some devices are powered from the PC while others are powered independent from the PC.
 

Reloadron

Joined Jan 15, 2015
7,501
All the 3.5" external drives I have need an external 12V supply. The 2.5" ones are USB only.
Yeah, my old external Western Digital I mentioned earlier has a 3.5" WD drive and the new drive I just purchased for a friend a 2.5" USB port powered drive.

Ron
 

Thread Starter

Domarius

Joined Sep 1, 2013
46
Ok guys, thank you so much for all of your input. Yesterday I made a few phone calls and had the government-funded power Supply Company come out and check my power points for free (Energex) since apparently any shock request is a serious issue and needs to be checked immediately.

The rather unsatisfying but fairly conclusive result seems to be this; they tested all the PowerPoints in my room and everything turned out fine. With one small problem; the specific socket that I believe I got most of the problem with the hard drive for power adaptor zapping me painfully, stopped working all together during their tests. So they said everything is safe as far as they are concerned and the only thing they're found was that one power socket wasn't working anymore.

My partner and I believe that this socket was the one that produced the most painful spark and all the other sockets I tried may have produced some sort of tingle but nothing as painful as that. So it was probably faulty and some way and on it's way out and the prodding and testing that the tradesman did finally tipped it over the line and it died. Also she seems to recall she has always received some sort of tingle from a power adaptor plug into a wall socket.

So perhaps minor Sparks and tingles are possible under normal circumstances and it was just one power socket that was faulty and causing the extra shock. I just have to get it fixed now.

@MisterBill2
In his last few posts @Domarius has stressed that no PC is needed for him to sense a shock or see a spark. He needs only the external HDD and its wall-wart. It's hard for me to believe the problem is anything other than a leaky wall-wart.
Based on the above I think you are right.

send me your mailing address by private mail and I will send you a resistor-capacitor combination that is often used to measure leakage current.
Thank you I will do that!
 

MisterBill2

Joined Jan 23, 2018
18,169
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.
 

RobNevada

Joined Jul 29, 2019
66
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.
 
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