I have come across many problems with laptop black screens, restart cycling and graphic faults and in 80% of the case its the mobo its at fault and not the actual hardware.
You see laptops run hotter than PC's and the motherboard goes through expansion and contraction because of temperature. This in the electronics game is called thermal stress. As this is a physical property the solder joints on the motherboard start to loosen off (go dry) and cause the electronic circuits to go open circuit.
It all comes down to motherboard design and how people operate their laptop. The name laptop is missleading, cos if you put it on your lap, bed covers or carpet the cooling vent at the bottom gets covered and it will run hotter than it was designed for, and reduces its operating life.
Remember reflowing is a final solution.
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