PC keeps rebooting after installing new PSU.

Sk3llyt0r

Commendable
Feb 17, 2016
1
0
1,510
First time poster. Not an expert, but I am not shy around electronics. Any help is appreciated.

Just got a new PSU for a transplant that I am doing. (taking old parts and putting in new case) The new case is bigger and has more fans and the old PSU (460 watts) was not able to work (not modular.) So I have the 24 pin connector in and one of the 2x4 pins going into the CPU port on the MB. I have used two of the modular ports on the PSU to power the fans and the HD and Optical. When i turn on the unit, the PC runs for about 3-4 seconds, the reboots. I get no video or anything. Not sure what is wrong.

I should note, that the old psu powered everything but the new fans in the case, and everything was working 5 mins prior to swap. (as in I could boot up and play a game if I wanted, but without fans on the case.) So im not sure what is wrong or how I can fix this. Is this a bad PSU?