Electrical tingling question

[Martin T]

Maybe I can pick the brains of some of you who actually understand electrical stuff - this is over my head and I am keen to identify the problem asap.

I initially thought I'd identified a problem with my guitar amp. Last night, when plugged in and playing through the amp connected to the mains, i picked up my iphone 5s, which was charging via usb plugged into my laptop, and the laptop itself is plugged into another mains outlet on the other side of the room. When picking up the charging phone with my right hand, which is aluminium, i noticed a non-painful but unmistakeable electrical tingling, NOT in my phone hand, but in my left hand on the guitar strings.

So I assumed it was the guitar side, went away and read a load of stuff about faulty guitar amps and became a bit paranoid that I need a new amp or at least a professional service for the existing one. I decided not to play connected to the amp again until the amp had been checked, as well as the mains outlets where this happened.

Fast forward to today, and I started to wonder if something else in the chain was at fault - when i remembered macbook pros are notorious for giving a mild electric sensation when plugged into the mains, and the user touches the metal casing while their person is grounded in some way.

I didn't think a phone charging via usb would be capable of doing anything similar - but according to various stories on the internet iphone 5s owners have reported similar mild shocks and/or tingling from their phone when connected and charging.

So, this time while holding my charging phone in my left hand (again connected via usb to my laptop, laptop itself plugged in to the mains, albeit a different outlet downstairs this time) I cautiously put the back of my hand against the radiator (ground as far as i understand) to see if the pattern repeated. I am fairly certain I felt the same kind of tingling building on the back of the radiator hand (equivalent of guitar hand last night), so immediately pulled my hand away to err on side of caution.

I then remembered my laptop charger has a mainland euro style plug (i think type e or type f) which i have plugged into a british three pin adaptor, which as far as I can tell does not sync up with the 'ground' or earth pin on the plug.

Could that be the culprit, or some combination, or could it be the house mains?

This is a bit of a splurge so apologies for that, like I say I am no electrician and might have everything back to front here - please forgive me if I am talking absolute rubbish but hopefully some of you will have some logical advice on how to eliminate the parts of the chain.

 

[mwatsonxx]

Firstly, unplug the appliances that you suspect are causing the tingling. You then need an electrician to inspec/test the earthing and bonding in your house, and test the suspect appliances.

 

[ericmark]

Electric can clearly flow though wires, but it can also flow with capacitive and inductive links, so yes one can get shocks from items which are in theory isolated. However because the current is limited these capacitive and inductive links are considered as harmless.

Looking at extreme cases in the building of Sizewell "B" power station we were getting sparks around an inch long from the crane hook caused by nothing more than high wind blowing past the crane building up static electricity.

However in the home as you have already highlighted the problem is which item or items is/are at fault. So we assume it is a real electrical fault, until we can prove otherwise. In old days we stopped having electric shocks by bonding all metal together, the idea is two independent faults can't result in two bits of metal within reach of each other having a different potential. Today we have double insulated stuff called Class II and extra low voltage stuff called Class III and in theory every item should have symbols on it to show what it is.

This means the transformer isolates and the little square bit at bottom means it has some overload device so it can't be damaged causing the transformer to allow a connection between mains and the outlet. However finding the sign is not always that easy, build a PC and the power supply should come with the sign on it and a separate sheet to stick on outside of the PC, but often the stickers are either not included or are not used. Also other countries have their own special signs which mean the same.

This sign means double insulated and the item does not require an earth connection, however where multi items are connected together as with say a drill and a drill stand with a magnetic bottom, you need to see the sign on both items.

This one means it is class III and uses a separated extra low voltage supply. So step one is check if the items are designed to work without an earth. So that's a good start equipment wise.

Now let us look at the house, today our houses should have 30 mA at 40 mS RCD's fitted, which will normally trip before we touch faulty equipment, it does not actually stop us getting a shock, or even limit how big of a shock, although it does limit the time, but in the main leakage will happen through other things than the human body first, so it will trip before we touch it. If not already fitted you can get through plugs to all the protection. This is likely the best short term option until you work out exactly what is wrong.

The house can have three earth systems TN-C-S, TN-S and TT, with the latter we always have a RCD/ELCB although it may not be 30 mA, a 100 mA was popular at one time, even 300 mA and with old houses you can still some times find the old now banned ELCB-v which is normally not built into the consumer unit (CU) and often has a large yellow test button. Likely best bet here it to take a picture of consumer unit and DNO head and let the guys on here try to identify what you have.

This plug in RCD costs just £7.18 that would seem the best quick fix option if you don't have it built into the consumer unit.

But really only way anyone can say if safe or not is to actually go there and test, it can't be tested on a forum.

 

[flameport]

I then remembered my laptop charger has a mainland euro style plug (i think type e or type f) which i have plugged into a british three pin adaptor, which as far as I can tell does not sync up with the 'ground' or earth pin on the plug.

