TNY286PG flyback, does not start

Hi VLimaye,

Good day and thanks for choosing Power Integrations.

May I request the following documents and waveforms? This way, we can further review your design and check if there's anything unusual.

1. Schematic diagram
2. PCB layout (Gerber files preferred)
3. Transformer datasheet of the actual transformer used in the design (from your transformer manufacturer with primary inductance information and number of turns of each winding)
4. PI Expert file (in PDF format) from the PI Expert Online tool

I would really appreciate it also if you could clarify the following below, so we can better understand the situation.

1. At what input voltage and output loading condition does the startup issue occur?
   1. Does the issue occur even at no-load condition?
2. What is the name of the device you're currently using? 

In the meantime, I recommend doing the following:

1. Verify if the soldered component in the board has the same and correct value as per the PI Expert design.
2. Double-check if the components are soldered to their proper places and correct orientations, especially the diodes.
3. Remove the transformer first on the board and verify with oscilloscope if the phasing of each winding is correct. If this is a flyback design, the primary winding should be out of phase with the bias and output windings. Please refer to the attached image for proper probing attachment. Let me know if you need any further guidance about this.

Thank you and looking forward to your response.

Best regards,

Tommy