How to find blown christmas tree light

How to Find a Bad Bulb on Christmas Tree Lights

Detangling your Christmas tree lights is the second worst thing about the holiday season. The first-place winner? When you’ve gone through all that hassle, undone all the knots and kinks, and you plug in your beautiful lights to find them totally dead. 

Hours of work for nothing. Plus, you then have to brave the cold weather, crowded stores, and close calls in the parking lot to get new strands of lights. (Or you just buy them online, but it’s still a hassle.) 

We want to take the stress out of your holiday season. So, let us give you an early Christmas gift! Follow these steps to find a bad bulb on your Christmas tree lights.

Step 1: Check the Outlet

First, make sure your lights are really plugged in. (We know it’s silly, but we’ve all done it!) If you’ve plugged in your lights and nothing happened, unplug them and plug another appliance into the outlet. If that appliance doesn’t work either, find your circuit breaker and check for a flipped switch. You can also test the outlet with a circuit tester.

Step 2: Check the Wires

You might have noticed this when you were doing all that untangling, but check again. Look for any broken strands with wires poking through them. If you find any, it’s time to toss the lights and get a new set. If you don’t want all your hard work to go to complete waste, you can take off all the bulbs to use as replacements in the future!

Step 3: Check the Fuse

Christmas lights usually have little cartridge fuses inside the plug. They look like tiny glass cylinders with internal metal filaments like a lightbulb. Pop open the fuse cover and replace the fuses with those of identical size and rating.

Step 4: Check the Bulbs

This is probably the most time-consuming step. Depending on the lights, you might not know where the outage actually begins. Some lights have a single circuit, so the whole strand goes out if a single bulb isn’t working. Others have multiple strands, so only half your lights go out. To check the bulbs, follow these steps:

  • Identify the affected area, which will either be the whole strand or part of the strand, depending on the kind of lights you have.
  • Start at the problem area and inspect each bulb. You’re looking for any bulb that is loose in its socket, darker than the others, or has an apparent break in the filament or casing. 
  • Tighten or replace problem bulbs. Make sure all the bulbs are tight, so you don’t have to go over the strand again!
  • Test each individual bulb. If the previous steps didn’t help, it’s time to test each bulb separately. (Sorry. It’s the worst.) Take out each bulb from the problem area and place it in a bowl. While you have all the bulbs out, check the sockets for corrosion or debris you can clear out. Plug in the strand and insert each bulb, one by one, back into a socket. If it lights up, take it out, and place it in a separate bowl to use when you’re done testing the others. If it doesn’t light up, throw it away and replace it with a brand-new bulb. Or? Purchase a light tester.

Step 5: Make an Upgrade

If you need to get some new lights, we recommend upgrading. LED Christmas tree lights are more durable and efficient, and they often come in cool colors or with fun features. 

Step 6: Give Us a Call!

Sometimes trying to fix your Christmas lights means discovering more problems with your home’s wiring. If you notice issues with your circuit breaker or outlets during this whole process, take a deep breath and call us. We bring cheer to our DFW electrician customers all year round. Give us a call today!

How to Find the Bad Bulb on Christmas Lights

It’s the universal condition: every holiday season, homeowners across the country dig boxes of holiday decorations out of their attics or basements only to discover miles of burned-out Christmas lights! When you’re hanging your Christmas decorations and preparing for guests, the last thing you want to worry about is broken string lights. Let Mr. Electric help you find the bad bulbs on your Christmas lights so you can concentrate on the fun stuff!

Or, save yourself the time and hassle by scheduling an appointment for our holiday light-hanging services. You deserve a totally stress-free holiday!

What You’ll Need to Fix a String of Lights

Grab your dead strings of lights and a few simple tools, and you will bring those lights back to life in no time.

  • Voltage detector or Christmas light tester tool
  • Safety glasses
  • Outlet
  • Replacement bulbs at correct voltage rating


Troubleshooting Christmas Lights

The trick to string light repair is to eliminate easy solutions first, and then move on to trickier ones. First, figure out if the problem is just a single bad bulb or a wiring issue.

Before you start looking for a burned-out bulb, check for the following:

  • Loose bulbs
  • Damaged or frayed wires
  • Damaged outlets or electrical plugs


If you aren’t sure whether the problem is a malfunctioning outlet, you can check it with a multimeter.

