Fix Holiday Icicle Lights

So! Every year you take the box of holiday lights off the shelf, plug them in, and only half of them work. Don't pitch 'em, you can FIX them, and it's pretty simple, actually! Just follow this recipe - it's not frustrating - in fact it's very gratifying.

The -very- first thing to do is to take your string of lights, and stretch it out on the floor or handy table. Here I am using a table in the Hub area of TechShop Pittsburgh. The string of lights is plugged in at the top left corner of the photo, and loops around counterclockwise. The end is at top right in this photo.

In addition to the string of lights, you will probably need some replacement bulbs. We don't entirely know how many yet. Maybe you saved the extras that came in the box last year, maybe you will need to go buy some new ones. Alternatively, if you have several strings, you can scavenge the lights from one string and use them to fix several other strings. (That's what I do.) [Any scavenged lamps should go in the "Untested" bowl described later.]

NEW INFO JANUARY 2022! Commentor "esbede" has found a source for replacement bulbs IN QUANTITY - 612Vermont.com, and specifically HERE. Several voltages, and several choices of quantity. Thanks, esbede!

Step 1: SECRET TRICKERY #1 - Bulbs Are Wired in Series, and in Groups

In the olden days of LARGE holiday lights, one bulb would burn out, and it would not affect its neighbors. That's because all of those bulbs were 110 volts, and wired in parallel. (Just like the individual light fixtures in your house - each one is independent of all the others.)

These little guys are different. They are arranged (electrically) in "chunks" - some number of bulbs connected in series. (See the photo.) Each bulb is rated for a low voltage, 2.5 volts (AC) in this case. When you string a bunch of 2.5v bulbs in "series", they share that voltage between them, like holding hands. A string of ten bulbs would operate properly at 25 volts, 40 bulbs would take 100v, and so on. If you were to plug one of these little guys into 110 volts, or even 10 volts, it would burn out in an instant. *pfft*!

So! If you have a LARGE string of lights, it probably has several of these chunks. When you take the set out of storage, some chunks may have ALL of the lights working fine. (Happy happy!) Some chunks may have just a few lights burned out. (Meh.) And some chunks may have ALL of the lights off. What's going on here?

Step 2: Secret Trickery #2 - the SHUNT!

Unlike regular house lights, there's a little extra gizmo inside each of these bulbs. It's called a "shunt". It's sort of the inverse of a fuse. The shunt is a wire with HIGH resistance. When the bulb is new, all of the electricity passes down the path of LEAST resistance, which is the main filament, and we get that nice warm light. The (high resistance) shunt does not pass any electricity. When the main filament burns out, the gap has INFINITE resistance, and the shunt is supposed to take over, allowing some electricity continue to flow through the bulb. (The shunt does not get hot enough to glow.) When the shunt works properly, every other bulb in that Chunk should stay ON.

Ah, but there is mischief afoot. Sometimes the shunt-magic does not "turn on". This breaks the circuit in that chunk, and all of the lights in that chunk go dark.

Step 3: Think, and Chunkify!

OK, so let's step back and review the big picture.

(A) If -any- of the lights in a chunk turn on, that means that all of the bulbs either are working happily, or else they burned out and their Magic Shunt worked properly. All of those bulbs are still "holding hands", and electrical current passes all the way from the left end of the chunk to the right end.

(B) If -all- of the lights in a chunk are OFF, its very likely that -one- of the bulbs burned out, but its shunt did not work properly. There is a gap in the line - like someone "dropped hands" - and now the power does not flow. :( The other bulbs in that chunk may be OK, or they could perhaps be shunted out. We can't tell. Yet.

We can take this new knowledge and create a scheme to find and replace all of the bad bulbs. We'll get to that in the next step.

The first thing, though, is to mark the boundaries between "chunks". I use colored masking tape for this - you'll see yellow tape in the photo. You could use yarn, or a piece of ribbon, or anything at all. We simply want to break the big project down into smaller sections. Divide and conquer! My light string had four chunks.

You'll notice in the photo above that SOME of the lamps to the left of the yellow tape are OK, and some are dark. ALL of the bulbs to the right of the tape are dark.

Step 4: The Sorting of the Bulbs

So here's the plan, Stan. This is the straightest line between here and DONE. You can do this.

• Draw three circles on a piece of paper, or grab three bowls, and label them "Untested", "Working", and "Failed". Seems silly, but it helps keep track of things in case you get interrupted or distracted. ("What, cookies for me?!?! How nice!")

• If your string of lights has a "dark chunk", pull out -ALL- of its bulbs and put them in the Untested bowl. We don't know whether they are dead or alive, but we are about to find out.

• Go to a chunk that has at least one lamp turned on. Pick a socket that has a working bulb, and put another mark on that socket. It's going to serve as our Special Testing Socket (STS). You can put some different colored tape tape on the STS socket, or a piece of ribbon, or nothing at all. I just took care to keep the STS centered on the yellow envelope that you see in the photo.

