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16  Hardware and U-Boot firmware / Hardware / My modified Sheevaplug on: August 23, 2010, 01:31:49 PM
Hi,

When my Sheevaplug power supply took a turn for the worse, I decided it was time to do some modifications.

I had already modified my old V1.3 pcb  by fitting and enabling the Esata  connection, (see old posts).

I have never used the Sheevaplug as a "plug" computer, my mains power strips are difficult to reach and full of heavy cables. I could never see the point of struggling to connect a USB stick, the console cable and the esata cable in the dark under my desk, so I have always used the device on the desktop or on a shelf with the supplied mains cable.  The connections are still fragile, and one has to be careful that they are not disengaged.

The Sheevaplug although not in the same central heating radiator class as the Guruplug, still runs very hot. There is not enough cooling in the tiny plug enclosure.

So I decided to make a new enclosure. I purchased a "Hammond" extruded die cast aluminium box from Maplins and mounted my Sheeva pcb and my 500 Gb Sata 2.5 in hard drive in it.

I obtained some new heat sink padding, which I put between the I.c.s and the Sheeva aluminium heat sink. The original heat sink pads were very thin and was missing in two places, a very shoddy job by Globalscale  originally!) I mounted the stack on the lid of the box with white grease heat compound between the Sheeva heat sink plate and the lid. I used the coil springs from the old enclosure to give some expansion when the heatsink expands, I did not want to strap it too tightly and damage the ic cases or lead frames.

The reason I mounted the pcb on the lid was that I can slide the lid out of the case and then work on the pcb at my convenience, it still being heat sunk to the lid. ( I can also connect the console mini usb with the lid out.)

It became apparent that it was going to be difficult to connect to a Sata hard drive in the case, since the Sheeva pcb Esata connector pokes though the end plate, so I had to bodge an out and in cable run.

I am using an external 5V 3A power brick. 

In use the box does not get appreciably warm even after many hours running. I have Debian Squeeze installed on the hard drive, running very nicely. I am now building the ultimate low power home server.  Cheesy

When I can find a couple of 5.1mm power connectors I will make a little power breakout cable, and measure the 5V current draw into the enclosure.

I have attached some pictures of the box

regards

Patrick
17  Hardware and U-Boot firmware / Hardware / Re: SD cards and heat?? on: August 23, 2010, 04:09:20 AM
Hi

I cannot find a copy of the mechanical specification from the official SD card association, but checking several vendors shows the "CLAIMED" operating temperature range of SD cards as -40 deg C to + 85 deg C (ambient)

I too wonder what the operating life is  at +85 deg C.  I think the main problem would not be a constant elevated temperature, but a continual cycling between normal ambient +20 and +85 deg C The thermal expansion and contraction will induce mechanical stress in the I.C. connecting elements resulting in premature failure.

regards

Patrick
18  Hardware and U-Boot firmware / Hardware / Re: GuruPlug Server Plus Heat Problems on: August 18, 2010, 10:55:20 AM
Hi,

The 7/17/2010 news item about the replacement get well kit is NOT on the Globalscale news web page.

This is a copy from the NewIT forum:-
Quote
7/17/2010 Guru Plug Server - Professional Upgrade Kit

First of all, we wish to thank our loyal customers who have been very patient and stood by us while we were resolving the “Heat Problem” with the GuruPlug Server Plus!

Further to our announcement about a week ago, we are pleased to advise of the permanent solution to the problem. In the coming weeks (not months), we will be releasing the simple to install “Professional Upgrade Kit”. Part of this kit includes a micro fan with wire harness.  This fan will not only dissipates the heat being generated by the CPU, but also brings the GuruPlug Server Plus back in line with its original specifications. Therefore, those of you who bought the Plug specifically to run 2 x 1Gb ethernet will be able to do so freely and without limitations.

The “Professional Upgrade Kit” together with full instructions, will be provided free of charge on request to all existing users of the GuruPlug Server Plus, but there will be a nominal shipping and handling charge . We will be issuing instructions shortly on how to obtain a kit.

Those of you who receive units from shipments starting in August 2010, will have the kit already installed and you will be able to run all applications to the fullest from the get go.

We apologize for not making this announcement sooner, but we wanted to do our “due diligence” and carry out exhaustive field and thermal tests to ensure you will be receiving  a quality and robust product which captures the “always on eco friendly” philosophy of the “Plug Computer”.

Thank-you once again for your encouraging support while we were dealing with this problem, and we hope you will  check our web-site regularly for details on more new and exciting products that will be introduced in the coming months.

