I'm a technician at a school department and we recently replaced 30 PCs in a lab w/ refurb Dell 780s. Four out of the 30 have PSU fans that rev full speed and stay there until shutdown. The four are on the same table, side by side, and I thought that to be to much of a coincidence. Thinking maybe it was a power issue, I tried moving one to a known good location in the room, but it still fired up like a jet engine, so I guess it was just luck that the 4 that had the same issue ended up side by side. Before I send them back, I'm looking to see if anyone has any insight into the issue. There is no change in fan speed at all while the machine is running, it's full throttle all day.