Real Simple answers your questions.
Q. How do I find the broken bulb on a string of lights?
West Hollywood, California
A. Get ready for a hands-on approach: The best way to locate the culprit (don’t hate us) is to pull each one out and test it in a working string. The good news, though, is that you can skip that laborious process and still light up a blacked-out string with the Light Keeper Pro ($16, amazon.com). It sends a harmless charge down the wires so the working bulbs will light.