Finding Bad Bulbs on Incandescent Christmas Lights

Incandescent string lights are wired in a series. That means the electricity must pass through each bulb to complete the circuit—and a single bad bulb can make the whole string go dark. Larger light strings may contain two circuits. In these cases, you may notice that only one section of the string goes dark.

The easiest way to find faulty bulbs on incandescent Christmas lights is with a Christmas light tester. Simply bring the light tester close to each bulb. The tester’s indicator will light up when it’s near a functioning bulb.

If you have a non-contact voltage detector, bring the detector close to the wire section between each bulb to test for voltage. The dead section of wire will be the section after your bad bulb.

If you’re sick of your incandescent bulbs burning out, consider switching to LED lights—especially if you’re concerned about light safety. LED bulbs use less energy, produce less heat, and last longer.

Finding Bad Bulbs on LED Christmas Lights

Many LED Christmas lights are made without removable bulbs, so the circuit won’t fail if a single bulb breaks.

If you have LED Christmas lights with removable bulbs, the troubleshooting process is similar to incandescent bulbs. Starting at one end of your strand, or in the dark portion of your strand, use your voltage detector or light tester to locate the faulty bulb or dead length of wire.

If you don’t have any voltage detectors or other tools but you do have a replacement bulb, you can go down the whole length of the string and switch out each bulb, checking to see if that solves the problem each time. This approach takes patience, of course!

How to Replace Christmas Light Bulbs

Make sure you have replacement incandescent or LED bulbs in the correct voltage rating and color. Unplug your lights before removing or replacing any bulbs. Carefully screw in the replacement bulbs and plug your lights back in. If you have replaced the bad bulbs on your Christmas lights but you still experience problems, the issue may be bad wiring. Consider replacing the lights at this point.

Running out of time before the big holiday party? Expert electricians are just a click or call away! Call Mr. Electric at (844) 866-1367 or schedule an appointment online. 

Eternal garland or light bulb with a jumper

A garland assembled on ordinary miniature light bulbs or modern LEDs is a constant companion of all winter holidays.

Many I like this decorative lighting not only for the New Year, but also on weekdays days. The main thing is to turn off the strobe or flicker mode.

However, the real headache in such jewelry has always been the failure of a single light bulb. It is worth burning out any element in the serial chain, and the whole garland immediately ceased to shine.

Anyone with a multimeter and electronics skills can still try to find the problem themselves. What about everyone else?

Cut out the defective element from the chain and connect the wires directly? Under no circumstances should this be done.

If you reduce the number of lamps in the garland, thereby changing the resistance in chains. The load and stress on the remaining elements will increase, and they will the seeds will start to burn one by one.

In the end, there will be a short circuit and a fire on the Christmas tree.

Old Christmas tree garlands

In the USSR there were “cunning” cartridges with a long tongue in the middle. When the garland burned out, each light bulb had to be unscrewed 1.5-2 turns and the tongue closed.

If the garland began to shine, so you found a faulty light bulb. If not, the cartridge was screwed back and the search continued.

A imagine that two lamps burned out at the same time - you are tormented by twisting the cartridges.

There were also attempts to produce special cartridges with a rubber base. bottom of the chuck additional contacts were built in, which could be closed by ordinary squeezing fingers.

Like this In this way, they tried to facilitate the search for a faulty element.

However, all Still, the question of replacing the lamp remained relevant. Many people still recommend together with one garland, immediately buy a spare one and use its bulbs for replacements.

The advice, by the way, is so stupid. Models change from year to year and in a couple of years you simply won’t be able to find the right light bulb for sale.

And with a donor garland, the New Year's illumination will serve both you and your children. However, there is a more sophisticated solution to the problem.

Bulb device with shunt

Not many know, but engineers back in the 50s came up with the so-called “eternal” a garland in which a burned-out light bulb “repairs” itself and all the lighting continues to burn without your intervention in its insides.

Similar the invention was originally used in the subway on old cars. There the lighting in the car is also made according to a sequential scheme.

On the “mustache” light bulbs, where the tungsten spiral is attached, is additionally wound thin wire.

At the same time, she does not initially make contact with the legs of the electrodes while the bulb is alive and not burned out.

How does it all work in an emergency? Some mistakenly believe that when the tungsten burns out, the legs of the “antennae” spring, and thereby close the contacts on the wire. This is not true.

