Author Topic: It's that time of year again... Christmas tree lights  (Read 4290 times)

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Offline NivagSwerdnaTopic starter

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It's that time of year again... Christmas tree lights
« on: December 19, 2019, 02:59:53 pm »
So... dusted off the old Christmas Tree lights (incandescent strings), tested them, put them on the tree and then 24hrs later a segment doesn't work... so...

Although the incandescent technology won't be us beyond the last spare bulb (we have a few) it got me to wondering again how I could go about working out the broken bulb...  it seems that the wiring goes from the 240V plug to a set of parallel strings and that a single failure in one of the strings leads to the string going out.  I have read about gadgets that help diagnose but I don't know how they work.

I was wondering... maybe I could unplug the set from the mains and inject a signal into both sides of the string... say square wave on one side and an exactly out of phase signal into the other side.  Then I could measure the amplitude at the two pins of the light bulb which will give me two voltages for each of the phases... four measurements in total.

Does that sound enough to identify which direction the fault lies?  (I have to factor in the flow in the reverse direction around the correctly functioning strings)
 

Offline rvalente

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Re: It's that time of year again... Christmas tree lights
« Reply #1 on: December 19, 2019, 03:37:23 pm »
Usually to fix the lights all you need is some patience, spare bulbs and a meter in continuity mode.

 I do not believe the segment is bigger them 15 lamps in series. So you could check eye naked for broken filaments.

As for testing in a fancier way, maybe using a waveform gen and a probe, you could try to find the electric field in the string. Just a thought
 

Offline richnormand

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Re: It's that time of year again... Christmas tree lights
« Reply #2 on: December 20, 2019, 02:12:10 am »
I use a AC voltage detector as sold in many home improvement stores. These are cheap and will beep when an outlet is live.

Separate, by hand, the wires between the live and the neutral.  Check to find out which is the live at the plug.
Follow it to the first bulb, then keep separating the wires and tracing until the signal dies down. The open bulb will be close.

This also works with LEDs as I found out this year (open blue LED in an old string).

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Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #3 on: December 20, 2019, 03:56:09 am »
I use either a multimeter or I just get a known good bulb and swap it into one location at a time. Most of the time with the push-in miniature lamps it's not the bulb that has failed but one of the wire leads has broken or is bent around and not touching the contact. The type we've had here at least as far back as the early 70s has shunts in each lamp that prevent a burned out filament from opening the circuit.

While I've been LED everywhere else for years I'm not fond of LED christmas lights. They flicker, most of them are dim, they all have exactly the same colors immediately identifiable as LED, there's just something I find icky about them. I'm using 1970s C9 lights on the outside of my house and my tree has a mix of C6 strings from the 40s-50s and some 90s C7 bubble lights, all of it incandescent.
 

Offline GreyWoolfe

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Re: It's that time of year again... Christmas tree lights
« Reply #4 on: December 20, 2019, 01:28:01 pm »
I use either a multimeter or I just get a known good bulb and swap it into one location at a time. Most of the time with the push-in miniature lamps it's not the bulb that has failed but one of the wire leads has broken or is bent around and not touching the contact. The type we've had here at least as far back as the early 70s has shunts in each lamp that prevent a burned out filament from opening the circuit.

While I've been LED everywhere else for years I'm not fond of LED christmas lights. They flicker, most of them are dim, they all have exactly the same colors immediately identifiable as LED, there's just something I find icky about them. I'm using 1970s C9 lights on the outside of my house and my tree has a mix of C6 strings from the 40s-50s and some 90s C7 bubble lights, all of it incandescent.

We have just the opposite experience.  We have gotten rid of all of the incandescent lights.  We have lights on the tree that are very bright, garland hung around that are somewhat dim, which is perfect and some fairy lights on shelving units and all have a different shade of white.  The outside icicle lights are also quite bright along with the lights on the outside tree.  The LED lights on the reindeer are not as bright but still very noticeable from several houses away.  None of us notice any flicker at all.  I much prefer the LED lights.  I do miss the bubble lights of the 60's on the tree that I grew up with, though.
"Heaven has been described as the place that once you get there all the dogs you ever loved run up to greet you."
 

Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #5 on: December 20, 2019, 04:48:29 pm »
My mom can't see the flicker either, just the other day I was over there and noticed that she had LED lights on the lower half and incandescent on the upper half of a tree outside her front door. She didn't notice they were different but I could see the flicker immediately and she was astonished when I used the slow-mo video feature on my phone to film the tree and playing back the flicker was extremely obvious. Some of the LED christmas lights are much more flickery than others but I've yet to find any that don't flicker.

I think I mostly like the incandescent stuff just because it's vintage though and old stuff I remember from when I was a little kid is part of what makes christmas feel cozy.
 

Online ebastler

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Re: It's that time of year again... Christmas tree lights
« Reply #6 on: December 20, 2019, 04:53:01 pm »
Candles, anyone?
We still have them on the tree in the living room. Accept no substitute!  8)
 
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Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #7 on: December 20, 2019, 04:57:34 pm »
Yikes, I'll use 70 year old strings of incandescent lamps with cloth covered wires but I'm not letting open flame anywhere near the tree. Evergreen trees are quite flammable and can go from a small flame to a huge fireball in a matter of seconds.
 
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Online Zero999

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Re: It's that time of year again... Christmas tree lights
« Reply #8 on: December 20, 2019, 07:08:00 pm »
My mom can't see the flicker either, just the other day I was over there and noticed that she had LED lights on the lower half and incandescent on the upper half of a tree outside her front door. She didn't notice they were different but I could see the flicker immediately and she was astonished when I used the slow-mo video feature on my phone to film the tree and playing back the flicker was extremely obvious. Some of the LED christmas lights are much more flickery than others but I've yet to find any that don't flicker.

I think I mostly like the incandescent stuff just because it's vintage though and old stuff I remember from when I was a little kid is part of what makes christmas feel cozy.
Cheap LED lights do flicker. Get the type which are run from a proper DC switched mode power supply and they won't flicker, unless they're RGB with low frequency PWM. Avoid LEDs powered straight from the mains using a resistor/capacitive dropper and rectifier.

Back in the 90s, I made some nice Christmas lights with just red LEDs, which looked much better than some of all blue ones which seem to be fashionable nowadays. I don't know what happened to them. I've toyed with the idea of making my own Christmas lights again, with a greater range of colours, but haven't bothered because it's cheap to buy them, although being able to choose different colours would be nice.
 

Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #9 on: December 20, 2019, 07:23:28 pm »
I don't think I've ever seen any that had a proper SMPS. Here in 120V land miniature christmas lights are invariably series wired and directly mains powered. I was surprised when I initially started discussing this stuff with a British friend to discover that transformer powered miniature lights are common there. I suppose with the higher voltage drove things toward a different design and things just kind of stuck.

I do think that eventually LED tech will get where it needs to be to make this sort of thing really good. Phosphor type LEDs in a rainbow of colors will allow a bit more variation in color output and better brightness matching from color to color. It would also be nice to see more true red LED decorative lights instead of the reddish-orange that is typically used.
 

Offline Syntax Error

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Re: It's that time of year again... Christmas tree lights
« Reply #10 on: December 20, 2019, 09:44:52 pm »
My father described Christmas lights as being at least two open circuits in series.

@james_s : Over here in Brexitland, we kinda gave up on the trauma of 'Dad' fixing the xmas lights the old fashioned way. Now every tree and house is strung with LEDs. PSUs are tiny switch mode boxes, not those solid brick transformers that will break concrete, and toes, when dropped. Compared with incandescent lamps, LEDs are so cheap there is no incentive to treasure and maintain lamps from year to year. And certainly no need to hold a mix of replacement bulbs at the correct rating. Some local councils recycle defunked lights to keep copper and plastic out of landfill. Furiously cold white LED's are in vogue this year.

btw, we have some very ancient festive lamps, made in China even back then! Sometimes we gently power these through a dimmer circuit. Pictured are 12 volt chinese lanterns from what we suspect is the mid 1930's. But if you guys have a more accurate date, then please do tell.

Season's Greetings EEVBlog.
 
