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Power supply, power switch or motherboard?

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January 19, 2013 11:28:54 PM

I came home today to find my beloved Windows Xp Pro machine shut down due to a power fluctuation. I pushed the power button to turn it back on and nothing. :fou: 
I built this pc around 2008 or so and use it far more than this rotten Windows 7 pc. Is there an easy way to tell if the problem is the switch on the chassis, the 500 watt power supply or the motherboard?
Specs as far as I can remember:
CPU Intel Pentium 4 541 Prescott 3.2GHz LGA 775 84W
PSU AcBel API4PC23 500W ATX 12V v2.0/Intel EPS 12V v2.1 SLI Certified CrossFire Ready Active PFC Power Supply
MOBO: Foxconn 945P7AA-8EKRS2 LGA 775 Intel 945P ATX Intel Motherboard
I did notice that the light for the network cable was still on and the switch on the back of the power supply still had power as well.

I want to thank the wonder full folks at American Electric Power for making my birthday so enjoyable. :fou: 

I've got more than 500 gigs of stuff on that xp machine, darn it. :cry: 
a b ) Power supply
a b V Motherboard
January 19, 2013 11:38:27 PM

On the plus side you probably have not lost your data. Unplug the power supply and let it sit for 10 minutes. Then plug it back in and try it. Make sure your outlet has power.

I would definitely believe it is the power supply. The switch on the chassis is a simple momentary contact switch. If you want to you can jump the same leads manually on the motherboard.
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a b B Homebuilt system
a b ) Power supply
a b V Motherboard
January 20, 2013 1:48:45 AM

Don't panic yet.

On a few occasions I have had an odd situation in which the computer shuts down for some reason and will not re-start when the front power button is pushed. However, it would start if I did one of two things:
(a) disconnect the power cord from the back of the PSU, as jnkweaver suggested, and leave it off for at least 10 min. Then reconnect and push the front button.
(b) this is almost the same - don't disconnect, just switch off the power button on the back of the PSU and leave it off for 10 min, then switch on and push the front button.

Recognize that, when you "shut down" you do not turn off everything inside your case. A small part of your mobo keeps monitoring the front button and a few other things so it can start up again when asked. I hypothesize that the real problem is that in some odd conditions the BIOS on the mobo gets caught in a loop and fails to "see" the push of the front button. BUT if you switch off (or disconnect) the PSU and wait for its output capacitors to discharge, the mobo and BIOS actually DO run out of power and shut down. When you turn on the power again, the BIOS does a cold boot and starts back into its "dormant" state properly, ready to respond when the front button is pushed. In other words, I do NOT think the PSU is necessarily bad - it might just be a fluke that can be fixed. That is, at least on my machine.
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January 20, 2013 2:04:58 PM

Swapped out the PSU and it still won't start. Grrr....
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a b ) Power supply
a b V Motherboard
January 20, 2013 6:49:26 PM

You are sure the psu you swapped it with is good?

With the computer off is there a led green light on the motherboard lit? I tried to look at the manual but the Foxconn tech site crashed on me. You may not even have the light.

You are sure you had the 24pin and 4 pin connected? The front panel power switch attatches to the mb. try jumping those pins momentarily.
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