If its a Rev 2 (green) pcb then usually its just one of the 2 upper mosfets and also replace the drivers (IR2104).
( If its an older (yellow pcb) than it may be more . )
You have to be careful when removing mosfets, you don't damage the PCB. Don't use a solder sucker ! It loosens traces.
Put the soldering iron on 2 legs at a time, and twist it out each side at a time as your heating it. Then tap the board on the table to remove solder filling the holes.
I've got a circuit for a simple MOSFET tester that i will post.
BTW, Any companies drive can be blown by a number of different ways. There is No such thing as a bullet proof drive (just search these forums). I made my drives repairable just so the customer doesn't loose his investment when Sh#t happens (lol) (maybe years down the road).
There is a servo drive comparison review on the web that says "Larken wouldn't have made his drives repairable if they didn't blow" , but he fails to mention that my drive didn't blow, unlike 3 others he tested that did !