Identifying a Xistor

[perdrix]

I suspect it's a FET.  Piccie attached.  It's totally shorted.

[aqibi2000]

FD8880

https://www.onsemi.com/products/discretes-drivers/mosfets/fdd8880

Test it out of circuit too

[perdrix]

Thank you!

Addendum:  I removed it and checked out of circuit - definitely short between Drain and Source (both directions).   Quite how that happened I don't know given that it's rated at 45A and is protected by a 3A fuse!  Yeah, I know - corollary 16 of Murphy's law: When you fit a fuse to protect an expensive device in a circuit, the device will always blow first so as to protect the fuse.

PS Mrs. Murphy's Law: Murphy was an optimist.

David