CPU fan turns of then on. No post no speaker beeps. HELP!

[davidccc]

Hi so i have built my cousins computer and when i turn it on, the psu fan and gpu fans seem to be turning but the CPU fan spins for a second, then stops. Theres no post, and motherboard speaker beeps. Things like my Optical drive work etc and case leds/fans, but this is the problem. Its gigabyte 970a ds3 mobo , Amd fx 6100 black edtion, 4gb of Ddr3 ram, Asus geforce gtx 550 ti 1gb, 500gb WD blue, and a 500w no name branded PSU that came with the case (35 bucks). Yes, i did use standoffs and almost sure i plugged in all required for the PSU. At first i thought the problem was the PSU so i bought a 500w coolermaster elite series PSU and plugged it in but same problem-(I also got a PSU tester and idk much about psus but the old PSU when plugged in the tester lit up on all of the things but the newer one didnt light up the +5v sectionthingy) . I have tried a different piece of ram from my computer and same results. What i have noticed also is that i can see the slightest of twitching in the cpu fan every 2 seconds or something.I got everything at Frys and i remeber hearing that the CPU was open box. Is it possible it could be the motherboard? CPU? Please respond, because i am on a very tight schedule with my cousin expecting it to be done in the next couple or 2 days (i have the OS ready to be installed). Thanks! This will really help me and take a knife out of my throat and heat. I forgot to add - when i was putting in the CPU for the first time with the heatsink I put it on top, then readjusted lifted off the heatsink and put it the other way.. did i break the bond and should i apply new thermal paste/ is it dry?

 

[davaross]

If the CPU was open box it's possible it was faulty / damaged, is there another one you can try in its place.
Failing that make sure all of the power cables are plugged in firmly expecially the 12v 4 pin rail for the cpu. Also check the cpu fan is connected correctly and that the CMOS battery is not flat. With regard to moving the heatsink if the heatsink was on for more than a few minutes before you removed it then yes you will need t clean off the old thermal paste and re apply.