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Why does my Dell Dimension E521 reboot on its own?

I have a Dell Dimension E521 that reboots on its own.  I've tested, replaced and/or removed the RAM, Optical Drives, All add-on cards & PSU.  Additionally I've reloaded the OS ( Media Ctr 2005).

After all of this the PC continues to reboot and/or shut down on its own.  Sometimes during its process of rebooting it will shut down completely after trying to reboot a few times.  There are no visible signs of leaking caps on the mobo/any other cards.  I'm down to CPU, MOBO and I/O Front Panel card.  Before I begin buying replacement parts I'd like to get some advice.

The problem occurs regardless of what is being done with the computer.  From idle to busy the out come is the same.
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1namyln
Asked:
1namyln
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1 Solution
 
dbruntonCommented:
What if you boot from a live Linux CD such as Ubuntu does this still occur?

If it does then it is the motherboard.
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edbedbCommented:
If what you are saying is accurate, it is most likely the motherboard, CPU or GPU. It is seldom the CPU. If you have an onboard graphics adapter, try an add on.
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PCBONEZCommented:
Dell E520/E521 have known capacitor issues.
You need to inspect your caps.
http://www.badcaps.net/forum/showthread.php?t=7462

Those cases 'breath' better than the Optiplex mini 'roaster oven' cases but eventually the iffy caps do go bad.

Please note that Chemicon KGZ series and/or OST [brand - any series] often fail with no bloating at all.
- I KNOW at least some E521 got KZG caps and they go bad. I've rebuild a few.
Nichicon HN & HM were defective from 2001-2004 and may also have been used.
- The board looks like a Foxconn-for-Dell build and Foxconn sometimes used them.

As specific caps used on a given model board can change during production you may have some, all, or none of the problem caps on your board. - But you need to look.
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nobusCommented:
not sure, but did you try another Power Supply ?   that's the first candidate, together with the mobo.
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1namylnAuthor Commented:
I was finally able to try the computer running UBuntu, so far so good.  I haven't had any reboots that I can tell.  I did try another power supply.  Could this still be the CAPS?
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dbruntonCommented:
Switch back to Media Centre and see what happens.  You've swapped both OS and power supply.  Can't tell which one did anything if anything did occur.
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nobusCommented:
it always can be a bad mobo - not necessarily bad caps.
but disconnect whatever devices tyou can to test - or disable them in the bios
you can also try updating drivers, run a disk scan for errors, etc...
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PCBONEZCommented:
Sounds like bum PSU now.
Possibly bad caps in the PSU you removed. - Not at all uncommon.

You could open it up and take a peek.
Not all problems are caps and not all bad caps bloat, but all bloated caps are bad.
If you find any bloaters in there you'll have a solid answer.
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1namylnAuthor Commented:
The PSU tester I'm using is a simple green or red tester from Antec.  In the past its always proved to be very accurate.  Simple but accurate.  I don't know much about UBuntu but with it running on the computer everything seems to work with no issues. As a reminder though, the computer will reboot even before it gets to the BIOS sometimes.
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dbruntonCommented:
>> As a reminder though, the computer will reboot even before it gets to the BIOS sometimes.

If it does that with Ubuntu then the problem is either the PSU or the motherboard.  If this is the second PSU it has happened with then the chances are that it is the motherboard.
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1namylnAuthor Commented:
It does not do it with the Ubuntu test load.  This is a load from the optical drive and the hard drive.
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dbruntonCommented:
Have you tested the hard disk?

I don't see that in your test range in your question.
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nobusCommented:
for testing, i suggest to download ubcd, and run memtest86+ for ram for a complete pass at least - and the disk test you need :  http://www.ultimatebootcd.com/      
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1namylnAuthor Commented:
dbruton: I have tested the HD.  The test loads have all been tried on another drive.  Same problem exist.

I've tested the RAM with MSFT RAM Checker.  Everything passes.  Does the Ultimate Boot CD contain a different RAM checker that would provide for a different form of testing?
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nobusCommented:
i don't know, but it is accepted as one of the best Ram diags
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PCBONEZCommented:
I suggested you look inside the OLD PSU. [In case that wasn't clear.]

That kind of PSU tester tells you almost nothing about a PSU's condition.
- They put a TINY TINY load on the PSU and check voltages - that's it - that's all they do.

They do NOT tell you:
1 - If there is excessive Ripple, EMI, or other Noise in the power. [As bad caps would cause.]
2 - If the voltages will be correct [in spec] under a real-world load conditions.
3 - If the PSU will even run with a realistic load on it.

The parts necessary to put a realist load on a PSU would weigh in at something over 10 pounds.

Connecting the PSU to a system or a realistic sized test load and checking voltages with a voltmeter would answer #2 and maybe #3 but you still won't know #1 and that one *WILL* result in the problems you were having.

Lacking an O'scope and a realistic load the only way to verify that the PSU you removed was a problem is by visual inspection.
- IF you see something bad - then there is confidence it was a problem.
- If you don't see anything bad then you still don't know for sure [could be a problem not obvious visually] but at least you tried.

Such an inspection takes like 10 minutes and 'if' there is obviously a problem in there knowing so can save you hours or days of 'easter-egg' trouble shooting and the stress of wondering if you've fixed the problem or not.

So, why are we bypassing an easy short check that at least -could- answer loads of questions?
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1namylnAuthor Commented:
Pulled the PSU apart and I could see no signs of swollen and/or bursted caps.  I'm going with the motherboard as the root of the issue, any objections?
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PCBONEZCommented:
Yes, I completely Object to bad motherboards. - Doesn't everyone? .. jk
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PCBONEZCommented:
Bad jokes aside:

I finally found a decent photo of an example of your board.
I was loaded with the defective Nichicon HM's I mentioned checking for 8 days ago.
It also has a few that are either KZG [bad] or KZE [okay] Chemicon caps. [Two visible.]
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Given that and if you have the same caps I'll give a 99+% chance the board can be repaired simply by replacing SOME of the capacitors.
- DIY if you have the soldering skills & tools would probably run $20-$30.
- Badcaps.net charges around $85 [I think...].
- A replacement board [even if new] will likely have the same bad caps you have now.
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Dell-Dimension-E521-Caps.jpg
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1namylnAuthor Commented:
Purchased the replacement board today.  Thanks to all for your efforts.
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