Just changed my power supply and comp is slower..

My last power supply burnt out, so I replaced it with another one..
With my old power supply, my computer turned on really fast, like less than 2 minutes or so.
But with my new (not brand new) power supply, it takes like around 5 tries to get my computer to work and become fully loaded at the desktop screen. Once everything is loaded though, it runs as fast as my old computer..