"nokia" 5v charger...

[caboose89]

Hi all!

This is my first post, so go easy

I ordered a pair of second hand nokia Bluetooth headphones last week, with the listing saying they weren’t charging properly, and the battery only lasting half an hour. A bargain at a fiver, I thought. My plan was to crack them open, and get a new battery.

Then they arrived...
and i saw the charger.
Living in the uk, alarm bells started ringing when it came with a two pronged EU charger.
It looked genuine from the printing on the case, but I was still wary.
Then Dave's voice was heard in my head; "Don't turn it on; take it apart".
So, for your delectation, here is what I found ( see attachment ).

It looks like it was intermittently charging because the solder holding down the 400V capacitor is loose.
No fuse. No full rectification. No opto-isolator.
The worst part, however, is the un-snipped leg of the transistor. While it isn't touching the nearby terminal, it is resting just above ( about 0.5mm) the trace... which is directly connected via the diode to the mains live rail. And the leg of the transistor? Ah, it’s only directly connected to mains neutral. 
All I can say is thank god I don’t have a euro adapter, and thank god for Dave Jones and his catchphrase!

Hope you all enjoyed!

Caboose

PS: Can anyone recommend anywhere I can buy a uk, electrically sound USB charger? I want to get one, and cannibalise it to charge the headphones. I’ve nicked a genuine nokia charger from someone for now, but I have to give it back.

PPS: While I know my way around electronics in general, can someone explain why the main electrolytic doesn’t explode when the live rail goes into reverse phase? I realise the other leg is on the right side of the diode, so the PD will never be +240 across the legs the wrong way, but doesn't having the wrong polarity on one leg for 50% of the time have a detrimental effect?

PPPS: The board is in the bin, but I've kept the lead 

[SeanB]

I have the real Nokia that that one is a knockoff of right here. Differences are the real one is laser engraved and not screenprinted ( the 2d barcode is crisp and not smeared) and the real one is a little bigger and has a better moulding.

The diode is a half wave rectifier, the capacitor just has a much higher ripple current through it, and will fail in the usual spectacular way rather much sooner than with a full bridge, but the manufacturer does not care, as it is out of the taillight warranty by then, and he saved 3 diodes cost as profit, along with the cost of the solder and board space. He gave extra value with this one, that uncropped piece of lead was his profit on the unit, as the cut leads are sold for the scrap copper content.

[amyk]

There is no optoisolator because this is an unregulated SMPS of the simplest form --- a blocking oscillator with a secondary output coil.

While I know my way around electronics in general, can someone explain why the main electrolytic doesn’t explode when the live rail goes into reverse phase? I realise the other leg is on the right side of the diode, so the PD will never be +240 across the legs the wrong way, but doesn't having the wrong polarity on one leg for 50% of the time have a detrimental effect?

There's no reverse voltage because the diode doesn't conduct for the negative half of the cycle.

What's more worrying about this one is the insufficient creepage between primary and secondary.

[Stephenniall]

Its scary how many of these chargers are used every day ! - In the UK Your probably best going to The Carphone Warehouse for a charger, Or another shop similar to that. I wish Nokia would start to use charging through USB like all the other bloody manufacturers !

[Kremmen]

I think all recent Nokias charge from USB. At least my Lumia does. Haven't seen anything else recently.

[lapm]

i have couple year old Nokia phone, Charges just fine from usb (has that micro-usb connector). Heck it even has smalll white led to indicate, connected and chargeing states...

[SeanB]

Old E52 which charges with micro USB, and I have the same cable now to use with the new Samsung. Most phones from the last 2 years use micro usb, aside from those from a certain Cupertino manufacturer, though they have to include an adaptor to sell them into the EU.

[mariush]

I still use a Nokia 1200 that doesn't have usb.  The charger is still 5v or around that value, but the jack is a tiny regular one, like the headphones jack.

Anyway, yeah, horrible charger, not sure if they could have made it cheaper. Actually yeah, I know... those metal connectors. I guess it was too hard to stick a solder gun and solder wires in that plug.

[Simon]

I fixed a powerpack for a set of scales at work that had a "flying rectifier"  yes 4 diodes soldered together in mid air.......

[peter.mitchell]

On the Nokia line of smartphones and feature phones they use the standard micro usb but on things like bluetooth headphones/headsets and dumbphones they use the classic cylinder jacks.