Industrial application. Feed with 48VDC from switching power supply (90 to 240VAC in), 12v output 0.9A, about 300KHZ. Free-wheeling diode rated 60V at 2A. Circuit output feeds two regulators of 3.3V and 5V. When the circuit fails usually chip case damage by pins 3 & 4 and diode is shorted (B360A-F) attached 5 & 3 volt regulators also damaged. Replacing the damaged regulators and diode, circuit works as normal. I have some twenty boards that have failed. This only happens in China and India running 220VAC and not Europe and elsewhere. No 120VAC models to date. Any suggestions? Thanks Mike