Gainward GTX 770 Graphic Card

Hello...

I'm from Portugal and I'm trying to diagnose an Nvidia GTX770 that has some problem related to power supply. If you connect only the 8-pin power cable, the gpu will warm up and display the image "please power down and connect the pcie power cables for this graphics card" because need the second 6 pin connector, but when I connect the second 6 pin cable not show any sign of image on display and not warming gpu ... Do you have any tips for giving me what I should do to diagnose the problem?

Thank you

Are you using the proper PCIe video power connectors? Never use any "adapter", only use the proper power connectors direct from the PSU.
There is also a small issue between the 8 pin CPU connector and the 8 pin Video connector. Though they are keyed differently, but different by one and only one key pin, it is possible that one can force the CPU 8 pin into the Video card. I've seen it done. That creates an improper "short" on some of the signal lines. This may show up when you plug in another (6 pin) power plug into the video card.
Verify the labeling on the video power connectors, they should all say something like "PCIe" or "Video"

Hello

I'm using the direct cables from PSU. And de video card works and show's image if i connect only and the 8 pin connector but how the graphics card need 8 + 6pin only with 8 pin connected shows a message in display " please power down and connect the pcie power cables for this graphics card ". I shutdown computer and connect 6 pin, when try power up again the graphics card not show any image and gpu processor not worming up.

Maybe my problem is relater with 6 pin phase circuit in video card, i dont know... other graphics card work well with this 8 + 6 pin PSU 650w