TOP258 voltage drops on load to zero

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i am building an AC-DC smps from 230V AC to 5V, 2.5A DC using TOP258 based on design by PI Expert online. I am able to get 5V DC output without any load. But as soon as load is applied, voltage drops to zero. Then again ic tries to start voltage goes up a little and transformer makes some noise and voltage drops to zero all within 1-2 sec. Can anyone detect any problem?

Note: I am using PC817 as octocoupler due to unavailability of given one. Also not using choke and using SR360 as output diode instead of MBR340

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SMPS_TOP258.pdf2.02 MB

Hi,

Thank you for considering Power Integrations for your solution.

It looks like you might have the transformer wound incorrectly. Please check for the right polarity at the primary and secondary

Best Regards,
PI-Kryten