Replacing a Christmas light Bulb
Replacing a Bulb
The ideal replacement is one from an identical "replacement" string bought at the same time as the "operating" string. Anything else is a much less desirable option.
Many strings have two separate circuits of bulbs. Within each circuit, all the bulbs are wired in series. They each see the same small fraction of the line voltage, but only as long as the bulbs operate identically. Different strings can have bulbs of significantly different resistance, yet all bulbs will operate at the same voltage, as long as the bulbs are similar within a circuit. But if we place a high-resistance (typically dimmer) bulb in a generally low-resistance (typically brighter) circuit, that bulb can see far more voltage than it was designed to handle. In that situation, the bulb may simply burn out in a fraction of a second.
Another issue seems to be warm-up time: All incandescent bulbs increase their resistance as they warm up. But even bulbs with the same ultimate operating voltage can warm up at different rates. And if a fast-warming bulb is placed in a slow-warming string, it can quickly see much more voltage than expected, and may blow out.
It is much, much better to buy two strings to operate one string, and then use the other simply for replacement bulbs. But that requires prior planning.
For existing strings, there may be an option: If two or more strings were bought at the same time, we can take one out of service, put it in a zip bag and use it for replacement bulbs.
For existing lone strings, there still may be an option: Convert a 100-bulb string to a 50-bulb operating string and a 50-bulb dark replacement string. That can be as simple as taking bulbs as needed from one half of the string and using them in the other half. Of course, then we end up with half a string that looks like it desperately needs work.
An alternative is to cut the string in the middle and end up with one fully-working short string plus a short string of replacement bulbs that we can keep in a bag. Typically, three wires are twisted together across most of a string, but only two are twisted at the start, middle, and end. So if we look for the two-wire section in the middle, we can cut there (after first turning the power off). On the working half, we can fold each of the two just-cut wires back upon itself and wrap each separately with tape, or separately insulate with electrical heat-shrink tubing.
on Dec 07, 2009 | Specialty Electrics