I just saw a really sweet tool that will help you find the burned out / bad LED on a stran without having to go pull each light and test it individually. It's my understanding that it's in the prototype phase right now but hopefully it will be out shortly. The inventor is also a member of LSH & DLA. Cannot wait to get my hands on one of these. I spent hours trying to find those burned out LED's last year. I been told it will be available for around $25 - $30. A Deal if you consider your time. I'm not sure if I can give out the name so I won't at this time.
Scott