The last NEWS item is the /7/5/2010 item about how not to overheat your GuruPlug

cheers

Patrick
19  Hardware and U-Boot firmware / Hardware / Re: "Official" replacement PSUs - anyone had one? on: August 18, 2010, 05:15:36 AM
@c128

I have received a suggestion that the power supply you received as a replacement for your Sheevaplug may in fact be a Guruplug power supply.

If it is, then that raises an interesting question:-  are all Guruplug supplies fitted with a low grade 85 deg C mains filter / reservoir capacitor, and will  Guruplug's power supply fail prematurely ala the Sheevaplug, bearing in mind the Guruplug appears to run at even higher temperatures?

Another question is whether there is any way of positively identifying what  replacement power supply your received, are there any part numbers on it?

As I wrote the above another question crossed my mind,  What certification have GlobalScale done on the Sheevaplug with the new power supply. I do not believe that the original CE or UL or FCC qualifications would stand if the complete power supply is redesigned and replaced?

I have purchased a Open-rd Ultimate, imagine my chagrin, having just read of a complaint in the Open-Rd forum that the Open-RD components  are running at elevated temperatures, looking inside my Open-rd, I find there is NO heatsinking of the CPU, memory or ethernet chips!:-
Quote
Hi

Just wonder to know if it is normal that the Open-RD board  becomes
very hot around the DDR2-SDRAM memory chips.
The memory chips are the hottest area, around 44/46 degrees Celsius,

The Open-RD Client in the enclosure become very hot soon.
Both the boards I have here (1 base and 1 client) return such
temperature (taken with an IR thermometer)

Thanks





I despair that the design engineers at Global Scale / einfochips have been given a primary design goal of cost reductions, instead of product quality and  longevity!

regards

Patrick
20  Hardware and U-Boot firmware / Hardware / Re: "Official" replacement PSUs - anyone had one? on: August 15, 2010, 04:47:11 AM
Hi,

What is making me VERY nervous is the fact that GlobalScale appear to have changed the design of the new version 2 power supply to a version 2A

If you look at the picture provided by c128 (above) you will see that it differs slightly from the pictures in the GlobalScale pdf instruction sheet  put out a  few weeks ago.

The  thing that worries me is that the new new version 2a power supply appears to have a generic, cheap 85 deg C  aluminium electrolytic capacitor in the mains rectified reservoir position, whereas the picture in the pdf instruction sheet appears to depict a capacitor with a lot more lettering and numbers on it. Unfortunately  the writing on the cap is not clear enough to read for positive confirmation.  I am guessing that capacitor may have been a better quality 105 deg C cap and even maybe a low ESR type that will stand up to the application

The 400V 33ufd  CapXon  shown in the picture of the power supply delivered as the replacement to C128,  has NO additional markings. If it doesn't state 105 deg C then it is not, If it doesn't say low ESR then it is not.  It does not have any type markings to indicate a quality product.  In that position in that application it will DIE sooner than later.

I think someone has done a cost saving exercise on the new replacement power supplies and replaced what may have been a promising  long lived  power supply with one that may be no better than the original!

Here is a quote from the CapXon website, there is very little on the website about ESR and even this note is very vague, no real numbers:-

***********

ALUMINUM CAPACITORS

 When you use aluminum electrolytic capacitors, remember the following.
polarity

    * Regular electrolytic Capacitor has polarity.
    * Reverse voltage causes short circuit breakage of the capacitor or leakage of electrolyte. Where the polarity in a circuit sometimes reversed or unknown, a bi-polar capacitor should be used.

 
Overvoltage

    * Do not apply overvoltage continuously.
    * When overvoltage is applied to the capacitor, leakage current increase drastically.
    * Applied working voltage to capacitors should not exceed the rated working voltage of capacitor.

 
Operating temperature and life

    * Do not use the capacitor over the max operating temperature.
    * Life time of the capacitor depends on the temperature.
    * Generally, life time is doubled by decreasing each temperature 10℃.Generally, life time is doubled by decreasing each temperature 10℃.
    * Use temperature as low as possible.

 
Vent

    * It is recommended at least 3mm of space around

**********


Remember I measured the temperature on the body of the failing cap in the original power supply in my Sheevaplug at over 70 deg C after an hour of use.

regards

Patrick





21  Hardware and U-Boot firmware / Hardware / Re: SheevaPlugs with a - (dash) in the S/N from GLOBALSCALE on: July 20, 2010, 02:03:33 PM

Have a look at:-


http://plugcomputer.org/plugforum/index.php?topic=2002.0

cheers

Patrick
22  Hardware and U-Boot firmware / Hardware / Re: ARMADA-100 Plugcomputer on: June 30, 2010, 12:13:49 PM
Hi,

The time has come to move away from the concept of a plug (in) computer. Instead use a separate power brick design.

