Computer starting up, shutting down instantly, then doing over again

Jan 30, 2015
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4,510
Hello everyone, first time poster, occasional lurker. (I put this post in the motherboards section because I feel it's probably the problem, I'm sorry if that was a mistake!) I've got a problem and, despite googling and referring to other threads, I decided I need to ask my own question. I'll try to give as much background info as possible.

So I'm rebuilding my computer out of old parts. Each time I bought a new part, I'd throw the old one in a box. Now all of the originals are ready to be put back together. I tested them, and everything worked around 3-4 weeks ago just fine.

So I found a case (crummy 'server tower' from the local school district 5+ years ago) and started installing the components. Once I was done, the computer turned on for a fraction of a second and turned off. That was it. So, thinking I messed up the standoffs somehow, I took it out of the case and tried again. No luck. Then I switched power supplies and tried starting it with only the cpu and ram, as well as tried each ram stick to see if one of those was the problem. While the pc didn't start, it did however begin to turn on, spin fans, turn off, and repeat infinitely. Progress, right? Well even trying more solutions, like clearing the cmos and reseating the cpu/heatsink, I'm still stuck at this restarting business. The mobo has worked for years! Does anyone have a solution, or did the mobo just poop out? Thanks everybody, and sorry for the long post, just wanted to be thorough!
 

SBMfromLA

Distinguished
Let's see... when you installed the motherboard... did you remember to use the posts so the board doesn't touch the case? Are you sure you plugged in everything.. It sound like some kind of power disruption... Are you sure that case is in working order? Perhaps the power/on switch has a short/loose wire in it or something?
 
Jan 30, 2015
4
0
4,510


Yup I made sure the posts were installed. I plugged in everything I could think of (24 pin, cpu power, gpu power) and I used 2 power supplies (one nonmodular, one semimodular). I tried the power on/off switch as well as shorting the power pins with a screwdriver with the same result. On more of a side note, I've had problems with PSUs getting funky because of a different PSU's cable (i think it was HDD power or something). Thinking this was a problem, I made sure all of the PSU's cables were from the same box as the original.
 
Jan 30, 2015
4
0
4,510
Update: so I noticed that the same effect continued whether the cpu's 8 pin power was plugged in or not. Thinking the 8 pin was broken or something, I tried the other psu wihtout any luck. Status: still stuck.