PC keeps on turning back on after shutting down

Hi,

 

I am not sure whether this is a problem with the AX750 psu or not!

 

sometimes when the pc has been running for a long time ie 1 hour and i select "Turn Off Computer " in windows XP, it turns the PC off and the psu off (as i can here the relay click from the psu), and after 1 second it switched it back on again (I can hear the relay click back on from the psu as well) and starts windows again. Now if i turn the PC off using the Power button on the front of the PC then it shuts down the PC as normal without restart it again which is ok. The problem only happens if i shut down the pc using the "Turn Off Computer " in Windows. It only does this if the PC has been ON for a while and it does not do it all the time. If the PC has been running for a few minutes and then i select "Turn Off Computer " in Windows XP then it shutsdown OK (no restarts), it only happens if it has been running for a while.

 

Why is this happening?

Could this be a fault with my AX750 PSU?

the make and model of the motherboard

 

is Gigabyte GA-EP45-UD3LR Socket 775 motherboard

 

I have not tried the PSU on another system,

 

But i never used to get this problem before even with the ax750 psu

 

I started to get it recently and it is intermittent,

 

I turned my PC on in the week end for 10 minutes and shut it down

with no problems.

 

What is going on.

Thanks for the reply!

 

I do have the chipset drivers installed for this motherboard.

Basically i was not getting any problems before then i transfered the pc

components from one case to another case i removed the CPU gave it a clean with Arcti clean and installed a higher performance cooler on it. Then i started getting this problem. The strange thing is that it shuts down fine when you press the power button and it is very intermittent.

I ran my PC for 1 hour for 4 days this week and shuts down fine no problems.

Infact this week i have had no problems at all with the shut down process. It has shut down fine no problems.

 

I have noticed that my MB has Wake on Ring and Wake on HPET somelike that enabled in the bios.

 

The relay click that you hear when the psu switches on and off is that relay on the input side? Is the MB turning the PSU on or is the PSU turning itself ON?

 

My question is that as power switch turns the PC off OK, is this a PSU problem

or a MB problem.

"is this a PSU problem or a MB problem." I doubt either. Sounds like the motherboard's CMOS battery was weak. A bit of corruption in the stored settings (1's changing to 0's) can cause startup and shutdown problems, including rebooting issues, if quick boot is enabled in the BIOS. Some BIOS's will self-correct the problem eventually, some won't. The Wake on Ring option is there to enable the system to boot from the internet via and old style dial up telephone modem connection. HPET is the BIOS option for the more recent vintage High Precision Event Timer; it allows a 64-bit operating system to make full use of 64-bit registers. With the system off and plugged in, a trickle of 5volt power is supplied to the BIOS chip and sensors. When you press the case's power switch a momentary short is created. The short is detected and the BIOS sends a signal to the power supply to wake up. The supply stabilizes all voltages and then sends a power good signal back to board. Board sends O.K. signal back to the supply. Relay click, full power to the board. Cliff notes version anyway.

 

ps: The HPET setting is only useful for 64-bit versions of Vista and Windows 7 and 8. Xp doesn't have the necessary code to use it.

Thanks for the response Garvin,

 

Would a weak CMOS battery cause my problem where you click on shut down PC from windows and it turns every thing off and after 1 or 2 seconds turns everything back on?

 

Even if you switched it off from the mains when it has just shut down,

When you switch the main back on the pc switches on by itself. WOW.

 

How come PC Shuts down fine (no problems) when shutting down the pc via pressing the power button on the case?

 

Last week i ran my PC for 1 hour for 4 days and no shut down problems at all,

it seems to have fixed it self, I will try this week.

 

How long to CMOS batteries last i bought my MB in December 2009

Are they rechargeable? Should i replace the CMOS battery with a new one?

I do not turn my PC on often and is sometimes off for months, would this make the battery lose charge?

 

Thanks for the new pointer.

"Would a weak CMOS battery cause my problem where you click on shut down PC from windows and it turns every thing off and after 1 or 2 seconds turns everything back on?"

 

Yes and no. Corruption in the CMOS settings can.

 

"How come PC Shuts down fine (no problems) when shutting down the pc via pressing the power button on the case?"

