Troubleshooting a PC that won't turn on

My Media Center PC just locked up in a way that I haven’t seen before. It was playing a movie, and then froze with a stutter like a skipped CD. The power and restart buttons on the front wouldn’t work, and I had to pull the plug. Now it won’t turn on.

Where would I start in troubleshooting this? I doubt the issue would be the power button itself, but I still dusted out the inside and reseated the connector for the front panel buttons. The light on the motherboard is on so I know there is power, but I don’t know what else to try. I can’t swap out for an equivalent motherboard because it is a P4 with AGP. This might be the motivation to finally upgrade, but I would rather not.

Would it be a short on the motherboard? I think I’ve read that a motherboard won’t allow itself to power up if there is a short, though I don’t know it that would prevent the shutdown too. Is it possible to get short from dust? Nothing has moved or changed in there.

Any beeps, flashing lights, front panel lights, anything like that?

Given the info so far, it sounds like the video card died, so the computer won’t even power up without a working video card.

I’d say upgrade.

Possible power supply issue. Do you have another (known good) one you can swap in?

I had a mysterious no-power issue similar to yours a couple of months ago. I turned off my (always on) server to install another hard drive and the bugger would not turn on. I messed around with 3 different power supplies and MacGuyvered up a manual on/off switch to the mobo before I finally figured it out: capacitor rot killed my mobo. Apparently some mobos of the P4/AGP vintage used substandard caps that are prone to losing their electrolyte. Look inside your computer near where the cpu is. There should be several large-ish capacitors. Are any of their tops bulging or is there goo escaping from them?

I managed to get a (used) identical mobo for my server on ebay for $30. Best part about that is that I didn’thave to reinstall any software.

Good luck!

I had a PSU fail and the LEDs still indicated a supply to the motherboard. Can you check with a voltmeter, or beg/borrow/steal a PSU to test with? Dust causing a short is highly unlikely and it would still boot without a video card. Dud capacitors might be an issue.

Swapping in known good parts is really the only things you can do at this point if youre not getting any beeps and if youre getting LED lights.

You might want to try reseating everthing and trying to boot with the bare minimum (hard drive, ram, cpu, video) and seeing if that helps, but usually you need to start doing swap outs. It also helps to google the model of your motherboard/computer and see if its prone to bad caps or early death.

You can test the power supply by unplugging the connector from the motherboard and jumper the pin connected to the green wire to one of the pins connected to a black wire. (refer to this image: http://www.smpspowersupply.com/connectors-pinouts.html) This will turn on the power supply. You can then test the output with a multimeter.

If the power supply works, it is almost certain that the motherboard has failed. The mobo contains the circuits that take the 5 volt and 12 volt supply from the PSU and convert to the other voltages the motherboard needs. These circuits are the likely source of failure. This is not feasibly repairable, so a replacement mobo would be in order.

You can troubleshoot other hardware failures by the post beep that happens when you boot a computer. One short beep is normal, any other type of beep indicates a failed or missing component.

could also be a stuck power button on the case. to check that you’d have to disconnect the button from the motherboard and poke a screwdriver in to jump the connectors. just don’t touch the metal part with your hands… if the fans spin up then that’s it. if not, its anything else.