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Author Topic: Fried SheevaPlug !!!  (Read 23182 times)
doublecheese
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« on: May 24, 2010, 06:10:42 AM »

Hello Friends

I have a question for you experineced guys ....

I have bought my SheevaPlug from MeteoShop in Czech Republic and I have been using it 24/7 for my MeteoHub software since the last 4 months. It has been working flawlessly althought it always felt very hot when it's on ( to my feeling that is )

Last week out of sudden it all went dead on me. No Blue or Green Leds, no heat , no nothing.  I replaced the electriciy cable just incase but the SheevaPlug did not work at all.

So I took it to my local electronics repair shop and once we opened the SheevaPlug, we realised that the condensers on the right side of the Sheeva was Fried up  and melted somehow !!!!!! Also the 1.5V Button Cell Battery (AG10) was gone fatter !!! it was almost 50% as fat !!

Here are some photos of what happened...







Here is after the Condenser Replacement ..





Now my SheevaPlug Started to work, there is electricity flowing through the circuits. However my Sheeva now only blinks GREEN LEDS and also flashing Green/Yellow on the netwrok connection. I can not get the BLUE leds working, it's only flashing Green Leds....

Also in these 2 pictures you could see how the condenser were affected (fried) by looking at the small metal cover covering the condenser box.





Any of you expreinced guys can tell me what is going on in my Sheeva ?  Is there something to fix it or is there something I must do to get it to work again ?

Thank you for your support.

Regards
DC.
« Last Edit: May 24, 2010, 06:13:27 AM by doublecheese » Logged

superpat
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« Reply #1 on: May 24, 2010, 06:50:18 AM »

Hi,

You do not have to go far down the hardware forum

Read:-

http://plugcomputer.org/plugforum/index.php?topic=1318.0

There is a KNOWN problem with Sheevaplug supplies. Globalscale the SheevaPlug designer and manufacturer is "supposed" to be offering a $10 "new design" improved replacement supply to owners out of warranty. They haven't made it available yet.

 If your plug  is in warranty contact your supplier.  If you are in the EU  then you have TWO years warranty by EU regulation, contact your supplier!

 If only the caps are blown you may be able to get them replaced with proper low ESR power supply caps, but normally other stuff in the supply is blown. 

A lot of people cut the 5V plug off the power supply and wire it to a 5V 3A wall wart  power plug.

Its all in the thread above

regards

Patrick

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fragfutter
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« Reply #2 on: May 24, 2010, 06:58:33 AM »

You only have a two year waranty, if you bought it from a supplier in the EU (i think you also need to live in the EU). EU law doesn't matter to globalscales or some asian shop if i (EU resident) buy something from them.
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doublecheese
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« Reply #3 on: May 24, 2010, 07:09:10 AM »

The thing is I have already opened it up and replaced the parts myself .... I think I have my warranty voided , haven't   I Huh

Or else, I could send it back to MeteoShop in Czech Rep.

My problem is if I can fix it somehow myself , I don't need to send it back and wait for all that replacement period.


It would be good to replace it with a newer design !!! However again I had on my SheevaPlug the MeteoHUB software already installed, I doN't know how to upload this software again if my Sheeva was replaced...

Sad Sad Sad
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Billy
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« Reply #4 on: May 25, 2010, 07:20:58 AM »

Hi doublecheese ,
I had the same problem with my meteohub system running on the sheeva.
I solved it within 20 minutes by replacing the defect power supply  with a 5V 3A wall wart  power plug.
Everything was running well again.

All is described as already mentioned in http://plugcomputer.org/plugforum/index.php?topic=1318.0.
Cheers and have fun with your Meteohub.
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doublecheese
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« Reply #5 on: May 25, 2010, 07:54:56 AM »

Ok I will try this and keep you updated

Thanks for the help guys Smiley))

But I want to ask you something , after the condensers were replaced my sheeva works as well , the problem is that now it only blinks GREEN LEDs , but the BLUE LED won't flash !!!!.

Do you mean that if I replace the power supply with a 5V 3A power plug, my sheeva will start blinking BLUE again ?

This is what I didn't understand since my electronics knowledge is next to zero , I need to tell this to my electronics repair shop and he will do the replacement for me.

« Last Edit: May 25, 2010, 07:59:29 AM by doublecheese » Logged

doublecheese
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« Reply #6 on: May 26, 2010, 01:44:22 AM »

Ok I read the thread throughly and I will replace the existing Power Supply with a 5V 3A power supply.

I will keep you guys updated, thanks for the helps.



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doublecheese
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« Reply #7 on: May 26, 2010, 06:23:13 AM »

Here it is .

I found a Chinese made 5V 3A adapter and bought it.

Replaced the existing power supply with this one and VOILA !!!!

My Sheeva is working again ( at least the blue light is on !! ) I will try it at home this evening with my MeteoHub software.

Do you think that making extra holes on the SheevaPlug case, help to be cooler?

Here are the final pics.

