halp! my computer won't turn on

before i dive into what's happening, here's what we're dealing with (i built this rig for about 500 bucks in the summer of '09, added the 2tb drive later):

PSU: corsair 400w http://www.newegg.com/Product/Product.aspx?Item=N82E16817139008

mobo: biostar TA790GX XE http://www.newegg.com/Product/Product.aspx?Item=N82E16813138140

CPU: AMD Athlon X2 7850 BE http://www.newegg.com/Product/Product.aspx?Item=N82E16819103678

RAM: g.skill (2x2gb, DDR2 1066) http://www.newegg.com/Product/Product.aspx?Item=N82E16820231166

GPU: ati radeon HD 4670 w/ 512 mb ram http://www.newegg.com/Product/Product.aspx?Item=N82E16814161252

plus 2 SATA HDD's (2TB storage drive and 640GB OS drive) and an IDE dvd-rom drive

running windows 7 Professional (x64)

with that out of the way, i've got a pretty serious problem on my hands. my computer won't turn on.

when i first got this computer up and running, i played around in the bios a bit, trying to possibly unlock my x2 into an x4 (no success). i honestly can't remember if i reset the bios settings to the default after that or not, but yesterday after returning home from work, i powered my PC up, and low and behold, i had 4 cores reported as working! windows wanted me to re-run the windows experience test (i figured what the heck, i needed to go get a drink anyway). i started the test, got my drink, sat back down, and watched as the whole system just turned off. didn't restart itself, didn't go through shutdown, it was like someone pulled the plug. i hit the power button (after smelling for anything burning, which i didn't smell) and got no response.

per the corsair site, i unhooked everything but a case fan from the psu, and shorted the indicated connection on the 24-pin connector w/ a paperclip to see if the psu was bad (the fan and psu fired right up). with everything hooked up, when i hit the power button, i get about 1/2 a second of power to the case fans, then the PSU acts like it's unplugged (no power to anything, no lights, no beeps, no nothing). i tried clearing the cmos, with no effect. i'm at a loss for what to try (i don't have a known working compatible mobo/cpu to test with, all ive got is a 5 yr. old laptop). please help!

If you haven't already, remove everything except one stick of RAM installed to the 1st DIMM slot, the CPU and HSF, and the videocard. This includes ODDs, HDDs, SSDs, fans (except the CPU fan), sound card, TV card, NIC, etc.... then reset CMOS w/ the power to the board OFF (PSU ON/OFF switch in the OFF position). After the CLRRTC jumper (CMOS jumper) is re-installed on pins 1-2 (default RUN position), power the board back up. You might also want to check out the "Help My Pc Won't Boot!" Troubleshooting Guide at the top of this forum.

thanks for the reply i tried as you suggested, and was still rewarded with bupkiss. there's an LED on the mobo that usually is lit up when power is applied to the system (whether or not the system is running). this led is not on, but like i said i've verified that my PSU is putting out power. this leads me to believe that the fault is in the mobo (but i'm pretty newbish when it comes to hardware problems like this, so i could be wrong).

oh, btw i have read through the troubleshooting guide you mentioned

try to hit the reset cmos jumper or pop the battery out for a few with no power to the mobo

thanks, wage. that was part of what redduc suggested and i tried with no success. i have noticed, though, that when trying this (attempting to power up after resetting the CMOS), the intake fan on the bottom of the PSU will spin about 1/8 of a turn, like it's about to start, but then nothing else.

jamesxross said:

thanks, wage. that was part of what redduc suggested and i tried with no success. i have noticed, though, that when trying this (attempting to power up after resetting the CMOS), the intake fan on the bottom of the PSU will spin about 1/8 of a turn, like it's about to start, but then nothing else.

Click to expand...

That's pretty common. My computer does that when power first hits it.

Try pulling EVERYTHING off the board. Just leave the CPU and the CPU fan on. Unplug EVERYTHING else that's not needed (except the power button), and see if it will at least beep at ya.

with absolutely nothing plugged in except for the cpu and cpu fan (not even any ram) i still get nothing. *sadface*

gasoline and a match?

*buries head in hands* this isn't going to be a cheap fix, is it? what am i looking at replacing here? the mobo? the cpu? both? something else?

Upgrade time haha probably just try the mobo first.

any help on a replacement mobo would be hot specifically, i'd be looking for one with am 2+/am3 socket (in case the cpu does need to be replaced, i'd probably wind up going am3) and one that would let me use my ddr2 1066 ram (though if not possible, i suppose ddr3 would be acceptable, but it would make my wallet sad). also, i'd really prefer to keep the price below $70 if possible (again, it would make my wallet sad). i'll keep looking, but any advice/help would be great.

the problem has been identified (by a member of a different forum). apparently, the problem lies in the VRM (voltage regulation module), responsible for regulation of voltage from the PSU to the CPU. this was confirmed by attempting to power on the system with the 4-pin CPU power cord unplugged (all the fans i had connected immediately spun up, which is what the person who told me to conduct this test predicted would happen if the VRM was dead).

any chance this might have killed anything else? or would it be best to just get a new mobo first and then get a new cpu and/or ram if needed later?

if you are on a tight budget id just go for the mobo if you feel like it go ahead and do a rebuild, newegg has a decent rebuild kit up for amd for 370 combo deal
http://www.newegg.com/Product/ComboBundleDetails.aspx?ItemList=Combo.644144

they usually have a few more combos like that or you can just get whatever lol

definitely on a tight budget

i've spotted the following 2 that seem to be very similar to my eyes:

http://www.newegg.com/Product/Product.aspx?Item=N82E16813130307

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=5019773&CatId=2838

i'm very hopeful that all my other hardware made it through unscathed (*fingers crossed*) and the mobo is all i need to replace.

any deals or anything similar in quality but lower in price would be great (AM2+ socket, ddr2 1066 memory are my cpu and ram specs that the new board would need to conform to, again presuming my other stuff is still good).

I had a similar problem recently.
Go over the whole motherboard, very carefully in lots of light and look for any breaks in the copper. If there is a break, solder that ***** up with some more copper wire.

Hope this gets resolved for you.