So I had bought a used HP Z440 workstation as we use them at work. Attempted to upgrade the power supply and add a new video card. Been working great up until now. I got an evga 750 watt power supply and got connector cables to port the existing power supply to fit the motherboard the 440 has. Once connected to the computer it looked like it powered up fine but was not picking up the video display. I shut it off with the power button on the front panel - swapped the monitor settings and tried again. I was greeted by red and white blinking lights and after a few tries gave up and put the old psu back in. Now I got nothing with that either. Anyone got suggestions or did I fry my motherboard ?