Power turns off before POST

[haydnw]

Hi everyone,

My PC, which was running fine last night and this morning with no new hardware or software installed, now won't boot. My girlfriend was running FireFox when apparently it just lost all power.

Now when you turn it on, power comes on, the fans spin up, then it turns off again. This happens every time. There's not enough time for video output, and nothing from the PC speaker.

I've unplugged everything on the outside except video, keyboard and mouse, and everything on the inside except gfx card, mobo, fans and hdd (including power to everything on the inside). Still the same.

I've reset the BIOS according the Mobo manual (ASUS), by removing the battery and swapping the relevant jumper over for the required amount of time. Still the same. I did have the ASUS AI overclocking on but it's been like that for several days with the CPU and motherboard getting no hotter than 40oC when playing hours of Far Cry and usually hovering around the 32-33oC mark. Obviously the overclocking settings will have been reset when the BIOS was reset anyway.

What I haven't yet done is leave the power cord plugged in and hold the power button for 30 seconds to discharge static from the motherboard. This is because I went home on my lunch break to investigate this (that's right, my girlfriend broke it while I was at work!) and I didn't have time.

Help me! Any advice gratefully received!

P.S. It's an Akasa 400W PSU, ATX2.0 if that's relevant. Has already been powering the system with no problems at all though.

 

[Me__2001]

sounds like its shorting on the case, i'd of thought that it would have happened when you first built it though

if you can set it up outside the case and try it

 

[haydnw]

Thanks for the quick response! What parts could be shorting on the case? It is likely to be the motherboard or another component? Case hasn't been moved, but will definitely give it a try outside just in case somethings come loose.

 

[Me__2001]

its usually the the mobo shorting on one of the standoffs

 

[haydnw]

OK, I've now removed the motherboard and power supply from the case. They are both sat on insulating material. The power supply has the EATX (biggest plug) and the smaller ATX 12V plugged into the motherboard, and the power switch from the system is plugged into the motherboard. NOTHING ELSE is plugged in, not even the CPU fan. Still, the fan in the PSU comes on for about a second and then goes off along with all system power. The 'power' LED on the motherboard is lit throughout though.

I'm now sure it's not a short with the case. Is it most likely to be the PSU or the motherboard? I have a feeling it's the PSU but I can't really explain why. I could do with some ammunition when I ring the shop up to complain! Thanks.

 

[Me__2001]

plug the CPU fan in! if its still doing it something is broken, is it possinble to test the CPU or PSU with another computer ?

edit: just read your posts again and the PSU should be ok if it was a cheaper brand i might have thought it was that but akasa make some good stuff, also seeing as the power LED is on its more than likely not that, the only other thing is the CPU or the motherboard

 

[muckshifter]

Replace the MB ... it died.

 

[haydnw]

Thanks, dead mobo is what Overclockers said.

I now have the issue of needing to remove the heatsink / fan from the CPU, in order to remove the CPU to send the mobo back. Are there any issue with this? I used the Zalman thermal grease supplied with the HSF between the HSF and the CPU so I assume it will just pull off rather than being actually stuck to the CPU? Or will the grease have dried and stuck?

I knew just enough to build this PC, I didn't think I'd be disassembling it two weeks later. Grr....

 

[Me__2001]

the grease should still be soft, gently rotate it left and right and it should come straight off, if your really worried warm up the heatsink with a hairdryer

 

[haydnw]

Thanks! Will have to do the same with the Zalman heatsink on the chipset too, and replace the old fan back onto it. Next (and hopefully final) question - what can I use to clean the old grease off the CPU and chipset before I put the heatsinks back on when the new mobo arrives?

Thank you for all your help, it's really got me out of a hole.

 

[Me__2001]

your gonna need some thermal interface cleaner and some lint free cloths, wipe of whats left with a cloth then put some cleaner on another cloth and wipe it until its clean

 

[haydnw]

Thanks for the help. I've now replaced the power supply with a different make / model and initially got exactly the same problem. If I left the screws on the Zalman HSF a little loose then the PC booted fine. I then eventually tightened them up entirely and it's now working fine. In conclusion, I have no idea what the problem was - can't have been the mobo because it was tested as OK, can't have been the PSU because it did the same with a new one, can't have been bad wiring in the HSF because it did it with the stock AMD one, which only leaves the CPU. And that seems to be working OK now! How long for is another matter entirely...

 

[.-=ManQ=-.]

Im intrigued to know how this panned out.

Im sure it was your PSU What was it ?

Do tell !



edit: sorry didnt see the reply tagged at the end

 

[Me__2001]

strange , maybe the NB heatsink screws were messing with something, have you put any washers under the screw heads ?

 

[.-=ManQ=-.]

Does sound like that (screws without washers).

Anyways, as long as it's alive again.

 

[Taino]

Let us bow our heads

I believe a prayer is in order, please step up to the podium.







Carpe Diem

 

[haydnw]

Hey guys,

The heatsink on the NB was/is held on with just the standard Zalman fixings it came with, which were plastic expander pins through some metal arms. I can't see off the top of my head that that would have caused a problem, but can't remember exactly. Whatever it was, it seems to have disappeared now (touch wood). Still, it gave me a chance to get another SATA hdd, fit a side 80mm fan, ditch the fan controller and tidy up the cabling (new PSU has modular cabling too)

I'll let you know if I ever find out what it was...

 

[haydnw]

seems to be working OK now! How long for is another matter entirely...

About nine days. It's just died on me again - exactly the same as last time. It's now with the local PC repair guy to see if he has any ideas.

 

[.-=ManQ=-.]

Ah ! Ok, this smells like a familiar problem, assuming your getting the same symptomes as originally reported.

I suspect it coudl be your electricity supply.

Have you either tried the PC on a different power socket? A different room or another floor is always good to test this as ring mains tend to be split floor by floor.

Otherwise, try the machine in the same room but using anti surge protection.

I had a customer last year who brought a pc back twice, then I gave her a surge protection socket block and never saw her again !

Just a thought !

 

[haydnw]

Thanks for the reply - it is running through a surge-protector anyway, and always has been. I've also tried it straight into a wall socket in another room, and in another surge-protector.