Thanks all Smiley









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fragfutter
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« Reply #8 on: May 26, 2010, 07:15:04 AM »

The sheevaplug has less heat issues then the guruplug. And now that the powersupply is outside, there is even less heat generated inside the case.
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superpat
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« Reply #9 on: May 26, 2010, 09:17:00 AM »

Hi,

The Sheevaplug may have less heat issues than the Guruplug   BUT....

The SheevaPlug power supply has had lots of failures and is still failing due to HEAT in the power supply enclosure.  There have been lots of P.S. failures all due to the same cause.

The capacitors used in the power supply are low quality "commercial"  grade with a unspecified  ESR. They are not suitable for the application they are being used in.  The electrolyte in the caps heats up  and vents through the pressure relief system, in some pictures I have seen they appear to have blown apart.

ESR == Equivalent Series Resistance, a theoretical perfect capacitor would have 0 ohm ESR, but in the real world all caps have more or less ESR.

I measured  using a Prism Electronics AIM 6451 LCR Databridge, the ESR's of the capacitors in my working Sheevaplug P.S.   The worst was the nominal 6.8ufd cap. This measured 5.9ufd on the bridge and the ESR  was measured at 19.78 ohm @ 100HZ.  I think my Plug power supply is about to die!

(Typically one would expect  approx 5ohm ESR.  For a sanity check,  I measured a spare 10ufd from my junk box, the ESR of this was 5.25ohm).

If the capacitor is supplying a varying DC load current, or a high ripple current, then a heating effect in the capacitor electrolyte occurs, proportional to the ESR.  watts= Iripple^2xESR.
 
I measured the internal temperature of the power supply using a thermocouple, (Tenma 72-6700 digital thermometer fitted with a remote type T thermocouple),  thermocouple positioned adjacent to the 6.8ufd capacitor.  The PS was closed up and the Sheevaplug restored to normal. I tested it on my workbench using the figure 8 mains lead. The Sheevaplug was standing on a wooden surface on it's rubber feet.

Ambient temp 17.5 deg C start, end 20.1 deg C  (central heating came on during tests)

1. Internal power supply temperature  start 17.5 deg C  end after 60 minutes running Meteoplug app on SD card (no hard drive )  60.8 deg C

2. Internal temp start 60.8 deg C,  end after 70 minutes running  500GB USB hard drive  powered from SheevaPlug constantly reading / writing 10GB file  71.6 deg C

I did not measure the temperature at the CPU or memory  packages. at the time I did the tests the power supply was the only thing I was interested in.

The caps in the power supply are marked 105degC operating, but  this does not take into account the problems with ripple or varying dc currents found in mains switching power supplies.  The caps are 105 degC RX type, are manufactured by Yalecon, a Chinese company, I searched hard for a full specification for them, but could not find one.

The capacitors in the SheevaPlug power supply should be LOW ESR type, especially designed to for a switching power supply application, bridge rectifier filter capacitor.

I hope that GlobalSCale will soon make available the replacement power supply they said they would offer. Has anyone received one yet?

regards

Patrick

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doublecheese
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« Reply #10 on: May 26, 2010, 02:11:49 PM »

OK , I can confirm that my SheevaPlug and MeteoHub are working again......

While testing the unit I saw that the the metal thingy under the circuit board was getting very hot, so I decided to make some holes on the Sheeva Case. Maybe it will take out some of the excess heat ......



BTW, Patrick
I have a Flir T360 Thermal Cam , I will take some pictures with it of the Sheeva later this weekend , maybe it will help your research ?
« Last Edit: May 26, 2010, 02:14:42 PM by doublecheese » Logged

mhtsaras
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« Reply #11 on: June 09, 2010, 12:43:24 PM »

You don't have to be a rocket scientist to know that the excess heat is making the life of electronic devices shorter
I have some heat problems with my sheevaplug (especially the summer period) and I was thinking opening a few holes on the plastic case like you did, or adding some sort of extra passive heat sink.
Are those holes working? and making the device cooler? measuring the temperature of the plug with the holes covered or opened?
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dattaway
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« Reply #12 on: June 09, 2010, 02:01:03 PM »

I wish my Sheeva also had the option of an attractive aluminum case.  Serious heatsinking.
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doublecheese
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« Reply #13 on: June 09, 2010, 11:54:37 PM »

You don't have to be a rocket scientist to know that the excess heat is making the life of electronic devices shorter
I have some heat problems with my sheevaplug (especially the summer period) and I was thinking opening a few holes on the plastic case like you did, or adding some sort of extra passive heat sink.
Are those holes working? and making the device cooler? measuring the temperature of the plug with the holes covered or opened?


Yes these holes are definetely working, now when I touch my SheevaPlug it's much cooler than what it was, you can easily feel the difference.

However not to forget that , I took the power supply out and replaced with an 5V 3A adapter.  The power Supply was causing most of the heat.


These holes I made are especially good for that metal thing under the circuit board, that was getting hot too.
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fragfutter
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« Reply #14 on: June 10, 2010, 12:56:53 AM »

that metal thing is the head spreader. If you remove it you will find the CPU and the memory chips. Between the head spreader and the chips there is some thermal tape to assure contact.
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