I had an LED floor lamp that I bought from the local Scandinavian Cheap Furniture Store that started to rapidly blink rather than stay on. Although I thought that I might have gotten a cool (albeit rather dim and unadjustable) strobe lamp, I was much more interested in reading than partying. I am at that age now. So after tracing the problem down to the power supply, and having little luck getting said Scandinavian Cheap Furniture Store to talk to me about getting a replacement, I figured I could fashion one of my own using the 5 volts used in USB power supplies and devices.
Step 1: Your Old Power Supply
Check out your power supply. I imagine a lot of companies manufacture LED reading lights along similar lines. Check the output voltage on your existing (or malfunctioning) power supply and find a diagram of the wiring polarity if it is there. Remember that with LED's, polarity matters.
It is important to note that the lamp was designed for 4 volts and I am putting 5 volts through it. You should put a resister in line to bring down the voltage to the specified 4 volts or your lamp will over heat and probably burn out your LED prematurely.
Although I did not do this in this Instuctable, be carfull! I am keeping a weary eye on my lamp and I definatly would not leave it on when I am out of the house.
Step 2: Find a Male USB and a USB Charger/power Supply
In this case I salvaged an old printer cord and the charger that came with my now defunct Kindle.
Step 3: Get Your Tools and Supplies...
Heat gun (or a cheep cigarette lighter)
Heat shrink tubing (1/4")
Step 4: Get Your USB End
Leave about a foot. Also cut the old plug/power supply off your lamp.
Step 5: Loose Fit the Heat Shrink Tubing
Put it on now because later will be too late!
Step 6: Separate Your Wires
With USB your white and green wires go away, they are for data that you're not using. We are just using the red (5 volts) and black (common).
Step 7: Strip
Carefully go around the insulation with a sharp knife. And make one wire shorter than the other so both splices are not at the same place and end up resting against one another.
Step 8: Check Your Voltage
To make sure your scavenged parts are okay to use.
Step 9: Twist, Test and Solder
Once twisted but before the soldering is complete, you should gently test the whole thing to see if your lamp comes on. If it does not, you probably have your wires crossed (polarity inverted) and you need to switch them.
Time to solder. I find it easiest to put my iron under what I am soldering and bring the solder down on top of the wire splice.
Step 10: Tape It Up
Put a small amount of tape on each splice and a little on the outside of the insulated pair.
Step 11: Shrinky Tube
Gently move the shrink tube over your work, being carful not to disturb your tape. Then shrink it with the heat gun. I have used a cigarette lighter when I didn't have a heat gun around.
Step 12: Read a Book
Here my lamp plugged into my old USB charger!
REMEMBER to keep an eye on the temperature! Retire the project if it gets too hot!