Def. broken. Powers on but then off after about 5-10 seconds. On the plus side it did come with the 1TB SSD and 64GB of OEM RAM.
I'm guessing the PSU is fried, I could probably swap it out with a known good one to make sure or just buy a new used one for $40…
I ordered up a used PSU from eBay to swap out for the “broken" one in the “free" Pro. Swapped out the PSU, powered it back on and ... turns off after a few seconds.
Turns out it wasn't the PSU that was broken, it was the I/O board (which is connected to the PSU and I replaced both when testing). Derp!
Ordered up just the I/O board and they send me the I/O board with a PSU connected.
Long story long, I now have a working Mac Pro and 2 extra Mac Pro power supplies.
While doing all that I repasted the CPU/GPUs on it and that reminded me how serviceable the 2013 was. Sure it's a Mac and I'm grading on a scale, but 4 Torx drivers, a spudger and ice cube tray let's you pretty much take everything on it apart. No paired parts, no soldered storage/RAM/CPU, the internal connectors aren't super fragile (except for the damned WiFi antenna which I hate).
It's refreshing.
"I have an idea, I'll print labels with the specs of the Pros so I know which is which.”
Doh!