How To Easily Test Incandescent Christmas Light Bulbs!

For low voltage, "series string" bulbs only. Not especially recommended for LEDs. Use a multimeter with a diode test instead for any LED Christmas lights.

[@OBC-radio]

I will always prefer the warm glow of incandescent Christmas lights. We still put up C9 lights on the house with the painted ceramic bulbs. A bonus is they conveniently melt the snow off themselves, unlike their cooler LED counterparts.

[@aliciabrown4075]

Thank you thank you thank you. I've been at this for 5 hours working with a pre-lit tree and going from bulb to bulb didn't work so i took all of them out and used a battery to find the 3 bad ones that was so much easier and you are the only person who made a video that made sense to this single mom of 5 on a budget. My kids are going to appreciate you so much tomorrow night when we finally finish decorating and more than half our tree is actually lit. Especially my fur baby she loves laying under the tree until the presents take up her space.

[@uxwbill]

I'm thrilled to hear this helped you out. I hope you have a great Christmas!

[@anad8087]

This comment is so cute. I'm happy this worked for you, I'm about to try it, too.

[@NAEEMAH74]

My good sir, may you be greatly rewarded for sharing this awesome idea. 🙌🏾

[@PistolPC007]

Your tip saved Christmas for us here in Germany. We had several Schwebogens that several bulbs were not working. Very easy to diagnose and ALL lights are working now. What is a Schwebogen you ask? It's a decorative candle holder from the Ore Mountains in the Erzgebirge region of Saxony Germany. The first ones were metal but now they are made from wood. During the holidays EVERY house has a Schwebogen(s) in just about every window. It's very pretty when you drive around the region.

[@uxwbill]

I am glad to hear it, and I even learned a new word!

[@deanspanos8210]

I'm gonna use this to test my hanukkah candles.

[@ashleywiederhold3094]

Thank you! I don't have my light keeper pro yet, so this came in handy! Actually, I didn't have a 9v batt handy either, but I had a small hearing aid, cell-type battery and it produced enough energy for a small glow to tell it was working! :)

[@megan23247]

Omg this worked perfectly my friend. Ty so much for posting this! I don't have a light checker thing but I did have a 9 volt battery! Ty again!

[@Dechieftian]

great idea! Thanks for very much and Merry Christmas.

[@georgez8859]

Thanks for the tip Bill, and a Merry Christmas to you and your family

[@binhminh417]

Very helpful tips! Thank you.

[@PastPreserver]

Good tip have a Merry Christmas 👍:)

[@marlene.r1178]

Thank you soooooo much I just wrapped my lights around my tree low and behold not working all the other videos I watched talking about buying a device this 9 volt battery did the job without me having to go out any buy any equipment

[@SpeakerFreak95]

This is an excellent idea, I'm totally stealing this. Thanks!

[@MIW_Renegade]

SpeakerFreak95 same lol

[@KrissBartlett]

glad your back thanks there bill

[@aprilw7ancnickols31]

What a great idea, thank you!

[@pesodinocha5676]

Trying this right now and hopefully with good results 👍🏻

[@avrilwong4896]

YOU are a freaking genius! I was going literately crazy... 😰👍🏼👍🏼

[@teh60]

Good tip Bill, thanks.

[@marthavasquez6925]

God bless you!!!! Thank you for that tip.

[@XeonProductions]

I totally forgot about the 9v battery test. If you don't make any new videos this month, I wish you Happy Holidays!

[@uxwbill]

Thank you for the holiday wishes and for watching! I have a couple of videos in varying stages of completion, so hopefully one or two more will appear in the near future.

[@MommaMarmar]

This was so helpful!! Thank you!!!

[@Polythene_Pam]

GENIUS! Thank you!

[@balinoruo]

Thanks for the tutorial. High in Seattle trying to fix some bulbs. It's legal, and I have cancer. Not an issue. ;) Thanks my friend.

[@Truthaddict42]

What a coincidence

[@filipmac1545]

Great idea, keap up the good work!

[@lorelous54]

Thank you very helpful.

[@twocvbloke]

Back in the 90s, we had a little gadget that you put a 9V battery into and it had angled contacts at one end (connected directly to the battery) and tested the bulbs in this manner, probably still in the christmas decs boxes somewhere, but LED has since replaced the incandescent ones that over the years gradually conked out... :)

[@Samspianopage]

Hiya William. Merry Christmas bud nice to see you posting a new video. I should do a couple of Chrimbo numbers on the piano for you to go along with your videos LOL.

