LNK364PN DIP-7 IC – Low Power Offline Switcher IC

I had ordered 45 Nos. LNK364PN and found 21 to be defective. All the ICs were made by Power Integration with nos. etched on them but those having 1833 as manufacturing code were defective. It seems all the ICs were genuine. I wrote to Robu and am awaiting their response. Since I was in a hurry I went to the local market in Kolkata and bought 30 Nos. LNK364PN made by some other company. The nos. were printed on the IC and not etched but were cheap. I thought at least these would work but to my bad luck the same problem happened and the SMPS were not working. After a lot of research work and sleepless nights, to my utter surprise I found all ICs bought from Robu and the local market which did not work had pin configuration altered. Pin 3 which is the Bypass (BP) originally was pin 1 for the defective ICs and Pin 1 which is the Source (S) originally was pin 3 for the defective ICs. When I made the changes on the PCBs it started working. Never in my more than 20 years experience in electronics I have ever had a experience something like this. It was my hard work and study which lead to the solution. How could such things happen is beyond my imagination. Pin alternation without any reason should be an offence as a person would be fooled if not known. I would request Robu to have a talk with their suppliers about this and in turn let the manufacturers know about it.