In many cases the cause of output stage blowing is faulty firing circuitry, causing a IGBT to fire the same time as an opposing one in the bridge etc.
This causes a dead short, the IGBT's can generally be checked with a meter but are best removed for accurate testing.
It looks as though there is lower power IC damage, usually replacing the IGBT's without first testing the firing circuits, result in blowing them again.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.