Even if initially the legs were spring-loaded, the tungsten filament would not have had enough effort, to keep them. They do not move anywhere even in the event of a thread burning.

It's all about clever application of the chemical properties of materials.

Initially shunt resistance is several times greater than that of a tungsten light bulb, so all current goes through the coil. The shunt itself is made of aluminum and coated with oxide layer.

Oxide acts as a kind of insulator.

OK mode, the voltage on the light bulb is small, but as soon as the spiral burns out, the current the light bulb stops flowing, and it rises to the mains 220V.

This moment, the breakdown of the oxide layer occurs. Current begins to flow through the shunt.

Thus, a burned out light bulb becomes an ordinary jumper in a common circuit.

Yes, of course, she herself stops shining, but this has practically no effect on the operation of the garland. Just a slight increase in brightness.

Is such a garland dangerous?

At the same time, many are afraid that due to a change in the resistance in the circuit, the rest of the lamps will also begin to fail, and in the end everything will end with a banal short circuit.

First, shunt resistance is chosen so that in the operating mode at the passage of current through it did not affect the performance of the entire fairy lights.

Resistance wire should be equivalent to the resistance of the filament in cold condition.

And secondly, even if, in an emergency, an excess of the current load in several times, this same shunt will simply play the role of a fuse and burn out, breaking the chain.

One more plus such “protection” - without any devices you will see which particular light bulb chain needs to be replaced. Frankly, this was originally for this the whole idea is thought up.

Not at all for in order for the garland to shine further, and in order to quickly find and replace the burnt out lamp.

Such garlands, most often of foreign execution, can still be found in our stores.

For identification, look closely at the flask. thin wire next to bases are easily distinguishable without any microscopes.

Single minus - power surges.

increasing the voltage in the outlet, burnout may occur on all flasks oxide layer in shunts. That's when you really get the hang of it.

Bulb in such a garland can even be broken by destroying its flask. At the same time, the remaining “balls” will still glow.

Analogues of the “eternal” garland

In addition to miniature New Year's garlands, similar lamps are also produced under the cartridge E27 on voltage 60V (tram lamps). Only in them instead of anodized jumpers use a thin anodized plate.

Principle work is the same. This lighting method was common in retro wagons. old type.

Bulbs screwed into SPL-55 lamps. In the common people they were called "boobs".

If the jumper did not work, then the entire side of the car was turned off.

Of course, an incandescent light bulb in garlands is already the last century and everyone switched to LED models or even laser backlights a long time ago.

But even in them you can sometimes encounter a similar trick - one LED burned out, the rest continue to shine (and this is when connected in series!).

Does the magic “bridge” work here too? No, this is just a property of the pn-junction, when it fails, it either breaks through or breaks.

Moreover, the breakdown can be reversible, that is, the broken pn-junction can be restored. Here, as they say, how the card will fall.

How to fix a garland - Lifehacker

December 28, 2018LikbezDo it yourself



As a rule, garlands have a rather simple design and typical faults that are easy to fix even without special skills and tools. But in some cases, you may need a soldering iron and a multimeter. Therefore, you may still have to turn to a familiar radio amateur.

The cause of a garland malfunction, like any electrical engineering, is the failure of one or more circuit elements. Everything is usually repaired by replacing a faulty part, which can be found in another garland or some kind of broken equipment.

Careless handling of the electric garland can result in electric shock or damage to the device. You perform all actions at your own peril and risk. Lifehacker does not bear any responsibility.

How a garland is arranged

All electric garlands are arranged in the same way. In older samples, these are light bulbs connected in one circuit that light up or flash when connected to the network. In modern ones, a controller is added to glow in different modes and the bulbs can be replaced by LEDs.

Usually, old or decorative garlands have two wires, or to be more precise, one, which is connected in the form of a ring and twisted. Modern models have five wires. Four LEDs are located - these are branches. The fifth - general - remains empty.

At the far end, they all connect together, and their other ends go into a small box with a button and a plug.

Inside the box is a controller - a small board that contains a chip for creating effects and a few parts. A diode bridge, a capacitor, a pair of resistors and four (or two) thyristors that control the glow of each of the branches with lights of the same color.

In the photo on the left, the four black parts are thyristors. The blue one next to it is a capacitor, small light-colored edges are resistors, behind the scarves with a microcircuit are a diode and a button.

In the photo on the right is the reverse side of the board, two wires from the bottom - mains power, a row of wires from the top - lines of branches of each color and a common one.