[@juliankilburn5493]

Great - used it yesterday to mend my Mum's Christmas lights - one rogue bulb I could see a mile off and one that appeared intact till tested

[@juandelamora5418]

great advice thank you very much

[@carstuff4u942]

Great video!

[@mickstreet2636]

Brother your brilliant. It worked. Thanks so much.

[@JessicaNunezPerez]

thanks for this very help tip

[@bigblockelectra]

I just did this for a GE Christmas tree.....the G E trees have non-serviceable fused bulbs in them. When they fail, about half the strand of lights goes dark, defeating the purpose of having individually shunted bulbs. I ended up cutting them out of the series and replacing them with ordinary lights. Each strand already has a 3 amp fuse on each side of the plug.

[@blitzsquidward5983]

Thank you this is cool

[@dadecoza]

When I clicked the thumbnail I just assumed it is a bigclive video much to my surprise it turned out uxwbill decided to upload a video!

[@heathervaughn2244]

Thank you SOO much!! This is great! Thank you! Thank you!! Merry Christmas to you and your family 🤗💖

[@mikesteinbugl5138]

Heather using a 9 volt battery only works on incandescent bulbs. This will not work on the new LED bulbs.

[@heathervaughn2244]

@@mikesteinbugl5138 Thank you, these were older bulbs so it worked perfectly.

[@leemaldonado6889]

Thank you so much!!!!!!!!!!!!!!!!!!!!!!

[@campinghack0675]

Thank you

[@jamiemarchant]

Merry Christmas Bill :)

[@FennecTECH]

Thank you :D

[@bluestreak711]

My grandfather had a square bulb checker. It was just big enough to house a 9v battery like that and had to copper metal pieces on each side of the 9v, so you could essentially do this same test without having to pull out the wire. I am actively looking for a replacement. Please comment below if you know where I can find them. In this day, one probably could be 3D printed, but I do not have access to one of those.

[@uxwbill]

eBay is a magical place, and probably the quickest way, unless you got seriously lucky at a thrift store or flea market. I'm pretty sure that you can have something 3D printed for hire.

[@utterden]

Merry Christmas Bill

[@TCGProductions03]

Please upload more!

[@Bluethunderboom]

What's the name of the heavy duty 9 volt battery product on the front right corner the one has red trim with black background?

[@uxwbill]

"Gettop".

[@MeWantHoneycomb]

there we go, thank yoiu. i have a string of vintage bat lights that have a multitude of burnt out bulbs so i took the liberty to pull them all out.. (replacing them is the real challenge since the 50 string lights i got at dollar tree don't quite fit). but now at least i'll know which bulbs work...

[@tanyaedmondson3161]

Hi! Do you know how I can find out how many volts my Christmas tree bulbs are? Can I use a volt meter?

[@uxwbill]

Most Christmas light strings are wired in series. One problem with volt meters and Christmas lights is that the average volt meter doesn't put a load on the circuit like the bulb would. The meter could read incorrectly. The bulb draws a lot more current and this pulls the voltage down to the normal value. You may also have a very hard time getting the probes in the socket without causing a short circuit. Even if you do get the probes to make contact, you could be shocked quite easily. The very high electrical resistance presented by the meter may also keep the string from working at all. You might try this: Find out how many circuits your string of lights is divided into. Small strings are usually just one series circuit. Larger strings usually have two. A really long string may have three, but I've never seen that many or more. You can do this by removing a bulb and plugging the string in. If some bulbs are still lit elsewhere in the string of lights, you have more than one circuit. Make a note of how many bulbs went out, including the one you removed. Put the bulb you removed back. Now remove a bulb from the part of the string that was still lit. Count how many bulbs went out that time, including the one you removed. If none of the other bulbs went out with one bulb removed, you have a string of lights that is wired in parallel (each bulb then operates from the standard voltage in your part of the world, usually 120 or 240 volts). This is common with the old C7 (large) bulbs. Examples: Single circuit string of lights, 30 lights: 120 volts divided by 30 bulbs = nominal 4 volts per bulb A two circuit string of 60 lights where half of them went out when you removed one bulb is treated as two strings of 30 lights, so this still works out to a nominal 4 volts per bulb.

[@gabbysgoods827]

I’m going to try your method. That is very interesting way to do that without spending a bunch of money on those bulb 💡 machines. That unbelievable smart hack. I’ll let you know 🤔 if it works I sure do hope so.

[@uxwbill]

It works. Most recently, I restored a light-up angel to life by verifying three bulbs were blown. (I do have one kind of "bulb machine" that I bought on a severe discount. I've never actually used it for its intended purpose!)

