Christmas lighting problem

Factual Questions
1

Well, this is embarrassing, since I’m an electrician by trade. I’m having a problem with a string of outdoor lights that I’m hoping someone can figure out for me.

Here’s the setup: I have about six or seven strings of lights on an outdoor tree. These are the miniature type, non-flashing, all identical and from the same manufacturer, two-wire strings. If one bulb burns out, all others stay lit (according to the package).

One of the strings that is located in the middle is the problem child. Only half of it is lit, and it’s the half on the power side of the string. In other words, there is darkness from the male end to about halfway up the string, then the rest is lighted, and all the strings downstream from this one are lighted, as are all strings upstream.

For the life of me, I can’t figure out how this can happen, and don’t know how to fix it. Any help to solve the mystery appreciated.

2

That set has a bad connection/loose bulb (one of the bulbs that is out).

You need to pull each one and replace it firmly with an extra bulb that you just move socket to socket.

So, grab an extra bulb, and pull one out bulb and replace with the working bulb

or

buy a xmas bulb tester tester
or
go to the plug end and and slide open the tiny fuse box on the strands plug end. Common ones have two fuses…one each for the dual strand of lights you describe. One might be blown — especially if you have seven strands connected in-line!!

3

:smack: What a total brain fart on my part! I wasn’t thinking about the bulbs being on two different lines. I’ll check the fuses. By the way, it can’t be a bulb problem (see OP).

4

It can be a bulb problem. Take a bulb out and see how much of a probelm that is.

So, while all the bulbs look like they are in their little ol’ sockets, the tiny wires each bulb has must make contact with the bulb socket.

The test bulb allows you to pinpoint the problem, because those little bulbs have tiny wires, and if one is broekn, the circuit is broken.

If you don’t have a test bulb/spare, scavenge one from further down on one of the other strands.

5

Yes, it can. Even on the type where the rest stay lit if one burns out, a loose connection can hose the whole string.

6

Just for a bit of background how xmas lights work . It has a diagram showing how part of a set of lights can go out via a bulb problem, though it takes 3 wires instead of two… You would have 2 sets of 50 bulbs running parallel in a single strand.

Fun info on that page showing how the bulb shunt provides protection against the whole string going out. Note that the shunts aren’t 100% effective, I’ve seen tools designed to fix strings by forcing the shunts to connect properly, a broken shunt is just as bad as a broken bulb. As a result, these protected strings can still actually go out via a blown out bulb.

7

::much waiting as Chef pulls every light::

Ho

Ho

Ho!

:stuck_out_tongue:

8

If it isn’t a fuse, then I think I’ll just suffer through with that half string out; it’s too damn cold to fuss around out there.

9

This thread is an embarassing reminder of how long it’s been since I worked in the field. Crap. :frowning:

10

From Cheesesteak’s link:

I don’t see how simply removing a material coating could lower the resistance of the shunt at 60 Hz. There must be something more complicated going on. Anyone know what it is?

11

Just remember to throw it away, and get a new set after Christmas for cheap/