Pc wont always turn onn, but stays on fine

[commentator8]

Hi all,

I have a PC that when running stays on fine, but can take an hour of turning it on and off to get it to start up. It will either not output anything to the screen or output a blinking white underscore. It sometimes turns on (fans turning etc but no output) then after twenty seconds restarts.

I have swapped the ram, graphics card, power supply and have tried with and without the hard drive connected. There is nothing besides the screen plugged in currently. Does this mean it must be the motherboard? And is it logical to say so given that it runs fine (without crashing or losing power) when it does manage to turn on? I cant see it being the CPU, and that doesnt leave much.

Any ideas welcomed, but the customer needs it back fast...

Edit: on occasion when i turn it on it turns off after a few seconds then comes back on and keeps spinning without output.

 

[glricht]

Sounds like a heat-related problem, probably on the MB. My guess is a cracked trace on the MB: when the MB is cold there's no contact, but as the MB heats up with repeated attempts to power on, the trace expands and eventually makes contact and now all works as designed.

Either don't turn off the PC and let it get cold (short-term circumvention) or replace the MB.

 

[commentator8]

In a case like this, where the computer is say 3/4 years old - is it worth replacing the motherboard? With all the problems that involves (finding a compatible one, integrating the new drivers etc. Isnt it easier to just buy a new system and clean install (assuming that is an option)? Or am i overestimating the dificulty involved in changing the MB?

 

[FCONE]

I would not replace a MB in a 3-4 year old PC unless they had a lot invested in it. At that point (especially if you have an electrical or heat related issue) more parts may be damaged and soon to fail.

 

[FoolishTech]

sounds like MB.

I had a personal system years ago with the same issue - ran great as long as you didn't power it off. Trying to get it back on might have taken 5-10 minutes of constantly power cycling it before video would display and it would POST - then it ran great for weeks/months at a time without issue.

Problem was the capacitors. They were bulging and burst all over the place.

 

[commentator8]

The capacitors look good in this system, so i'm tending towards a cracked trace, but at this point the problem can be written off as a MB nasty, whatever the cause. Yes, that is a technical term...

Thanks all.

 

[joydivision]

I've seen this symtpons with bad PSUs too, but the PSU will pass any test fine.

 

[johnrobert]

I have a very high end late model Dell desktop with same problem
I put it down to PS, but maybe I am wrong
just cant throw it out even though I have no use for it
It runs perfectly when it does turn on after trying for about 10 mins