[@gabbysgoods827]

@@uxwbill all I have to do is take the white one and take wire out than put wire back in. I didn’t get my Christmas 🎄 tree decorated this year because my mom Passed 6 months ago and I had a very hard time doing that but I really want to and I’m going to go try this. I hope 🤞 I don’t have to take all of lights off of the Christmas 🎄 tree

[@matthewbest7513]

What about the bulbs that have a shunt that shorts out bulb when burns out. That may not be good for the battery.

[@uxwbill]

It doesn't really matter much because a nine volt battery can't deliver much current to start with and you'll know within a second or two if the bulb is good.

[@bakonfreek]

I might find this useful, but my folks will probably just buy a new set of lights at Walmart with my employee discount should the need arise (so I'm gonna get onto testing these so I don't have to join in on a holiday themed shopping trip).

[@richardshort4587]

Are you smart enough to make a voltage dropper fed from the main 9 volt battery that offers various voltages and also perhaps add different bulb receivers all fed from the chosen voltage. Just asking. I'm not smart enough when it comes to electronics. Thanks

[@uxwbill]

The "quick and dirty" voltage dropper is just a resistor of a suitable value, placed in series with the bulb. You can find the right value with Ohm's law. Numerous calculators for this can be found elsewhere online. This works, but wastes energy as heat that you can ill afford to lose with the very limited capacity of a nine volt battery. A fancier approach is to use a linear regulator of the 7800 series (last digit indicates output voltage, e.g., a 7805 outputs five volts DC). The data sheets for these often include an example circuit. They're still inefficient and require about two volts difference between input voltage and output. They can also only regulate downwards (can't boost a lower voltage). The most efficient approach is a switching regulator. Many are contained within a single part costing very little. You can buy finished modules on sites like eBay that are ready to use as soon as you hook them up. These can also sometimes boost a lower voltage to a higher one. Really, though, if a bulb tester is what you want to build, I'd start with a better power source than a nine volt battery. Even the best examples contain only a small amount of electrical energy. You could get a small variable regulated DC power supply, which while more expensive than any of the above, would let you easily set any voltage you want (and limit current as well, if needed). You could also string together batteries in series, and place wire "taps" at the battery terminals. The more batteries between negative and your positive connection, the higher the voltage at that point. This also isn't all that efficient, but it is cheap, easily built, and will work.

[@richardshort4587]

@@uxwbill Thanks for the in-depth reply much appreciated. Since I commented I found a 9 volt DC power supply from an old keyboard in my junk pile. Can’t read what the output amps are as it’s marked up. Would a inline variable resistor on the positive side work as a voltage dropper? If so what value would I need thank you.

[@uxwbill]

Yes, a resistor will work. Be careful with plug-in power supplies. Some are unregulated, which means their voltage will be considerably higher when no or a light load is attached. The adapter probably has a current rating of a few hundred milliamps. Attach a volt meter (any multimeter will do just fine) set to DC volts to the output of the power supply you found and see what it reports. If the voltage is much higher than what it's rated for, the power supply is unregulated and should be used only with caution to avoid burning anything out. You could determine the current rating of that power supply with a suitably heavy adjustable resistor and a volt meter. Attach a volt meter and start with a high resistance setting. When the voltage drops to around what the power supply is rated for, you will have found its current rating. Record the resistance value and use Ohm's law to find out how much current was flowing. (You can set your meter up to measure current if you have one, but this may be less precise.) Deduct another 10-15% or so for a safety margin.

[@richardshort4587]

uxwbill Thank you very much again. Let me wish you all the very best for Christmas and 2021.

[@joedry1774]

Hi Bill, did you ever post the video on ER pXe ? If you did, what is it called. Thanks :-)

[@uxwbill]

No. A new version was supposed to come out at some point. I held off in the hopes that it would. It never has and I don't think it will.

[@joedry1774]

uxwbill Thanks for the reply and yeah I did notice they haven't updated the software in a couple of years. Don't know if the project was discontinued or what.

[@LazyHubbStudios]

The 9 volt batteries can infact be used to test c7 bulbs. It works just fine.

[@JohnSmith-xq1pz]

What an fight idea.

[@northhankspin]

Cool!!

[@onemansvideos2134]

Thank you...but for the set I had the 9v was to much power kinda strange so ended up using a 7.5 volt lipo from one my old ps3 controllers was able to just plug the wires into the plug of the battery

[@onemansvideos2134]

@@averageemogirl oh stupid me I was thinking my rc car remote lipo haha funny you are correct 3.7v

[@Erdie5]

Sometimes I'll measure resistance of half the strand. Then a quarter, etc until I get down to just a small portion that contains the open bulb.

