New psu not working

[stefan.geb1]

Hi there. I bought a Lenovo Y900 that came with a cooler Master 600w bronze plus psu. In my old computer I had a cooler Master 750w psu that ran without a problem. Now I wanted to replace the 600w in my new rig with my other 750w, but after I installed it amd pressed the power button, everything flashed up for a second, then stopped for 3 seconds, and repeated over and over. Any ideas what went wrong there? Thanks

 

[elbert]

Specs please. Did you check the CPU power plug? Test with only the motherboard pluged in to see if it will load to bios.