"middle string, of 3 LED strings does not work other 2 work"に関する回答I noticed this post is a year old but decided to answer anyway. You probably have either found the problem or used the set to cannibalise to replace bad lights in another set. The problem with the middle set is not the fuse. There is one or more bulbs that probably have a corroded or broken wire. Find the bulb and replace with same color if lights have bulb covers or fix the wire on the bulb. I answered another post that tells how to fix a broken wire.
"Can't get plastic cover off of led bulb to check the bulb"に関する回答I noticed this post is 4 years old but decided to answer anyway. You can use a pair of pliers to hold the bulb socket while twisting and pulling on the cover. Hope this helps someone.
"Half of the string of LED Christmas lights doesn't light up."に関する回答Regarding lights with a broken wire, if you are handy with a soldering iron, they can be fixed. First thing to do is check the light to see if it is good. Remember, LED lights are polarized. So using a "light fixer" for the original mini lights, remove the bulb from the socket and touch the leads to the light tester. If it does not light, reverse the leads and try again. If it lights good. If not discard the light. To repair the light, First find a piece of stranded wire and strip off about 2 inches of insulation. Next, separate about 4 strands of wire and twist them together. Keep doing this until all strands have been used. Next, heat the soldering iron. While the soldering is heating up, prepare the leads on the light. Use a small file or your wife's or girlfriend's emery board to clean the leads until shiny. Next, dip the leads in soldering flux. I use a quick clamp to hold the light steady. Tin booth leads of the light. Tinning the unbroken led will make it stronger so when you insert the bulb in the...