DC Power Jack - minus to chassis?
If you have a socket similar to the shown below, you can see two tabs and metal ring. One of the tab is connected to the center pin (usually +), the other is connected to a small sleeve/tab inside (usually -). The plug albo makes a contact with the body of the socket (also usually -). The standard way is to connect the tabs to + and - on the PCB and let the body ring make contact with the chassis.



https://media.rs-online.com/t_large/F0487842-01.jpg