i agree with you , other disadvantages of ic,s are because of fake ones which find their way in the market. by the way does the protection work . as in case of short circuit it completely turns off the smps?
Hello stewin,did you draw pcb?
I make f meter (finally ) and with BJT measure 25kHz with core RIK10 4050
With core from CFL it will be more,maybe 30-35kHz (not measured)