Please help. Pc trouble.

I got great advice from you lot last year when I was putting together my pc. So I'm back for some help, please.
My pc was running, I went away and when I came back, the pc was off and wouldn't turn back on. It just won't start. I turn it on, lights and fans start, and within a second or two it stops. Then after a while it will try to start again. It keeps repeating this.
My guess is the processor is the fault. Anyway of finding out for sure?
I have an intel i7 920 with a Noctura cooler and it was running at 3.2ghz. The inside of the case was a bit dusty but nothing major.
I've tried cleaning the dust, replacing thermal paste, removing battery, removing sticks of ram and lots of other things. I even got hold of a test card but that doesn't seem to tell me anything.
I just would like to know. I don't want to buy a new processor and find out, that was not the problem.
Any advice will be greatly appreciated because I'm completely lost.
Thanks.
Sorry for the long post.

Curry Addict

disconnect all your connections and check for browning/pushed pins. reseat all the connections and try it.

Will try that when I get home this evening. I have disconnected and reconnected all the major things, but I will go through everything this evening.

marco_polo

To rule out a switch problem disconnect the front power / reset switches and then start the the PC by grounding the two pins that the front power switch (pwr_sw) was connected to (see motherboard manual if in any doubt at all). Simply touch both together briefly using something like a philips screwdriver (Perfectly safe talking millli-amps of current here).

If the problem remains then I would disconnect everything bar the PSU from the motherboard (including the CPU ) (maybe leave one fan connected as a visual queue) and see if the endless reboot cycles continue. If the same thing endlessly happens with nothing else at all connected I would say it is likely a problem with either the motherboard power control circuits or the PSU itself.

ScumLord

Something like that happened to me too, I think it turned out to be faulty RAM, try removing sticks and see if it makes a difference.

[If the problem remains then I would disconnect everything bar the PSU from the motherboard (including the CPU ) (maybe leave one fan connected as a visual queue) and see if the endless reboot cycles continue. If the same thing endlessly happens with nothing else at all connected I would say it is likely a problem with either the motherboard power control circuits or the PSU itself.[/QUOTE]

I disconneced everything. Then swtched it on, and it worked. I then re-connected the cpu power and the fault happened again.

marco_polo

Just for completeness it would do no harm to fully reset the BIOS by removing the CMOS battery and shorting the pins for 30 odd seconds.

What you have described does make me suspect that the 12V rail on the PSU could be shot, and is falling over at the point that 12V power is needed.

Unfortunately I cannot rule out a motherboard or CPU problem either, it may be difficult to isolate the problem component without having other components to swap in

B00MSTICK

PSU would be my 1st guess too.

Br4tPr1nc3

take your ram out, and put it back in. then try start your computer up.