[@uxwbill]

I did that last year with a string where one half wouldn't light. All the bulbs tested good, and I never did find what was wrong that half. Just as suddenly as it stopped working, it started again and continued through the season.

[@clionaj3517]

Definitely going to use this hack.. also do you think one of those fairy light bulbs could be wired to the low voltage audio jack of a phone?

[@uxwbill]

A phone's audio output won't manage enough voltage or current to light a bulb, and you may damage the headphone driver by trying. You might be able to (dimly) light a very efficient LED, though.

[@jefferyb304]

I've had some LED's instantly let out the magic smoke when I put them across a 9 volt. Of course my experience with LED Christmas lights used outdoors was the leads would rust off.

[@uxwbill]

I'm quite surprised to hear that the LEDs would be that "tight" on their tolerances.

[@Xenon777_]

You could also test the resistance.

[@uxwbill]

Mentioned in the video.

[@Dragondezznuts]

How long would a bulb last on a 9 volt ?

[@uxwbill]

It depends upon how badly the rated voltage for that bulb is being exceeded. Maybe a few tens of seconds in most cases?

[@juliahaley74]

Your fab , I'm going to get my 9 volt out of my smoke detector right now to test... thanks 😊

[@uxwbill]

Go and buy a nine volt battery. Don't take one out of a safety critical device.

[@mickstreet2636]

Brother your genius . It works thanks so much.

[@shawns156]

Erm, using a straight 9v without any voltage dropping or current limiting is enough to send peoples blood pressure high.. These bulbs are rated for 2.5V each, 9V will shorten your bulb's life very quickly!

[@uxwbill]

Not as much as you'd think. The test is very short since you'll know almost instantly if the bulb is good. I feel pretty certain that the terminal voltage of the battery drops sharply because of its high internal resistance. Operating voltage of the bulb varies.

[@OldCarAlley]

They make a little gun that you plug into a socket or just plug the plug it in, pull the trigger a few times, and it fixes the shunt in the bad bulb. 99% of the time the lights aluminate... the bad bulb still out, now can be replaced. I have one, it works great. Also divide the bulbs by 120 volts, that will give you bulb voltage. They make one for LED light sets too, but I really don't care for LED Christmas lights. I may put a couple of videos of my really old vintage lights up in the next day or two.... so check my videos out in a few days.

[@uxwbill]

I have some C7 light strings made by General Electric in the 1940s. They've been passed down through the family since new. Every year they keep working without fail, while more of the modern strands fail.

[@rrcoster]

Im first leave a comment lol thanks for the tip

[@letsnotplaywithelectricity9346]

Using a battery to test bulbs is a secret? I though it was common knowledge :)

[@uxwbill]

I wouldn't pretend it was a secret, just something I happened to think of since the batteries were right there. I don't doubt that many others have done the same. If anything, I thought I'd "pay it forward" by making a hopefully helpful video.

[@letsnotplaywithelectricity9346]

Of course, I only kidd :)

[@liveuntetheredmusepodcast4832]

As I was testing my set of (very cheap bulbs) I purchased at Walgreens at a clearance price of just $1.99 for a 30 foot stand of mini, sounds like a steal.. but of course the year later, the set didn't work, (well three out of the four boxes). As I was getting ready to test these lights and bulbs, I got to reading one of the warning labels, and it read "Only use these light for temporary use of 90 days max~!" I couldn't believe what I was reading, we have come this far to throw things out, even Christmas lights are a one time use now!? Ridiculous,.. of course they were made in China, and yes you get what you pay for, but I've seen everything now. Yes I could get them to work, but at what expense of worrying about the electrical cord heating up causing fires, because there is a time limit on them! Trash at it's best! "Hear that China!" So before you even get ready to test your lights out, make sure they are even worth wasting time on! Otherwise chaos could be down the road for you, or just a million head pains!

[@uxwbill]

The quality of Christmas lights has been poor for many years. We have two strings of GE Christmas lights dating from the 1940s and using C7 bulbs, and still use them alongside the more modern lights. I'll be surprised if those GE lights ever fail. A rather newer string of bubbling lights from the 1980s (made in Hong Kong) came pretty close to hitting 30 years before the sockets got flaky. Not great, but leaps and bounds beyond what regular lights manage. If the most basic checks failed to produce a working strand of lights, I used to pull all the remaining good bulbs and recycled the rest. I have so many spare bulbs that I don't often bother doing that any longer.

[@zx8401ztv]

It's unfortunate that most christmas tree lights are now leds and run from a crappy low voltage adaptor, i always liked the direct mains type, im used to the 20 x 12v bulbs in series. The safety freaks have made everyone stupid, common sense is thin on the ground. Real bulbs look nicer to me, leds just look cheap :-(

[@MetallicBlade]

Especially when you look at a LED variant of a traditional C7 bulb... its just not the same. Feels like something is missing.

