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Installed a new power supply

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Hello all,

I am hoping someone can offer some insight. I have none.

My question: What do I check next?

My PC died a few weeks ago, wouldn't boot up, I don't remember the details, but I called one of the IT guys at the office telling him I thought the power supply was shot, he agreed.

Fast forward 6 weeks, had never gotten around to fixing that dead desktop in the basement, but now I need last year's tax returns and they are on the hard drive that is in the dead PC so off I was to Best Buy this AM to get a new power supply. The old one was 300 watt. The geek squad advised on the 400 watt model they had in stock I bought it and off I went to do my taxes.

I opened the PC, and started with the easiest stuff first, detached the 4 pin plug from the motherboard first and immediately replaced it with the 4 pin plug from the new unit. I got through all the plugs one by one, taking one out and replacing it with a new one till all were out. Then I remounted the new power supply in the case and fired it up...This was way too easy I thought. Took about 20 minutes and that included searching for a phillips screw driver to open the case.

Of course I was wrong. When I plugged in the PC and hit the on button on the front the the light on the front came on but not the laser mouse, or the lights on the keyboard. I listened for fans and nothing. No hard drive soundds, no beeps. Nothing it sounded dead.

So I opened it back up, unplugged it to get the lights all off and back to it's previous state, then plugged it back in, nothing, so I hit the power button on the front again and the 3 fans all spun for about a half second and slowly stopped, leaving only the blue light on the power button as indication that the thing was even plugged in.

I have checked and rechecked all the connections. I have swapped through all the SATA connectors from the power supply to the hard drive...every time I tried it same result. A few spins of the case cooling, cpu and power supply fans and a blue light...no boot up.

This leaves me with the question...What do I check next?

Thank you to any kind soul that actually reads this. I really need the tax refund that i think I am due...baby on the way and home under construction.

Edited by BuckyBoy, 21 March 2010 - 11:23 AM.

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    Grumpy Ol' MSgt (Ret.)

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Well, the PSU would have been my first suggestion so if you are sure you connected it properly, then I am afraid it could be more serious. When you push the front panel power button, all that does is short two pins on the motherboard, which signals the PSU to start up and 12V is applied to the fans. What appears to be happening next is nothing, so the PSU immediately shuts down, and the fans stop.

So POST is barely starting which indicates a problem with the motherboard, CPU or RAM. Do you hear any beeps? You can test your RAM following the canned text below. Swapping in a CPU, if you happen to have one compatible, might work but if the motherboard is bad, it could take out the new CPU. So you don't have many options.

Since this does appear to be an old system, your best bet might be to remove that hard drive and install it in an enclosure attached to, or as a secondary drive installed in the computer you are using now. Then copy off all your data you don't want to lose.

You can test RAM using one of the following programs. Both require you to create and boot to a bootable floppy disk or CD to run the diagnostics. Allow the diagnostics to run for several passes or even overnight. You should have no reported errors.

Windows Memory Diagnostic - see the easy to follow instructions under Quick Start Information.
MemTest86+ (for more advanced users) - an excellent how-to guide is available here.

Alternatively, you could install a single RAM module and try running with that to see if it fails. Repeat process with remaining modules, hopefully identifying the bad stick through a process of elimination.

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    motto - Just get-er-done

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I just have had a brand new computer do something similar. Put it all together and i got fans running, power on light on the case and unable to do anything else. no BIOS, no beeps, no nothing. So when i pulled it back apart i noticed the heatsink paste had barely touched the CPU. Thankful that Intel CPU's will shut down before burning up like AMD cpu's. You might try reseating the CPU with new thermal paste to see if it cures the problem.

A easier fix for you is to install the old HD in another computer as a secondary drive. You should be able to access the data from the drive and transfer any files you want to the OS system drive.

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