LED Light Bulb DIY Repair at Home

05.08.2019

A LED light bulb is a modern and efficient light source. LED bulbs are safe – they do not contain mercury or other toxic elements and do not cause harm when they are broken. However, the first thing that encourages us to buy these bulbs is their cost efficiency due to low electricity consumption. What’s more, LED devices are rather reliable and usually serve all their lifetime. Thus, the advantages of this light source are evident: it’s bright and serves long.

Traditional incandescent light bulbs cannot be repaired at all, while in LED bulbs you can repair almost everything. You just need to find the malfunction, make some repair and prolong your light bulb lifetime. If you are familiar with repair operations you can even find all necessary tools at home; all you need is to find some time for that.

LED bulb

LED bulb operation is based on the abilities of some materials to emit light under certain conditions. The working element of the bulb, a light emitting diode is a semiconductor device that emits incoherent light when electric current runs through it. LEDs emit light only if you use DC current.

LED

How does a light emitting diode work?

Let’s use a popular SMD LED in the 5730 housing to illustrate the LED operation.

You can find its specifications below:

Peak direct current (IFPM) 260 mA
Direct current (IFM) 180 mA
Reverse voltage (VR) 5 V
Dissipation power (PD) 0,63 W
Beam angle 120°
LED lens type transparent
Operation temperature (TOPR) -40°C – +85°C
Storage temperature (TSTG) -40°C – +100°C
Soldering temperature (TSOL) 260°C
LED

To put it simply, a LED transforms the electric current into light emission. This light source consists of a semiconductor crystal on a non-conductive base, a housing with contacts and an optical system. To increase LED stability the space between the crystal and the plastic lens is filled with transparent silicon. Aluminum base reduces overheating. Under normal conditions heat emission is low.

LED

The more current runs through the diode, the brighter it lights. However, due to internal resistance of p-n transition, the diode heats up and under high current it may burn out – the connection conductors melt and the semiconductor burns. Thus, to ensure the needed current value, a bulb should contain a power supply – a driver, and a heat dissipation system – a heatsink.

Now let’s have a closer look at the bulb.

LED

LED bulb main parts

  1. Dissipator. It reduces the irregularity of a light flow and extra lightness of some emitting elements. It also ensures lighting under a certain angle (for household lamps it should be wider).
  2. PCB with LEDs. A board on the aluminum base that contains LEDs. The amount of LEDs is very important for heat exchange; therefore, it should correspond to the bulb design. There is thermal paste between the PCB and the heatsink to increase heat transfer.
  3. Heatsink. A quality heatsink is designed for heat withdrawal from bulb components. It is used to prevent LEDs from overheating. Heatsink ribs make heat withdrawal and dissipation more effective.
  4. Bulb cap. It is screwed into the lamp socket and ensures a reliable contact. Caps are mostly made of copper-zinc alloy with nickel coating. To ensure protection against electricity current breakdown caps of most LED bulbs have a polymer basis.
  5. Driver. This is an electronic circuit diagram designed for transducing AC current into DC current of a required value. Excessive current leads to LED burnout. A quality driver ensures bulb operation during voltage jumps and LED operation with no pulsation. There are a lot of circuit designs for LED drivers. We demonstrate only a couple of them:
    Driver
    There are simple drivers where voltage is limited by a resistor or capacitor, as well as more advanced drivers using microchips. This type of drivers not only limits voltage but also ensures the optimal power consumption and performs protection functions. Drivers with microchips are more modern and efficient but more difficult to produce and, therefore, more expensive.

Bulb operation and troubleshooting

The bulb operation principle is rather simple: AC current is provided from electricity line to the driver through contact wires, where it becomes DC and runs through LEDs that transforms it into light. The heat is withdrawn using a board containing LEDs and a heatsink.

Scheme

LED bulbs first seem different, but they have a similar design and are made using the same principles. If you master repairing just one bulb, it will be much easier to fix the next ones.

Most modern bulbs have SMD LEDs connected in series as a light source. The circuit design is in the picture on the left.

