How to repair led christmas tree lights

How To Fix Christmas Lights

The joyous holiday season is nearly upon us, but there’s one tradition I hope to avoid this year: dealing with burned-out Christmas lights.

Each holiday season I unpack, untangle, and plug in the previous year’s mini lights, only to discover they don’t work. Sometimes individual lights are burned out, and other times the entire string seems dead. Are these lights worth saving, or should I just toss them out and buy new ones?

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I admit that diagnosing and fixing Christmas lights can be frustrating, but with a little determination and a few specialty tools, you can repair most faulty light strings.

How to Fix Christmas Lights

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1. Diagnose the problem.

Carefully inspect each string of lights before plugging it into an electrical outlet. If you see cracked or slit insulation, frayed or bare wires, or damaged plugs, discard the string.

Now, determine if it’s actually a bad bulb causing the malfunction or something else. If it’s a smaller light set, it’s likely wired in series: the electrical current passes through each individual bulb in order to complete the circuit and illuminate the set.

The More You Know
  • A Brief History of Christmas Lights

Larger light sets often have two or more circuits wired in parallel, which explains why sometimes just a section of the string goes dark. In most cases, simply replacing one bad bulb will fix the entire set or one darkened section of it.

2. Find the bad bulb, and swap it out.

Locating the one faulty bulb that’s causing the problem can be tricky. The best option is to use either an electrician’s multimeter or a tool specifically designed for repairing Christmas lights, such as the Lightkeeper Pro. It combines a voltage detector, bulb remover, bulb and fuse testers, and shunt repairer in one compact tool.

You may be able to reveal the bad bulb by simply plugging the lights into an electrical outlet. If you’re lucky, the “bad” bulb isn’t actually bad at all. It may just be loose and needs to be pressed down more firmly into its socket.

Also, remove the bulb and look closely at the two tiny wires protruding from its base. They should be firmly attached and not touching each other. Plus, each wire should be laid flat against the outside of the bulb. When you push the bulb back into its socket, the wires complete the electrical connection.

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GE Long String White Mini Clear Lights (100 Count)

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You can also test the bulb using the LightKeeper Pro, or a multimeter. If you discover the bulb is burned out or damaged, replace it with a new bulb. Just be sure it has the proper voltage rating or you risk damaging the whole light set.

3. Fix the faulty filament or shunt.

If all or part of a string of lights is dark, the problem may be a broken filament or a faulty shunt. (A shunt is a device that allows current to continue flowing through a circuit by creating a path of lower resistance than the original path. In incandescent holiday lights, shunts are small wires wrapped beneath the filament.)

If a bulb’s filament breaks, the shunt redirects current through the base of the bulb, maintaining the electrical circuit. A faulty shunt may sound like a catastrophic failure, but you can often fix it with the LightKeeper Pro.

Simply plug in the light strand and remove a bulb that’s in or near the dark section. Next, insert the tool into the bulb’s socket and squeeze the trigger to activate a piezo circuit. A high-energy pulse will shoot through the set and after about 20 pulses any faulty shunt should be re-activated. Pretty cool, right?

Gear Up for the Holidays
  • The 8 Best Artificial Christmas Trees
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If you’re still having trouble locating the broken circuit, try using a voltage detector. You can buy one for about $10 or so, but there’s also one built into the LightKeeper Pro.

4. Replace the fried fuse.

If the voltage detector doesn’t find anything wrong, there’s one more thing to try: Check the tiny fuse located behind a small sliding door on the male end of the plug. If the fuse is fried (you can check it with the LightKeeper Pro), replace it with a new one of the same amperage, which should be indicated on the plug. If after all the testing the light string still doesn’t illuminate, it’s time to get some new lights.

5. Upgrade your lights.
Related Story
  • The 10 Best Christmas Lights

If you’re buying new lights, consider upgrading to LED Christmas lights. There are many benefits to LEDs that make them a great choice over incandescents. They’re more energy efficient, last much longer, and can be programmed to display different colors and patterns. Plus, LED lights are more durable and less likely to break than traditional bulbs. Here are some of our favorite string Christmas lights for indoors and out.


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Joseph Truini

Joe is a former carpenter and cabinetmaker who writes extensively about remodeling, woodworking, and tool techniques. He has written eight books and is a contributing editor to Popular Mechanics. He also appears on the Today’s Homeowner TV show, and co-hosts the weekly Today’s Homeowner Radio Show. Joe writes from his home in Roxbury, Connecticut. 

