Can a usb charger kill a phones touchscreen?

Forums › Off topic › Can a usb charger kill a phones touchscreen?

mb82

132 posts

Master Geek

# 204442 1-Oct-2016 17:54

Curious, I had an iphone, touchscreen started playing up, got a cheap replacement android, did not notice touch screen issue at first, plugged into same usb charger now occasionally the touch screen glitches.

With my old iphone I could feel voltage/tingling on the phones casing while charging, I always assumed this was a grounding fault of the phone itself?

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1906 posts

Uber Geek

# 1643917 1-Oct-2016 18:01

Yeah I think you should be throwing out that charger, destroying it if you can so someone else doesn't pick it up.

Was it a cheap charger? Always amuses me when people buy the cheapest charger they can get for their $1000 phone.

mb82

132 posts

Master Geek

# 1643925 1-Oct-2016 18:18

Standard apple wall charger

MadEngineer

1906 posts

Uber Geek

# 1643930 1-Oct-2016 18:43

Not the recalled model by any chance?

michaelmurfy

Mr Snotty
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# 1643932 1-Oct-2016 18:50

2 people support this post

MadEngineer: Not the recalled model by any chance?

Or a fake Apple charger (tonnes of those around).

mb82

132 posts

Master Geek

# 1643934 1-Oct-2016 19:14

MadEngineer: Not the recalled model by any chance?

I remember seeing that recall at the time and checking, I somehow determined mine were not part of the recall? maybe from my phones serial number. Looking at it again I believe it is part of it, infact I have two of them. Thinking of it the charger was from my old iphone, so serial number would not matter.

Trying to find what the actual issue / reason behind the recall is.

Will take them in next time im in town

mb82

132 posts

Master Geek

# 1643940 1-Oct-2016 19:24

does not look related:

https://www.youtube.com/watch?v=dP6sEH8hPjQ

Fred99

8723 posts

Uber Geek

# 1644047 2-Oct-2016 08:31

That "tingly" feeling you report suggests AC, and the fact that you could feel it suggests that there's a lot more than 5v getting through.

Wall-wart chargers should be class II double insulated, which means as well as well as being built with double layer of physical insulation between anything at mains voltage inside the device, the electronic / electrical components inside - even if they fail - the output and any exposed metal etc should still remain electrically isolated from the mains voltage side of the device.

I very much doubt that a "genuine" charger should fail the way you describe - that would be very unusual. Knock-off imitation chargers from China - for sure. Don't use it - but don't just throw it out yet either, it might be a serious safety hazard, you're probably not the only person to have one, the products should probably be recalled and at least listed on official websites like this: https://www.recalls.govt.nz/ and even if it's fake - the maker would probably want to know so they can put some warning out, and it may be newsworthy enough to get publicised in the media.

CYaBro

3169 posts

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# 1644053 2-Oct-2016 09:06

Can you post some photos of the charger in question?

The recall from Apple is for the power plug adapter part, not the charger itself.
IE the removable part that has the pins on it that fit into the wall power socket. The part you would change if you needed to use the charger in another country.

If yours is round then it should be replaced.

mb82

132 posts

Master Geek

# 1644131 2-Oct-2016 13:23

Fred99:

That "tingly" feeling you report suggests AC, and the fact that you could feel it suggests that there's a lot more than 5v getting through.

Wall-wart chargers should be class II double insulated, which means as well as well as being built with double layer of physical insulation between anything at mains voltage inside the device, the electronic / electrical components inside - even if they fail - the output and any exposed metal etc should still remain electrically isolated from the mains voltage side of the device.

I very much doubt that a "genuine" charger should fail the way you describe - that would be very unusual. Knock-off imitation chargers from China - for sure. Don't use it - but don't just throw it out yet either, it might be a serious safety hazard, you're probably not the only person to have one, the products should probably be recalled and at least listed on official websites like this: https://www.recalls.govt.nz/ and even if it's fake - the maker would probably want to know so they can put some warning out, and it may be newsworthy enough to get publicised in the media.

I am sure the charge is genuine, yes it is round, and has the numbers on the inside indicating replacement. If the recall is due to the fault in the video, then that is not part of the problem. Not saying they shouldn't be replaced. A google suggest it is somewhat common to feel tingling. How can I measure the ac voltage on the phones casing?

MadEngineer

1906 posts

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# 1644196 2-Oct-2016 15:50

You don't measure it. You throw the charger out.

Those making fake products don't give half a bee's dick about the safety of their products.

richms

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# 1644243 2-Oct-2016 16:08

Very common to get enough leakage on the output. There is a capacitor between the output and the mains to reduce RF interference from the power supply, and it will leak enough that you can sometimes feel it.

Only takes a few 100uA to cause you to feel it on a metal phone as you move your finger over it, not a safety hazard at all. Touchscreens usually have something in their scanning to get around it so not sure why you would be seeing it affected like that. I have only seen them go loopy when on a crap powersupply that put out massive ripple on the 5v

Richard rich.ms

MadEngineer

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# 1644245 2-Oct-2016 16:20

Typically you can feel AC with dry hands from around 50volts. There definitely shouldn't be that voltage on the DC side of your charger.

Sure, keep plugging your expensive devices into it and risk death or simply throw it out.

Fred99

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# 1644268 2-Oct-2016 16:37

richms:

There is a capacitor between the output and the mains to reduce RF interference from the power supply, and it will leak enough that you can sometimes feel it.

I do not believe that at all.

That would carry the risk that if the capacitor fails (hardly uncommon), then it would put 230V to the 5V output, it would be an extremely dangerous design (with potentially lethal consequences).

Sh!t quality knock-offs more likely to use things like poor quality cheap transformers for example, which don't have adequate insulation for a Class II device between primary and secondary windings.

richms

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# 1644275 2-Oct-2016 16:46

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Fred99:

richms:

There is a capacitor between the output and the mains to reduce RF interference from the power supply, and it will leak enough that you can sometimes feel it.

I do not believe that at all.

That would carry the risk that if the capacitor fails (hardly uncommon), then it would put 230V to the 5V output, it would be an extremely dangerous design (with potentially lethal consequences).

Sh!t quality knock-offs more likely to use things like poor quality cheap transformers for example, which don't have adequate insulation for a Class II device between primary and secondary windings.

That is why they are supposed to use actual class Y rated capacitors for it. Without them it will generally not pass the emissions tests. Different designs either just put a single cap to 1 side of the AC or have a pair of them, one to each side so it makes somewhat of a divider which lowers the voltage present. The crapness of most clone adapters will usually leave them out since they dont care about compliance, and they will just have nothing there.

If you get a digital multimeter between the shield of most wall warts and real earth, you will see 60-80v present, Touch it and it drops to near nothing because of the impedance of those caps.

Richard rich.ms

MadEngineer

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# 1644277 2-Oct-2016 16:50

Fred99:

richms:

There is a capacitor between the output and the mains to reduce RF interference from the power supply, and it will leak enough that you can sometimes feel it.

I do not believe that at all.

That would carry the risk that if the capacitor fails (hardly uncommon), then it would put 230V to the 5V output, it would be an extremely dangerous design (with potentially lethal consequences).

Sh!t quality knock-offs more likely to use things like poor quality cheap transformers for example, which don't have adequate insulation for a Class II device between primary and secondary windings.

He's correct:

https://youtu.be/wi-b9k-0KfE?t=13m28s

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