Hi, new here and would like to thank you all for doing such a great job,,, looking for repair help so if there is a central place to go first let me know. Mac Pro, 2010 5,1 single CPU, radeon 5770, 2 SATA + 1 SSD startup, 32 gb ram began acting sluggish so rebooted. Chimed and powered up to the point where it was ready to load the Sierra OS and monitor went blank with HDs still spinning. Replaced graphics card with a new radeon 580 destined for Mojave upgrade so I knew it wouldn't show the boot sequence,,, same thing, blacked out at about the point where the OS would be expected to load. Same thing with another 5770 from my other dead 2010 5,1 with cpu issues. Replaced the battery and tried booting into other backup drives with OS's on them, SMC resets, Pram resets, reseat ram multiple times. Then it got worse and would not accept any keyboard commands most of the time, though would usually show the question mark folder with all HDs pulled. Processor light would flash on and stay off as expected as well as the diag lights. Stripped it down to just the backplane, wifi, and bluetooth card with all lights working as expected according to the "Apple Technical guide (2010)" I'd suspect bad HDs except the screen blacking out at OS loading point behavior is the same when booting into all three, though honestly haven't used my backups in forever as the system has been rock solid. Tried replacing the entire cpu/ram sled with the one from the other computer with the processor light on and no boot and it worked fine as far as no light on and booting to OS load before screen blackout. At my wits end and have ordered another one from ebay only to have the seller leave town for a week before shipping. Day trading and losing $ trying to work from my laptop,,, the thought was to have 2 machines ready to swap out,,, Help please!