 

Using the case's power button held in for four or five seconds initiates the board's shutdown procedure irrespective of the contents of the CMOS. The board usually briefly notifies Windows of this fact, giving it split seconds to halt what it's doing and hopefully prevent corruption from creeping into the Windows indexes and/or the Master File table. Using the case's reset button gives no warning, emergency shutdown immediately. Corruption almost always occurs. I'm unsure what corrupt setting in the CMOS causes the PC to restart automatically, but I've run into it on three differnet machines over the years. Usually, CMOS batteries, depending on how full they were to start with and whether you're disconnecting the PC from the wall power, last about 2 1/2 to 3 years before their lifespan is questionable. Since motherboard manufacturers buy batteries in big lots, it's also hard to know how old they were before they were installed in the motherboard. If the system remains plugged into the wall full time, then the batteries can last longer because the supply is providing a trickle of power to the board. If you regularly turn a power strip off that a PC is connected to then you're relying on the CMOS battery to maintain your CMOS settings. Most motherboard's use a CR2032 lithium ion battery. It is not rechargeable. You can find them at most drug stores, Radio Shack, Best Buy, camera shops, ect. The only other common possibility I can think of is a possible stuck power button switch.

Thanks for the reply Garvin,

 

I have ran my PC for 1 hour for 4 days last week and it shut down fine every time - no problems. It's strange how can a problem fix it self?

I will try agsin this week. Don't know if i will able to repeat it again?

 

So when you power down via the power switch it does not take any notice of the cmos settings and when you power down from windows it does. right.

 

When you leave the PC plugged in the trickle charge is saving the cmos settings, so the cmos battery is not being used, hence saving the battery power is this right?

 

One last thing if its a possible stuck power button causing the problem

Shouldn't it the pc restart when you shut down via the power switch as well?

 

I forgot to mention that when i had this problem, i have also tried switching the mains power of just as it shuts down (switches every thing off) and when i switch the mains back on a few seconds later the pc powers on automatically. Can Corrupt Cmos settings do this as well (With mains off inbetween)?

 

Sorry to be a pain, just trying to get to the root cause of the problem.

 

Thanks!

'It's strange how can a problem fix itself?" Easy. Microsoft Windows operating systems are far more bulletproof than most would believe. It keeps multiple redundent backup copies of critical files. It also has numerous error checking routines running in the background. If these routines encounter a problem, it will attempt to fix it. If it's a Windows file or driver corruption problem as Ram Guy suggested as a possibility, then Windows will frequently draw from one of it's uncorrupted backups to correct the problem if it can. If not, then reinstalling whatever frequently fixes the problem. Some things need to be uninstalled first then reinstalled. Windows is also in communication with the BOS chip and the BIOS program. If a problem is detected, this information can be passed to the BIOS. If the BIOS is written to self-correct, it will when notified by Windows.

 

"So when you power down via the power switch it does not take any notice of the cmos settings and when you power down from windows it does. right." When you boot the system, the BIOS hands off those settings to Windows and the appropriate drivers. With this information, Windows knows how to communicate with the components on the motherboard to make use of them, including how to shut them down. If you use the power switch to shut the system down the BIOS chip briefly notifies Windows to alert it to stop whatever it's doing quick and then it starts shutting stuff down fast. It already knows what's in the CMOS for settings from when the system was booted up.

 

"so the cmos battery is not being used, hence saving the battery power is this right?"

 

Correct.

 

"One last thing if its a possible stuck power button causing the problem

Shouldn't it the pc restart when you shut down via the power switch as well?" Depends, it may only be intermitently sticking; it might have a bit of corrosion on the conctacts or dirty contacts; it might have a stray wire filament making contact. It's hard to say whether it's the switch or not without taking it apart and/or running a continuity check on it. Sometimes just cycling the switch a few times clears up the problem.

 

"when i switch the mains back on a few seconds later the pc powers on automatically." This is why I added the possible problem with the power switch possibility. From a thousand miles away, all one can do is list possibilities. From your description, it sounds like you either have a corruption issue in the areas we've mentioned or a power switch issue. One other note, I've yet to see a genuine power supply problem just disappear; usually they get progressively worse.

