What part number is on the other ones that have not failed. Should be a parts list(equipped with) on the inside of the door with the part numbers. If you can't find it, get a smart amp that fits them all.
Not much more we can tell you without knowing what year etc. You can also call Haas or a factory outlet and give hem the serial number and they can tell you every part that is on it. On most, if you are not using your 4th axis, you can swap that amp into it------Check them first.
Mike
Two Haas VF-2's, Haas HA5C, Haas HRT-9, Hardinge CHNC 1, Bother HS-300 Wire EDM, BobCAD V23, BobCAD V28