Looking at the pictures of the Armada there could be  7 or 8  devices connected to it.

In my house, every mains socket outlet is groaning with extra mains power cords already.

For instance there is a double 13A switched outlet behind the TV stand. This has to feed:-

TV, DVD player, VCR. Satelite box, Freeview box. cordless phone  power supply.   This means an extender board on the floor behind the television stand.

AND A JUNGLE OF LINE CORDS!

To which you want me to add another 7 or 8 devices line cords and signal cables    Rubbish!

Ever since I bought my Sheeva plug I have NEVER plugged it into a wall outlet. I always use it with the provided mains cord, so I can get to it easily to change cables, SD cards, reset it etc.

I have now  bought a die cast aluminium box to mount the sheeva pcb, a sata drive and a USB hub, powered with an external power brick  NO MORE OVERHEATING WOES!

I have also just purchased  an Open-Rd Ultimate. for its video graphics capability and separate power supply.

The form factor of the Sheeva and the Armada is very "smart"  but hugely impractical.  I measured the temperature using a thermocouple meter at the 6.8mfd capacitor in my Sheeva plug power supply running a usb drive as 70 deg C.  The LIFE OF A CHEAP COMMERCIAL GRADE CAPACITOR IS ONLY AROUND 300 DAYS AT 70 deg C    The Sheeva Plug is not a very durable product.

Is the Armada going to be any better?  There is a lot more loads, Can you get the heat out?  Are the power supply components going to be better rated?

Go on use a separate power brick  You know it makes sense!

regards

Patrick



23  Hardware and U-Boot firmware / Hardware / Re: Wanted to buy -- Sheevaplug V 1.3 pcb from Sheevaplug with dead power supply on: June 19, 2010, 09:51:41 AM
Hi,

I thought I had better point out  GlobalScale are offering their $9.95 replacement power supply now

regards

P
24  Hardware and U-Boot firmware / Hardware / Re: Is my sheevaplug dead ??? on: June 19, 2010, 09:50:21 AM


Hi.

Yes it's $9.95 but  a  HUGE Fedex charge!

I have asked NEWIT if I can buy one from them!

P


copy of email from GlobalScale:-

Subject:     RE: Replacement SheevaPlug power supply
Date:     Fri, 18 Jun 2010 16:03:46 -0700
From:     Sales <sales@globalscaletechnologies.com>
To:     <patrick@XXXXXXXXX>
References:     <WEB707ir3wSimD3JkUw000070b9@web707.discountasp.net>

Dear Patrick,

The unit price of power supply unit is $9.95 USD plus $43.00(FedEx international Shipping).

If you are not in a hurry, our European distributor will start to carry the power supply units within one month, you can obtain a new unit from them to save the freight.

Best Regards,

/Support 1103/

Globalscale Technologies, Inc.

25  Hardware and U-Boot firmware / Hardware / Wanted to buy -- Sheevaplug V 1.3 pcb from Sheevaplug with dead power supply on: June 17, 2010, 02:09:55 PM
Hi

I would like to purchase a Sheevaplug V1.3  (the later single board version) pcb , from anyone whose unit  has suffered a power supply failure and who has no further use for it.

I.e.  if you out of warranty, and are not prepared to use an external power supply or have given up waiting for GlobalScale to come up with their $10 replacement power supply.

I  have an idea I would like to try which involves  permanently embedding the Sheeva pcb in another device.  My own Sheevaplug is still running,  so I do not want to break mine up yet!

If you want to get rid of yours, please P.M. me with your price.  All I want is the pcb, nothing else.

regards

Patrick

26  Hardware and U-Boot firmware / Hardware / Re: GuruPlug Server Plus Heat Problems on: June 01, 2010, 05:58:39 AM
Hi,

There is still a lot of confusion regarding the Sheevaplug.

There were TWO hardware versions of the Sheevaplug.

The first had TWO pcbs  plus the power supply

The second known as V1.3  had only ONE pcb plus the power supply.  I am looking at mine dissembled in front of me at this moment.

I believe all the Sheeva's that have the failing power supply come from the second revision, (I may be wrong but I am 90% sure).  Therefore you CANNOT compare them to a two pcb GuruPlug, or  you cannot say "my Sheevaplug is perfect its lasted one+ years with no problems"....... WHICH version Sheevaplug are you talking about?

