Plug whine

[Haiku32]

My phone takes a very short time to charge (about an hour) and holds its charge for a good while (about a week before I need to charge it again) doing general phone stuff.

I've recently noticed that when I'm charging it and it's been charging for over an hour the plug makes a very loud, high pitched whine. I've taken this as a sign that it's finished charging. I think it's something to do with the transistors or whatever, but could it actually be a sign of a faulty plug?

I mean, it's worked fine this long and is still working fine, but if there's a chance that it could damage my phone, or worse start a fire, then it's no bother to replace it. Is this normal or does this sound like the beginnings of a problem?

[Will404]

Its probably a resistor, or something getting rid of the voltage, but just check it's not getting tooo hot, or making any odd smells

[Haiku32]

It doesn't get hot or make any smells, so is this just normal then?

[Will404]

I duno, none of mine do it, sony erricson, old and new nokia, and motorola (all the phones in the house), but maybe you just have better ears than the genoral public. If it is not getting hot then its not going to cause a fire, what phone is it, you could search on google and see if anyone else has the same thing, or if its really concerning you, you could go into the shop you got it and ask.

But its probably some form of resistance, my speakers buz when off, and my stereo makes a humming noise nd I think my brothers digital photo frame squeels, but these have all been working for a couple of years now with no ill effects, so you will probablly be fine

[Haiku32]

I've searched on google and couldn't find anything specific to my phone (k850i).

I guess I can live with if it won't do any harm, cheers .

[Will404]

for nokia, but seems the same kinda thing
https://www.expansys.com/ft.aspx?k=33986

Edit well put my W580i on to charge, and with my ear against the charger can hear a faint ticking noise like some kind of old clock. Will post back when charge complete.

[DDY]

I've got a few transformers which whine including my SE K800i charger, it whines while charging and louder when the battery is full. The whine was there when I first got the phone (charger) two years ago, it still does it and hasn't caught fire.

It's safe to continue using your charger, it's not uncommon for transformers to emit a high pitched whine during normal operation.

[Will404]

Oww I just made me think of thouse Ndiva GPU's a while ago which made a whineing noise when on low power/2D mode, nothing wrong with them, just the transformers getting rid of extra power

[Haiku32]

Upon closer inspection (ear right up to plug, felt very safe ) it just sounds like little short bursts, then when you switch the plug off it sounds like a fan powering down. Oh well, thanks for reassuring me guys .

[Will404]

any time m8

[Lourdes]

This is something that really annoys me, I've a few transformers that do it and can't have them in the same room as me.

[TAKTAK]

You get whine due to the mechanical resonance of the (toroidal?) coils in the transformer (http://en.wikipedia.org/wiki/Mechanical_resonance), due to the frequency of the signal passing through said coil (probably ~50Hz for mains), if said freq' is in resonance (driving freq = to natural freq) (http://en.wikipedia.org/wiki/Resonance) to the coil structure it's self then it can cause the structure to oscillate, which in turn causes the air around it to move, which in turn causes the noise which can range from high pitch to low pitch, it's usually too high for the human ear to hear >20000Hz, meaning that most of the time we don't hear it...

Anything with coils can have the effect:

TVs, Monitors, GFX cards, Mobos, PSU, Stereo, Transformers, etc, etc

[Will404]

You get whine due to the mechanical resonance of the (toroidal?) coils in the transformer (http://en.wikipedia.org/wiki/Mechanical_resonance), due to the frequency of the signal passing through said coil (probably ~50Hz for mains), if said freq' is in resonance (driving freq = to natural freq) (http://en.wikipedia.org/wiki/Resonance) to the coil structure it's self then it can cause the structure to oscillate, which in turn causes the air around it to move, which in turn causes the noise which can range from high pitch to low pitch, it's usually too high for the human ear to hear >20000Hz, meaning that most of the time we don't hear it...

Anything with coils can have the effect:

TVs, Monitors, GFX cards, Mobos, PSU, Stereo, Transformers, etc, etc

Yer, what I said *kinda*

[peterb]

You get whine due to the mechanical resonance of the (toroidal?) coils in the transformer (http://en.wikipedia.org/wiki/Mechanical_resonance), due to the frequency of the signal passing through said coil (probably ~50Hz for mains), if said freq' is in resonance (driving freq = to natural freq) (http://en.wikipedia.org/wiki/Resonance) to the coil structure it's self then it can cause the structure to oscillate, which in turn causes the air around it to move, which in turn causes the noise which can range from high pitch to low pitch, it's usually too high for the human ear to hear >20000Hz, meaning that most of the time we don't hear it...

Anything with coils can have the effect:

TVs, Monitors, GFX cards, Mobos, PSU, Stereo, Transformers, etc, etc

Hmm - not exactly...(but close )

A mains transformer consists of a laminated iron core (basically) - it is laminated for efficiency reasons (I won't go into skin effect) and each lamination is insulated from the next (electrically) and also split to reduce circulating currents and power loss in the core. However the iron tends to flex slightly with the alternating voltage, and this causes the hum at a frequency of 100Hz. Why 100? Because mains is 50Hz, but one cycle is both a positve and negative excusio, so the iron flexes twice for every one cycle.

A switched mode psu (as many of these plug type devices are) works in a different way. The incoming mains is converted to DC, and then powers a high frequency oscillator. This then goes to a transformer (for electrical isolation purposes and to transform the voltage). High frequency transformers are smaller, and use a ferrite core more efficient. Normally you can't here any noise because the frequency is too high. Voltage regulation is by controlling the duty cycle of the oscillator, so if the loading changes, then the frequency of the oscillator may change, and could bring that within your hearing range.

As to why it has recently started - it could be that with age something has worked loose. The transformers are often glued to the cct board to minimise vibration, and that may have failed. It could be a capacitor that is on the way out and that is 'singing', but without opening it up (don't, its dangerous!) it is difficult to tell. However from your subsequent description I think it is just the normal effect of the voltage regulator, and the transformer has just become a bit noisier because of age (as I described earlier).

If its working, I'd be inclined to leave it. If it bothers you, replace it. If it does fail, it is likely to fail safe.

[TheAnimus]

I thought that some people used a rectifier, then a resistor to get a voltage drop, before going into a standard regulator.

Then again i've never looked at a mobile phone charger, but its certainly a cheaper circuit for very low power devices!

[Agent]

How did you manage to type all that without mentioning magnetostriction Peter?