How to fix a garland if it does not turn on

Cause 1. Broken power wire

Thin wires are often damaged by breaking at the plug or coming off the board inside the control box.

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How to fix

Move the wire at the plug and next to the box. If the garland works, then the problem has been found and all that remains is to replace the cable by disassembling the controller unit.

If not, troubleshooting should start with the power cable. Open the cover, unsolder the two wires going to the board and replace them with a working wire with a plug.

If there is no visible damage to the board, this should help and the garland will work. Otherwise, the problem must be sought in the power diodes.

Cause 2. Burnt diode bridge

Power surges can destroy one or more diodes of the diode bridge. As a result, the board will not be powered and the garland will not turn on.

How to fix

Check all diodes with a multimeter and replace the non-working ones with good ones. Details can be taken from another garland or found suitable at the denomination indicated on the case.

How to fix a garland if one of the colors does not work

Cause 1. An open circuit in one of the branches

Due to poor quality, the wires can break off either at the board itself or somewhere between the LEDs. In both cases, the circuit opens and the LEDs stop glowing.

How to fix

Separate the dead branch from the rest and carefully inspect the wire to check its integrity. If it has moved away from the board, strip it, re-solder it and fix it with hot glue for reliability.

If there is damage on the cable between the LEDs, strip the ends of the wire and solder or twist them together, then insulate with heat shrink or electrical tape.

Cause 2. Burnt LED

Low-quality LEDs often burn. With a serial connection, this means the same open circuit as in the previous case.

How to fix

Finding a broken LED or light bulb in a series circuit is more difficult. One option is to ring each element with a multimeter.

You can also make a jumper of two needles connected by a wire, and alternately close the incoming and outgoing wires on each LED with them. The garland must be turned on. The LED, when closed, all the lights of the branch will light up, and will be defective.

To restore the circuit, a non-working LED can either be replaced, or simply removed and connected the ends of the wires to each other, insulating them. Without consequences, you can throw away up to five LEDs in one branch.

Cause 3. Thyristor failure

If the control thyristor of one of the lines fails, all LEDs of the same color stop working.

How to fix

You can fix the breakdown only by replacing the thyristor with a working one from another garland or a suitable one at face value. To check, you need to use a multimeter or resort to the following method.

Identify the wire of the non-working branch and swap with one of the good ones by unsoldering or cutting and connecting with a twist. If the defective line then works, then the problem is in the thyristor.

The wires that go to the thyristors are usually arranged in a row at one of the edges of the board. On the opposite there will be only two wires - this is power. It's hard to confuse them.

How to fix a garland if one of the colors glows dimly

Cause 1. Branch wire tear

Due to a break in the wire inside the wire, contact is broken in the circuit of one of the branches. The current still passes, but it is no longer enough to light all the LEDs.

How to fix

Carefully inspect the entire branch. Move the wires at the board and each of the LEDs of the switched on garland to determine the damaged place. As soon as you find it, all the LEDs will light up in full force. Next, it remains to restore normal contact by soldering the wire or stripping and connecting it.

Cause 2. Broken thyristor

Due to a faulty thyristor, one of the lines may not have enough current for the normal operation of all LEDs.

How to fix

This breakdown is treated only by replacing the thyristor with another one. You can check the performance with a multimeter, or by transferring the wire to one of the working lines.

How to fix the garland if it flashes randomly in any mode

Cause 1. Failure of the capacitor

Drying, leaking or swelling of the electrolytic capacitor causes malfunctions of the controller.

How to fix

Carefully inspect the capacitor. If it is swollen, darkened, or electrolyte streaks are visible on it, then a replacement is necessary. Examine the case to find out the rating and voltage, and then find an analogue with parameters no less than the original ones. Carefully unsolder the old capacitor and install a new one, observing the polarity.

Cause 2. Broken resistor

Burnt resistors also cause controller malfunction and unstable lighting modes.

How to fix

Check the resistance of the resistors with a multimeter and replace the faulty ones with working ones of the same rating. If visually the parts are intact, it is still better to replace them to rule out a malfunction.

How to fix the garland if all LEDs are on at the same time and do not blink

Cause 1. Chip failure

Damage to the controller chip causes all LEDs to light simultaneously and without blinking. The modes stop working, and when you press the button, the lights turn on and go out when you release it.

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