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240V Power Socket with USB outlets leaks current/not grounded ? Answered

I just got a 3 pin wall power socket (240volts/EU style) that comes 2 built in USB charging ports.

I replaced my wall power socket with it and both the USB charging ports works fine and so does the power socket (when I connected my 240volt desk lamp to it).

However, when I happened to make a call on my iPhone whilst it was charging (from one of the usb ports), there was a "tingling" sensation when I held the phone to my ear.  This is a repeatable process... turn the switch off/disconnect from the USB port and the "tingling" goes away, turn it on/connect the phone to the USB port and the "tingling" is back again.

There is obviously a grounding/current leakeage problem from this "Socket".  I can't feel the "tingling" when the connected phone is being held in my hand. It is very apparent when the phone is held next to my ear.  

I have ascertained that the connection to the power socket is correct ie.  Live, Neutral and Earth are all correctly wired.


1.  Is there a way to detect this leakage other than only using my ear ?  ( I need to show the manufacturer that this is a real problem either with a video or be able to measure this leakage objectively).  Is there a electrical device /detector for this ?

2.  How dangerous is this situation ... Could it have electrocuted my family ?

3.  What is the cause of this ?  Is it because of poor earthing/grounding in my house wiring ?


Hi. Did you manage to sort this. I am trying to do something similar

No resolved technically. I sent the "leakage current" I measured (see one of my earlier posts) to the supplier and was given a full refund. I have since found even some of the more reputable chargers have similar leakages.

If it is in any way like old amplifiers (the ones with metal casings meant to connect a vinyl player) then try to reverse the cables on the socket.
Not sure if they are properly labeled, if you switched them by mistake or if it is a cheap and possibly dangerous china model but try the switch and check if your ear feels better.

Old the old amps you could slide your finger over them it felt like the metal was humming and with a slight rubbery texture, switch the plug in the socket (EU style) and the things feels like any other metal case.

1. It is called a voltmeter, connected to the metal part and good ground like your water mains or Earth from a power socket.
2. I don't know if you did but if they are still alive I guess it means all is fine.
3. See above explanation plus:
In most cases it is a high frequency voltage with the 50Hz signal from the mains voltage over it.
An oscilloscope would certainly help you to show it.
Usually originating from badly designed electronics or in the case of very old devices as an accepted thing.
Without knowing the cause of your problem I would assume you got a china knock off with some filters and safety features missing.
If you can't find the correct labels for the electrical safety that correspond to your country bin it or get your money back.

@Downunder35m, thanks for the reply and 1 further question... this leakage current ... I am assuming it to be in the 100's of uA range.
Reading your comment wrt "high frequency voltage with the 50Hz signal from the mains voltage over it." .... is this leakage current likely to be a dc or ac current ? (I have been trying to measure a dc current !)

You will have a hard time measuring it at all.
Your only real chance is an oscilloscope.
Even good digital multimeters struggle with these high frequencie overlays.
You can be almost certain it will be either a pure AC signal or a high frequency DC voltage with the AC on top of it.

Here's my attempt at measuring the leakage current... my electrical/electronics circuit theory is some 40+ years old and somewhat rusty ... so please correct me if my method is in anyway in-correct.

1. I connected a 1k ohm (measured 991 ohm) resistor between the case of the iPhone and the power socket Earth and measured the voltage across the resistor with a scope. See attached Figure. With peak amplitude of 0.44volts across 991 ohm, that's ~0.4 mA of leak current (is there a proper term for "leak current" ?).


Try again with 500kOhm or 1M Ohm ;)
You are dealing with extrem low currents here, your 1k resistor will break the voltage down.
But it shows that you have nothing to fear, just like in the old days it is just annoying.
You could fix it with proper filters in your socket but the safe thing to do would be to dump it.


2 years ago

@rick harris, thanks for the great video. I can confirm that the socket I have here is also a Chinese made cheapy. This is why I want to be able to show/prove in a video that this socket is not up to scratch/might even be dangerous.

@Downunder35m ... I live in Asia, so I know what you mean about wrt electrical items lacking in safety standards ... I just had a 50W, 240volts to 110volts transformer (wallwart) literally come apart because the plastic casing is brittle. (LOL ...wrt duct tape in your comment .... they had better use non chinese made duct tape ...)

@steveastrouk ... unfortunately, my (very old) trusty Fluke 73 multimeter was unable to detect any current leak .... it's resolution is only down to 10mA (I guess I would have been in deep do-dah if the leakage is in the order of 10's of mA ?). WRT: house wiring .... I have checked that the Live, Neutral and Earth are all going to the correct socket posts and measured the voltage to be as expected. For now I have ruled out the house wiring. (This was my first suspect).

Thanks guys for your feedback. I am going to try to get my hand on a meter that measures in the uA range.

I opened a few cheap wall warts already and was shocked by the low part count - not sure if I want to know what the video reveals LOL
Here we have enough problems with the standard sockets you can buy in the shops.
Due to a loophole everyone can sell these things without any qualification or legal consequences if something goes bad once the customer left.
Common problems include:
Plastic getting brittle after a few years - the entire things falls apart.
Switches failing - either getting stuck on burnt contacts or fail to close.
Contacts for the plug failing - overheating is a common problem as only thin sring steel is used instead of thick contact areas that can handle the rated current.
I had one of them in my house and the connected heater started to fail randomly.
A quick check showed no symptom but when I wanted to plug it back in I could it only get it half way and the socket was slightly brown.
Since I am renting I contacted the agent and a sparky replaced the entire lot in the house after realising all sockets are the same.
Should have kept one or two, they would be a great addition to your vid.
It is actually quite shocking when you start checking electrical things that originate in Asia...
Imagine going to space in an asian space shuttle:
Has anyone some duct tape left, I think our main window is leaking....

1.) Yes, a cheap ammeter/voltmeter will show what you need to see.

2.) Yes.

3.) Probably cheap Chinese crap, your profile doesn't say where you are in the world to take it further. Its also not impossible you may have a wiring problem

It has to be said though, that you can feel a lot lower current than is a real problem. .