Thanks very very much for the detailed response!

 

just want to clarify one point

 

"when i switch the mains back on a few seconds after shutting down the PC, the pc powers on automatically."

Am i right in saying that corrupt CMOS settings can do this as well as a sticking power switch?

 

The reason why i am doubting the power switch is because

This is a new PC case and when i finished assembling my PC i used the power switch to power down my pc (without a monitor, mouse or keyboard connected) quite a few times and i had no problems. The restart problem started when i connected everything up and shutdown the pc via windows.

 

The other problem i had after i finished building my PC is that when i switched it on, it would power down after a couple of seconds, then power up again and then power down and so on. I got rid of this problem my managing to get into the bios and change from Quick boot to normal boot and it now starts up fine every time!

 

Thanks again, You've been very helpful!

No problem.

 

"Am i right in saying that corrupt CMOS settings can do this as well as a sticking power switch?" It's rare but I've seen it happen. Never read a decent explanation as to why. The CMOS holds more than just the settings as well. I suspect that the BIOS, due to the corruption, is misreading the shutdown command as a restart command. The BIOS chip amounts to a tiny dedicated cpu that runs a tiny BIOS program. This BIOS program doesn't have the room for complex error-checking subroutines. Removing then reapplying power has the chip go through it's initialization routine. If it reads the corruption as a restart, boom restart.

 

I only listed the power switch possibility because I've seen that as well. On a new case, it's remote.

 

The power up, power down power up, power down, power up you initially had that was fixed when you disabled the quick boot option points to corruption in the CMOS. It can also take several reboots for the BIOS to clear all of it from the main copy and the backups.

The only other possibility would be corruption in the flashed BIOS version but I'd rule that out because the problems would not go away as they did in your case. Anytime I swap out to a new case or change out/upgrade hardware the first thing I do is disable the Quick Boot option. I don't renable it for several reboots. This gives the BIOS time to run it's complete component checking routines and update all of the settings that are transparent to the user and are not manually configurable. I try to keep in mind that all computers are simply glorified switching machines with a zillion switches, just barely more complicated than an abacus. If someone hasn't written a routine to detect faulty switch settings, the machine has no way of knowing that; they're as dumb as a rock.

One possible reason for the power up when the power supply switch is flipped on at the PSU is in Bios under Power Management..

There you will find a option for what should happen in case of power loss. If this option is set to "power on" the system will auto power on/up anytime the switch on the PSU is turned off them back on.

 

I use this option on some of my bench rig setups since I don't have a power switch setup or connection to a case switch.

Instead of using a screw driver to jump the pins it easier to just flip the switch on the power supply to on to get the rig to power up.

 

So this is something to look at in bios under "power management" if its set to ON this would be the reason it auto powers up when you place the power switch to on at the back of the power supply.

thanks for the reply Garvin and The wolf

 

So it can also take several reboots for the BIOS to clear all of it settings from the main copy and the backups. So does this mean that the bios clears some of ts corrupted settings each time the PC is booted. So it kind of fixes itself, which is surprising i didn't know bios's could do that. I can understand it checking memory, drives etc. and update those but clear other settings i didn't know. Windows can also fix corrupt settings in the bios as well.

 

I can't seem to repeat the problem anymore and i'm kinda getting tired of turning on my pc for 1 hour everyday and switching it off to see if the problem reoccurs.

 

I am going to fit a new Zalman 9500-AT cooler to my MB in April so i will make sure i replace the CMOS battery which should reset the CMOS as well.

 

Thanks for help Garvin!

 

regards

 

fifo

No problem. Corruption in the setting that TheWolf alluded to could cause one of the two symptoms you were having. Still unsure where the corruption would be for the Windows shutdown restart problem you were having.

I have had new motherboard batteries last only a few days and some last a couple of years. Normally when they start getting weak you will notice that the clock is incorrect. I use a Asus X58 board and I had updated the bios after installing the board and I had several restarts after shutting down Windows 7 and found I had to go to a early bio update to solve the problem. I try to remember to replace my batteries one a year and keep backup batteries on hand. When you do change your battery make sure you reset your time in bios and check Windows time also.