You know how Christmas lights always used to work-- if one went out, EVERY single light on the entire string immediately went out? Well, NOW the packages say that “if one goes out, the rest stay lit.” Well…
That’s NOT what happened at all. One bulb went out and every other bulb instantly went dark. I traced it back and found that it was the first bulb on the string. In fact, when any bulb went out, every other bulb after it went dark (which seems to happen a lot.) Does this sound like “if one goes out, the rest stay lit” to you? Why does it seem to be so impossible to design Christmas lights so that if one bulb goes out, THAT bulb, and ONLY that bulb, is the ONE on the entire string that goes out? Is this actually just not possible for some electrical reason? Does anyone know? Why, God, why?
in ancient times when Xmas lights used large bulbs (4 or 7W) it was a usual method for only the burnt out bulb to go dark. those used more materials, were heavier, hotter and used more electricity.
modern Xmas lights are wired differently and smaller.
They’re wired in series, which means each bulb is connected to another by one wire. When one bulb goes out, which means the filament burns through, the circuit is broken, and they all go out. This does allow the simple blinker circuit used in most lights though. A little switch made of flexible metal heats up and seperates from the contact and the power goes out until it cools down, creating the blinking effect.
modern lights are wired in series thought if they say that “if one goes out, the rest stay lit.” then there is a shunt in the bulb to allow electricity to flow even with a burnt out bulb. these can be poor quality products and not always work.
A string of Christmas lights uses a massive amount of electricity compared to say a cell phone charger and when you can buy a string of lights for $2.00 it’s much too expensive to use a step down transformer and run them in parallel. How it’s supposed work is each light has a shunt that will close when the bulb burns out, however it doesn’t always work that way in practice.
It’s a matter of the bulb voltage. If you are using the style of Christmas lights that use 120V bulbs, you can run them in parallel without a stepdown transformer. Most Christmas lights don’t use those kinds of bulbs, but instead use little bulbs that are meant for about 3V each. With those, you either wire them in series, or use a stepdown transformer and wire them in parallel.
In parallel, each bulb would have 120V (but a very low amperage) going thru it. 120V is not a good thing to have exposed, if bulbs fall out and little fingers start poking in (or tinsel shorts it out to create fires).
In series, the voltage is spread out in proportion to the resistance of each bulb to the total resistance - roughly equal across all bulbs.
The oldest (relatively) big glass bulb lights were 120V (parallel) but used those smaller screw-mount bases so it was less likely a bulb would accidentally fall out and expose 120V. Of course, the lights failed more easily, so the November chore was to go through the entire strand and replace any dead bulbs.
My10-year-old mini-bulb strands had about 5 wires, and it seems each wire fed every fourth bulb; so a burned-out bulb meant 1/4 of the strand, every 4th bulb, went dead.
So - wire in parallel but have a step-down transformer, or wire in series and don’t have one. Guess which way is cheaper?
Are the newer LED strings any better about this? I replaced our older outdoor strings with LEDs this year, and none of the bulbs have gone out yet (knock on wood). I got tired of the problem in the OP, with half a string of lights being out and not being able to tell which bulb is bad.
I’m guessing the technology is not there to make tiny bulbs that can withstand 120 or 240 volts. In the early days even the large screw-in type of Christmas lights were run in series.
LEDs don’t really burn out the way the old incandescent lamps did. With a string of LED lights, the power supply running the entire thing is more likely to fail than the LEDs themselves, in which case the whole thing will go dead anyway.
Basically, the “one can fail, but it won’t kill the whole string” type has a “shunt” in each bulb. The shunt detects when the bulb filament fails and will then kick in and bypass the bulb, keeping the circuit complete. The problem is that shunts often fail, so you are back to finding the defective bulb/shunt.
I remember those old Christmas lights… .my grandparents used to have several sets. They were much bigger and kind of flared out and then came to a point. I really don’t remember what happened if one burned out, though. I have to say, I would pay a lot more if I could ever find lights that wouldn’t do this, and I can’t be the only one! It just doesn’t seem worth it to find really cheap lights when they all end up burning out and you’re lucky to get one year out of them-- it costs more in the long run. (This post NOT funded by the Acme Christmas Light Co…
with modern wired in series miniature bulbs you have to use the bulbs made for that string, both the number of bulbs in the string (voltage of bulb) and the base have to be the same.
often i see packages of spare bulbs for sale along with the strings. it is probably wise to get a package or two when you buy the strings. keep the spares in a labeled package to mate them with the correct string later.
LED strings are likely to last many decades and are maybe a best buy. i don’t think there are ones sold with anything to replace except maybe a fuse.
It seems wasteful to buy an extra string to keep one string running but that’s the only realistic way to do it so I’ve gotten into the habit. It seems every manufacturer has bulbs that operate on a different voltage, and there’s no way to keep getting them from the same manufacturer year after year; Home Depot may buy strings from Xi’an Xmas Co. one year and Beijing Bulbs, Inc. the next year
I’ve only had two LED strings. A cheap one had bulbs go out and they were not replaceable. An expensive string has been on most of the day for nine months, has replaceable bulbs, and not one has failed. Most of the LED strings I’ve seen flicker horribly, the notable exception being one I paid $30 for online, and the Martha Stewart brand from Home Depot.
As others have said, when a bulb burns out there’s a shunt that’s supposed to keep the others lit. Occasionally a shunt fails and the whole string (or a portion of the string) goes out.
A shunt failure isn’t the only, or even the most common, reason for a bunch of bulbs to go out. If a bulb is loose (or missing completely) then obviously the shunt won’t work.
When I have a string go out the first thing I do is go through it wiggling each bulb. Usually I’ll find one that causes the string to light when it’s wiggled. Then I can simply shove it in tighter or, if that doesn’t work, replace it.
I have dozens of incandescent strings of mini lights, as well as incandescent C9s that line the roof and assoted lighted figures. What kills bulbs is A) the turn on surge when you plug a string in, B) Not promptly replacing dead mini bulbs, and C)mini light manufacturers want to have the “brightest” string, so the tradoff is reduced life. I have all mine plugged into Insteon (computer controlled electronic ) dimmers, I have them “fade on” over a period of 2 seconds, and run at 90%. This reduces bulb loss to maybe a half dozen C9s and a dozen mini-lights every holiday season.
I get the idea that at what they cost the intent is not to fix them, or even replace bulbs, just toss them if they break or at the end of the season.
(All the incandescent bulbs in my house fade on over two seconds also. I’ve noticed a significant decrease in bulb mortality, and it’s easier on the eyes than walking into a dark room and the lights slamming on).
My LED strings did come with replacement bulbs; even if the bulbs will never burn out they can still break. But at $30/string, I’m only buying one or two strings a year. It’ll be a while longer before I have as many as I want for the front yard.
RE old christmas lights. There were all kind of gimmicks to deal with finding burnt out bulbs. Shorting switches and devices, dummy bulbs, bulbs with shunts or filled with neon. All the gimmicks had drawbacks and didn’t become common. It wasn’t that much trouble just to simply take a known good bulb and try replacing them one by one, since the typical string had 7 or 8 bulbs and were easy to unscrew as opposed to 50 bulbs that you often have to pry out with pliers or your fingernails.