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Online Zero999

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Re: It's that time of year again... Christmas tree lights
« Reply #11 on: December 21, 2019, 09:50:57 am »
I don't think I've ever seen any that had a proper SMPS. Here in 120V land miniature christmas lights are invariably series wired and directly mains powered. I was surprised when I initially started discussing this stuff with a British friend to discover that transformer powered miniature lights are common there. I suppose with the higher voltage drove things toward a different design and things just kind of stuck.

I do think that eventually LED tech will get where it needs to be to make this sort of thing really good. Phosphor type LEDs in a rainbow of colors will allow a bit more variation in color output and better brightness matching from color to color. It would also be nice to see more true red LED decorative lights instead of the reddish-orange that is typically used.
ebay seems to be full of 12V or 24V Christmas lights if you explicitly search for them.

Colour has always been a problem. The old incandescent lamps have a low colour temperature, making blue and green dim and dies fade due to heat, so the colours wash out after awhile. It's true modern LEDs are often a bit blue or cold looking, even the mixed colours. My set which has red, yellow, green and blue use phosphor for red, yellow and possibly green, with blue only being plain LED, and the blue is a little brighter than it should be. It's still dimmer than the other colours, due to the poor sensitivity of the human eye, at that end of the spectrum.
 

Offline Electro Detective

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Re: It's that time of year again... Christmas tree lights
« Reply #12 on: December 21, 2019, 10:05:49 am »
It's that time of year again... Christmas tree lights

:scared: :scared: :scared: :scared: :scared: :scared:


fwiw they didn't have all this stuff back in Christ's day, did they even have readily available cheap MIC candles?

so why do we 2000+ years later.. risk life, limb and or sanity to set up these circus sideshow displays?  ::)


Where in the good book does it state or imply 'thou shalt without question expose wallet, and break ass to set up chrissie lights..
and troubleshoot if necessary with whatever means at your disposal.
Yoel Have A Nice Day..' 


???

 

Offline tooki

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Re: It's that time of year again... Christmas tree lights
« Reply #13 on: December 21, 2019, 03:35:40 pm »
Candles, anyone?
We still have them on the tree in the living room. Accept no substitute!  8)
We were absolutely shocked at our first Christmas in Switzerland (1992) when everyone put candles on their trees. In USA, where we moved from, that is absolutely unheard of in the modern era.


Yikes, I'll use 70 year old strings of incandescent lamps with cloth covered wires but I'm not letting open flame anywhere near the tree. Evergreen trees are quite flammable and can go from a small flame to a huge fireball in a matter of seconds.
FYI, to the other shocked Americans: 1. A properly hydrated Christmas tree will not go up in flames if a single candle flame licks a branch for a second. (Ideally you should cut a fresh edge onto the trunk so that it can absorb water better.) 2. One NEVER lights candles except when the tree will be actively supervised. So that means the tree is lit only a handful of times the whole season. 3. It’s nonetheless a wise precaution to keep a fire extinguisher at hand, just in case. Xmas tree fires do happen every year to people who have violated the prior requirements, especially the one about keeping the tree hydrated, since dry evergreen needles do indeed burn exceedingly fast.
 
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Offline madires

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Re: It's that time of year again... Christmas tree lights
« Reply #14 on: December 21, 2019, 03:56:45 pm »
I've upcycled some old "made in China" tree lights with small incandescent lamps which where popular about 15 or 20 years ago. The lamp's diameter is 5mm. ;) This asks for LEDs and a capacitive dropper PSU. And because we like fancy stuff I bought color changing LEDs (the slow changing type) to replace the incandescents. Looks quite nice and the neighbor's LED lights are all single color. 8)
 

Offline German_EE

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Re: It's that time of year again... Christmas tree lights
« Reply #15 on: December 21, 2019, 04:25:58 pm »
Go Jewish, seven lights and we're done  :-DD

https://en.wikipedia.org/wiki/Menorah_%28Temple%29
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline Electro Detective

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Re: It's that time of year again... Christmas tree lights
« Reply #16 on: December 21, 2019, 11:12:13 pm »

Go Jewish, seven lights and we're done  :-DD

https://en.wikipedia.org/wiki/Menorah_%28Temple%29

That's a burglars 'Gold Christmas' depending on the neighborhood  >:D  and how many gates and cameras going or not..   :scared: 

 

Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #17 on: December 22, 2019, 03:43:28 am »
The lights have always been my favorite part of Christmas. I'm not religious so I don't really care about that aspect of the holiday but the lights and decorations are a nice way to brighten up what is in this part of the world the most dark and gloomy time of the year.
 