The problem with the failing power supplies are standard commercial quality capacitors, used in an application they might not survive.  SOME people may be lucky and receive a Sheevaplug with a capacitor in the power supply capable of lasting for years.   Other people have obviously received a  SheevaPlug with capacitors that fail after a few months.  I do not believe that the failure is directly related to the ambient temperature the Sheeva is in, although an ambient outside the GlobalSpace specified environment will not help reliability.

I have said before in many threads, the power supply failures are due capacitor failure due to electrolyte heating due to the capacitors having high ESR. A capacitor used in a switching power supply has to be designed for that role and have a defined low ESR and a tolerance for applied ripple currents and varying dc loads. A general purpose capacitor may or may not have a low ESR and be capable of working for extended periods in a switching power supply.

I have done some measurements on the SheavaPlug:-

Quote

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.



regards

Patrick



27  Hardware and U-Boot firmware / Hardware / Re: Sheeva PSU preventive maintenance on: May 31, 2010, 07:06:07 AM
Hi Christian.

The problem with the capacitors is not that they dry out, but that the liquid electrolyte in the capacitors heats up due to the  electrolyte conducting  ac ripple current and heating, eventually blowing  the electrolyte out through the overpressure vent, (the radial frangible lines on the end of the capacitor).

The "goodness" or ESR (equivalent series resistance), of the capacitor can vary with age and ambient temperature, normally upwards.  The heating effect is Watts = (Iripple) squared x ESR , or the heating effect is directly proportional to the value of the ESR. 

READ :- http://wiki.xtronics.com/index.php/Capacitors_and_ESR

This is a mains switching power supply. It can give you a nasty shock.  MAINS IS CONNECTED DIRECTLY TO THE CAPACITOR WITH NO SAFETY ISOLATION.  Please make sure that the PS is disconnected from the mains and the caps are discharged BEFORE you work on the supply.

The capacitors in the Sheevaplug  V 1.3 ( second generation) 's power supply:-

The problem capacitor is the mains full wave rectifier smoothing cap. Fitted as standard  is a general purpose 400V 6.8 ufd 105 deg C aluminium electrolytic.   I would recommend fitting a special purpose power supply filter capacitor with defined LOW ESR, 400V 6.8ufd  125 deg C aluminium electrolytic.

Also worth changing is the "snubber" capacitor, a 400v 22 ufd 105 deg C capacitor. Again I would replace this with a special purpose power supply filter capacitor 400v 22 ufd 125 Deg C LOW ESR  part.

The 125 deg C parts will also give you a bit more margin.

You will have to find a supplier of good quality power supply filter capacitors. Places like Maplins will sell you general purpose capacitors, that will be no better than the ones already fitted.


Once again I must reiterate, if you are not trained to  work on hazardous  mains power supplies, then get someone who is competent to do it for you!



regards

Patrick


28  Hardware and U-Boot firmware / Hardware / Re: GuruPlug Server Plus Heat Problems on: May 29, 2010, 08:07:40 AM
Hi,

There appears to be some confusion about failures in the two devices.

The SheevaPlug problem is failure of a poorly specified capacitor in the power supply. This fails due to electrolyte heating caused by ripple current or varying DC load currents. The heating is caused by the capacitor having a high ESR, (being a gen purpose commercial capacitor and not a proper high spec power supply capacitor. Typically the use of a USb drive, powered by the Sheevaplug power supply is the worst case heating effect for the Sheevaplug

see my measurements in my reply #9 in http://plugcomputer.org/plugforum/index.php?topic=1734.msg10498

From what I have read, (I do not have a Guruplug), the Guruplug problem is that the temperature of the SOC and memory chips rises above their reliable operating point (they are commercial spec devices 0-70 deg C range), due to an inadequate heatsink and no way to vent the heat from the internals of the case. The more elements you use in the device the hotter it gets. There also appears to be driver issues which cause the ethernet physicals to run hot, which makes it worse.  Obviously the power supply heat will also contribute to the problem.   The Guruplug has a different layout to the Sheevaplug, in that there is an extra board in the Guru, and the whole thing is stacked up in a sandwich.

There are a  couple of reports (unconfirmed) that the Guruplug power supply is also dying. I have not read a definite report of this yet, or seen any pictures of a blown Guru power supply.

regards

Patrick
29  Hardware and U-Boot firmware / Hardware / Re: Fried SheevaPlug !!! 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

30  Hardware and U-Boot firmware / Hardware / Re: Fried SheevaPlug !!! 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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