I had a lousy couple days trying to get a miner running, both ending with non-responsive main board. I was thinking maybe a power supply issue but it worked with another (3rd) main board, with the exception of the peripheral (Molex) output. However the power supply has a single 12v rail and all the other 12V accessories worked.
Then I saw this PCI-e Riser with what looks like a solder blob across the four square traces. Does this look capable of killing a MB?
Here is another riser from the same order.