New Graphics Card and PSU: Screen stays black

[Aindreas]

Hello there, I bought a new graphics card (Radeon HD7770) and PSU (Corsair CX500M). After installing I plugged my PC back in but the screen stayed black (no signal whatsoever). I checked whether all cables were connected properly, and tried again, no change. Then I got a different monitor and switched from HDMI to VGA, still no improvement.
So I put the old PSU and graphics card in thinking I need to install it first, but now the screen stays black on the old PSU and Graphics card. I tried with no graphics card and connected to the inbuilt VGA connection (on motherboard), but still nothing. I have tried to reboot bios by taking out the battery and additional memory, but still nothing.
I now have the new PSU and Graphics card in the PC, and have tried every cable connection possible. I turned on the PC with the 4-pin CPU power cable plugged out one time to see if it made any difference, and it sounded different (though all the fans were working).
I am at the end of my knowledge and could use some help.
Is it the PSU, the Graphics card, the Motherboard, something else?

 

[Tmagic650]

Did you connect the power supply to the new graphics card using the connector marked PCIe?

 

[Aindreas]

Yes, there was only one cable that fits in both the PSU and the Graphics card, and PCIe is written on it.

 

[Tmagic650]

If you have more than 1 PCIe slot, is the video card installed in the slot closest to the CPU?

 

[Aindreas]

Issue Solved!

Tmagic650, thank you very much for you time!! I only have 1 PCIe slot, but eventually found a solution.

I fixed the issue by doing several things simoultaneously, so I dont know which one was the problem:
1. I placed a jumper over the clear CMOS location on the motherboard. I found a nice video showing how by typing in 'clear CMOS location' in google and clicking on the first video. (edit: was going to post link here but it wasnt working)
2. I booted the PC, which showed no change, so I switched the CMOS back the way it was (it should have reset by then)
3. I removed ALL the memory in the PC, and replaced one of them only (I have a feeling this was the solution, but cant be sure).
4. I got a different power lead from my PSU to the mains socket.
5. Before starting it again, I found the speaker for the motherboard and attached it.
6. Booted PC and all is fine. I do not know which step(s) solved the issue, so if you have a similar problem give them all a try.

 

[Tmagic650]

Thanks for the update and good luck