• Pull the working lamp out of the STS, and set it into the "Working" bowl. All of the remaining lights in that chunk will go dark.

• (1) Take a bulb from the "Untested" bowl and plug it into the STS. If the bulb lights up, remove it and place it in the "Working" bowl. Yay!

• (2) If the bulb does not light up, but all of the other lights in the Testing Chunk -do- come back on, this indicates that the bulb has failed, but the shunt worked. Pull the bulb out of the STS. Pull the dead bulb out of its plastic base. Put the base in the "Failed" bowl, and the lamp in the trash can. (Avoiding future confusion about that lamp.)

• (3) If the bulb does not light up, and none of the other lights in the Testing Chunk come on either, this indicates that the bulb burned out AND had a failed shunt. This is the critter that turned the whole chunk dark. As before, pull the bulb out of the socket, and remove the dead bulb from its base. Drop the dead bulb in the trash NOW, and put the base into the Failed bowl.

Repeat the previous three steps until the Untested bowl is COMPLETELY empty.

Once the Untested bowl is empty, put new (or scavenged) bulbs into the empty bases found in the Failed bowl. Repeat the above testing process for these bulbs, too. If they are new, they should work. If they were scavenged, we don't know, we have to test them to see.

Step 5: Put Good Bulbs to Work!

OK, now you have some bulbs that you KNOW are working properly. I use the first of these to go and replace the dead singletons in the other Chunks, because I like the quick gratification.

When you take out the dead singletons, be sure to put them immediately into the "Untested" bowl. At some point, you will need to go back and test them as described in a previous step.

-- We are almost done! --

The last step is to refill all of the sockets in the "dark chunk". Nothing will happen until you fill ALL of the sockets in that chunk. When you do, you should be greeted with many happy little lamps all coming on at once. Hurray!

...And what if the dark chunk does NOT come on? In my experience, it means that I either skipped a socket, or else a bad bulb snuck into the "working" bowl while I was having a cookie. Pull all of the unlit bulbs out of that chunk, run them through the test/repair process one more time. I bet you will find that the same thing has happened to you. :)

THAT'S IT! You are done. Have two more cookies as your reward.

Comments

[esbede]

EXCELLENT! Actually CACKLED when that chunk (had 2 bad chunks out of 6) lit up!!!. One down, one to go...
QUESTION: I have a 300-bulb icicle string, 6 total chunks, = 50 bulbs/chunk. Assuming a 50 bulb chunk thinks like a 50-bulb set, why aren't brand-new 2.5v (listed for 50-bulb set) bulbs working? They are very dim if they work at all. Tried 3 different brands, all new, all 2.5v. Are bulb voltages the problem or is it something else? Can I test a socket to determine voltage needed? I have no 3.5v bulbs to test with, but 3.5s are not for 50-bulb sets anyway. Throw a sentence or 2 in your article about bulb voltages. (And, no, I no longer have the little tag from the end of the string!)
And THANKS for finally explaining in real language what the shunt was/did!!
An address will get you a BOX of cookies

[MacMarty]

OOooo, I like cookies. You can send them to my attention at my maker space address. (Alas, TechShop has gone poof.) Protohaven, 214 North Braddock, Pittsburgh, PA 15221 Protohaven.org, a great place, check us out!

As to the bulb thing, here's what I think. In addition to a nominal voltage, bulbs have other characteristics, specifically including resistance. (Just measured one of my spare bulbs, it's 3.2 ohms.) For a chunk of lights to all burn with the same brightness, their resistance has to match. I bet your new ones have a slightly higher resistance. Putting in 50 new bulbs might work, but (a) that would be spendy, and (b) that might cause the whole 300-bulb set to overload its fuse, and then NONE would light up.

Know what I would do? I'd put one of those new bulbs at the BOTTOM END of an icicle group, where it will not show as a gap. Sneaky and cheap carries the day!

[esbede]

no cookies quite yet....
1. Is there a way to check AMPERAGE on the sockets using a meter??
2. 'd'y'know 2.5 bulbs come in 3 different mA (watt) flavors: the standard 170 mA (.42w), a 200 mA (.50w), and a 100mA (.25w) which i just ordered, based on a chart (see .image below ) from 612vermont.com (also available via Amazon)
Aaaand...
3. I did your clever suggestion about putting all the 10 'new' dim ones at the ends of the drops, but instead put them all in on the mainline (not on the drops) of the same chunk. !!The entire section lit up but all 50 bulbs were dimmer than the remaining 250 bulbs; the new 'mainlined' bulbs were not lit at all. Today will try the scatter method (does the end of a drop make a difference, where the juice changes direction??)
Advice to all: WHEN YOU GET A NEW STRING OF LIGHTS, SAVE THE TAGS (or don't do what i did & let the tags just rot of because you like your outdoor lights up longer than your neighbors)

[MacMarty]

Excellent Sleuthing!
1) No. Amperage is about the amount of power drawn by a load, such as an individual lamp, or the whole string of lamps. It's not something that can be MEASURED at an individual socket. Hence the rating for the several lamps you see advertised at 612Vermont.

