Sign in with
Sign up | Sign in
Your question
Solved

Power returns to mobo after PSU is switched off.

Tags:
  • Motherboards
  • Power
Last response: in Motherboards
Share
August 8, 2013 1:27:20 PM

Hi All,

Hoping some genius out there can help me out with something that's really bugging me!

I have recently put together my first self build. Specifications are as follows
-Asus Crosshair V Formula-Z AM3+ AMD 990FX DDR3 ATX
-AMD AM3+ Black Edition Vishera 6 Core Processor 3.5 GHZ overlocked to 4.2 GHZ
-Cooler Master Silent Pro 720w PSU
-16GB Corsair Vengeance DDR3 1600MHZ
-128GB SSD SATA 6Gb/s 2.5" Solid State Drive for OS installation
-UEFI Windows 8 64 bit
-Asus AMD Radeon 6450 HD 625MHz 1GB PCI-Express HDMI Low Profile
-24x SH-224BB DVD-RW SATA OEM Half Height

First off for the most part everything seems to be running smoothly (Thanks to Carey Holzman's great videos!). So this is more a niggle then anything else!

When I shut down the PC - I can see the Start Button still illuminated on the mobo.I know That's Ok!

Then I turn the switch on the PSU off, and about 3-5 seconds later the mobo start button light goes out. Again I know that's normal. So I am ok with that!

But here's the strange thing. 2-3 seconds later the mobo start button lights up again for 2-3 secs and then goes off until I turn on the PSU switch again.

I suppose my question is why does it go off then come back on again. I would think the behaviour would be once it goes off after the PSU is switched off it should stay of until PSU is turned back on, right? Note its just the start button lighting up, no fans spinning or any other action going on.

Same thing happens if I use the switch on the power strip, or on from the wall socket, or bypass the power strip and go straight to the wall socket, or use another power strip via another power socket elsewhere in the house.

I have also removed everything else connected to the PC, and even removed the Power cable. Same behaviour is observed either way.

This behaviour is replicated each time I repeat the above steps.

One other thing to note, is the next time I boot after this behaviour is observed the Q-Code on the motherboard reads 40, and not AA. As a novice I am not hugely up to speed on these thing but I understand AA to be a normal boot from previously shut down state and 40 to be more of waking up from sleep.

I cant see anything out of whack on the bios either. The system is set to power off in the event of power loss, and nothing else is popping out at me.
I have cleared CMOS also. But no Joy!

I have also turned off the windows fast boot option under power settings but again no joy!

One last thing, I only have the PSU that I bought for the build, and have no spare one at this point so I have not been able to check with another PSU.

Besides if I start tinkering at the kitchen table again this week I am afraid the Mrs will take a rolling pin to my head!

Thanks for taking the time to read and any insight would be greatly appreciated.

Rich

More about : power returns mobo psu switched

Best solution

a b V Motherboard
August 8, 2013 1:42:02 PM

more than likely a faulty or failing PSU, happened with the one 750 watt PSU i had in a build, eventually had to pull the plug to get it to fully power off, any time that the power button was hit, it would go on, then stay on until the plug got pulled. popped in a differnt unit and the problem went away. no other changes were made
Share
a b V Motherboard
August 8, 2013 1:47:48 PM

its a possibility that the psu is damaged, but it could also just be the way it dumps its residual current so its not sitting in the system till next power on. you best email your motherboard/psu manufacturer and see if they have an answer...
m
0
l
Related resources
!