There has been an issue occurred with chips LNK419EG.
These were bought in Ukraine in quantity of 20 pieces. On the basis of PI Expert calculations 20 identical power supply units were assembled with the next parameters: 72V 0.41A.
Although, only 15 units work properly. Experimentally it has been found, that after replacing the chip on the another such one, power supply unit starts and runs with the necessary parameters. And vice versa: after replacing the chip in the working unit with one of those 5 chips it doesn't work properly yet. So, obviously the problem is in those chips.
Before we've been working with chipsets PFS710, PFS708, LCS703, LCS702, LNK409EG, LNK408EG and there haven't any similar issues occurred.
Could it be the defective batch of chips? Please advise.
The inscription on the chip is "1236 LNK419EG OL324A".