You know if you’re here that it must be almost time for Christmas and you have some busted old lights. Not to worry though fixing them is probably easier than you think. Always check to see if your lights have fuses. If there is a little sliding door on the plug in then it likely does. Do that first. If the fuses are good, or you don’t have fuses then you know what time it is. Its time to remove one bulb at a time and replace it with a bulb that is known to be working until you find the bulb that runied your whole string. Its boring and slow work but not particularly difficult. Best of luck this holiday season.