Either get an adaptor which connects all 3 pins properly, or change the plug for a UK one, or get a new power lead with a UK plug.
The earth pin is there for a reason - not connecting it will result in problems.

 

[Martin T]

Either get an adaptor which connects all 3 pins properly, or change the plug for a UK one, or get a new power lead with a UK plug.
The earth pin is there for a reason - not connecting it will result in problems.

Thanks for all of your replies. I will be buying a new laptop charger after reading about how unreliable the knock offs are.

So do you think it sounds like it is coming more from the laptop/phone side of things rather than guitar amp?

I was confused because it was the guitar strings which felt tingly originally but not the phone, but if the guitar was plugged in to a switched on amp am i right in thinking touching them provides a path to earth, so would i feel it there even if it is not the guitar per say that is 'live'?

I always found electric circuitry the most non-intuitive thing to understand when doing physics at school, as you can probably tell.

 

[Cigaro]

This is actually fairly common even with (some) properly-functioning chargers and is (in most cases) caused by a suppression capacitor connected between the output and input side of the switching transformer inside the charger.

The capacitor will pass a small (but enough to feel) amount of current. In my experience, iPad chargers are quite notable for it - both of the ones we have have done it since new.

Having said that... if your laptop charger is supposed to have an earth connection and doesn't, you need to remedy that no matter what. In some chargers the negative of the output is connected through to earth and this would prevent the "tingling" effect if the earth was in place.

 

[securespark]

Is it an earth pin or is it plastic?

 

[Martin T]

Is it an earth pin or is it plastic?

The uk adaptor has plastic 'earth' pin - the actual charger plug itself has a euro style connection either type e or f as displayed here:

https://www.worldstandards.eu/electricity/plugs-and-sockets/

So i am guessing that is not earthed properly when used with my adaptor.

I am away out to buy a mac charger after having read horror stories about the cheaper third party ones. Just wish they weren't so expensive.

 

[flameport]

So i am guessing that is not earthed properly when used with my adaptor.

That's exactly it.
Take a hammer to the adaptor to prevent it being used again - it's defective by design.

horror stories about the cheaper third party ones.

which include damaging/destroying the device they are supposed to be charging.
As well as the fire and shock risks.

 

[Martin T]

That's exactly it.
Take a hammer to the adaptor to prevent it being used again - it's defective by design.

Thanks for your advice.

Does it sound right to you that I would feel the tingling effect touching the guitar or radiator - i.e. the grounded element, rather than the phone as connected to the laptop circuit?

 

[flameport]

Certainly possible, it all depends on which hand has better contact to the metal items, whether your body is near earth potential or that of the phone and various other factors.

 

[SimonH2]

OK, I can provide some specific knowledge here, having looked into this in the past.
The Magsafe power supplies used for quite some time have a 2 pin figure of 8 connector built in, to which various cables or adapters can be attached. There is a metal button which is used as a mechanical key, especially when using a "duckhead" adapter.
If you look at this item on eBlag you can see how the adapter has a standard figure of 8 connector and a slot that the button slides into for mechanical support. You can also see in the picture the metal button on the power supply.
This metal button doubles as an earth connection depending on what adapter/cable is connected. I've found that the "13A plug" adapters I have all have plastic pins and don't earth the supply, while the cables I have (some that came with 13A plug, one that came with a European plug which I cut off and replaced) are 3 core and do connect to the button. Using such an earthed cable removes the tingling I sometimes get in the palms of my hands if I use the unearthed adapter.
On one occasion, I used my DMM and measured something like 90V on the laptop casing. Clearly the load presented by the DMM dropped the voltage somewhat, but still a not inconsiderable voltage. IIRC I also tried measuring the current available, and found it to be very low in value - perhaps not, no mention of it in any of my posts on the topic.

 

[John D v2.0]

Cheap chargers can have poor separation between mains and elv sides, leading to live conductors being connected through to the output side. If those are in turn connected to the case of the device, depending on polarity you could get a fair shock when also touching something else earthed I otherwise connected to the electrical system

 

[Tdw1982]

I get it with my iPad and iPhone on normal Apple chargers.
I can’t feel it if I gently run a finger over any other metal object whilst holding my phone (while charging), so if I am turning on a touch lamp for example.
Never worried about it.

 

[ericmark]

The type E and F euro plug can be combined as one plug so it fits in either a German or French socket, it has both the side earth bars and the earth hole.

this adaptor you can see has the side connectors and if the plug also has the side connection to earth not problem.

There is a two pin version of the Euro plugs

these do not have an earth and the converter shown will not accept any plug needing an earth so is reasonable safe, also since screwed onto the plug it can be fitted to items sold in the UK. Although this converter

will also not take any earthed plug, because it's not fixed to lead it can't be used by sellers in the UK to convert from EU to UK plugs.