This is happening on brand new Optiplex 3040 mini towers fresh out of the box at our company. It only shows a black screen if I use the built-in display port. I added an EVGA PCIe video card so I could configure the PC and that works perfectly - even the display port works. The PC is configured and ready to go until I pull the video card out, at which point the built-in display port stops working as well. Any clues?
We are using the same AOC LCD monitors with over 15 3040 microtowers and all have worked flawlessly. These same monitors even work with these 3040 minitowers using the display port but only if I have a PCI video card installed. That's the weird part:
PCI Video card in, built in display port works.
No PCI video card, built in display port does not work.
Never mind, it was the first 2 we took out of their boxes. I have to RMA them because after trying everything I grabbed the 3rd and 4th and they are working fine.