Chosen Solution
This may be outdated, but I’ll give it a try. Mac Pro 5,1. Upgraded to 6-core 3.33 processor a few years back, with Radeon 560 video card, USB3, 48GB RAM, 500GB SSD boot drive. The machine screams; it is WAY faster than my 2017 iMac 3.5. Everything functioned normally for a long time under 10.14.6. I moved offices and powered the Mac Pro down. It sat for about three months. Now upon boot there is NO video output; the screen is black from either the DVI or HDMI output of the card. The monitor is known good. The machine POSTs and chimes normally, but then it stops and never displays any image on screen at all. I have followed the Mac Technician manual to the letter more than once beginning in the “No Video” section on page 53: http://tim.id.au/laptops/apple/macpro/ma… Those steps include replacement with a known good (alternate) video card, NVRAM and SRAM resets, etc. I have reinitialized the SSD with a new copy of 10.14 and tried booting from a regular 3.5” drive. I have even replaced the backplane board. I went back to page 33 in the manual, disassembled the machine, and tried to start from scratch. Everything works as predicted, with one exception: On page 36, the manual says: “Shortly after boot start, verify that a red-colored LED is illuminated within the optical audio-out jack at the rear of the Mac Pro. If so, software drivers have been loaded.” In fact, that LED does not illuminate on either backplane board, and the manual does not offer any guidance in this case. (“If the red is not illuminated, then do … what?) I’m dubious that this is a critical piece of this puzzle, but it’s the only thing I can find that’s not loading as predicted. Anybody have any ideas here? I’m not a technician but I’m a logical guy and I’m more than willing to take things apart if it might help (obviously). If nobody has any ideas, I’ll just try to sell it for parts, but I’d like to get it running if at all possible. Thanks!
My suspicion would be an issue with Mojave. Surely you have one drive in the machine with a lower system like Sierra to eliminate a possible Metal problem. Was this originally a 4,1? If you do still have an older video card I would also try that. Did you use DosDude to upgrade or Apple? While upgrading the systems over the years, did you ever skip a major system? (Thus missing a possible firmware update). Have you ever changed out the PRAM battery? I have a 2010 I’m building right now and taking to the Xeon X5690 3.46GHz CPUs.
