Powering on and off without 8 pin with only PSU, MOBO and CPU

[cobdan]

My computer was working perfectly fine for awhile then randomly when I tried to turn it back on, nothing happened. I found out my PSU was dead and bought a new one, but when I plugged it in, the computer only turned on for about a second and turns back off. I took everything out except the PSU, Motherboard and CPU, and same thing happens it only turns on for a second and shuts back off (the PSU fan turns on and same with the CPU fan, only for a second though). Then people were saying try it without the 8 pin from the MOBO to PSU and now it turns on and off repeatedly for a split second, until I unplug the PSU. I checked for bulges from the capacitors on the MOBO, but doesn't seem like there are any. I would like to know what I should do.
CPU: i7 4770k
MOBO: AsRock Extreme4 z87
PSU: EVGA G2 650

 

[jeremymau]

I hate to say it, but I think your defective power supply toasted your motherboard. If you installed the new power supply and hooked up the cables as it's supposed to and still doesn't work, then yeah it's dead. You could try to reset the bios, but that's about the only thing you can do at this point. (you will have to look at your motherboard manual on how to do that..some motherboard have a reset button, but usually only on higher end boards)