Computer runs fine, but won't stay turned off?

Hello everyone, thank you in advance for any help!

I home built my brother a computer almost 1 1/2 years ago and have replaced the motherboard (Asus P5Q Deluxe) three times (third one works while turned on) and the power supply once (Corsair 520HX to the 620HX), my YouTube video shows the problem with shutting off. The first two motherboards the whole computer would not post, the third motherboard works flawlessly while using the computer, but ALL of the fans either stayed on never turning off or surged on-off-on-off over and over until I pushed the switch on the back of the PSU. Why am I having the same issue with three motherboards and two different PSU models? I will list the specs of the computer below, note that I have tried the EVGA 9600GT, G.Skill DDR2 2x1GB, Western Digital HDD in my computer which works flawlessly! The only thing I have not tried in my computer is his P5Q Deluxe mobo, Corsair 520HX and the 620HX PSU. I'm hoping it's just a BIOS setting, I really am! I have also assembled the motherboard outside the PC case with the same problem!

YouTube video > http://www.youtube.com/watch?v=kUfIJS_hU4E

Never had any overclocking!
Asus P5Q Deluxe
Q6600 stock clocks
G.Skill DDR2 2GBHZ 4-4-4-12 2.0V
EVGA 9600GT
Corsair 620HZ PSU
Western Digital HDD

I have tried resetting the real time clock (CMOS), I don't want to update BIOS unless this is a known problem.

Last sentence of my first post in bold letters, if it is a grounding problem it's in the motherboard.

I did not have the PC case switch connected to the mobo, I've already tried three different PSU with two different brands. I used a Corsair 520HX, 620HX and Enermax Infinity 720W PSUs, my Enermax when connected to the mobo went into protection mode indicated a short circuit event! I think these Asus P5Qs are garbage, other Asus mobo are much more reliable. I'm going to ask for another model mobo, if Asus refuses I will buy either a more reliable model or a different brand mobo!

A couple of questions.

1. When you assembled the MB outside the case, did you disconnect the Power On lead wire from the case Power On button and instead use a screwdriver to short the Power On switch on the MB header to start the system? Maybe the case Power on lead wire or switch is shorted causing the system to power on randomly like that.

2. I have an ASUS P5B-VM DO 965 micro MB running. Same era as your 975. No problems for a long while and one day I upgraded the PSU to a brand new PCP& C 610w Silencer. Went great, really quiet in the bedroom with the new PCP & C unit. Then I found the system was powering on randomly (same as your system, not to desktop just powered on with fans running) when I shut down and left the room and came back. I thought I was imaging things. I swapped out the brand new PCP & C 610w unit for an new OCZ 450w unit and my random restarts ceased to exist. System was back to normal as it had been for years. I know you tried a couple of PSU's. If you are feeling industrious, perhaps trying a different PSU may solve the random restart problem like it did mine.

oops, you lost me there. A PSU can indicate the MB has a short?

Well, I watched the video all the way through this time. The MB can not trrigger the PSU to start up. It's the other way around. The PSU triggers the MB to be something 'live' if you will. The MB has no power source other than the PSU to power on. MB can not power itself on.

The PSU gives beep code errors? I was not aware of PSU giving error code related to the MB?

I guess you mean the manual to the PSU? That's all right not necessary.

The MB does not supply power to the PSU is what I meant.

The MB power button on the video is a feature many MB's do not have. That onboard 'button' is for enthusiasts who have the MB removed from the case working on the board. That button serves the same purpose as the front panel header power on swithch on the MB. The header the case power on button attaches to to power on the board. Touching a screwdriver to the power on header does the same thing as the button you are referring to does.

Yes. That's what it does, turn on the power source to the unit. The power supply.


Anyway, I know you are frustrated with the situation and the 975's you have tried. There were a lot of those ASUS boards sold and many still working I'm sure. I have two ASUS 965's still running to this day. I suppose it's possible you have two bad ones. My theory of a bad power supply could easily be solved by install the PSU in another system. If no short out occurs, my idea is incorrect. I don't doubt you. Just trying to provide some input. You seemed to have worked your but of trying to solve it.

I did something I never thought I would do, use my brother's Corsair 520HX and his 620HX on "my" MB. My MB did not come on by itself like the last three P5Qs did, another thing it powered off completely just like it should! I sat there for an hour reading a book just waiting to see it come on by itself, it did not. I've been to the Asus forums and three posts down from mine a poster was reporting the exact same problem, it wouldn't completely shut off.


He said he would leave the room only to find out later that his computer has turned itself back on and would do so many times. I then went to NewEgg and looked through the 1 egg reviews only to find someone with the same problem, the P5Q is said to be an erratic behaving MB. When I get my forth P5Q I will post back on what happens. It it happens again I'm all ears for a new MB, probably a Gigabyte board. All my brother wants is a computer that works for internet and eBay stuff, no gaming!

Sorry, I don't follow. Who's MB is the 975, your's or your brothers?

EDIT. So you hooked up two different Corsair power supplys to the 975 MB and the restart after shutdown still occured?