Lamp stopped working? Knob popped off and can't secure it again? What piece of junk, right? But not the kinda junk you toss, the kind you fix. One of our floor lamps had a socket that went bad right after the knob cracked and fell off. But it's a nice looking lamp, and I wasn't about to trash it!
I did a little web searching to see if I could find instructions for how to replace lamp sockets -- yeah, they are out there. You can do your own search, or find a book at the hardware store, etc. You'll want to follow reasonable, sensible precautions to work safely and to repair the lamp to a safe state.
In my case, just the socket itself was bad, though I bought the entire assembly from the hardware store. They are pretty cheap so no big deal.
Fixing was just a question of unscrewing the cap over the socket, pulling the socket out of the lamp (feed the lamp cord into the base to give some slack), and then swapping in the new socket -- after pulling that socket out of its assembly.
I preferred to swap one wire at a time to ensure the right wires remained on the right screws/tabs of the new socket. You'll probably want to make sure you get the same kind of socket, too -- like, 3-way vs on/off, same watt rating, etc.