dcollis
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Exploding Pi

Sat Mar 01, 2014 10:03 am

I suspect that this is the result of a dodgy charger, but take a look at these pictures:
Image
Image
Image
https://picasaweb.google.com/1131623384 ... redirect=1

The Pi was plugged into a surge protector and into my TV (it's our one of our XBMC Pi devices). There was an extremely loud bang (enough to make the baby cry) and a extremely worrying flash and a smell of burning.

The back had been blown off the Samsung charger and the Pi was burned along with the case around where the charger was plugged in.
I unplugged it, very very carefully.

The HDMI swicher it was plugged in to also no longer works, but thankfully everything else works.
So, was it the charger? Is this a problem anyone has seen before?

jdb
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Re: Exploding Pi

Sat Mar 01, 2014 10:12 am

That is a high-energy flash. The only possible source is the mains-level voltage supply to the charger.

This means that the high-voltage insulation between the primary and secondary side of the transformer has failed somehow: either through the primary side exploding and contaminating the board such that there was a flashover or through failure of the transformer itself.

The high voltage then took the path of least resistance to ground: across the pins on the micro-USB connector on the Pi. Stray voltages probably made their way through into the HDMI switcher as well.

- What is the output rating of that charger?
- Is there any indication that it may be a "fake" charger?

Can you post more detailed pictures of the top/bottom of the PCB inside of the charger and also of the charger rating label?
Rockets are loud.
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jamesh
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Re: Exploding Pi

Sat Mar 01, 2014 10:14 am

Blimey, never seen that before. Looks like a lightening strike, but that would have taken out more stuff.

I'd guess the charger, since that is upstream of the Pi, unless the Pi shorted and overloaded the supply.

In other words, no idea.

EDIT: JDB beat me to it, and knows more than I do!
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GTR2Fan
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Re: Exploding Pi

Sat Mar 01, 2014 10:17 am

A scorch pattern that size and colour suggests a failure of isolation between the mains and low voltage sides of the power supply to me. I've had a USB-output wall-wart spontaneously explode on me in the past with similarly devastating results. Luckily mine only had a £200 sat-nav plugged into it at the time. :(
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Re: Exploding Pi

Sat Mar 01, 2014 10:18 am

What else was plugged into your RPi at the time? Did you have a back powered USB hub?
Are you sure the Samsung charger was a genuine part? Or was it a Chinese fake from fleabay? Do you need to contact your local Trading Standards? Or Samsung?

I'm surprised that you didn't trip your RCD (if you don't have an RCD, then it's time to get your whole house rewired). You should have isolated the circuit at the consumer unit circuit breaker before pulling the broken charger, 230V WILL KILL.
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dcollis
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Re: Exploding Pi

Sat Mar 01, 2014 10:36 am

It did trip the rcd, forgot to mention that.
There was nothing else plugged into the Pi - just the HDMI, network and power cable.

More pictures of the charger here:
https://picasaweb.google.com/1131623384 ... redirect=1

I have my suspicions that it might be a fake Samsung charger. I think it's a backup rather than one that came with a phone. I'll check my Amazon purchase history and see if I can find it.

dcollis
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Re: Exploding Pi

Sat Mar 01, 2014 10:43 am

Mystery solved, I think: http://www.amazon.co.uk/gp/product/B005UDFFBQ/

Pretty sure it didn't have any 1 star reviews when I bought it (I would have checked that), but it has plenty now.

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Re: Exploding Pi

Sat Mar 01, 2014 10:51 am

dcollis wrote:Mystery solved, I think: http://www.amazon.co.uk/gp/product/B005UDFFBQ/

Pretty sure it didn't have any 1 star reviews when I bought it (I would have checked that), but it has plenty now.
You should talk to your local Trading Standards about that. There's BS1363 for ALL electrical items sold in the UK. Trading Standards should have a word with Amazon to get that product withdrawn.
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Re: Exploding Pi

Sat Mar 01, 2014 10:52 am

If that's a genuine Samsung charger then I'll eat my hat.
Rockets are loud.
https://astro-pi.org

dcollis
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Re: Exploding Pi

Sat Mar 01, 2014 10:55 am

Mixed reviews - looks like the seller that I bought from "abc radio", is no longer one of the sellers listed in Amazon for it. So, quite possibly if you order this now it would be fine.

Abc radio also goes by "AFC EXCLUSIVE LTD".

Looks like they've given up selling: http://www.amazon.co.uk/gp/aag/main?ie= ... NZUE7WTFPM

I guess the lesson here is to pay closer attention to which seller you're buying from when not buying from Amazon directly.

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Re: Exploding Pi

Sat Mar 01, 2014 2:27 pm

This is why your Pi exploded:
fake samsung.jpg
fake samsung.jpg (123.23 KiB) Viewed 5769 times
There's less than 1mm separation between the live mains and the track (which no longer exists) for DC +5v.

