Mobo won't start with CPU connected

[JK_]

Hi, every few months my pc wouldn't startup. On pressing the power button the fans would start, hdd's too but only for a second. Once I got the POST beep everything would go off. It would work again if I unplugged it at the mains and then plugged it back in.

Now to my current problem, it is doing the same thing however the mains solution no longer works. All of the capicitors seem to be fine, I've tried a different psu and worked trough removing and adding the components to try and find the problem.

It is a fairly old system and so I suppose it could be down to the age, and I will be building a new pc soon but it would be nice if this one still worked.

The specs are:

Mobo - Asus M3N78VN

Processor - AMD Athlon 64 x2 6000+

GPU - XFX Radeon 6450

RAM - OCZ 2 x 2GB 800MHZ

HDD - 80GB and Samsung 750GB

Thanks!

Forgot to add that everything else will run if the CPU is not connected or if the wire is not plugged in (hence the title).

 

[terry4536]

The motherboard will never boot without a CPU. What beep codes do you get with the CPU installed? What BIOS do you have (probably AMI)? Have you tried bread boarding the motherboard?

The motherboard or CPU could be bad. There may be an intermittent motherboard short. The power supply may be failing.

The only thing that unplugging the power supply does (differently than powering it off) is that it resets the power supply. This indicates that it is detecting a fault. Try measuring the voltage output of the PSU.

 

[JK_]

Hi, thanks for the quick reply. With the CPU installed there's 1 short beep (the same if it is unplugged or not installed). As for the BIOS I've got no idea. I've also tried a friends CPU which presented the same problem as mine making it seem more likely to be the motherboard. I'm going to try bread boarding it in the morning. I've had 3 different power supplies in, the shortest one being a week and they've all suffered from the problem, it used to be once every few months but now its a problem affecting it completely.

Thanks

 

[JK_]

I tried bread boarding this morning and it worked! No idea what the problem has been though. The first time once it started working I put it all back in without testing everything and ran into the same problem, so I pulled everything out and took my time. Thanks for the suggestion.

 

[terry4536]

It could of been a motherboard short with the case. Or it could have been a bad electrical connection. As long as it is working, that is great. Good luck.