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Computer turns off then on again at startup

Posted on 2006-05-11
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After running fine for a couple of years, my computer has developed a strange problem. When I turn it on everything lights up as normal and the fans start spinning for a split second and then it goes dead for about one second. After this, without me doing anything, it all lights up again and loads normally except my bios is reset.
Is this likely to be a power supply problem? My friend suggested it could be caused by the motherboard battery failing but I'm sceptical about this.
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Question by:jonnymedcalf
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by:Callandor
ID: 16660466
It could be the power supply or bad capacitors on the motherboard.  See www.badcaps.net for examples of bad caps, though a capacitor could be bad and not show it.
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by:jonnymedcalf
ID: 16660621
My capacitors look fine and the symptoms don't really fit with those on the website. The computer works absolutely fine once it powers up again for instance. I suppose the only way to check would be to try another power supply.
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by:jools
ID: 16660834
As callandor said, the PSU would get my vote to check 1st.
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by:jools
ID: 16660904
I had some bad caps on one of my old boards which got replaced and the system is still going, not bad for an Abit BE6II these days, unfortunately, the pictures on the badcaps website don't really show the problem in detail. You're looking for capacitors which look either swollen or perhaps have a small discharge coming from the top (or bottom). I had more swollen caps than leaking ones and I thought the problem had all but gone away.... apparently not it would seem.
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by:ganongj
ID: 16661043
Hmm, i'm sorry, I don't agree at all with the other posters.  You have a problem that seems like it is the battery for sure.  Your skepticism notwithstanding, from what you've described, it is the problem.

Jim
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by:jonnymedcalf
ID: 16661428
Thanks for the suggestions. I'll try changing the battery first and then if this doesn't work I'll try a different power supply.
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by:tfjeff
ID: 16664224
I seriously doubt a battery would cause that...infact, the computer would probably run fine without the battery (with the exception not keeping correct time and the bios reverting to default settings).  I'm saying power supply too...but it could be a problem with your on/off switch...you might check into that as it's much cheaper/easier to test than the power supply.
jeff
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by:nobus
ID: 16665341
did you add any hardware? maybe your power supply cannot handle the load. Check what youneed here :

http://www.jscustompcs.com/power_supply/      

you can also test it by disconnecting devices (disk, cd, ram , cards, etc. . .)
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by:jonnymedcalf
ID: 16666137
I did not add any hardware and my power supply, if working correctly, should easily be powerful enough.
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by:mjcoyne
ID: 16666146
I agree with ganongj -- replace the battery and reset the CMOS (your manual will have information on resetting this, but if you leave the battery out completely for several seconds while swapping in the new one, that'll suffice for a reset).  The computer has lost it's ability to recall it's configuration, so it resets to factory defaults.  The ability to recall such configuration data requires power, and that power is supplied by the computer's battery.  The information is maintained in the CMOS.

Sure, a computer, once configured, would run perfectly without a battery -- until you turned it off.  This is like a car -- once you get the engine started, there's no need for a battery, either -- until you shut the car off.
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by:nobus
ID: 16666299
try booting from a knoppix cd; if it remains stable, it is an OS issue, if not, it is a hard problem
www.knoppix.org
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by:mjcoyne
ID: 16666379
"try booting from a knoppix cd; if it remains stable, it is an OS issue, if not, it is a hard problem"

If it's resetting the BIOS on every boot, the problem occurs during the POST, well before it even goes looking for an OS...

Speaking of that, do you get any error beeps from the BIOS during boot?  Do you have a case speaker hooked up so you can hear them if they're there?
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by:nobus
ID: 16666475
MCjoyne, you don't have to answer me, let that be the asker's privilege.
As to your comment - it is only true IF it is a battery/bios case.
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by:mjcoyne
ID: 16672671
I'm sorry, nobus -- the asker's original question indicates that his BIOS resets with every power-on cycle ("After this, without me doing anything, it all lights up again and loads normally except my bios is reset.").  This indicates to me that the BIOS is being reset during the POST, and it's likely that the ESCD is lost, perhaps due to a failing battery.  Whatever the cause, I'm sure you'd agree that the BIOS reset is occurring before the system looks for a bootable device.

