Appreciate your insights wndsnb. Over the weekend I am going to take out each board and heat them up to the point so that the sinks are resoldered. If I find some are really out of place them I am going to take them out and solder them individually. Once cold, I will clean them with canned air. Finally I am going to check the signals also with multimeter. Then will put them one by one into miners and see what happens. I did not buy the test zig. Would you recommend it?
They used to work fine and were producing 75 TH @ 2728 watts each. We had a strange hot week during early Jan and that killed them. Now I think the problem is it is so cold that the boards are finding it difficult to start and of course some of them developed heat sink problem during excessive hot days.