Question Electric shock from a laptop

Jacobean

Member
Hi All, I know this is going to be a bit of a weird first post but I really need people's views on if this is possible or not. I was working on a setup as follows: Laptop with mains plugged in to a multisocket and laptop was connected to the TV via an HDMI cable. I was working away and had just gone into a teleconference when as I put my hands up to the headset (which was usb wired connected to the laptop) all hell broke loose.....

I had what I can only describe as a complete vertigo experience and I went to stand up and I felt this crawling sensation that came from the back of the neck and went over my head. There was also like a strange buzzing going on, my vision went all funny, I hit the floor then as I pulled the headphones off suddently everything went back to normal and I was left with a tingling sensation in my ams and legs. At the time I assumed it was some kind of internal health event but after looking over everything the next day I noticed the HDMI socket and usb socket on the laptop are right next to each other and on the same side as the powered cable and the TV cabinet is damaged. Is it possible that this could have been caused by a surge coming to the headphones? Two days on and my arms feel sore from the inside. I'm about to have a shed load of medical tests and if a shock is possible then I want to mention it but have no idea of the likelihood this could occur and don't want to bring it up if it's more likely I will land on the moon in the next five years. No burning smells or evidence of charring on any of the leads, what do you think?
 

John7

Well-known Member
Doesn't sound like an electric shock to me. Laptop PSU's output around 19 Volts, HDMI and USB ports operate at 5 Volts. None of these voltages would be enough to cause a shock. Any voltage surges high enough to deliver an electric shock would likely destroy laptop/tv or headphones

Your unfortunate event seems to be a bit coincidental to me. What is the damage to the TV cabinet you mention and where is it? Any photos?
 

noiseboy72

Distinguished Member
The tingle you felt is probably coming down the HDMI connection from the TV. It's called functional earth noise and is not dangerous, just a bit unpleasant. If you had your hands to your head, you would have amplified the effect and the shock of it probably caused your little episode.

The voltage is normally around 50V or so, but the current is very low and the source impedance very high. A bit like touching an electric fence!

To reduce the effect, you need to get a better earth to the TV. A wire from a metal outside of any of the AV sockets on the TV attached to a radiator is normally all you need to dissipate the currents without you being aware of them.
 

Jacobean

Member
Thanks for the replies guys! Here's the damage to the TV, sorry pic not very sharp due to my rubbish mobile! this case damage was already there before the event happened so it wasn't caused by it. But I just wondered if it's possible for the TV having been dropped (going by the damage to the case) some how could have caused a surge down the HDMI and with that socket being so close to the USB the headset was plugged in to, caused me to experience something as I put both my hands up to adjust the headphones. I've used the headphones before so it would have to have been some kind of variable event rather than a base line issue. It's just the crawling sensation going up the back of the neck and over the top of the head was a very similar sensation to what I felt when I accidently touched a mains live wire a few years back albeit this one was no where near as strong as that. Could the functional earth noise tingle have caused the dizziness? I think may be a bluetooth headset is my best bet........:)

If this is a possibility then I might bring it up at the next hospital appt before I start to go through a raft of neurological tests.
 

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DavidG1

Active Member
As a retired GP this sounds like a simple ’faint’. You stood up, went dizzy, your vision started to fade, you collapsed, you got tingling in your arms and legs. This is nothing to do with electronics or the headset you were wearing.
When you stood up your blood pressure dropped, causing your brain to be momentarily starved of blood. All the symptoms you describe are pretty typical apart from the persistent soreness of your arms. Hopefully all your tests will be negative
 
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Jacobean

Member
I don't think it was a straightforward faint because it started while I was on the sofa and then I stood up because of it and then went down on the floor, not because I went unconscious. I just went down on my knees because I could not understand what was going on with my head and vision. At that point I ripped off the headphones and then it all stopped and I was left with the tingling arms and legs. Now the timing of the headphones could definitely be a coincidence as I went down on my knees that would counter a drop in BP and help to resolve it, if that was the root cause. But I can't stop thinking about the creeping feeling over the skull and how similar it felt to the previous occasion, I did accidentally touch a live wire. I'm only exploring the idea because at the moment the hospital is about to embark on tests for a TIA and if there was some external influence then I would want to make sure it was known. Hopefully getting the devices all checked over this week, I know it's unlikely but I want to be sure there is no risk to anyone.
 
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ufo550

Well-known Member
As a retired GP this sounds like a simple ’faint’. You stood up, went dizzy, your vision started to fade, you collapsed, you got tingling in your arms and legs. This is nothing to do with electronics or the headset you were wearing.
When you stood up your blood pressure dropped, causing your brain to be momentarily starved of blood. All the symptoms you describe are pretty typical apart from the persistent soreness of your arms. Hopefully all your tests will be negative
I would also concentrate on medical advise.

If you examine your lap top and it’s power supply, you will probably find it’s powered by extra low voltage power supply, via an isolating transformer. In essence, almost impossible to receive an ‘electric shock‘.

The tv will almost certainly be Class 2 (box within a box symbol), so it has no earth connection to house wiring. You could get the lap top and tv Pat tested.

And do not ‘Earth’ your tv; Class 2 equipment should not be earthed. It is highly dangerous.

PS I once fainted sat in a chair in my local AE. While the doctor was away, I decided to look at my hand injury, and promptly fainted.
 
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Jacobean

Member
So had a guy come round to check the set up and PAT test what could be. Didn't get as many answers as I was hoping but this is what he did confirm:
1) The Laptop plug and power supply PAT tested fine
2) The TV cannot be PAT tested due to the damage on the casing
3) The TV is a Class1 device rather than a Class2 which is unusual for a TV

I've tried to look up the difference and as far as I can see a Class1 is normally made of metal and has an Earth. Does this mean that Earth leakage is more of a possibility? and if it is, could that have gone across the HDMI? If that leakage did go across the HDMI and was relatively low, would it always trip out the RCD's?

The TV casing is plastic so I don't understand why this would be a class1. Was it a later trend to make TV's class2 devices?
 

ufo550

Well-known Member
Class1 equipment works by limiting the size & duration between exposed conductive parts (metal casing of appliance) and extraneous conduct parts (metal pipes e.g.) and the mass of earth, by connecting the appliance to the main earthing terminal of the supply, at a point when a fault would be generated.

Class2 is appliance designed by the manufacture, to insulate (double insulated) the appliance from exposed or extraneous parts. The casing can not become live, under normal circumstance. It would be difficult to make a washing machine as Class2, but a tv or luminarie can easily be.

What is the damage to the casing of the tv?

Some appliances use functional earthing to operate (I’m not clever enough to know why), but only a few mA, that would not be enough to cause an electric shock.
 

Jacobean

Member
Hi ufo550! The pic higher up in the thread shows the damage to the edge and a gap into the TV. So could a few mA being passed through the ear cause some sort of prickling effect and affect balance for a few seconds?
 

ufo550

Well-known Member
Hi ufo550! The pic higher up in the thread shows the damage to the edge and a gap into the TV. So could a few mA being passed through the ear cause some sort of prickling effect and affect balance for a few seconds?
Your pics a bit grainy.

Your headphone leads are not connected to a supply that could give you an electric shock.

I’ve had an unpleasant sensation, when stepping out of my car and placing my foot on the ground. That’s static electricity, not a low voltage electric shock.
 

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