Tools & Materials 
Replacement socket
Continuity tester
Screwdriver
Next to the cord plug, the most common source of trouble in a lamp is a worn light bulb socket. When a lamp socket assembly fails, the problem is usually with the socket-switch unit, although replacement sockets may include other parts you do not need.
Lamp failure is not always caused by a bad socket. You can avoid unnecessary repairs by checking the lamp cord, plug, and light bulb before replacing the socket.
Tools & Materials
Replacement socket
Continuity tester
Screwdriver
Socket-mounted switch types are usually interchangeable: choose a replacement you prefer. Clockwise from top left: twist knob, remote switch, pull chain, push lever.
Tip 
When replacing a lamp socket, you can improve a standard ON-OFF lamp by installing a three-way socket.
HOW TO REPAIR OR REPLACE A LAMP SOCKET
Unplug lamp. Remove shade, light bulb, and harp (shade bracket). Scrape contact tab clean with a small screwdriver. Pry contact tab up slightly if flattened inside socket. Replace bulb, plug in lamp, and test. If lamp does not work, unplug, remove bulb, and continue with next step.
Squeeze outer shell of socket near Press marking, and lift it off. On older lamps, socket may be held by screws found at the base of the screw socket. Slip off cardboard insulating sleeve. If sleeve is damaged, replace entire socket.
Check for loose wire connections on screw terminals. Refasten any loose connections, then reassemble lamp, and test. If connections are not loose, remove the wires, lift out the socket, and continue with the next step.
Test for lamp cord problems with continuity tester. Place clip of tester on one prong of plug. Touch probe to one exposed wire, then to the other wire. Repeat test with other prong of plug. If tester fails to light for either prong, then replace the cord and plug. Retest the lamp.
If cord and plug are functional, then choose a replacement socket marked with the same amp and volt ratings as the old socket. One half of flat-cord lamp wire is covered by insulation that is ridged or marked: attach this wire to the silver screw terminal. Connect other wire to brass screw.
Slide insulating sleeve and outer shell over socket so that socket and screw terminals are fully covered and switch fits into sleeve slot. Press socket assembly down into cap until socket locks into place. Replace harp, light bulb, and shade.