Computer Turns Itself On!

[Bluemagic]

I just got a 'Mad Dog' 500W PSU from CompUSA to use with my new setup (in signature) and after I shut Windows down, most of the time it waits a few seconds and then fires itself on again! It'll happen if I do a hard reset as well. I have to unplug the power at night to make sure it doesn't freak me out while I'm sleeping. Anyone heard of any similar problems or know what this might be?

 

[towert7]

There are only two things i can think of.

Eaither the computer is doing something like a "wake on lan" feature,
Or the bios is doing some sort of power feature that keeps the computer on.

Check the bios for some power features.

~Hope this helps

 

[UndeadRoadkill]

Towert7 is probably right, I had a PC that would surprise me by turning itself on when the network cable was plugged in, and later I learned that it was the motherboard's 'wake on lan' feature.

 

[Bluemagic]

I checked the bios and all of those features are turned off. Good idea though; I had completely forgotten about that feature. Any others?

 

[Bugalaman]

did you try to reconnect the power button? maybe check if tehres a short somewhere too..

 

[BossNoodleKaboodle]

I have a computer that does the same thing. Its a motherboard thing I believe, because it does it with multiple PSU's, and it only seems to do it when I use the power button to shut the computer off, rather than the OS directly. Do you press the button and the computer shuts down or do you click start, then shut down?

P.S. its a Gigabyte Intel 865 mobo that does it to me.

 

[slowbiznatch]

I'd like to know what causes this, also. In the past I have found that replacing the power supply or motherboard solves this problem, just depending on the given situation.

 

[compslckr]

check your bios and see if you have "power back on after power fail" enabled. on my old system if i enabled this it would restart after i shut it down after a few minutes.

i would also recomend turning it off, unplugging the power switch from your motherboard and see if it turns on again, if it does then the power switch is not the problem, but if it does not turn back on you can assume that the power switch may be the problem.

 

[raz-0]

another interesting thing is the wake on modem crap. Because having a couple phones, a fax machine, a modem, and an answering machine on a phone line became common, they upped the juice on the phone line because lots of people were exceeding the ringer load rating for the line. The net result is that if you don't load the bajeebus out of your lines, the regular fluctuations in the ringer current can wake up your pc with wake on modem.

these days I have no modem, and have two phones on one line. They constantly ring a half ring due to only having a ringer load of like 4 now.

 

[msny]

If you have set the computer to shutdown and it restarts there is a setting in Win XP you can try. This works for some poople.

Go to Start > Settings > Contol Panel > System icon double click. Select the advanced tab and click the settings button
under Startup and Recovery. Make sure the Automatically Restart button is NOT checked and save the setting.

If it is already unchecked then you probably do have a hardware issue of some kind.

 

[[Spectre]]

Or it could be gremlins

 

[Qwertyman]

Or it could be gremlins

its not gremlins, its angry dwarves.

 

[Renegade87]

Now if it would only go to work for you too

 

[Bluemagic]

Well the problem stopped happening for about three days, and now it's back again. The 'auto reboot' after a BSOD is turned off, and I searched the BIOS again to see if anything would be causing it. I'll try taking the connection for the power on out and put it back in and see if that does anything. Thanks for your suggestions guys, keep 'em coming!

 

[Ice Czar]

I'd like to know what causes this, also.

PS_ON signal

+5VSB rail, otherwise known as softpower on
with ATX your board always has power unless you switch the supply itself off or unplug it
that power is employed for Wake on LAN, Wake on WAN, powering up from the keyboard ect.

either the supply is falsely reading the signal, something is sending the signal or the mobo is inappropriately sending the signal

Early PCs using the PC/XT, AT, Baby AT and LPX form factors all use a mechanical switch to turn the computer on and off. Newer form factors, starting with the ATX/NLX, and including the SFX and WTX, have changed the way the power supply is turned on and off. Instead of using a physical switch, these systems are turned on by a signal from the motherboard telling the power supply what to do. In turn, the motherboard can be told to change this signal under software control. This is what allows Windows to shut the power down to a PC, or what allows such features as turning a PC on from a button on the keyboard. This feature is called "Soft Power" and the signal that controls the power supply is called "Power On", or alternately, "PS On" or "PS_On".

This feature would seem to create a small "chicken and egg" situation however. How can the motherboard tell the power supply to turn on, electronically, when the motherboard is also off due to not having any power from the supply? :^) The answer is the other "Soft Power" signal, which is called "+5 V Standby" (or "+5VSB", or "5VSB", etc.) This signal is the same output level as the regular +5 V lines from the power supply, but is independent of the other provided voltages and is always on, even when the rest of the power supply is turned off. A small amount of current on this wire is what allows the motherboard to control the power supply when it is off. It also permits other activities that must occur while the PC is off, such as enabling wakeup from sleep mode, or allowing the PC to be turned on when activity is detected on a modem ("Wake on Ring") or network card ("Wake on LAN").

as a note take care to kill the +5VSB power to your board and then reground your case and ideally yourself when swapping any components
covered in full in the ESD & Electromigration Rant