Pc not posting

[eclaire]

Hi,

Got a pc that won't post. No beeps, nothing, and when powered on shuts itself on within a few seconds. It had been acting slightly screwy previously (details below), maybe there's just enough info here for someone to diagnose before i randomly start replacing parts.

Fault happened after i plugged in a network cable. Assuming i might have caused something to short, I've breadboarded it, removed as much as possible inc video and ram, removed cmos battery etc. No luck. So long as either EPS cable or the CPU are installed, shutdown is within a few seconds. Remove either and the fans/led's etc will spin and the lcd poster shows CPU INIT. But I gather that's not very helpful, and it could still be mb, PSU, or CPU.


System specs:

CPU: Q6600 (overclock to 3.0, previuosly to ~3.3, temps were good though)
MB: ASUS Striker II Extreme
PSU: Enermax Galaxy 1000w


Right, to the additional details I'd hoped might narrow it down:

Swapped video cards and cpu cooler a few weeks ago. Soon after I had some weird but intermittent issues. Had one or two shutdowns under load (gaming) but that stopped quickly. Potentially more usefully, when booting the pc would take a couple attempts occasionally. In the sense that it sounded like the fans spun up, stopped, then started again up to five or so times. Usually ended up booting fine, if not i would get a long beep. From pc speaker I'm pretty sure, but it might have been the PSU's as well. Once up and running it's been fine.

From threads I've read it seems likely to be the power supply, but it was fine until recently with a higher overclock and a much more powerhungry videocard (4850x2 vs 5770). I am, in short, well out of my depth...

Any guesses?
Thanks, and let me know if there's any more detail that might be useful.

 

[crewton]

I'd also lean toward your psu. Do you happen to have another psu around to verify it's your psu?

 

[geekapproved]

I'm trying to make sense of this.

when powered on shuts itself on within a few seconds.

Did you mean shuts itself OFF?

Did this happen after you downclocked the cpu?

 

[eclaire]

Oops, typo. Yes, it shuts itself off.


On reflection, it did the no-post, permanent beep (i.e. one continuous tone) until reset thing once or twice in the past as well, well before i last opened it up.

I guess it's a secondary issue now since whatever was problematic then is apparently dead now, but what causes something like this? I think the board uses an award bios, can't find any reference to that beep code. Supposedly denotes psu problem in supermicro boards.


Re testing with another psu, I have one that I don't trust (was attached to a motherboard that failed fairly spectacularly - been a bad year for computer disasters...). It will power on with the paperclip trick (but sounds a little funny), but attach it to the motherboard, and while the led's light up, the lcd poster shows gibberish. Power it on and everything goes dark instantly.

 

[eclaire]

Did this happen after you downclocked the cpu?

No, I downclocked in response to it

 

[PartialGenious]

You overclocked and put a bigger more powerful GPU in I would definitely say Power Supply.

Note: If you find that a system consistently fails to boot up properly the first time you turn on the switch, but that it subsequently boots up if you press the reset or Ctrl+Alt+Delete warm boot command, you likely have a problem with the Power_Good timing. You should install a new, higher-quality power supply and see whether that solves the problem.

from http://www.tomshardware.com/reviews/power-supply-specifications-atx-reference,3061-2.html

I just hope you actually have a decent power supply and did not ruin any other parts of your computer. The PSU is often overlooked I suggest buying a solid 500-600 watt PSU. Personally I suggest Corsair, may be expensive but in this case you get what you pay for.

 

[eclaire]

You overclocked and put a bigger more powerful GPU in I would definitely say Power Supply.

...

I just hope you actually have a decent power supply and did not ruin any other parts of your computer. The PSU is often overlooked I suggest buying a solid 500-600 watt PSU. Personally I suggest Corsair, may be expensive but in this case you get what you pay for.

I should've been more clear. Part of the reason i was unsure about the PSU causing the problem was that

a) I replaced the 4850x2 with a 5770, so power consumption actually went down by a decent amount,

and

b) It's pretty stupidly overspecified fro what is was being asked to do. Oh well, so much for the plan of flogging it on ebay for untold riches...