We have two trees, one is 12' and the other 7.5'. When a light goes out a section of lights go out, or so it seems. My husband spent days troubleshooting the 12' tree trying to get all the lights working. Finally, I convinced him to put a few strands of lights on it and forget about it so that I could get it decorated. I told him when we take it down, he can fiddle with it all he wants! The 7.5' tree had a few lights out as well so we did the same thing.