Hi. I have a decent desktop with an i5-4590, a local H81 motherboard, a cheap 450W power supply that I do not trust. This setup works fine for my desktop and a little csgo and dota. However, I now want a graphics card so of course I won't take risks with my power supply. So I got a new power supply (national but good company, you might not know the same but its 80 plus bronze, has japanese capacitors and you know - good specs), but it did not work with my desktop. When I press the power on button, the CPU fan and power supply fan starts and stops, then starts and stops, and so on until I close the whole thing down. I tried many things, resetting cmos, removing each component and installed them one by one. In the middle, without CPU power connector (4pin 12v), RAM, hard disks, and only the 24 pin, the cpu and psu fan spin for a long time. But without cpu power and ram, there was no display, when I plugged in the RAM or 4pin cpu connnector, the same thing happened, it started and stopped. Very confusing. So I took it to the service center from where I had bought the power supply. The dude said he'll look into it, the next time I went there, he used it before me and it was WORKING fine, he had a Gigabyte H81 motherboard and an i3 4th generation, which means the configuration is very similar to mine. Now, I was confident it was supposed to work. I installed to find the same problem, the cpu fan, psu fan spins and stops repeatedly. I am really tired about it now. All the parts of my desktop works fine, as I said the old cheap power supply runs the system very finely. The power supply works fine, I saw that in the store myself in front of my eyes and took it back with me. I cannot understand what the problem is. I tried so many things but I just am not able to use the better power supply. Everything is compatible and it should work. The motherboard has a 24-pin ATX power slot, a 4-pin CPU power slot. The old power supply has a 20+4 pin ATX pwr connector, and a 4pin cpu connector. The new better power supply that I am not unable to use has 20+4 pin atx power connector, and a 4+4 cpu pin connector. I think maybe my motherboard is not able to support the power supply, I mean the older one works but this one does not. I do not have a spare motherboard, and I just cannot buy another one as well because this works fine. I can't really see the problem. The older power supply and all of my components are perfectly fine. They all work and show up. The new power supply is tested and it's also fine as well. I can't find any solutions on the internet. Please help .