Monitor is black when I boot up after upgrade

[JohnnyAmazi]

I just tried to install more RAM, a new heatsink and new GPU. When I try to boot up my PC it starts fine but after a couple of seconds it shuts down and automaticly starts again after a couple of seconds. After that it seems to run fine, but the monitor is just black (I think it goes in to sleep mode because it thinks the PC is off. I've tried multiple ports in my new card, my old card and my motherboard.

The new RAM sticks don't seem to be the problem either because I tried without the new ones.

PSU: Silver Power SP-SS750M 750W
Motherboard: P8Z68-V PRO/GEN3
CPU: Intel i5 2500k LGA1155
CPU Cooler: Noctua NH-D14
Old GPU: Gainward GeForce GTX 560Ti 1GB
New GPU: EVGA GeForce GTX 670 4GB

 

[swifty_morgan]

power supply is?..........and please list all other hardware.

 

[JohnnyAmazi]

power supply is?..........and please list all other hardware.

PSU: Silver Power SP-SS750M 750W
Motherboard: P8Z68-V PRO/GEN3
CPU: Intel i5 2500k LGA1155
CPU Cooler: Noctua NH-D14
Old GPU: Gainward GeForce GTX 560Ti 1GB
New GPU: EVGA GeForce GTX 670 4GB

 

[swifty_morgan]

what was the old/what was the new ram?

remove all the ram. put back 1 of the old. remove new video card/put back old. reset cmos. what happens?

 

[JohnnyAmazi]

what was the old/what was the new ram?

remove all the ram. put back 1 of the old. remove new video card/put back old. reset cmos. what happens?

All the RAM was the same, Kingston HyperX DDR3 4GB RAM sticks. I had two sticks and bought 2 new ones (4x 4GB)

When I did all you said, the PC turned on and stayed on without that little shut down that always happened earlier. But there was still nothing on the monitor. Should I try again with a different monitor or something?

Could I have broken something while building? D:

 

[swifty_morgan]

could be anything yet. yes, if you have another monitor and/or another cable try them. just leave 1 stick in for now.

you are sure the motherboard is properly powered ( 4/8pin-20/24pin ) ( video card 6/6-8pin )