If one of diodes is dead, the rest won’t work. The most common failure reason is LED burning out (in most cases only one of them). However, sometimes several LEDs fail at the same time.

Burnt LED

LEDs may burn for different reasons. Among them are the low component quality, absence of current stabilization, LED overheating, and voltage jumps. Some manufacturers overload LEDs to make customers interested in high brightness of a small bulb.

However, in most cases it is possible to fix the LED light bulb. Moreover, the repair may be conducted even by an amateur. And the cost is lower than that of a new bulb.

To find out the failure cause you should disassemble the bulb – take off the dissipator and reach the inside. It may be glued to the housing so you may need to use a thin screwdriver to do that. It’s often the case that bulbs with a glass dissipator cannot be disassembled.

There is a board with LEDs inside. High-quality bulbs have only LEDs on this board. If there are some other components, it will overheat faster and the components will fail.

Next comes a visual inspection. You may locate the burnt LED just finding the black spot of some burning marks.

Burnt LED

In some cases, however, the LED may look undamaged. Then you can test and find a faulty LED using a multimeter. Most of modern multimeters have a diode test function. The test procedure is as follows: touch the anode with the red probe and the cathode with the black one. The working diode will light. If you change the probe polarity, the meter will display “1” and the diode won’t light. Neither will a faulty diode light during the test.

Bulb repair

LED replacement

Now when you have found a faulty diode, it has to be changed. It is soldered to the board. Overheating hazards are critical in diode operation. Keep in mind that soldering recommendations are included in diode technical specifications. For example, for 5730 SMD LED, which is widely used due to a good balance of size, power and light flux, the soldering temperature is 260°C (no more than 2 seconds).

Bulb repair

If the bulb design allows, you should take the board off the heatsink, desolder driver contacts and after that start changing the LED. The board may be fixed using a PCB holder (we then have both hands free). If possible, heat it up from below with a hot air gun. The temperature shouldn’t be high, about 100 ÷ 150°C, in order not to damage the working diodes.

It is convenient to take off the old LED with hot tweezers that heat up both outputs at the same time. Or you may do it with a self-made simple analogue – a copper conductor twisted around the soldering iron tip.

Bulb repair

You should replace the old LED with a new one of the same type. You may usually find LED marking on the bulb PCB. Mind the polarity during installation.

Bulb repair

There is a seemingly easier way to repair the LED – just install the conductor instead of the damaged diode, that is, connect the contact pads. It looks like this:

Bulb repair

If there are a lot of LEDs on the PCB and they are all installed in series, one of them missing won’t greatly affect the others. However, the voltage on the working diodes will be higher and the chances for them to burn are higher. There is no such risk with high-quality bulbs, where the driver sets the required current and reduces the voltage to the level safe for LEDs.

Bulb repair

Other failures

If all the diodes turned out to be working during the test, you should check the bulb driver and search for other damage, as well as check the conductors and contacts for discontinuity.

The driver in quality bulbs should be a separate PCB and be located in the bulb cap. Each manufacturer has a unique driver circuit design, so there are no standard repair recommendations. You should apply an individual approach here.

Bulb repair

You should test the main components with a multimeter, check the diodes and transistors for shortage, compare the resistor values, change the capacitors that lost their capacity. If there is an IC chip in the driver circuit, you should check the voltage on its outputs according to its technical specifications and decide if it’s working OK. Change the faulty components if needed.

Finally check if the disassembled bulb works fine and then assemble it. You may need to apply thermal paste, tighten the screws, and fix the dissipator.

In our store you may find the DIY LED Bulb Assembling Kits, as well as separate components: drivers, PCBs with LEDs, housings, etc. You just need to disassemble the bulb, desolder the old faulty component and install the new one. It takes only seconds to do.

Bulb repair

Here we’ve described the simplest variants of LED bulb repair without any complicated details. However, it’s obvious that this kind of repair work shows promise and potential. The cost of LED or driver replacement will be significantly lower than buying a new bulb. We may also add that you should use only high-quality components with good technical specifications for replacement. That may ensure a long and stable LED bulb operation.


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