Wow, do I have a doozy of an update! So, by some sheer luck, I found a second back in Japan for sale. It was listed as working and I jumped on getting it. Arrived yesterday and put it to the test. And now I'm stuck and need help on where to go/what to do.
So, went to a local camera store and they helped me test the sync port. I used an external flash (not on hot shoe) and used the digital back cable (I thought could be faulty) and the camera sync port (which could've also been faulty). The test button fire the flash off, so the issue is doesn't appear to be the sync cable or the port on the body from that test.
So, what's happening? The digital back (both of them) trigger the shutter, the mirror flips, images are recorded to the CF card. I'm getting black images from both backs, there appears to be no data in the histogram that the body displays. I have the lens aperture wide open, shutter speed matches on the body and digital back. I've tried both short (1/125) and long (4 seconds) and no change in the image captured.
I uploaded the manual here (). I'm not sure what to try to troubleshoot at this point. Any help would be appreciated!