Good evening to all, and may all your lights work. I encountered the age-old problem of half the strand not working. I discovered it before I put it up on the eaves. This year, I got an early start on my lightscape so I had time to troubleguess the offending strand. I inspected the wire for breaks. Then, I plugged it in to the wall socket. I removed one LED at a time, starting at the plug end. After the sixth LED, I was ready to quit. LED #7 proved to be the problem. The prongs of the LED were misaligned in the base, so they couldn't make contact with the socket. I pushed the prongs into position, put the LED in the socket, and the rest of the strand came to life. The whole task took 10 minutes. The best part is that I was able to live up to the expectation of my 7-year-old granddaughter who was observing the process. In her words, "Good job Granpa." I hope this answer is helpful to someone. Happy Holidays, from Phil in Kansas.