Hi! Today my customer brought in an iMac 27” 5K 2017. As he say, computer turned off by itself and caused all electricity at home to shut down. He felt burnt component smell. I took out the board and found burnt and swollen area on PCB under one of the CPU phase mosfets (Photos of the board in attachments.) I’ve measured dead short on caps next to the swollen area. I don’t have schematic for this board, but I guess it’s PPBUS line. I’ve removed some SMD components in this swollen area and started digging into the board. After I got through all burnt parts I noticed short is gone. I’ve assembled everything for testing and computer runs fine. I haven’t stressed it yet with benchmarks, but I’m going to test it tomorrow. What I want to ask you is, what is the chance, that it will run stable with 5 of 6 CPU phases? Do you think it will have problems with CPU VCORE on high loads? Also - is there any proper way to secure such canyon on the board or just cover it with layer of UV soldermask?
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