Sub: Missing enable on +5v sec pwr rail AMD Firepro D500-B/Mac Pro late 2013

Ref: 1/ MacPro6,1 Late 2013/A1481 MD878LL/A (3.5 GHz 6 Core Xeon E5-1650v2)
Gfx-B: APN: 661-7548 PPN: 820-3533-A AMD FirePro D500-B 3GB Vmem
2/ Figure 1 Gfx-D500-B Front Facing
3/ Figure 2 +5v supply (zoom-in)

Intro:
While troubleshooting a Mac Pro(6,1) referenced above I discovered the +5v secondary supply did not stand up on the D500-B graphics card as a result of a missing enable signal. The +3.3v secondary rail was the only rail that did standup. I tried to perform...

Any documentation such as schematic, boardview, service manuals would help.

Mahalo

Re: New Members - please post your introductions here

Greetings:

I just registered as my motivation is to locate documentation in support of repairing legacy monitors from Apple i.e. Apple Cinema Display 30" model A1083.

My current occupation is retiring...so far I'm pretty good at it. However I find great satisfaction in making repairs others have given up on. I hope the membership can help me down this journey with mutual support.

Regards

Background:
1/ MSEE
2/ 27 yrs. as a military contractor