Dear R_J thanks a lot. Yes I am checking and think TN LNK302/304-306 is IC901. I see you added L1 in the schematic which I didn't take into account in the first survey. I measuret the path and since its dc resistance is very low it looked like a simple short wire. Based on your very well explained photo of the Power supply board, I used a LCR meter and it shows a value of 1.14mH. Very close to that of the buck converter example in the datasheet for L1.
So I will try to order a LNK306 D sop-8c IC and make the replacement.

I have some LNK564PN, TNY264, TNY266 PN but I think they...

Dear R_J thanks very much for your help. I checked the tinyswitch datasheet and I am not sure this is the IC i am trying to identify. In the description i am refering pinouts as in the photo attached. I see pin 7 directly connected to positive of DC big capacitor. In the datasheet I see a network beetween this pin and positive HV DC. Also in the board are two photocouplers but seems not resistance from any pin of IC 901. to them. I don't know maybe another type of IC?...

I have a 5V 55A led Delta power supply with no output. I found this 7 pin IC 901 damaged as in the photo. All other elements look ok. I checked and every other surrounding componets diodes, resistors and capacitors look ok. I have 2 identical power supplies removed from a led wall which have the same defect with this ic burned but not a working one for reference. I founded by measurements that pin 7 goes to positive hot 450V 220uF electrolytic capacitor primary side. Pin 1, 2, 3, 4 connected together to pcb cooper trace. These four pins goes to negative side of 10uF 50V electrolytic capacitor...