Just a thought on electrical grounding issues - Any GRND imbalance between the external PSU and the server will result in a small current flowing through the card via the GRND traces. In a perfect world this should be negligible, however, to play it safe I would make sure the server and PSU are plugged into the same power strip at all times so they share the same ground bus bar. If you have a multimeter available I would also verify that the voltage difference between the grounds on the DC side of the 2 PSU's is exactly 0 is very very close to 0v.
Just a thought on electrical grounding issues - Any GRND imbalance between the external PSU and the server will result in a small current flowing through the card via the GRND traces. In a perfect world this should be negligible, however, to play it safe I would make sure the server and PSU are plugged into the same power strip at all times so they share the same ground bus bar. If you have a multimeter available I would also verify that the voltage difference between the grounds on the DC side of the 2 PSU's is exactly 0 is very very close to 0v.