Hi @mpeet59 ,
I would try replacing the [https://www.ebay.com/p/2087471518|DC-In cable] and check if that resolves the problem.
The supplier shown in the link is an example only to show what the part looks like and how much it may cost. There are other suppliers online that may suit you better. Just search for ''5C10G97330'' to get results.
Here’s the [https://download.lenovo.com/consumer/mobiles_pub/lenovo_yoga_3_pro_1370_hmm_201512.pdf|hardware maintenance manual] for the laptop.
Go to p.44 to view the necessary pre-requisite steps and then the procedure to replace the DC-In cable.