I didn't mean to upset you...
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by:nobus
ID: 16672800
You're right, mcjoyne, it slipped thru
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by:jonnymedcalf
ID: 16691532
Sorry I have not answered any of your queries but I have been working nights over the weekend.
Changing the battery has made no difference whatsoever.
Using a boot CD will not make any difference as the problem occurs well before the system looks for one. It occurs a split second after turning the power on,  before anything is displayed on the monitor. There are no error beeps during boot up.
I think the problem must be a knackered PSU. Unfortunately I do not have a spare at the moment so I'll have to buy a new one. As soon as I do, I'll let you know if this sorts the problem. Thanks again for all your suggestions.
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by:nobus
ID: 16692382
well, if it is not the battery or the bios, it will end up being the mobo... or possibly the processor
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by:mjcoyne
ID: 16697950
I'm skeptical the the PSU is the cause -- a bad PSU may cause many startup issues, but shouldn't cause the BIOS to reset.  As long as you're sure the replacement battery you tried was itself good, and your sure the CLR_CMOS jumper on the motherboard is in the correct postion (and that it's posts are not shorted by anything), I would try flashing the BIOS next.

What kind of motherboard/computer is this?
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by:jonnymedcalf
ID: 16699645
The computer is one that I built myself about three years ago. Apart from a graphics card that needed replacing (probably due to me overclocking it too much), it has been working fine until this problem occurred a few weeks ago. It has the following components:
Chaintech Zenith CT-9CJS motherboard
Thermaltake butterfly 480w PSU
Intel P4 Northwood 3.0Ghz CPU
Two Samsung Spinpoint 160Gb SATA Hard Drives
Nvidia 6600 GT 128MB Graphics card
1Gb PC3500 Memory
DVD writer
DVD Rom drive
Could the loss of power while accessing the bios cause it to be reset?
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mjcoyne earned 2000 total points
ID: 16704791
The PSU has a couple of milliseconds to so-called "assert power good" to the motherboard, or the computer will not even start the POST.  Since it is starting, and, aside from the BIOS being reset, completes the boot and apparently operates normally thereafter, I'm a little hesitant to pin this on the PSU.  Perhaps your BIOS got corrupted somehow (especially the Extended System Configuration Data (ESCD) section, which holds configuration information for the hardware installed in your system) or contains invalid data?

Have you entered the BIOS and selected "Fail Safe Defaults"?  There is also an entry called "Reset Configuration Data" which you may want to enable for a boot cycle so it re-initalizes the ESCD.  On the Advanced BIOS Feature Screen, there is a setting called "Show POST CODE" (it looks like you have to scroll down to see it).  If you enable this, we may see an error code that'll give us more information about what might be going on...

Your computer is not overclocked, is it?  I suppose all of those settings would have been lost when you re-set the CMOS anyway...

If it were my computer, I would suspect a corrupt BIOS, go to Chaintech's website, download the latest BIOS file (see http://www.chaintechusa.com/tw/eng/Download/dl_desc.asp?DCSNo=4&PISNo=144), and re-flash.  I hesitate to recommend this though because we are unsure of the exact nature of the problem, and if something goes wrong during the flash, your computer could be killed outright.
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by:jonnymedcalf
ID: 16708857
Mjcoyne,
I followed your advice and enabled 'reset configuration data' in the bios and this seems to have fixed the problem. I have turned the computer on and off several times and the problem has not occured again. Thank you so much for your advice.
You have saved me forking out for a new PSU!
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by:mjcoyne
ID: 16709420
Excellent news, jonnymedcalf!  I'm glad it worked out for you -- if it wasn't the ESCD, I was running out of ideas, and the next several things to try were somewhat dangerous to advise someone to do long-distance.  I also hate spending money on parts it turns out I don't need...:)
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