Power to CPU

By mestarspet ·
My CPU is automatically turning on without my assistance at Noon. It is turned off, not shutoff and then reconnects to power source. (It is not in Hibernate mode.) Windows XP
What is going on?

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All Answers

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Check BIOS

by tmalo627 In reply to Power to CPU

Depending on your mobo and BIOS version, some have an "auto-on" feature that you can schedule. To get to BIOS, start your computer and watch the screen as it boots for the appropriate button to press. This should be displayed during the manufacturer splash screen (when it says Dell, Sony, HP, etc.) It will normally say something like "To enter setup press F2." The actual key you press will depend on which BIOS you have. Common keys I have seen to enter BIOS are F1, F2, F10, or delete.

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Bios Browsing

by mestarspet In reply to Check BIOS

I did indeed check the Automatic Power Up in the Bios and it was Disabled- So no luck there. Also the Clock was set correctly!
Thanks for the idea.

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something to try....

by ---TK--- In reply to Power to CPU

Check Device Manager (Start>(right click)My computer>Manage>Device Manager) look for Network Adapters, right click the active NIC, go to properties, last tab is Power Manager. Make sure the second check box "Allow this Device to bring the computer out of standby" is unchecked...

Sounds more like a setting in the BIOS (was my first thought) like the first person stated... but this setting could also "wake up" your PC...

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Device Manager

by mestarspet In reply to something to try....

I did check the Device Manager and the Power Manger was correct allowing the system to return from Hibernation.Thanks for the idea!

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And if the above is of no help

by OH Smeg Moderator In reply to Power to CPU

Look for something else that turns on at the same time that draws a lot of Power.

Power Spikes produced by Air Conditioners, Fridges/Freezers, Washing Machines can cause a Ripple Effect to happen on the 5 V DC Rail inside the computer which makes the PS think that the system has been turned on so it starts the system.

When you turn off a ATX Power Supply it doesn't stop all of the power going to the M'Board at the very least the 5 V DC Rail is energized and relies on a Ripple on the 5 V Rail to turn the PS full on when you press the Front Panel On Switch.

The way to check for some other device turning on the computer is to place a Filter on the Mains Lead between the Mains Power Point and computer. And just the computer case. I've seen instances where turning on an External Dial Up Modem will cause enough of a Power Spike to cause the computer to turn on.

Of course this only happens in areas where the Mains Supply is at the lower end of the legislated Delivery.


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Power Draws

by mestarspet In reply to And if the above is of no ...

I had thoughts down this line because of a couple of things: 1. The system is plugged into a Power Strip which has a multitude of other electrical items, alarm clock, phone, TV, VCR, modem, and the other computer related items. Each of these items do not have a Noon Wake UP to cause a Power Surge to my knowledge.
2. Of all these things, why is only CPU powering up at Noon and not any of the other items?
Thank you for your ideas.

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Easy answer is

by OH Smeg Moderator In reply to Power Draws

That the others things get turned off where as the computer itself doesn't get turned off. It only is Shut Down.

The other items don't have a constant Power On need so the Power Switch actually breaks the circuit and turns them off. They can be a Single Throw Single Pole Switch or a Single Throw Dual Pole Switch. The Single Pole Single Pole switches are the cheapest and most commonly used but they only switch the Active Line in Theory. That of course depends on the power Point that they are plugged into being wired correctly as well as any other Power Strips and so on that are between them and the Power Plug.

The Single Throw Double Pole Switches are the ones used on some Power Supplies at the back of the computer and switch both the Active and Neutral Lines of the Mains and do not require the power points and so on to be correctly wired as they switch both lines off.

The Power Switches on Modern Computers are not a Power Switch as such they are a Contact Switch that is On when pushed in and off when not being touched. They cause a Drop in the 5 V DC Circuit inside the case which in turn turns the Power Supply Full On for 2 Seconds at which point unless it receives a signal from the M'Board it shuts down again. Of course with a working M'Board in Place the Power Supply will continue to function and supply the power necessary to run the computer.

The only solution to this is fitting a Filtering Unimpeachable Power Supply between the Mains Socket and the computer and only having it feed the computer nothing else like the Phone, Modem and so on and particularly the Monitor.

If you use one of the cheap UPS that doesn't filter the Mains and you have Power Spikes it will have no effect on stopping the Power Spikes turning on the Computer.


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Power Supply at Noon

by mestarspet In reply to Easy answer is

The suggestions are great and your idea of isolating the computer from the other sources sounds likea good plan.
A couple of questions: 1. Is there a Report Log of the Power Up Event? This might give me other ideas. 2. Since the phone, modem,and CPU are on the same circuit, it is possible the Phone Company runs a Noon power check every day causing the CPU to Power UP? If I can get a handle on what happens every day at Noon, it might be easier to isolate the problem

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Well in order of asking

by OH Smeg Moderator In reply to Power Supply at Noon

1. Is there a Report Log of the Power Up Event? This might give me other ideas.

No by default there isn't this option.

2. Since the phone, modem,and CPU are on the same circuit, it is possible the Phone Company runs a Noon power check every day causing the CPU to Power UP?

Not likely as the phone system is on a different circuit runs on 12 V DC and this power is provided by batteries at the Exchange.

While the actual Phone may require Mains Power that only is for the Handset not the actual Phone Circuit that the Phone Company owns and manages.

If the phone is faulty and feeding some form of power into the Phone System it will damage the exchange and do severe damage. For that reason most Phones need Approval to be used when they require Mains Power and this need to be isolated from the Phone Circuits.

I've seen in severe cases Power Spikes caused outside the home causing the computer to switch on. So if you have any Industry in the area this could Be the cause of the problem as well. Here a Newspaper starting the Print Run would cause the Burglar Alarms to trigger years ago at one place that I was working.

So you need to look at the area around the place that the computer is switching on if there is nothing at that premises and if there is any High Drain Industry that could be the issue here.

The only solution is to Isolate the Computer from the Mains with a Filtering UPS in that case.


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I can't find the post

by Jacky Howe In reply to Power to CPU

but someone recently had a similar problem. I think that a boiler in the basement was causing a lot of vibration when it kicked in. His mouse was very sensitive and it woke up his System. So while you are checking in the BIOS see if there is anything that will wake up the System if the mouse is moved.

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