Usually the MOSFETs and IGBTs fail in pairs. So there are probably less obvious failures elsewhere.Taking it apart I found one igbt and one MOSFET in pieces
Yes, the 4 electrolytic capacitors that protect the MOSFETs. There are also another 4 IGBTs, but the other set is likely OK. But verify.I'm probably going to replace all 16 MOSFETs and the 4 igbts. Would anything else be recommended to change?
Also check all the gate drive circuitry. Often resistors and diodes, sometimes transistors, blow up in the gate drivers. There is nothing quite as disheartening as replacing 16 MOSFETs and finding that they blow immediately because the gate drivers were also faulty.
Most likely it was the medium quality capacitors that dried out. Replacing with long life types earlier might have prevented this fault. See the index for recommended capacitor and MOSFET replacement part numbers.Could it have been something else that caused this or just unlucky?