I suggest you forward all relevant information about who and where you bought this device from to Trading Standards.
Rockets are loud.
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Re: Exploding Pi

Sat Mar 01, 2014 3:13 pm

And that ladies and gentlemen is why you should think twice about buying a cheap power supply...

Scratch that... Just never ever ever buy cheap power supplies....
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Richard-TX
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Re: Exploding Pi

Sat Mar 01, 2014 3:13 pm

http://www.righto.com/2012/10/a-dozen-u ... le-is.html

A very good review of various power supply/chargers
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Re: Exploding Pi

Sat Mar 01, 2014 5:41 pm

I wonder if it had a sticker that read:

5V nnnn mA
Made in China

anywhere on it..... ;-)
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Re: Exploding Pi

Sat Mar 01, 2014 6:19 pm

MaxK1 wrote:...5V nnnn mA
Made in China ..... ;-)
P1050789.RW2.jpg
P1050789.RW2.jpg (39.6 KiB) Viewed 5664 times
So that's a no?

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Re: Exploding Pi

Sat Mar 01, 2014 6:45 pm

I can see the electrolytic capacitor took a beating (bulged and leaked) despite being rated at 400v.
It's quite possible the capacitor leaked onto the board causing the mains supply to arc into the output supply - http://en.wikipedia.org/wiki/Capacitor_plague
Unfortunately China has a dodgy market for fake or substandard components it's quite possible that you had fake components to start with or the PSU design was simply rubbish.

Richard S.

MaxK1
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Re: Exploding Pi

Sat Mar 01, 2014 7:23 pm

And now they are printing fake labels hoping the Vietnamese take the rap... Whatever next :-)

But just in case the Chinese had nothing to do with it - My humble apologies!
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rpdom
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Re: Exploding Pi

Sat Mar 01, 2014 7:42 pm

redhawk wrote:I can see the electrolytic capacitor took a beating (bulged and leaked) despite being rated at 400v.
It's quite possible the capacitor leaked onto the board causing the mains supply to arc into the output supply - http://en.wikipedia.org/wiki/Capacitor_plague
Unfortunately China has a dodgy market for fake or substandard components it's quite possible that you had fake components to start with or the PSU design was simply rubbish.

Richard S.
Even so, the 5V side of the circuit shouldn't be anywhere near the mains input traces. There should be at least a 3-5mm gap and ideally the high voltage part of the circuit should be on one end of the board and the low voltage on the other with the transformer in between, and maybe an opto-coupler for feedback.

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Re: Exploding Pi

Sat Mar 01, 2014 8:00 pm

rpdom wrote: Even so, the 5V side of the circuit shouldn't be anywhere near the mains input traces. There should be at least a 3-5mm gap and ideally the high voltage part of the circuit should be on one end of the board and the low voltage on the other with the transformer in between, and maybe an opto-coupler for feedback.
What he said.

In fact, we've been testing a certain brand of micro-USB supply that meets all our (and the regulatory) requirements...
Rockets are loud.
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Re: Exploding Pi

Sat Mar 01, 2014 10:15 pm

And interesting video on the subject.
http://www.youtube.com/watch?v=T88ej64aXUM

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Tage
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Re: Exploding Pi

Sun Mar 02, 2014 3:19 pm

This is why I am saying that nobody should buy anything that is plugged into the mains outlet from cheap internet sources. (but how do you know when even Amazon is guilty?).

never connect a relay board you bought online to the mains voltage without having an electrical engineer checking it out!

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Re: Exploding Pi

Mon Apr 28, 2014 10:28 am

gsh wrote:And that ladies and gentlemen is why you should think twice about buying a cheap power supply...

Scratch that... Just never ever ever buy cheap power supplies....
Unfortunately, when buying an expensive one you can never know whether it's just a cheap one which has been marked up to an expensive price.

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Re: Exploding Pi

Mon Apr 28, 2014 10:46 am

piglet wrote:Unfortunately, when buying an expensive one you can never know whether it's just a cheap one which has been marked up to an expensive price.
Not always, no, but you can increase your chances of buying the genuine article if you purchase via a reputable supplier in your own region. Just because we can't guarantee that something is the genuine article, that's no reason to throw in the towel and just buy the cheapest on offer regardless of source.

You only need to ask anyone who's spent many years building custom PCs for a living or a hobby whether it's worth taking the cheapest option when it comes to choosing a PSU, and the answer will nearly always be a resounding no.
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MaxK1
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Re: Exploding Pi

Mon Apr 28, 2014 12:58 pm

About a week ago we had a story on some local news outlet about a cheap, counterfeit I-<thing> "power supply" that literally blew up in a kids hand when he plugged it in. The ER Dr. wasn't too optimistic about saving three of the kids fingers...
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Re: Exploding Pi

Mon Apr 28, 2014 4:06 pm

jdb wrote:In fact, we've been testing a certain brand of micro-USB supply that meets all our (and the regulatory) requirements...
Pretty please can you tell us more?

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