Don't Know what's wrong

[bootybill]

So my brother moved in with me and his computer was not handled politely at all when it was shipped. The case was cracked and there were packing peanuts everywhere. Almost all the parts work. His PSU worked fine when I connected it to my parts, ditto for the RAM and GPU. When we tried booting with the old board he had, the fans would spin up for about a second and a half then shut off. This happened every 3-5 seconds until we turned off the PSU. We bought a new board because all of the fans worked fine when we unplugged the cpu fan, so we assumed the cpu power was shot. With his new board, the motherboard powers on fine, but only when the GPU isn't plugged into the PSU, and something I haven't seen, though I'm fairly new to building PC's (this is only my 6th or 7th build), was his GPU fans would spin up when it wasn't connected, but obviously won't display or anything. I'm so done with his machine and I don't know what to do. We've tried a new PSU as well, it didn't work.

-Win 10 64-bit
-G.SKILL TridentX Series 16GB (2 x 8GB) 240-Pin DDR3
-WD Black 2TB Performance Desktop Hard Disk Drive - 7200
-Mushkin Enhanced ECO2 2.5" 240GB SATA III MLC Internal Solid State Drive (SSD
-Intel Core i7-4790K Devil's Canyon Quad-Core 4.0 GHz LGA 1150 88W
-Rosewill Photon-1050, PHOTON Series 1050W
-EVGA GeForce GTX 960 02G-P4-2966-KR 2GB
-ASUS Z97-A LGA 1150 Intel Z97 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard (OLD BOARD)
-L337 Gaming Z97-MACHINE (V1.0) LGA 1150 Intel Z97 (NEW BOARD)

 

[The Paladin]

the motherboard powers on fine, but only when the GPU isn't plugged into the PSU

does it power up normally without the GPU connected ?

then the GPU is fubar , get a new one. unless you can prove that GPU works on another system