Sniff it...does it smell burnt? If so, it's toast. Keep in mind that a simple short (posts touching, cap touching coil leg) will destroy these mosfets. Treat them like a mech, and always check your atty on a regulated mod after any work on your build or disassembly/ maintenance. I killed my last one when a coil leg found it's way into the deck of my Hussar Project X, of course unbeknownst to me...DOA !

Build .2 or higher, your mosfet will last almost indefinitely if you follow the above steps.