I have a set of Christmas lights for which the second half doesn't light up. My understanding is that the individual branches are in parallel whereas the lights in each branch is in series.
The plug at the end of the set works fine, so current seems to travel to the end of the wires correctly.
What could be causing this?
Best Answer
On Christmas lights, they are wired with a backbone of 2 wires carrying power through to the socket on the other end.
Then, they have one or more strings of 40-50. Each string taps one backbone wire at one end, and the other backbone wire at the other end.
Within each string, all lamps are in series. A failure will darken the whole string, except the bulbs have fusible shunts so if a bulb burns out, it will shunt and the other bulbs will remain lit (at a slightly higher voltage, burning them out faster).
When you have a segment with 40-50 out, that means a shunt has failed, or you have a loose socket or broken wire.
They make toners specifically for Christmas tree lights (a cheapie version of a Fluke toner, I presume) that will help you find the bad one.