How to Fix Christmas Lights

Note: We’re re-publishing this post (originally published Dec. 2, 2016 and written by Taylor Whitney) because, well, it’s about that time again, and this post is a perennially useful answer to a very common question. While you’re gearing up for the holidays, be sure to check out our latest Gift Guide and follow us on  YouTube, Instagram, or Twitter to catch our holiday deals.

Sometime in the near future you’ll venture into your dusty attic or musty garage and pull out a miserably tangled set of Christmas lights. As sure as Rudolph’s nose is red, one of those light strings won’t light up (if you ever manage to get them untangled in the first place). Millions will throw out their broken Christmas lights and buy new ones, but you will not. You are a strong, independent person. You will save Christmas (lights) this year.

Thankfully, it’s not too hard to fix Christmas lights. And iFixit’s repair community has already compiled lots of tips and tricks for how to do it—which I’ll be summarizing here.

Before you start

Make sure the lights are completely unplugged from any electrical socket before you start your repair. (Or you’ll be the Christmas ham.) You also need to know which kind of Christmas lights you have: Incandescent Christmas lights or LED Christmas lights. Incandescent lights work via a current running through a filament, which is different from their LED cousins. (Try here for LED light solutions.) This guide is for incandescent Christmas lights, so make sure those are the ones you have!

Before you can repair Christmas lights, you’ll need to identify the problem with them first. There are lots of different ways lights can break. If the entire chain is non-functional, a blown fuse could be the culprit. If a section of the light string isn’t working, there might be a bad bulb or a bad connection between the bulb and the socket (like a corroded socket). If replacing the bulb doesn’t work, it might be a bad socket or broken wiring that needs to be removed.

Here are some common ways to troubleshoot incandescent Christmas lights:

The string of lights won’t light up

Possible culprit: A blown fuse

The fix: Pick up the pronged “male” plug at the end of the strand. There should be a small door on the plug. Slide the door marked “Open” in the direction pointed by the arrow. Remove the two fuses, and inspect them by looking at them up against a bright background (the sky works). If the fuse is good, you should see an unbroken strand of wire running between the two metal contacts. (You can also use a multimeter to test for continuity.) Replace all blown fuses with new ones. Small fuses are inexpensive and can be found at most hardware, home improvement, or big box retail stores. Make sure that you read the specs printed on the non-functioning fuse so you can purchase the correct replacement. Fuse extraction can sometimes be difficult, stay patient! Try removing them like you would a battery.

Tip: If you’re blowing fuses in your lights repeatedly, it is likely not the light strand itself that is at fault. Often linking too many strands of lights together can cause the fuse to give out. Try plugging the strand into a different outlet, preferable one that is on a different circuit.

Bulb won’t work or a section of the string won’t work

Possible culprit: A bad bulb.

The fix for small lights where the bulbs pull out: Gently grasp each bulb, and pull away from the socket. Once removed, inspect the bottom of the bulb and ensure that the two bulb copper leads are in their proper location (see picture below), and not twisted or missing. (You can also test bulbs for continuity with a multimeter.) Where you find a problem bulb, replace it with a new one. Continue with each non-functional bulb in the chain, up until you find the culprit(s).

This is the proper position for copper leads.

The fix for large lights where the bulbs screw out: Gently unscrew each bulb and remove them from the socket. Replace the one you just removed with a new bulb and test the light strand. If the strand still has the issue, you can put the old bulb back in the socket and continue on down the line until you find the culprit(s).

String won’t light up—replacing a bulb doesn’t fix it

Possible culprit: Corroded socket

The fix: Over time, the contacts inside the socket can become corroded or filled with dirt and grime. This damage can prevent proper contact between the bulb and the socket, which often results in no power to the bulb. Use a small file or scratch brush to clean the wire contacts of the socket. Once the socket is clean, insert a new bulb into the socket.

I’ve tried everything and a bulb or section is still not working

Possible culprit: Bad socket or wiring around a single bulb.

The fix: If all else fails, the bulb socket may be broken beyond repair. Removing it isn’t too complicated though, and should restore functionality to the rest of your lights! There are two potential ways to you can approach this repair.

Using a wire connector: Use a wire cutter to remove the defective socket from the light strand. Strip about 1/2″ of insulation from both wires. Twist the wires together and insert them into a waterproof wire connector. Turn the connector several times until the cap feels secure, and you can tug on it without it falling off. If replacing the bad socket fixed the problem, consider putting in some silicone sealant into the cap in order to keep moisture out and prevent the wires from corroding.