Online Zero999

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Re: It's that time of year again... Christmas tree lights
« Reply #18 on: December 22, 2019, 11:13:24 am »
Candles, anyone?
We still have them on the tree in the living room. Accept no substitute!  8)
We were absolutely shocked at our first Christmas in Switzerland (1992) when everyone put candles on their trees. In USA, where we moved from, that is absolutely unheard of in the modern era.


Yikes, I'll use 70 year old strings of incandescent lamps with cloth covered wires but I'm not letting open flame anywhere near the tree. Evergreen trees are quite flammable and can go from a small flame to a huge fireball in a matter of seconds.
FYI, to the other shocked Americans: 1. A properly hydrated Christmas tree will not go up in flames if a single candle flame licks a branch for a second. (Ideally you should cut a fresh edge onto the trunk so that it can absorb water better.) 2. One NEVER lights candles except when the tree will be actively supervised. So that means the tree is lit only a handful of times the whole season. 3. It’s nonetheless a wise precaution to keep a fire extinguisher at hand, just in case. Xmas tree fires do happen every year to people who have violated the prior requirements, especially the one about keeping the tree hydrated, since dry evergreen needles do indeed burn exceedingly fast.
Better still get a Christmas tree with proper roots. I use the same one every year. It goes in a shady spot in the garden, over the summer and is watered regularly, especially durinh in hot, dry weather.

Having said that, I deem using candles to be too risky vs the benefit and prefer to use LED lights.
 
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Offline NivagSwerdnaTopic starter

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Re: It's that time of year again... Christmas tree lights
« Reply #19 on: December 22, 2019, 07:29:20 pm »
Goodness me... a couple of days go by and I come back and find the thread has been lively!

In the end I had to use a multi-meter and watch the ohms increase down the string... I have worked out it is a dodgy wire... just haven't worked out which one yet but with a bit of wangling the lights are currently lit.

Will switch to LEDs next year.
 

Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #20 on: December 22, 2019, 07:36:48 pm »
Another trick I have used since I was a kid is to take a known good bulb and swap it into the first socket, then take that bulb and swap it into the next and so on until you reach the end of the string. This of course only works if you have only one bad bulb and in a multicolor strand it will screw up the color ordering. You can also use a 9V battery to test each bulb individually.

Switching to LED has some advantages but it won't get you completely away from troubleshooting. I've had a number of LED strings and eventually they all failed. Some of them had individual LEDs fail and eventually the whole string crapped out, others faded and looked yucky after just a couple years. Ultimately I was disappointed to find the LED strings didn't last as long as the incandescent strings they were meant to replace. This was several years ago so they may have improved by now but the drive to keep costs low leads to cutting corners by using cheap LEDs and cheap plastics that rapidly yellow in the sun.
 

Online ebastler

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Re: It's that time of year again... Christmas tree lights
« Reply #21 on: December 22, 2019, 07:52:02 pm »
[...] cheap plastics that rapidly yellow in the sun.

Ah, there's your problem! In this part of the world (Northern Germany), we don't do much "sun" at this time of year.  ;)
 

Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #22 on: December 22, 2019, 07:57:41 pm »
We don't get a lot of sun in the winter but even on cloudy days there can be a lot of UV. It's also not uncommon to have cold, clear days where it's down around freezing or below but there is still strong sunlight during the day.
 

Online Zero999

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Re: It's that time of year again... Christmas tree lights
« Reply #23 on: December 22, 2019, 08:03:49 pm »
We don't get a lot of sun in the winter but even on cloudy days there can be a lot of UV. It's also not uncommon to have cold, clear days where it's down around freezing or below but there is still strong sunlight during the day.
Where do you live? Is it high up? Where I live the UV index never gets above 1 at Christmas time, even on clear days.
 

Offline james_s

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Re: It's that time of year again... Christmas tree lights
« Reply #24 on: December 22, 2019, 08:09:15 pm »
Near Seattle WA.

I've never actually paid attention to the UV index but I have certainly had plastics yellow in the winter.
 


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