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Author Topic: SheevaPlug power supply blown up  (Read 48214 times)

larzonov

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SheevaPlug power supply blown up
« on: 11 April 2010, 08:15:41 am »

Hello,

Yesterday evening I noticed my plug was dead, or to be exact, the leds on the Arduino I have hocked onto the USB didn't glow as they use to, instead they flickered as if the board didn't get enough power. I pulled out the power cord from the plug and put it back in but nothing happened, it was completely dead. But then it was to late in the evening so I decided to sleep on it..

Today I have opened up the plug to see what's going on inside and it seams that the power supply have blown up, it smells really bad and all the components in the power supply box are covered in some brown/gray stuff, probably one of the capacitors have blown up, see the picture:



The main board looks just fine, but of course I don't really know if it works since I don't have any power to test it with..

So now I'm trying to understand what could have caused this. I probably had too many things pluged into the USB and used up too much current. What I had was one unpowered USB-hub (plexgear), and on that one a 16GB sandisc usb memory stick, a webcam (logitech harrison2 chip) and a Arduino Duemilanove development board (with two micro servos connected but not in use). Yes it sounds like a lot of current...

Anyone have any idea if the components on the power supply board can be replaced or where to begin? It's really hard to see which components that needs to be replaced.. Maybe buy a new power supply from NewIt?

Anyhow, I should get my GuryPlug soon, so I will not be without a plug very long :) One of my goals have always been to build something solar powered so maby this is my chans with the sheevaplug...

/Andreas
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AlexGalkin

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Re: SheevaPlug power supply blown up
« Reply #1 on: 11 April 2010, 02:11:22 pm »

Khm.  Very funny....  Today my Sheeva has not wanted to switch on after moving to other wall socket and after I opened it I see absolutly the same picture.   

But I don't sure that capacitors were blown up. It usualy starts from top but here - not

It seems to overhead plastic glue...

But power supply definitely die - output voltage it 2v

It strange that not any emergency current interrupters...
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AlexGalkin

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Re: SheevaPlug power supply blown up
« Reply #2 on: 11 April 2010, 04:50:09 pm »

Found temporary alternative power supplier.  It seems that board is alive :)
So, will search external PS.
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alfon

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Re: SheevaPlug power supply blown up
« Reply #3 on: 11 April 2010, 08:32:46 pm »


Anyone have any idea if the components on the power supply board can be replaced or where to begin? It's really hard to see which components that needs to be replaced.. Maybe buy a new power supply from NewIt?


First of all, you should keep in mind is that capacitors in power supplies can remain charged even when disconnected, so you should exercise extra care and measure everything before touching it. Or risk getting a pretty nasty, possibly dangerous, shock. Which you don't want to do.

Assuming that you are knowledgeable and confident enough to avoid such danger, and that you are feeling adventurous, you could atempt to fix the power supply.

Electrolytic capacitors usually have an "artificial weak point", so to say, at the top. When they overheat, the weak point fails and the liquid exits from there. This helps avoid an explosion.

If you look at your picture, you will see a sort of inverted "Y" at the top (actually the side, as it is placed) of the capacitor at the middle of the board. This is the weak point of this capacitor. It is intact, therefore this capacitor is OK. Equally intact seems to be the capacitor at the bottom of the picture.

There seems, however, to be a blown-up capacitor at the top left of the PCB. It would seem that this is the part that needs to be changed. In principle, you could remove it and replace it with another one of similar specs (preferably one withstanding a higher voltage).

This assumes, of course, that the primary damage (assuming it is a blown capacitor) hasn't caused other components to fail too.

Whatever you do (find an adequate replacement power supply or fix the one at hand), you should also get a powered hub and an external PS for the arduino.

Best regards,
Alf

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larzonov

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Re: SheevaPlug power supply blown up
« Reply #4 on: 13 April 2010, 03:05:09 pm »

Thanks for your replies, sorry for being lazy and not writing until now..

AlexGalkin:
Interesting that the same thing happened to you at about the same time, weird.. I have not been able to check if my plug is working or not, I need to find a power supply that I can trust, since there is no more voltage regulators after the j3 connector..

Alf:
Thank you for all your input and the info about the dangers with capacitors, I always try to be careful when dealing with AC.

After doing some more analysing, I think the most of the scary black stuff that is all over the place is just burned glue, just as AlexGalkin mentioned, the diodes on the middle on the board are completely covered in it.  And I cannot tell if the capacitor at the bottom left of the PCB as Alf pointed out is blown or not. I have however, desoldered it and it doesn't look healthy at all, I will try to replace it, it's 1000uF 10V and should not be that hard to find. The other components doesn't look that bad, but if replacing the capacitor doesn't work it's probably time to give up..

Thanks

/Andreas
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AlexGalkin

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Re: SheevaPlug power supply blown up
« Reply #5 on: 13 April 2010, 07:35:23 pm »

Actually this power supply is not better that the most of similar AC-DC converters.  More over I suppose that it does not support 3A.

I got new PS in nearest electronic components store (I decided to get external version, but internal (like this http://www.chipdip.ru/product0/573809015.aspx, sorry the page in Russian) is good to just need to adapt the Sheevas case a bit) with 3A (15W) + socket. Total is about 20Euros. And now USB HDD is able work without external power...


