Before you hang your mini lights for Christmas or pull them out for your next party, be sure to plug them in to see if they are working properly before you go to the trouble of wrapping, hanging or swagging them. You might need to do a limited debugging - here is some technical background and a few troubleshooting tips.
Mini lights are linked in series. The galvanic current flows through all the bulbs continuously like water in a pipe. If a light simply burns out all the lights stay lit since the current can still flow through it's socket. If you break the pipe, however, then you stop the flow of current - and all the lights turn off. The pipe is broken when either a bulb becomes unseated, broken or the wiring is damaged.
Let's scrutinize a few steps to take to troubleshoot your mini lights. Take a limited time to go through this process but like all electrical appliances - don't use your lights if they are structurally damaged, the wiring is frayed, the plugs are torched, anyone at all is melted or if more than 10% of the bulbs are burned out. Any of these issues is a good presume to go shopping for new Christmas lights.
1. Untangle your lights if you have used the traditional post-Christmas throw them in a big heap in a box recipe of mini light storage. Set up shop at a table and consider using a computer power strip with a switch as your testing power middle point - it will save some wear and tear on your back.
2. Visually scrutinize each set to for the aforementioned offenses then plug in each set to diagnose their condition if the wiring and bodily condition passes muster.
3. If the set doesn't light at all, it might be a fuse. In most mini light sets, there are fuses in the plug. Use a flat head screwdriver (not a knife!) and gradually slide back the limited door. Take a look at the fuses inside and if they are blown, then replace them with one of the extra fuses that should have come with your light set. (That's an additional one presume to put your extra bulbs and fuses aside in a labeled envelope when you purchase your lights.) Remember that most mini lights are Ul rated to be linked no more than 3 sets in a row. Plugging too many sets in a row can be a presume you have a blown fuse. If you replace the fuse and the light set comes on then the fuse blows again then you have a wiring issue and should discard that set of lights.
4. If only half of your set comes on and the other stays off then you may either have a damaged bulb base or one of your bulbs have come to be unseated. Sitting at your temporary light mend station, look at each bulb in the set (or side of the set that is out if it is built in two circuits) and gradually press each bulb into the socket to ensure that each bulb is properly installed in its base. I don't recommend you take out and reseat or replace every bulb because you'll spend all afternoon doing it and more than likely you'll accidentally cross a wire or re-seat a bulb improperly and make the situation worse. If you find an empty socket, setup a new transfer bulb (that came with the set) or if a bulb is halfway out of the socket then reseat it and hopefully that will fix your string.
Other than an unseated or damaged bulb or a blown fuse, don't try to fix frayed wiring or mend damaged sockets. Mini lights are reasonably priced and it's not worth the risk.
Use only transfer bulbs that came with your light sets to replace a burned out bulb. Mini light strands are at constant voltage so for each dissimilar kind of string the bulbs have a dissimilar current rating so bulbs from dissimilar varieties of sets are not interchangeable even if they look identical.
Now that you've plugged in and debugged your mini lights make your list of what you need to replace and then what you'll be adding to your Holiday or party display. Have fun decorating!
