Powercolor 6850 1gb, no video signal but post and windows boots

[xgotxxricex]

Hello,

I recently bought a PC with a z68ap-d3 (rev 1) mobo, i7 2600k cpu, 600W psu (unreliable brand) and a powercolor 6850 1gb. The mobo on-board graphics work and can produce output to the monitor. However, the 6850 cannot produce output through its DVI or HDMI channels.

The POST and Windows start normally with either the onboard or the 6850 card enabled. I've updated the BIOS and the video drivers, as well as reinstalled the video card drivers. I've also reseated the card, cleaned the PCIe x16 slot, and secured all the power connections. I've also disabled the onboard card when running the 6850. Nothing works. I have not seated the 6850 in the other PCIe slot because that requires modifying the case, which I can't do if I want to return the PC.

Also, the computer recognizes the 6850 and even installed its drivers the first time I booted it. I think this is a hardware problem, with either the PCIe slot, the 6850, or the PSU not delivering enough power. Yes, I've already connected the 6 pin power supply to the 6850.
If it's a hardware problem, my only solution is to return the PC. Therefore, could someone here suggest any possible software problems so I could troubleshoot one last time?

EDIT: I forgot to mention that my monitors work fine on different computers, and that I am unable to test my 6850 on another computer. Also, my monitor's native resolution is 1920x1080; does the 6850 support this?

[Amy_i3]

Try one by one to put the gpu in different slot. Check that the gpu fan is working or not. 600w psu is quiet enough for the gpu you are using. The maximum resolution support is VGA - 2048x1536, DVI - 2560x1600, DisplayPort - 2560x1600 and HDMI 1920x1200. In bios check that your onboard / graphic card is enabled. I think the gpu is not detected in your system because of which you are not getting the display. Looks like a hardware fault.