One of my BTmine units went offline late last night.  Fans were off, PSU fans were also off, and the LED from the fpga board was solid red.  Could still access the tp-link interface.  Tried different PSUs, nothing changed.  After some poking around with a multimeter, it turns out that I definitely have a short between 12V and GND on one of the blades/modules.  I unplugged the faulty module and I'm back up and running with only one module for now.