R7, at 12k, is way too low ohmic value.
Please tell what is R7?...what package and power rating?
Also, what is your Z4 value....you could be overvoltageing your TL431 if its too low
Also, what is your transformer turns ratio...remember that "V referred to pri " is "vsec * NP/NS"
Do you know how to work out the polarity of a flyback transformer coils?.....ie, assign a dot to one end of one coil, then go through and measure it connected to another coil...see if inductance is more or less than the coil on its own....bla bla bla etc etc etc...
Also, are you using a PCB, or is this wired on a breadboard? (hopefully not breadboard and wires)
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Also, your D1 is in the wrong place.
Your sec diode is only 600v rated.....please tell what is your turns ratio.
You also have no rc snubbing across your output diode.
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Also your diode bridge is only 400v rated, and friends tell me that voltage transients in India are way above this.