4 pin cpu power socket causes pc to not boot

By SpikeP ·
Since leaving the computer (running XP) on standby recently it won't power back up. The fans spin briefly and stop. Unplugging the 4 pin cpu power plug lets everything else power up but of course means no cpu. No burning smells, no scorch marks. Am I in trouble?

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Insufficient information ...

by OldER Mycroft In reply to 4 pin cpu power socket ca ...

Which computer are you describing - make and model?
How long was this system on 'Standby'.
When you returned to it, was it still showing signs of being on 'Standby' or had it suffered from a power loss in the meantime?

Whatever gave you the idea that disconnecting a power lead could ever solve your problem?

Do you have the full spec for this machine?

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More info & Specs

by SpikeP In reply to Insufficient information ...

I have, to the best of my memory, (I'm not near the machine right now):
Asus M2N-MX SE Plus Mobo
AMD Phenom 8450 X3
NVIDIA GeForce 8600 GT
Windows XP SP3
320Gb HDD
It was built by a shop which closed 4 weeks before I could get a warranty repair.

The system was on standby for a couple of hours at most. The bower button was flashing when I returned but the machine would not power back up, though I would get a brief flash of the power button and all fans spun briefly but stopped instantaneously. Tried to reset it, no joy. Unplugged everything from mains power, waited, plugged back in, nothing.
I disconnected a power lead as I was testing the power supply, plug by plug. I have recently (about 4 weeks ago) installed a new PSU. It was to my surprise that I unplugged the 4 pin plug and all the other fans spun up when I hit the power button on the front of the case (including the cpu fan).

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Well as you have a new PS it sounds like

by OH Smeg Moderator In reply to More info & Specs

A dead CPU Fan. I would try replacing the Fan Heat Sink Combination and see if you have any joy now.

If that doesn't work you will be looking at a replacement M'Board and CPU maybe. It's just with the AMD M'Boards when the Board fails the CPU generally goes with it for some reason in my experience.

However a decent Computer Repair shop should still be able to get the M'Board and or CPU Replaced Under Guarantee though you may have to wait a little while while they get the replacement parts shipped to them from the Component Distributes here in AU. Generally AMD CPU's come from Sydney well they used to the last time I had need of one but it's been a long time now as I don't often use AMD CPU's I'm not sure where the ASUS Tech M'Boards come from or more precisely where their AU Distributors are as I personally do not use them.

However the ASUS Tech Fan/Heat Sink Combination for this M'Board CPU combination should be freely available for a Recommended Retail Price of $45.00 today. This is the unit ASUS Tech Recommends for this unit

The suppliers that I use don't list any other Coolers for that model CPU unless you want to go to the more expensive 92 or 120 MM fans. However you may be able to get a AMD unit cheaper.

Have you looked in the BIOS to see if something screwy has happened there? it's just possible that the CPU Fan has been disabled and this is the problem. You should be able to clear the BIOS by removing the Jumper from Pins 1 & 2 and refitting it to Pins 2 & 3 for a few seconds as per the Instruction Manual from ASUS. That may be sufficient to cure the problem or you may need to replace the actual CPU Fan itself.

OH BTW what PS did you get it's possible that it is marginal for that Unit and isn't supplying enough power or Current. Does the M'Board Monitor show any Error Codes when you apply power?

Send me a Peer Mail and I'll see what I can do to help you out here. I'm in Brissy and have Local Knowledge of who is doing what though I haven't heard of any of the shops closing their doors recently but as I don't work in the Domestic Side of things that not unusual.


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Not really maybe

by OH Smeg Moderator In reply to 4 pin cpu power socket ca ...

It sounds as if the FAN for the CPU has died and gone to Silicon Heaven. When this happens the Safety Circuity of the M'Board cuts in and prevents any Damage to the CPU. In the case of a dead fan it should stop the system from starting till the Fan is either replaced or Disconnected and the Short Circuit no longer exists.

The trouble here is that when you disconnect the CPU Fan there are another 2 Safety Devices that come into play one being the M'Board now fails to sense any Power Draw on the CPU Fan or any Speed Information from the CPU Fan kills the Power to the CPU and the system only runs for about 1 or 2 seconds. The second is the Temp Monitor which cuts the Duty Cycle of the CPU back when a certain Temperature is reached and if the CPU Temp continues to rise the CPU is stopped by removing the Voltage from it.

Replace the CPU Fan and if there was nothing else that happened the unit should work. However if there was another event that occurred that caused the Fan to Fry it's anyone's guess as to how much damage has been sustained. Over-voltage Events are a Killer of M'Boards, CPU and Power Supplies and depending on the type of CPU and Power Supply here all that may be required is a replacement Power Supply or if it is one of the cheap Nasty ones it could have allowed any excess Voltage through and destroyed the M'Board, CPU, RAM and so on.


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