Which one has died - CPU or Mobo?

singh_uk

singh_uk

singh_uk

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Joined
28 Aug 2006
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119
Hello,

My Corsair PSU recently died and it is sent off for RMA. In the mean time I have connected up a spare PSU.

I stripped the PC down to RAM, GPU and CPU. Out of the case, onto cardboard to avoid shorts.

With the old dead PSU, on powering up the PC, no video output, no post beeps, CPU/GPU fans did NOT spin up.

With the working PSU - CPU & GPU fans spin up for a few seconds then die, spin up again, and die, etc etc. Cant turn it off from the front (need to switch off from PSU). No beeps, no monitor signal.

Took out the CPU - now if I connect the CPU fan, it spins up and keeps spinning. The LED on the front of the PC comes on and stays on. I can turn the PC off from the front switch. Still no post beeps though.




From this - is it certain the motherboard is dead? Or is it possible the CPU is also / instead of dead? I dont have another system to test them on....
 
Try a battery out full bios / cmos reset. A power surge can corrupt the cmos settings, and prevent a PC from starting up, and with severe corruption the cmos clr jumper alone wont always be enough. With the battery in, and the powersupply plugged in using the cmos clr will normally corrupt the cmos just enough to trigger a reset to default during next power up.

Removing the PSU & Battery and then using the cmos clear jumper for at least 1 minute completely wipes the cmos, (but not the bios program itself as thats in flash), and can often revitalise a broken PC.

From your description its still possible that either the motherboard, cpu or both have failed, only way to tell for sure is by having some spares, or a using a port 80 post diag card to gain additional information.
 
This sounds like the same thing what happened to my PC!

It worked fine perfectly when i shut it down the night before. Then when turning it on the next day i would get a black screen because it would seem like its not connected to the monitor, and a constant beep every 5 seconds.

Sometimes the beep didnt start but i could get any image on the computer no matter what i did.

In the end i just sold everything and couldnt be bothered with it.
 
Corasik,


Thanks for the advice, I tried a BIOS reset but unfortunately no joy.

Is it possible the CPU could have died when the PSU went but not the motherboard? Or will the motherboard always go first?

I ask as I am trying to work out which to buy first (CPU or mobo)
 
Id say its more likely to be the motherboard, as it has its own regulators, to protect the CPU, and if a power surge did get through to the CPU I would imagine it would have had to toast the motherboard on the way.

Try it without the Ram/GPU and see if you get any post beeps with just the cpu/motherboard. (case speaker attached if it's not got a soldered on minispeaker) The CPU fan should be running flat out with no ram/gpu, not sure if the off button will work, but it should beep.

CPU's are quite sturdy, but of course there is always a chance its fried. Good luck with the diagnostics.
 
Same thing happened to me tonight. The only way to find out is to test the CPU in another motherboard. What I'll probably do is grab a cheap mobo and CPU on the MM, test everything, then sell it all again once I've diagnosed it.

...that's if it's still not working tomorrow when I get a chance to properly fiddle with it (thank god for laptops in emergencies!)
 
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