The DC-In jack on the motherboard is either loose or faulty.
If it is only loose, it will have to be re-soldered back onto the system board. If it is faulty it will have to be replaced.
In either case the system board will have to removed from the laptop to gain access to the socket so that it can be tested and either re-soldered or if necessary replaced.
Here’s a link to the service manual for the laptop. Click on the “system board” link in the Contents section to find the necessary pre-requisite steps and then the procedure to remove/replace the system board.
If you require a new part, search online for Dell E1505 Dc-In jack to get results for suppliers.
Here’s a link to one supplier. It is shown only to give you an idea of what the part looks like and what it may cost. There are other suppliers that may suit you better.
Был ли этот ответ полезен?