While I obviously can't know what's wrong in your particular case, I think the part that breaks most often in Yogas is the yellow power connector. My Yoga fell from a table when a toddler pulled on the power cable, and that power connector was the only thing that broke. Now some of the little wire connectors inside are bent so badly that it seems hopeless and I will try to replace the entire connector. In any case the symptom is the same after it has used up its battery charge, as it's no longer getting any power. (Another symptom in my case: When you listen very closely, a funny noise when connecting the power cable.)
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This piece is so fragile that the damage could also happen just by plugging in the power cord in a slightly skewed fashion.
While I obviously can't know what's wrong in your particular case, I think the part that breaks most often in Yogas is the yellow power connector. My Yoga fell from a table when a toddler pulled on the power cable, and that power connector was the only thing that broke. Now some of the little wire connectors inside are bent so badly that it seems hopeless and I will try to replace the entire connector. In any case the symptom is the same after it has used up its battery charge, as it's no longer getting any power. (Another symptom in my case: When you listen very closely, a funny noise when connecting the power cable.)