How unsafe can a china/ebay power adapter actually be?

[Razor512]

just discovered the EEVblog youtube channel and am completely hooked on watching all of the videos.

Was looking at the video on the chinese iphone chargers, and decided to take apart a 9V adapter that I got from ebay for $1.50 including shipping from china and the design seemed even simpler. (got it a few years ago to replace the broken adapter for a old land line phone)

took a picture of the inside


Chinese Power Adapter by Razor512, on Flickr

[JoannaK]

Well, if that Transformer (hefty metal Chunk) is well made, then it's most likely ok. It's really old design, though. Nowdays allmost all systems tend to be Switch mode power supplies cause those can be made smaller (and cheaper)

[mikeselectricstuff]

Nowdays allmost all systems tend to be Switch mode power supplies cause those can be made smaller (and cheaper)

..and with more scope for being dangerous.. fire, electrocution, damage to connected equipment, interference....

[c4757p]

Yeah, it's hard to beat mains transformer -> rectifier -> filter capacitor for fewer points of failure. If that transformer's not a piece of shit I have no problem with this.

[tom66]

That cheap cap might go bad after a few years, but screw it, it's $1.50.

[mariush]

That's actually a rather good looking chinese adapter.

Here's what my mom bought a while ago from a "everything for a dollar" type of shop in my country...  it can be scary sometimes:

Spot the typo on the label, the quality of the pcb and the pads, how the solder is dumped on it and how the transformer is connected.  Oh, and to add insult to everything, I think that capacitor was rated for 10v (not that it would have mattered)

 
PS. I actually ordered a cheap 1.69$ usb charger as order filler when buying some stuff from DinoDirect and it arrived a few days ago : http://www.dinodirect.com/eu-plug-usb-ac-dc-power.html   

Insides look like a typical two transistor switching power supply but it's only half wave rectified (single diode on live) and puny caps (2.2uF 400v and a 20uF 10v on the output)... oh... and what i think it's a pcb fuse (trace goes very thin for about half a cm on board)... i'm trying to finish these days my constant current load and I think I'll make a video with tests of this adapter to see what it's capable of.

[Psi]

How unsafe can a china/ebay power adapter actually be?

Phase can be connected to the output due to being assembled by 8year olds with no electrical knowledge.

That's how unsafe they can be.

[SeanB]

Razor, that one has a thermal fuse, a thing often omitted on the cheapies, along with any fuse. Double isolation layers, separate bobbin for the secondary, all makes it safe enough to pass the actual type certification testing.

[FenderBender]

I don't know...For$1.50 shipped, that seems like a reasonable adapter. I don' think it's the best ever but hey, full wave rectifier. Transformer looks okay.

[Razor512]

glad to know it is not too horrible, I have not purchased an adapter from ebay in a long time  (just don't feel right using a $1-2 adapter on a smartphone or other expensive device, especially with the crappy power where I live, power is suppose to be 120V  but when testing with a multimeter, the power will sometimes be 110 and other times it will go up to 135V and since it is a really old house, most of the outlets are not grounded

[T4P]

But it's unregulated 
I bought several brand new power packs for very cheap from a shop in china and they are a genuine surprise ... full-wave rectifiers isolation slots and MOVs(Surprise, surprise)!
the good stuff never seems to go out of china only the bad ones

[SeanB]

One I got in a pack did not even survive more than 2 seconds. plugged it into a socket, turned it on and bang, dead and smoke puff. Cheap n  Nasty junk. Took it apart and clearances were non existent, single diode rectifier and poor quality noname caps inside, along with no regulation or any isolation other than the wire enamel and the single turn of tape.

[JoannaK]

One I got in a pack did not even survive more than 2 seconds. plugged it into a socket, turned it on and bang, dead and smoke puff. Cheap n  Nasty junk. Took it apart and clearances were non existent, single diode rectifier and poor quality noname caps inside, along with no regulation or any isolation other than the wire enamel and the single turn of tape.

I had one cheapo-bran energy-save fluorecent lamp that died at the instant I turned light switch. Well, at least it was easy to replace and it didn't burn down the entire aprtment.

[JoannaK]

Nowdays allmost all systems tend to be Switch mode power supplies cause those can be made smaller (and cheaper)

..and with more scope for being dangerous.. fire, electrocution, damage to connected equipment, interference....

Yep.  In a word     Deadly 

[Fraser]

Due to the horrors that I have seen on the EEVBlog in the past, I no longer buy cheap power supples from China. The risks to safety and the equipment are just too high. Any saving could quickly be lost. The really scary fact is that some of these really nasty SMPSU's are appearing in UK retail shops on the highstreet. They look the business, complete with posh packaging but they are total rubbish inside. I bought a 'quality' Universal Ni-Mh charger block from a UK source for around GBP25 so it wasn't a real cheapie. When I opened it  I was horrified by the poor soldering and total cr*p pcb layout. It was a linear design but the transformer became very hot in use, to the pont that it could not be touched. I binned the unit as a fire risk and poor design. In retrospect I should have reported it to trading standards to get it withdrawn from sale. I have attached a picture of the rubbish Ni-Mh charger.

I bought several Ansmann XBase Deluxe Universal Chargers and they have been great performers. I also just ordered a Turnigy 6 after seeing Dave's review.

