I just recently purchased a nividia 7900 GTX (used). From the outside it seems to be fine, nothing wrong. However when I any games on it, it is not play correctly. It is either not loading the full image, or it flashes to black and back to normal quickly. I sometimes get vertical or horizontal lines that appear. I am lead to believe that it is not getting enough power. I am using a 350W power supply. Is this the issuse?
Only thing about the plugs would be that i am using a dvi to vga adapter. I do know that the adapter is not 100% the same as the output. The out put is DVI-I, and the adapter iI have is a DVI-A to vga. I don't think this would cause the issue. But I could be wrong.
What is the specs of the new unit? This card alone at full load draws roughly 125W but usual loads should be around 100w. Second these older cards are known to have thermal related issues that the bonding for the gpu and vram degrade over time. Try some very light games even very old ones and see if it produces artifacts. Also download msi afterburner or riva tuner and set the fan speed to 70% or higher to see if issues continue.