PS:  I believe that output voltage stabilizer (fasten on heat kink) is out in broken PS. But I don't want to fix my PS due a lot of melted and smelled glue.
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djrm

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Re: SheevaPlug power supply blown up
« Reply #6 on: 13 April 2010, 07:42:35 pm »

And I cannot tell if the capacitor at the bottom left of the PCB as Alf pointed out is blown or not. I have however, desoldered it and it doesn't look healthy at all, I will try to replace it, it's 1000uF 10V and should not be that hard to find.

The most highly stressed capacitor in a switch mode power supply will be operating with a high ripple current and needs to be of a kind known as 'Low ESR' (effective series resistance). If it is not then the internal resistance causes heat dissipation when the ripple current flows and this damages the capacitor, the result can be catastrophic.

If an ordinary capacitor is fitted by mistake instead of a low ESR one there may be the problem. I do not know, I have not studied the circuit of the power supply. In fact I dont even own a Sheeva Plug, but I am waiting to recieve my nice new GuruPlug one day soon.

hth David.
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corsarium

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Re: SheevaPlug power supply blown up
« Reply #7 on: 25 June 2010, 04:01:15 pm »

Hi everybody!
Im afraid that my sheevaplug died today  :( , after 10 months. Looks and smells like something inside was fried (i did not open it ...yet) but im afraid that my case is the same.
After changing the PS the sheeva revived?
How it was done..? my electronic knwoledge is not as good at it should be


Best Regards
Corsarium
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chemary

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Re: SheevaPlug power supply blown up
« Reply #8 on: 28 June 2010, 08:00:42 am »

Hello,
My SheevaPlug died today after 8 month of use, the signs are the same that others have had.
I used a regulated laboratory power supply to feed the Sheevaplug and it worked fine but is not a long term solution, is only for keeping my Server running.

The aspect of the PSU is the same that others have posted, I tested the output voltage and I get a fluctuating value between 2~3V so the Sheevaplug leds flickers every 1s but failed to boot.
As others stated the main problem of the PSU is the bad quality of the capacitors, I measured all and the only weird value noticed is the big 22uF/400V capacitor measured only 16uF. Can this cap be the cause of the failure, has anybody tried to replace it?

I have asked NewIt for a replacement and they offered me to order a new PSU. My question is, this type of failureds are not covered by the warranty that I think that for electronic products sold in Europe must be of at least 1 year?
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fragfutter

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Re: SheevaPlug power supply blown up
« Reply #9 on: 28 June 2010, 09:02:54 am »

The 400V capacitor is the one that normaly blows. As you already opened the case and didn't shock yourself i assume you know basics about electronics (or were lucky). Yes it can be replaced. There are special caps for switching PSU. Some other caps seem to be also of low quality, be prepared to have them blow up later. Alternative is to use an external PSU for 10bucks. This way you also move some heat out of the case.

If you are a european customer, this failure is covered by warranty (two years btw). But as you already opened the case yourself the manufacturer can claim that you made a misstake... So it's up to you and newit striking a deal.
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chemary

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Re: SheevaPlug power supply blown up
« Reply #10 on: 01 July 2010, 08:18:58 am »

I have bought a higher quality caps replacement for all the present caps on the board and now the PSU is working again and is much cooler!
The repair cost me ~3€ that is a big saving compared to the 25 USD (price+shipping) that Globalsscale offered me.

I'm electric engineer, I have taken care of not being shocked, basically don't touch the board while connected and discharge the caps with a resistor when disconnected but this seems to be unnecessary as they discharge very quick.

The caps are much large that the originals, I have had to rearrange the components on the PSU board and make a hole on the case for the big capacitor to fit all on the metallic case and close it. I will have to keep the PSU out of the Sheeva as now it barely fits in, furthermore it will be better to keep it cool.
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nr

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Re: SheevaPlug power supply blown up
« Reply #11 on: 05 July 2010, 03:13:28 pm »

Ah, I should have remembered to look here when I started having a few problems with my PSU:



Somewhat unbelievably, that PSU is still working. As long as I don't plug anything into the USB port that is. I have an external USB disk, which the plug just refuses to mount with any degree of stability now. The disk is powered, so it shouldn't be drawing too much power from the plug.

Other than wait for a replacement PSU (it's still in warranty) I'm a bit unsure what to do now. I'm OK with a soldering iron, so if anyone can point me in the direction of what needs replacing, and what to upgrade them with, I'll happily give it a go. After all, it's not as if I can make things much worse :)

Ta,
nr.
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nr

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Re: SheevaPlug power supply blown up
« Reply #12 on: 05 July 2010, 08:52:32 pm »

For the time being, I've butchered an old 5v 2a supply to power the plug. It's not pretty, but it works. The thing is more stable than it's been for weeks. And it means that I had a chance to get the soldering iron out, which is always a Good Thing. A cup of tea to celebrate I think. :)
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raj123

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Re: SheevaPlug power supply blown up
« Reply #13 on: 14 July 2010, 04:03:10 pm »

Hi,

Mine is flickering green and also ethernet port. No blue light. Do you think I have the same problem? Please let me know...

Regards,
Raj
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NewIT_Marcus

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Re: SheevaPlug power supply blown up
« Reply #14 on: 14 July 2010, 04:46:08 pm »

Hi,

Mine is flickering green and also ethernet port. No blue light. Do you think I have the same problem? Please let me know...

Regards,
Raj

Most likely; the PSU certainly seems to be the weak link on the original Sheevaplugs. (It's my understanding that current models are supplied with an improved version). See my reply to you in the other thread in which you posted this problem.
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