My solution to getting PSU's cheaply has been to hoard any high quality power supplies that I stumble upon. Ones that come from quality brands or professional equipment. I have a box full with all manner or current and voltage specs. I asked my office colleagues to save any power supplies from IT kit disposal. Compaq LCD panels use a lovely quality 12v 5A compact SMPSU. I suggest others talk to their disposals officer or IT support team and see if they will save you the power supplies from obsolete kit. On one occasion I managed to buy three new Radio Spares branded power supplies on ebay, rated at 9V 3A ......they cost me GBP3 each and are superb quality. On another occasion I bought a box of 140 (yes 140) 110-240v to 5V@1A USB chargers/power supplies from a Farnell/CPC ebay disposals outlet for GBP9 ($14) for the box full   The reason they sold so cheap....they did not have the mains input plug adapter which is sold separately. Found the PSU on Farnells web site....UK plug part was GBP1.29 each....bought a load of them. The PSU is a FRIWO brand unit, with UK and German approvals. It uses a custom switching controller and is excellent quality. I gave loads away to colleagues to replace cheap Chinese 5V USB chargers that they had been using.

Fraser

[rollatorwieltje]

I had a cheap Chinese power brick that caught fire under a bed... It was part of a cheap LED string with the power brick attached. The 230V input lead was not physically held in place at all. So obviously at some point the copper went and caused an intermittent short, but not enough to pop the 16A fuse.
Luckily someone was in the room when it happened, so the fire was limited to a charred power brick and a very bad smell.

Another 12V 5A brick I received from eBay was so nasty it would show up on my Rigol scope when it was turned on within +/- 2 meters.  I thought the power supply I was working on was bad, but it turned out to be interference from that brick. I popped the damn thing just by drawing 5A from it. After 45 minutes the output capacitors were completely dead and the transformer was well over 100 deg C.

[T4P]

You wouldn't believe me if i told you what a new samsung LED screen (Free if not i would NEVER buy anything from them) came with,
it came with a PSU so noisy that it radiated it's waves onto my table and my volt-stick would pick it up everytime i tapped the table, in fact i couldn't hear it on my speakers but it was very high frequency noise that my volt stick picked up from my speakers 

[mikeselectricstuff]

You wouldn't believe me if i told you what a new samsung LED screen (Free if not i would NEVER buy anything from them) came with,
it came with a PSU so noisy that it radiated it's waves onto my table and my volt-stick would pick it up everytime i tapped the table, in fact i couldn't hear it on my speakers but it was very high frequency noise that my volt stick picked up from my speakers 

I would expect the output of any non-earthed SMPS, good or bad,  to be  detectable on a volt-stick, due to the weak capacitive coupling to the mains input.

[T4P]

You wouldn't believe me if i told you what a new samsung LED screen (Free if not i would NEVER buy anything from them) came with,
it came with a PSU so noisy that it radiated it's waves onto my table and my volt-stick would pick it up everytime i tapped the table, in fact i couldn't hear it on my speakers but it was very high frequency noise that my volt stick picked up from my speakers 

I would expect the output of any non-earthed SMPS, good or bad,  to be  detectable on a volt-stick, due to the weak capacitive coupling to the mains input.

True to behold but my other non-earthed PSU my fujitsu laptop uses is not detectable on a volt-stick

[M0BSW]

Surely the rectifier,has to be a noisey one, those parts diodes approx £1.00, the cap approx 50p,you'd be better off making your own wouldn't you, it would be a lot safer.

[mianchen]

I don't see why people complain so much! $1.5 is roughly £1. With this much, It's barely enough to send a first class letter within the UK. Now you get a transformer + 4 diodes and a bit of PCB shipped all the way across the globe into your hand for only £1. Bargain, I would say! Safety? You might need to pay a bit extra for it. Can't complain for what you haven't paid for, can you?

[tom66]

It's pretty hard to screw up making an iron core transformer and make it unsafe. The core has a minimum size, or it won't work (it'll just burn from too little inductance I guess.) And if you have a certain core size, you can easily space the primary and secondary apart. Safe.

For a quid, it's bloody good. Unlikely to do its rated current and might fail after a year or so. But heh, it's only going to add a bit more to landfill.

[Zero999]

Insides look like a typical two transistor switching power supply but it's only half wave rectified (single diode on live) and puny caps (2.2uF 400v and a 20uF 10v on the output)... oh... and what i think it's a pcb fuse (trace goes very thin for about half a cm on board)... i'm trying to finish these days my constant current load and I think I'll make a video with tests of this adapter to see what it's capable of.

I don't know what makes you say that. It looks more like a transformer with a switch connecting the secondary to different taps and the usual rectifier and capacitor combination.

[peter.mitchell]

I picked up a box (25~) of 16v 2.5a ac wall warts from my old work, best thing i ever did! ac->dc is easy with smps, but they're almost never isolated; these on the other hand all are because they're just transformers.

They were used with small ups/power supplys keeping a float voltage on the battery, and providing transistor outputs for low battery and input fail

[mariush]

Insides look like a typical two transistor switching power supply but it's only half wave rectified (single diode on live) and puny caps (2.2uF 400v and a 20uF 10v on the output)... oh... and what i think it's a pcb fuse (trace goes very thin for about half a cm on board)... i'm trying to finish these days my constant current load and I think I'll make a video with tests of this adapter to see what it's capable of.

I don't know what makes you say that. It looks more like a transformer with a switch connecting the secondary to different taps and the usual rectifier and capacitor combination.

That quote is about ANOTHER adapter i have on my desk, not the one that I attached pictures of.

Here, posting picture with it to prevent any further confusion... I wanted to test it out and post a thread with it but whatever: