Power turns off before POST

[.-=ManQ=-.]

Damn! THis sounds like an awkward one to resolve, like my missus!

Your PC isn't called Julie by any chance is it ?

 

[Me__2001]

i've been doing some searching and its quite a common problem, works fine for a while then wont start, no solution yet. i'll keep looking

 

[.-=ManQ=-.]

Definately not vorus related?

 

[haydnw]

Nah, I've had Kaspersky on there with 3-hour updates, but the PC doesn't even get to POST. Does the same when I have only the PSU connected to the mobo with the CPU in place. Nothing else connected and it's still the same.

I figure that, given the above, it must therefore be either the PSU, the CPU, or the mobo. I've bought a replacement PSU and get the same problem, so it can't be that. The mobo has been sent back to the retailer I bought it from, and tested as OK, but this is an intermittent fault so they may have missed it. And the CPU has not been tested. So I'm down to the CPU or the mobo. The two most expensive bits to replace. Thanks for the continued help everbody, it's much appreciated.

 

[haydnw]

OK, so this time I managed a whole month before it went belly-up again! Exactly the same as last time, doesn't even get to POST. I've given up on trying to track it down, and am going to swap out the case, mobo and CPU. Does anyone think this might be dodgy wiring in the case power button? It's a really really cheap case, so I'm wondering if dodgy wiring in that might be the culprit? Opinions please...

 

[.-=ManQ=-.]

Like a bad penny the problem keeps comng back eh ?

I just sorted a friends PC out with exactly the same problem, locks up and crashes either prior or during post and even randomly once in windows.

Replacedthe PSU for a new 400W one and all is now OK, I had same prob with one of my machines and same thing.

Your SURE its not PSU ?

Have you given your components a blow job ? Tee Hee! I mean to clear the dust !!!

 

[Me__2001]

when you sent back the mobo's before did they say what was wrong with them ?

 

[haydnw]

No, they just returned it as No Fault Found, despite me telling them it was an intermittent fault. So I'm going to try again, if I can ever get through to Overclockers support. They were really good last time I rang them - no hassle or anything; I just can't get them to answer the phone now

 

[Me__2001]

so its the same board ?

 

[haydnw]

Yeah, but I can't be sure if it's that or the CPU. Can I?

 

[tjm4fun]

Interesting problem.
Have you swapped the cpu fan? since I missed which mobo, most new ones will shutdown almost immediately if they don;t detect the speed signal from the cpu fan. move the pcu fan to another plug, plug any 3 wire fan to the cpu position and try powering up. if it powers, go to bios, pc health or monitoring whatever they call it, and see if there is a cpu speed sense shutdown option.
Also you mentioned it came to life wen you loosened the hsf. this brings 2 other possibilities:
1. the mounting is flexing the mobo and has possibly caused a minute crack in the patters that opens on occasion.
2. the cpu is not properly seated, which can cause the same scenario.

Ditto for the nothbridge hsf.

Just a couple of thoughts that haven't popped up before.

 

[haydnw]

Interesting problem.
Have you swapped the cpu fan? since I missed which mobo, most new ones will shutdown almost immediately if they don;t detect the speed signal from the cpu fan. move the pcu fan to another plug, plug any 3 wire fan to the cpu position and try powering up. if it powers, go to bios, pc health or monitoring whatever they call it, and see if there is a cpu speed sense shutdown option.
Also you mentioned it came to life wen you loosened the hsf. this brings 2 other possibilities:
1. the mounting is flexing the mobo and has possibly caused a minute crack in the patters that opens on occasion.
2. the cpu is not properly seated, which can cause the same scenario.

Ditto for the nothbridge hsf.

Just a couple of thoughts that haven't popped up before.

Thanks for the new ideas...

I've swapped the CPU fan, yes. Tried it with the stock one instead of the Zalman one but same intermittent problem. Also tried the CPU fan on another plug. I have played about with the BIOS settings etc and the PC *will* boot without a CPU fan so I don't think that's the issue.

The mounting may well be flexing the mobo - this is about the only thing I can think of. Loosening the HSF on the mobo seemed to sort it out one time, but then the problem came back. The only thing is, unless I screw it down really tight it doesn't contact the CPU sufficiently.

Unless there's a problem with the lock-down mechnism on the CPU mount, I don't think it's the CPU seating that's the problem, I've looked into this too and taken it in and out a few times.

The mobo is going back to the retailer for a swap-out - I'll let you know how I get on.