This one isn’t a waterproof connector, but you should use one if you use your lights outside.

Using weatherproof heat shrink tubing: Use a wire cutter to remove the defective socket from the light strand. Strip about 1/2″ of insulation from both wires. Solder the wires back together or make a western union splice. Then follow the instructions in our How to Use Heat Shrink Tubing guide to protect the wires.

Be sure to check out our step-by-step Christmas lights guide. And if you have any tips or tricks to add, be sure to tell us about them in the comments. Now, go forth and save Christmas!

How to fix an LED garland - 5 reasons why it doesn't work, diagram, do-it-yourself repair

We are all familiar with Christmas tree garlands, consisting of multi-colored light bulbs. However, in recent years, products based on led light-emitting diodes have become very popular.

How they are arranged, what connection scheme they have and what to do if the garland stops glowing, we will consider in detail in this article.

What the Christmas tree garland consists of

What is a garland of LEDs, is it worse or better than usual?

Outwardly, it is almost the same product as before - wires, light bulbs (LED), control unit.

The most important element is of course the control unit. A small plastic box on which all kinds of backlight operation modes are indicated.

They change at the touch of a button. The block itself can be with a fairly well protected level of moisture and dust protection IP44.

What does he have inside? To open it, use the sharp tip of a knife or a thin screwdriver to pry the latches from the bottom and take off the protective cover.

By the way, sometimes it is glued, and not just sitting on snaps.

First of all, inside you will see the wires soldered to the board. A thicker wire is usually a mains wire that supplies 220V.

Soldered on the board:

  • controller that creates all the lighting effects
  • thyristors, each of them goes to a separate channel of the garland
  • resistors
  • capacitor
  • and diode bridges

The number of board elements depends primarily on the number of light channels of the garland. More expensive models may have a fuse.

LED garland circuit

Mains alternating voltage through resistors and a diode bridge, already rectified and smoothed through a capacitor, is fed to the supply controller.

In this case, this voltage is supplied through the button, which is open in the normal state. When you close it, the controller modes switch.

The controller in turn controls the thyristors. Their number depends on the number of backlight channels. And after the thyristors, the output power goes directly to the LEDs in the garland.

The more such exits, the more diverse the color patterns the product can have. If there are only two of them, this means that only two parts (or halves) of the garland will work in different modes - some bulbs will go out, others will light up, etc.

In fact, these two strings of diodes will be connected in two channels in series. They will be connected to each other at the end point - the last LED.

If for some reason you are annoyed by the flashing of the garland and you want it to glow evenly with only one color, it is enough on the reverse side of the board to short-circuit the cathode and anode of the thyristor using soldering.

The more expensive garland you have, the more outgoing channels and wires will leave the control board.

At the same time, if you follow the tracks of the board, one of the mains voltage outputs is always supplied directly to the final LED of the garland, bypassing all the elements of the circuit.

Causes of malfunction

Situations with malfunctions of the garland are very diverse.

At the same time, remember that the most important element - the microcircuit on the board, "burns" very, very rarely.

Approximately 5-10% of all cases.

You can even make a conditional rating of failures of the LED garland (in order and frequency of damage):

  • Poor contact on the wires
  • LED in one of the bulbs
  • Capacitor
  • Resistors
  • One of the
  • diodes
  • One of the thyristors
  • Controller IC

Poor soldering

If your backlight suddenly stops working, always check the soldering of the supply and outgoing wires first. It is possible that the entire contact was held only by hot melt adhesive.

It's worth moving the wires and contacts anyway.

The most common problem with Chinese garlands is the use of very thin wires that simply break off at the solder points on the board.

To prevent this from happening, all contacts after soldering must be filled with a thick layer of hot melt adhesive.

And when stripping such veins, it is advised to use not a knife, but a lighter. Instead of chipping away the insulation with a blade, heat it up a bit and melt it with a lighter fire.

After that, simply peel off the outer layer with your nails without damaging the strands themselves.

Damage to the LED

If the wire contacts are in order and you sin on one of the diodes, how can you check its malfunction? And most importantly, how to find it among the whole series of light bulbs?

First of all unplug the garland from the socket. Start with the last diode. A power cable comes to it directly from the control unit.

Outgoing conductor soldered to the same leg. It goes to the next branch of the light channel. You need to test the diode between its two power wires (input-output).

You will need a multimeter and its slightly upgraded probes.