2) That description of the 100mA bulbs on 612Vermont is VERY interesting. "Most commonly found on sets of 200+ lights or icicle light sets." That sure sounds like your situation!

3) There's nothing special -electrically- about being at the end of a drop. (It's still just one of the fifty bulbs in series.) My suggestion was merely as stab at fool-the-eye. Unfortunately it did not fool-the-bulbs. :D

We all are GREATLY interested in hearing how the 100mA bulbs affect the situation! Please let us know. I'm going to make an adjustment to the Instructable, pointing to 612Vermont.

[B-Heit]

Are icicle lights generally less reliable than regular string lights? It seems every year I have sections/chunks going out within a couple weeks of hanging them. This year I replaced all with new LED icicles by December Home from Meijer, and I have multiple sections/chunks failing in a couple weeks. Do you think they’re just bad quality? Can the LED’s be tested/repaired the same as you describe here? I’m frustrated and not sure where to start.

[MacMarty]

On the sets I have seen at my Home Depot, the individual LEDs do not seem to be replaceable. :( This is a real bummer.

[gameboy02123]

I have the same exact issue. Picked them up this year and multiple sections about 2 to 3 foot have just stopped.

[gameboy02123]

I found the issue if with this resistor. They apparently not 100% water poof and water gets into this and makes it not work right.

[shericarlson]

What a great article! It answered most of my questions! I still have some questions though:
1. I've read that sometimes a fuse is blown and needs to be replaced. Do you ever test for that?
2. Sometimes my icicle lights don't go out completely; they fade out, so the strands next to them continue to be bright, but the faulty strand has very dim lights shining. What causes this? How do I fix it?
3. I'm confused about why you separate the bulb from its base if it's dead. How do you put a new bulb into the base? And where do you find these base-less bulbs?

[MacMarty]

1) Yes. My sets have a little compartment in the molded plug, covered by a sliding door. If a fuse is burned out, that set will not light AT ALL. If the fuse is loose or rusty, taking it out and reseating it might turn things on again.

2) Sounds like you have a set whose shunt conducts more power than mine, and allows the lights to partly light. The thing to do here is pluck out all bulbs in that chunk, and put them in the "untested" bowl, and plug each of them in the Special Testing Socket. I bet most of them are OK.

3) I separate the bulbs from their bases because not all base/socket combinations are the same between vendor, or from year to year. Many new sets come with a few extra bulbs and fuses, I keep then in a ziplock bag in the storage container. Some merchants do sell extra bulbs as well. (My Home Depot had some this year.)

Installing new bulbs into bases takes good eyes and dexterity. To take out an old bulb, look for and straighten out the tiny wires that come out of the bottom of the base, then you can pull the bad bulb out. Put a new bulb in, then carefully fold the wires up around the SIDES of the base, so that they will contact the metal tabs in the socket. (Photo coming soon.)

[windybovine]

On a known good bulb (not an imposter), what's going wrong if the light does not work but and the shunt works -- a specific socket has this problem? There is no apparent electrical device inside the socket and enough volts to drive other lights. Have tried multiple good lights on that socket and same reult.

[MacMarty]

Wow, that's a tough one. I think your analysis is correct - something is wrong with the socket. I regret that I don't have an answer. If just that one is acting that way, I'd mark it with some tape for future reference, and just live with it.

[JonathanC201]

So great... Thank you!

[StandardIssueSike]

Thank you for the write up! Question though: where can I purchase replacement multicolor LED bulbs for the ShowHome icicle lights?

[MacMarty]

Did a little Googling, looks like an email to [e-mail] might be a good start.

[gschlichtmann]

I really want to thank you for taking the time to put this together it helped my daughters and I spend some quality time. And it worked! We had one bulb which had a contact rusted and actually broke off right after we removed it. For the ones that know the game “among us” I got my daughters attention by telling them that the good lightbulbs were crewmates and the bad light bulbs were impostors I needed to be found!

[RobertaB25]

Thank you so much! I was about to throw my icicle lights away after wasting hours trying to fix them. Then, I went on Google and found your page. I had my set of lights fixed in less than 20 minutes after following your instructions. During the test, I came across 5 bad bulbs which I replaced and wallah, I have working Christmas lights! Thanks again and Happy Holidays! (:

[DanaB104]

Thank you, thank you, thank you. My question is what do you do with the items placed in the "fail" bowl? Thank you again. Dana

[RobertaB25]

Take the bad bulb out, throw it away, and keep the empty base. You will insert a new bulb in the saved base.

[choppedupcoconut]

Wow, I have a "chunk" of lights out but they are already installed on the house lol. I didn't bother to test them before I installed them(dumb huh?)
Good instructable. When I go to take the lights down I will use this procedure to fix em. I was planning of tossing them and buying new ones next year. Hopefully I won't have to do that now.
Thanks!