[@zx8401ztv]

They don't have the colour and warmth of a bulb, but im old fashoned. Bulbs remind me of little candles, or i could be mad lol :-D

[@uxwbill]

All of the LED Christmas light strings I've seen here run directly from line voltage, sometimes with a series resistor in line. There isn't even a filter capacitor to try and reduce the flicker, something that is extremely noticeable in my peripheral vision.

[@zx8401ztv]

uxwbill, Perhaps being 120 volt mains is deemed safe enough, but the 60hz flicker would be annoying. If they added a bridge rectifier plus change the resistor, 120hz may be less annoying :-)

[@randomrazr]

no way

[@uxwbill]

Expand on this.

[@randomrazr]

simple and i never knew u could do this. would have saved me alot of trouble back in the day of preLEDs

[@ashleyjean7496]

Ur brilant

[@RetroPCUser]

Comment

[@twocvbloke]

Reply

[@jesseellis6981]

Maybe don't do this on LEDs? The first one I tried was blown dead by the test, and I knew it was a good bulb.

[@uxwbill]

Definitely don't do this with LEDs. Use the diode testing range on a multimeter. It doesn't even have to be an expensive meter. Many will dimly light an LED in that testing mode. Or (briefly!) use a 1.5 volt battery or two.

[@pikadroo]

Just go buy a light keeper pro people. Just do that.

[@uxwbill]

It's hard to argue the advantages that something you already have and can use will bring to the table.

[@pikadroo]

Should be equally as hard than to argue the advantages of saving time by using the right tool for the job. Trust me, go get one and you will be making a video on it in no time. 😉💡🎄

[@uxwbill]

Anything I have to go out and buy incurs what could be called the Thirsty Truck Tax, especially as I'm one of those old fashioned weirdos who sometimes wants to shop in a physical store and see a product before buying it. As it is, I have a Stanley Tool Works branded Christmas light tester, bought on closeout somewhere years ago for less than a dollar, that does most of what the Light Keeper Pro thing seems to do. I've only ever used it to test VF display filaments, defroster grids in car windows, and for the presence of power in electrical boxes where a meter wasn't too practical -- never for its actual intended purpose. :-)

[@pikadroo]

uxwbill I completely understand tour resistance I felt the same way. The light keeper pro is more than a non-contact voltage detector. You plug it in to the light strand push the trigger and it fixes the bulbs that didn’t shunt properly when the filament burned out. Pulling the trigger can also show where a loose connection is and if all that fails (and it rarely does) then use the non-contact voltage detector. You can endlessly save strands with this tool and it pays for its self quickly. As your someone who likes to preserve old tech I would think you would welcome this tool to preserve the warm glow of these old miniature lights. I think you would really appreciate how this tool allows these old strands to be fixed up like new. Cheers!

[@ashleywiederhold3094]

@@pikadroo I absolutely agree with you!!!! The lightkeeper pro is absolutely amazing and extremely time-saving and efficient. I would also recommend it @uxwbill. For the price, it pays for itself within one or two uses, I'd say. However, I'm in a position where I don't have that tool, but I do have a 9v battery and that's about it. I'm sooooo glad I came across this until I get my lightkeeper pro! This works great when you're in a pinch, but the lightkeeper pro is going to save me sooooooo much TIME and money. It's really a superior tool. :) Between these two techniques, I never have to worry about those annoying Christmas lights again!!!

[@Palosrob]

Thanks for calling them Christmas lights, and not holiday lights.

[@northhankspin]

That whole happy holidays crap is so 1998...

[@vwestlife]

Why? This same technique would apply to the strings of orange and purple lights they sell for Halloween. Maybe we can adopt the UK term and call them "fairy lights".

[@uxwbill]

I _think_ it's just another politicization, e.g. "let's not possibly offend someone who doesn't celebrate Christmas", rather than someone's taking offense at the use of a generic term for lights that are now frequently used during other holidays and beyond. (I have a set of these lights with plastic ears of corn on them.) Both sides of the argument strike me as pretty silly .We're intelligent enough beings* to know what Christmas is, even if one doesn't personally observe it, and it's not as if someone who says "Christmas" is doing so to be offensive or malicious toward someone else's beliefs. In other words, don't pet the sweaty things. :-) * Maybe. The bulk of KZbin commentary on "other" videos makes me wonder.

[@sliperymangravy3069]

The fact that this comment only had 9 likes is why I have no faith in humanity.