Hi, I have a 2009 mac pro 4,1 that has been flashed and upgraded to a single tray 6 core xeon machine running El capitain with 32 gigs Ram, 2 1TB 7200rpm HDDs, 4 port pcie usb 3.0 card and a geforce 120GT GPU which i use strictly for audio production. Recently i woke up one morning to fire up the mac and i didnt hear any chime like usual and both my monitors said no signal? So I checked online forums and was told its most likely the GPU so i ordered an nvidia 8800GT efi 64 specifically for my model of mac installed it and still had the same problem? So i checked each stick of ram by itself to rule out any faulty sticks they were all good, i pulled out my hard drives a checked those and they were good, i reset the pram with the key commands and still nothing? I checked for any red or orange lights on the logic board and cpu tray and still saw no issue, all fans are working fine, at this point i decided to take it into a repair shop and the told me it was probably the CPU so they replaced it and still didnt solve the issue? Then they said it was the logic board so i had a new one put in which was flashed to 5,1 and was mojave ready and still no chime and no video signal and ive even tried multiple monitors and tvs and also new cables??? So at this point and hundreds of dollars later i dont know what else it could be ive practically replaced the entire machine except for the CPU tray so in my mind its a firmware issue which is hard to diagnose since i cant get any video signal to troubleshoot or something on the CPU tray is faulty but id really like that to be my last resort as ive spent a good deal of money as it is already so any solutions would be appreciated thanks...