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PC turns on after shutdown


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I have a VX 550 power supply that I've had for some years now, but there has been some strange issues. I will try to give an overview of the relevant events:


I think I bought it for an AMD build some years ago and it worked fine.


Then I rebuilt the system to an Intel i7 2600 CPU with an Asus h67-m pro motherboard. It was here the problems started. When I shut down the system, everything shut down fine, but after 1 second the computer turned on again. I checked (and disabled) all wake functions and tried "everything" - but I was forced to always use the power off button at the back of the PSU after shutdown. The computer would then try to start but there were of course no power.


This was irritating - but I could live with it. I tried other OS'er (e.g. booting from Linux CDs with no other disks), tried with almost no memory, disks disabled, latest BIOS, no USB devices, no network - but the problem was always there. I even returned the motherboard for testing, but they found no issues with it and could not reproduce the isses. With all this testing in mind, I concluded with this being a PSU problem, but because the PSU was expensive - I didn't want to buy a new one.


Last week I got a new motherboard for my computer - Asus H77-m pro due to some other issues. I was hoping this also would fix the irritating auto-turn-on issue - but to my disappointment - the issue was exactly the same. The computer turned itself on after shutdown. When it turned itself on - I got a warning from the motherboard that it had detected a power surge and had stopped (before booting Windows).


As I worked on installing new drivers, and setting up the new motherboard I suddenly saw that the issue had disappeared - it shutdown fine and stayed off. I have had no single unintended start after that. I think the thing that resolved it was a BIOS update for the motherboard. There were more recent BIOS for the new motherboard than the old one. So for now it seems fine.


So the questions are:


1. Has there been any such incompatibility issues between 550 VX and these Asus Motherboards?

2. Even if the issue is resolved for now in a BIOS - it seems strange that the motherboard detected this as a power surge issue?

3. Should I replace the PSU even if it is OK for now? I am afraid that there now is a "hidden issue" that might damage some components in my PC.

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PSUs and motherboards have to "handshake" for the PSU to turn on. This is done with a signal called the "power good signal". It could very well be that the delay of this signal was not compatible with what Asus had programmed into their BIOS until their most recent revision.
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  • 4 weeks later...

When I tell Windows to Shut Down my machine will power off. 1 second later it will power back on. The only way to stop this is the switch off the PSU.


I'm getting the latest update from MSI for my motherboard, but at the time I built it I brought it up to date.

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At this point I will assume that I need to give more details.

I will not restate my Specs, as you can see them on my profile.


When I click the Windows "Shut Down" option my PC will fully shut off, then 1 second later it will turn back on.


I have fully updated the BIOS and drivers for all hardware in my machine.

I have verified that each of the connections for the switches and LEDs are correctly connected to the board, even checking the polarity on each.


The only way to keep the machine from powering itself back on is to flip the switch on the back of the PSU or disconnect power from the PSU.


Any help with this issue would be appreciated. I bought the PSU back in November, and I am hoping that I don't need to have it replaced on Warranty.

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