Hello,
From your description it sounds like a bad capacitor on the board. If it's not that then it could be the board was damaged by possibly a power surge of some sort. I have also seen this happen when moisture gets on the board like a drop of water/pop/coffee hits the right spot and doesn't out right kill the system but still damages it.
I could suggest opening up the system and checking the capacitors for bulges and leaks but it may be harder to do with the system being a laptop.
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