Hi @mjsmith,
Did you prove that the power adapter port was faulty by testing it using an Ohmmeter or a Voltmeter, between the input side of the port and the wires on the cable plug on the output side of the port?
''If not'' here's the [https://dl.dell.com/content/manual31913329-inspiron-5406-2-in-1-service-manual.pdf?language=en-us|service manual] for the laptop that may help.
Go to p.25 to view the procedure to remove the power adapter port. You only have to get as far as unplugging the port cable from the motherboard and then test if it is OK or not.
''If you have'' and the the port is OK then the schematics for the motherboard would be needed to help find out what's wrong.
What is the model number of the motherboard, (usually printed somewhere on the board itself)? Unfortunately I can't find any schematics online using the laptop make and model number so hopefully the board number may show some results.