To the tips of the probes of the tester, tightly wind thin needles with a thread so that their tip protrudes by a maximum of 5-8 mm.

From above, wrap everything with a dense layer of electrical tape.

Since the LEDs are soldered, simply pulling them out of the light bulb as in ordinary garlands will not work here.

Therefore, you will have to pierce the core insulation to get to the copper cores of the wiring. Switch the multimeter to the diode continuity mode.

And you begin to sequentially pierce the supply wires near each suspicious diode.

If your garland is not 220V, but 12V or 24V, which is connected from such a power supply:

then a working LED from the multimeter battery should light up.

If this is a 220V backlight, then check the multimeter readings.

On the working elements, they will be approximately the same, but the faulty one will show a break.

The method is certainly barbaric and damaging to the insulation, but it is quite working. True, street garlands after such punctures are better not to be used outdoors.

Chaotic blinking

There is a situation when you turn on a garland and it starts blinking randomly, sometimes brighter, sometimes dimmer. Changes channels by itself.

In general, one gets the impression that this is not some kind of factory effect, but as if the garland "has gone crazy".

The most common problem here is the electrolytic capacitor. It may swell a little, swell, and this will be clearly visible even to the naked eye.

Everything is solved by replacing it. The denomination is indicated on the case, so you can easily purchase and pick up a similar one in radio parts stores.

If you changed the capacitor, but this did not give an effect, where to look next? Most likely one of the resistors burned out (broken). Breakdown visually determine quite problematic. You will need a tester.

Do measurements of resistance, having previously recognized its nominal (normal) value by marking. If it doesn't match, change it.

Part of the garland does not light

When any of the channels on the garland does not work completely, there can be two reasons.

For example, a breakdown on one of the thyristors or diodes responsible for it.
To be sure of this, simply unsolder the wires of this channel on the board from your place and connect the adjacent channel there, which is obviously working.

And if at the same time another channel also stops working, then the problem is not in the garland itself, but in the components of its board - a thyristor or diode.

Check them with a multimeter, find suitable parameters and change them.

The garland shines dimly

There are also not quite obvious accidents when the LEDs of a separate channel seem to be on, but rather dimly compared to the others.

What does this mean? The controller circuit is working fine. When the button is pressed, all modes are switched.

Dialing diode bridge parameters and resistance tester also does not reveal any problems. In this case, it remains to sin only on the wires. They are already quite frail, and when such a stranded wire is torn, its cross section decreases even more.

As a result, the garland is simply not able to start the LEDs in the nominal brightness mode, since they simply do not have enough voltage. How to find this torn vein in a long garland?

To do this, you will have to walk along the entire line with the handles. Turn on the garland and start moving the wires near each LED until the entire backlight lights up in full force.

why the Christmas tree lights are dim

why the Christmas tree lights are dim

According to Murphy's law, this may be the very last section of the garland, so be patient.

As soon as you find this area, pick up a soldering iron and disassemble the wires on the LED. Clean them with a lighter and re-solder everything.

Then isolate the soldering area with heat shrink.

scheme, rain, curtain on the window, self-repair

LED garlands have replaced the usual ones. They compare favorably with obsolete incandescent lamps in their characteristics - long service life, reliability, efficiency and safety. LED rgb garlands are used in festive illumination, illumination of buildings and trees, in advertising. Garlands differ in their design, characteristics and connection scheme. You can repair the LED garland with your own hands - for this you need to familiarize yourself with the design features of the product.

By design, the products are:

  • Traditional. They are a thread on which diodes are fixed. They are 5-12 meters long.
  • Light curtains - "rain" or "waterfall". Several luminous threads are fixed at a certain interval on one.
  • Fringe. The garland-curtain on the LED window is a kind of rain, it has a shorter length and a different level of threads.
  • Light grids. Threads are connected in a network.
  • Tree garlands called clip light.
  • In the form of balls and icicles.

Each of the listed types finds its application in different areas.

Garlands can also be classified according to the type of food. There are devices that are powered by the mains - they just need to be plugged into a power outlet. Products of the second type require connection through a step-down transformer, as they operate on a voltage of 12 V or 24 V. They are safer - even if the insulation is damaged, a person is not in danger.

Garland design and layout

LED garland control board

Outwardly, the LED garland is no different from the usual one. It also has wires, lamps and a control unit, which is the most important element.

