Desktop computer doing some weird sh*t (turns on/off/on/off)

[jasonxc]

Last month, I went on a short trip out of town and decided to turn off my computer to save a few cents on the electric bill (I normally leave it on for weeks at a time). When I got back and pressed the power button, the hardware turned on as normal, but it turned off after a few seconds before showing anything on the monitor. After a couple seconds, it automatically turned on again, then turned off, and repeated the cycle until I said WTF and switched the PSU to '0'. So I tried unplugging my hardware components one at a time (hard drives, RAM, video card, etc) and testing to see if the computer would stay on for more than a few seconds, but it made no difference. I figure it may be a PSU, mobo, or CPU problem. Any thoughts?

Here are my system specs:

Antec P180B (w/P182 features)
Corsair 520W SLI Certified Modular ATX Power Supply (CMPSU-520HX)
Gigabyte GA-P35-DS3R LGA 775 Intel P35
Intel Core 2 Duo E4400 2.0GHz
Crucial Ballistix 2 x 1GB DDR2 800 (PC6400) Cas 4
Seagate 250 GB Hard Drive x 2 (single platter version)
Seagate 500 GB Hard Drive (7200.11)
BFG GeForce 7900 GS OC 256MB
Samsung SH-S183 SATA 18X DVD Burner Black
Edimax EW-7128G PCI Wireless Card

 

[mechBgon]

As a starting point, try removing the case's Power Button wire from the motherboard's pinout. Now make a momentary electrical connection between the Power Button pins on the motherboard's pinout using the tip of a screwdriver, like this :camera:.

If the system starts up and stays running, then your case's power-button switch may be stuck in the electrically-closed position. I don't think that's the issue, actually, because you'd see monitor activity before it shut down again. But you can at least rule out the easy thing first.

Beyond that,

1) try a different surge supressor, or bypass it and plug directly into the wall as a fact-finding step. I saw an incident where a surge supressor took a hit (apparently from the electricians installing a heater that night) and the computer connected to that surge supressor was faking a HDD failure very convincingly

2) if possible, try a different power supply that has enough wattage and quality to run your rig.

 

[jasonxc]

Thanks for the input mech. I tried the screwdriver trick and plugging it directly to the wall (tried that earlier), and it does the same thing. Does it take more than 520W to run a rig like mine? If so, what wattage would you suggest?

 

[mechBgon]

A quality unit like your Corsair should be great for that loadout. If nothing else comes to light, maybe remove the motherboard, lay it out on cardboard, threaten it a bit (they fear water and electric shock), and then benchtest it with just the bare essentials? CPU/heatsink/fan, video card, one memory module, and no case wiring, no drives, no other cards, no keyboard/mouse/peripherals.

If it still cycles, try shutting power off, pull out the RAM and video card, and see if it gives beep codes (hook up the case speaker if it doesn't have an onboard code speaker). If it still cycles after that, try removing the CPU itself and power on the absolutely-bare motherboard, using the PSU fan and/or beep codes as your indication of whether it's staying powered up. If it cycles at that point, you can try a different PSU and there's your tiebreaker.

Good luck!

 

[jasonxc]

Ugh, I guess it's time to stop being lazy and put in some real effort (was hoping for an easy fix). I may pull out the sledgehammer to add to the intimidation factor. I rewatched Office Space recently, so I'm familiar with the proper disposal method for faulty equipment.

 

[olmer]

PSU or mobo sc. Since you have not touched mobo ? first try another PSU or test it on its own.