A common problem for lamps is a bad connection with the bulb and contact tab in the bottom of the socket. Make sure the lamp is unplugged. Use a screwdriver tip to scrape off any corrosion, and then prying it up a little.
If the problem remains, take apart the socket. Most sockets have a "PRESS" mark stamped into the upper cover. Squeeze the cover there, and work it off.
Remove the insulating cardboard sleeve. Check the wire connections. If they look good, the next thing to troubleshoot is the cord.
Remove the wires from the screw terminals, noting how they're connected. If there's a silver wire and a copper wire, the copper goes on the brass screw. If both leads are copper, the lead with the ridge on the side of the insulation goes to the brass screw.
Use a continuity tester to check the cord. If there's a switch somewhere on the lamp or cord, make sure it's "ON" when you test.
If there's continuity in the cord, replace the inner socket. Be sure to get a replacement that matches the original.
We also add an "underwriters" knot that protects the new leads from being yanked off the terminals.
Then connect the wires to the new socket. Twist the bare ends of the wire, hook them clockwise around the terminals and screw them down.
Put the socket inside the sleeve, and the sleeve inside the cover. Push the cover back down on the base and orient the switch in the desired direction.
If the lamp still doesn't work, it's a good idea to have a professional take a look at it.
Fixing Cord Plugs
The plug end of a lamp or appliance cord may pull lose of it's cord connection. Replacement is fairly easy, however.
For basic flat cords, you can use a "quick-connect" plug. The plug pulls apart by squeezing the prongs together.
Feed the end of the plug through the back of the cover. Spread the prongs apart and insert the wire into the back of the core.
Squeeze the prongs together. They have small metal spikes that penetrate the cord's insulation to make contact with the copper wires inside.
Slide the cover down onto the core to complete the job. For a little stronger connection, use a plug with screw terminals.
Start with a clean end on the cord -- sometimes called "zip cord" because the two side pull apart easily. Strip about 3/4" off the end of the two wires and twist the lead strands together tightly.
Hook each lead to fit around the screw terminals and attach the lead that has a ridge on the insulation to the silver terminal.
If the screws aren't color-coded, this lead goes to the wider plug prong. Work the cover back down over the core.
Fixing Grounded Cord Plugs
Most cords with grounding plugs are molded right onto the cord end. However, they can fray and work loose. If this happens, it's best to replace the plug.
Cut off the old plug and strip the ends of the wire. Many cords have an outer sheathing of insulation. Strip it back about 1 1/2" with a utility knife and cut off the excess.
Strip about 3/4" off the end of each lead. Feed the cord through the plug's back cover and connect the wires. The plug terminals are located in the back.
NOTE: Terminals on the face of replacement plugs covered by a removable cardboard disk are illegal and not a safe choice.
The green (ground) lead goes to the green screw. The white (neutral) lead goes on the silver terminal. The black lead goes around the brass screw.
Finally, put the cover over the plug and screw down the cord clamp.