The unit is a small plastic box with buttons that can be used to change the operating mode. It is usually manufactured in a high-quality case with an IP44 protection level. The level of protection depends on the room in which the garland will be installed. On the street, frost-resistant products will be required. Soldered wires are located inside the block. Also inside there is a board on which the controller, thyristors, resistors, a capacitor and diode bridges are soldered. Expensive models may be equipped with a fuse.

LED garland diagram

LED Christmas tree garland diagram

Mains voltage is supplied to the power supply unit. It passes through the diode bridge and resistors, then it is smoothed by the capacitor, after which the voltage is applied to the supply controller. When the button is closed, the modes are switched. The controller controls thyristors, the number of which depends on the number of backlight channels. After passing through the thyristors, the voltage is supplied to the LEDs.

The variety of illumination colors depends on the number of outputs. If there are only 2 lines, the garlands will work in two modes - dim and light up in turn. More expensive products may have more channels.

The main causes of malfunctions

The microcircuit, which is the main working element, rarely burns out. The most frequent breakdowns include:

  • Poor contact on the wires.
  • One of the LEDs is broken.
  • Condenser failure.
  • Resistor burned out.
  • Diode bridge or thyristor problems.

The scheme of the Chinese garland on light bulbs may use cheap low-quality components that will have to be replaced.

Poor soldering

If the LED section does not work, check the contacts of the board

If the garland stops working, first of all, the quality of the connections of the supply and outgoing wires is checked. With a weak contact, the device will not receive voltage. This problem is common with cheap Chinese garlands. They are made using thin strands that break easily at the junctions.

To ensure a reliable connection, the contact points must be filled with a thick layer of hot melt adhesive.

LED burned out

Ringing the wires of the garland with a multimeter

In the garland, the LEDs are connected in series. If one element burns out, the entire chain will stop working. You need to repair the circuit by replacing a non-working component. To determine a broken light bulb, you need a multimeter. Thread thin needles to the ends of the probes to test the diodes. The tip should protrude 5-8 mm. From above, everything needs to be wrapped with a dense layer of electrical tape.

First of all, the garland must be disconnected from the mains. The check begins with the last diode, since the power wire from the control unit is directly connected to it.

The LEDs are soldered, so just pulling them out like a normal light bulb will not work. To check, you will have to pierce the insulation until copper wires appear. The multimeter must be set to dial mode. After that, you need to sequentially pierce the supply wires next to each suspicious LED along the entire length of the circuit.

If a 12 or 24 V garland is used, the diode should light up when touched by the probes. When powered by 220 V, you need to check the readings obtained with a multimeter. They will be almost the same for working elements, a break will be recorded on a faulty diode. With this method, the integrity of the insulation is violated. If a street garland was checked, it can only be used indoors.

Chaotic blinking of bulbs

When chaotic blinking, the problem lies in the electrolytic capacitor

When the garland is turned on, a situation can be observed when the diodes randomly light up with different brightness. Such flickering is not related to operating modes and the factory effect, but is caused precisely by problems in the garland itself.

The probable cause of this effect is the breakdown of the electrolytic capacitor. It may swell, and it will be clearly visible to the naked eye. A broken component must be replaced with a similar one at face value. The capacitance value is indicated on the element body.

If replacing the capacitor did not help, the resistor may have burned out. You will need a tester to test it. By marking, you need to find out the nominal resistance, and then compare it with the measured value. If the parameters do not match, the resistor must be replaced with a new one. After replacing the bulbs, they should stop flashing.

Part of the garland does not light up

Checking the board by reconnecting the wires

The failure of one of the channels can be caused by two reasons. These problems are associated with circuit components - breakdown of a thyristor or diode. To check, you need to separate one posting from a non-working channel and connect it to an adjacent, obviously good one. If it also does not work, the malfunction is related to the thyristor or diode. They need to be checked with a multimeter and replaced with new ones.

Dim light

The LEDs on a particular channel may dim compared to the others. This is not related to the operation of the controller circuit, the dialing of the components will also not give results. The most likely cause is the wires. They need to be inspected for breaks and kinks. After finding the problem area, you need to take a soldering iron, disassemble the wires and install new segments. The contact point must be securely insulated with heat shrink tubing.

DIY garland

LEDs for making a garland

A garland of LEDs with your own hands can be no worse than a store-bought one. It's easy to create. To do this, you will need:

  • soldering iron;
  • electrical tape;
  • heat shrink tubing;
  • LEDs;
  • resistors;
  • power supply.
Making an LED garland with your own hands

The algorithm of work is as follows: