power supply turns off after about 4 seconds?

[Coxy01]

Hi,

The story so far:

PC working fine, no previous errors.

Went to turn PC on as usual; power supply fan and internal fans start fine. Then the power supply switches off after about 4 seconds before getting as far as a bios beep.

I thought the issue was likely to be the power supply so I took a power supply form my other machine and hooked it up to the offending machine. behaves in exactly the same way so the problem is not the PSU itself.

Took PCI cards cards out (as a stab in the dark as im running out of ideas) no difference.

So basically after the power supply turns on it finds something it doesnt like and powers off a few seconds later. why does it do that? what else can i do to pin point the issue?

The offending PSU works fine on my other machine and the power cable from the wall socket is also good.

is it worth swapping the CPU out? would that make any difference? could that power the PSU off?

any advice would be great

cheers

 

[againstTheWind]

Perhaps the CPU is overheating.

Is your heatsink fan mounted properly with a thin layer of thermal compound between the processor and the heatsink? Make sure the snaps are properly secured by trying the gently lift the fan.

Good luck

 

[Coxy01]

Thanks for the reply.

Its been working about a year working fine. It was built in a proper computer shop so I assume this issue would have happened earlier if there was a potential issue with the temperature?

no changes to hardware or software, I guess I can trouble shoot this by trying my other P4 CPU/heatsink and fan in there? I was planning to do that but I didnt want to bother if that wasnt likely to be the cause, If you think its worth trying that I'll give it a go, just strange it would suddenly be over heating for no apparent reason when the fan is still working. Also, would it register the tempterature that quickly even before getting a bios beep?

Thanks

 

[franklin97355]

Sounds like a "crowbar" from the power supply. when there is a short or too much power draw the power supply will shut down to protect itself. Take all parts out of the case and hook up just the ps and cpu/heatsink.See what you get then. Check for bad/bulging caps as this is another thing that can go wrong over time.

The answer is "42"

 

[paparazi]

I agree with franklin97355 on this one, although initially I would leave the motherboard in the case and only remove if the problem still cannot be resolved.
certainly check for bulging/leaking capacitors see:

http://www.badcaps.com

For good visual advice on this.
But essentially disconnect everything from the motherboard apart from what is required! so pull off IDE cables, floppy cables, all addon cards, all molex power connections to CDroms/HDD's etc, even the front panel header connections.
Just leave:
The mainboard with graphics card, one stick of ram, heatsink/fan with CPU in place and the power supply.
Clear the cmos (cmos clear jumpers) next to the button battery
Momentarily touch the pwr (power) header pins with a small flat flade screwdriver
I bet now you have post???

Likely culprits:
Hardware failed and shorting to ground: CDrom device/HDD/addon card
Front panel switch jammed ie: reset button etc
The CPU fan connected to the wrong header (must be to the CPU fan header)
Fan not fitted correctly and so the CPU rapidly overheats.
Something shorting in one of the I/O sockets (carefully examine, USB's particularly)

Martin

Martin

We like members to GIVE and not just TAKE.
Participate and help others.

 

[paparazi]

Oh! and that includes devices that are plugged in to the PC, so no external hard drives, printers, blue tooth dongles etc etc all of which could cause a non post.
Martin

We like members to GIVE and not just TAKE.
Participate and help others.

 

[edfair]

AT 4 seconds I would suspect a fault in the power down timeout circuitry rather than a crowbar shutdown. You might try pulling power on a hard drive and see if that changes the time delay as that would affect the power draw and possibly eliminate a crowbar.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[paparazi]

As I have said so often.
Please help by including more information on hardware/software setup (best done in the initial post)
Thanks
Martin

We like members to GIVE and not just TAKE.
Participate and help others.