Macpro with no Video

Hi All,

I have purchased an old Macpro 2010 for 3 months it worked properly one fine days it the screen showed no video output message tried checking Ram every thing seemed correct as it produced chime latter took the video card ATI Radeon HD 5770 1GB to repairer found DVI socket was not working hence got the Mini DP to VGA connector to connect my monitor it worked again after 2 months the dp to VGA connector stopped working during night time around 3 am , next day tried using the second DP socket on the video card it worked one day due to power failure the Macpro was shutoff when electricity resumed my monitor showed no video output message fan was working it seems everything on video card is working but dont get videos after 2 months of slumber purchased a old Nvidia 710 gb card I installed it and successfully got the video signals I was able to upgrade my High sierra to Mojave while re starting due to power failure it kept re starting and never produced video signals tried using all the output sockets i.e VGA , HDMI and DVI sockets none of them produced video output but the Fans on card are running what may be the reason my Videocards are failing is macro so delicate it can t handle sudden power failures . What you all suggest . I have purchased this old macpro out of my 5 years of saving .