Repairing Old LED Bulb at Home

Hi guys, I am working in my lab room, and suddenly with a small explosion, my room light turned off. This one is 5 watts Orient company LED light. This one has been working well for two years.

Tools required:

1) Hammer

2) Plier

3) Soldering tools

4) Screw driver

5) Multimeter

6) Basic components and electrical knowledge.

Hi guys, I am working in my lab room, and suddenly with a small explosion, my room light turned off. This one is 5 watts Orient company LED light. This one has been working well for two years. So, today we will learn about the internal circuity and repair this LED. Because Led’s has excellent power to withstand over the years, we will troubleshoot the small internal Led’s first and then the main circuitry. Also, I will tell you some common problems, which can be repairable if you are a techie, which may save you a little money.

To expose the circuit, we have to open the outer cover(diffuser). This helps to diffuse the light equally in all regions of the room. We can remove this cover by hitting a little bit with a hand or a small hammer. Don’t hit too much or hard because this may damage the circuitry

After this, with the help of a screwdriver, unscrew these small nuts from the led PCB. Screws are given to make better contact with aluminum so that PCB will not overheat or burn out. Then desolder the positive and negative wires from the main PCB. Remove the standard aluminum plate with the help of a small screwdriver and hammer.

Remove the excess solder from overhead to get the wires out of the white shield. You can use desoldering pump or wick method to remove excess solder.

Now pluck out the driver PCB from the white shield; this is the Main LCD operating PCB, having different components mounted and output a dc voltage of 40volts at 0.22 Amperes. POWER tells you the rating of any led voltage x Amperes = Power.

40x0.12= 4.8watts (5 watts).

De-soldering may take some time; due to log time oxidation, solder joints become very dry; try to remove it with an excess flux and a high-power solder iron, with 400*C. 

Because everything is designed of aluminum to keep the led PCB cool, it may be hand for you to make a better solder joint with a low power soldering iron. So, keep the temperature above 400*C.

If you can see the ID number or manufacturing number on the Led PCB, then gather info about this from google by datasheets. Mine one doesn’t have any manufacturing info, so I will leave this step; this will help you find 1) the life of the components 2) Current consumption. 

Get more info about this from here.

The driver PCB has different components- Transformer, MOV, diodes, resistors, capacitors (electrolytic and polyester), Inductor, a bridge rectifier, and a constant current regulator.

All the Led’s in PCB are joined in series; to power on the Led, we need at least 40volts. In driver PCB, there is a transformer in the circuit to step down the voltage. 3 electrolytic capacitors, 2 polyester film capacitors, one 7mh Inductor, and a 170 ohms resistor. Driver stage has doubled layer PCB, so SMD components are mounted on one side and through-hole components on another side. At the bottom layer, there is a Schottky diode, 0.5A rectifier, and a led constant current driver IC (bp2863). See datasheet from here.

Check the voltage value across the end of the driver stage. If this is more than 30 volts, then okay otherwise, we have to repair this. 

check the Led’s one by one, keeping the multimeter in continuity mode. If all are turning on, then okay otherwise, we have to change any specific or all of them. 

If only one Led is not working, then we have to remove this Led; either we can place a similar new one or a resistor of 0.5 watts 270 ohms.

If the circuit is burned or damaged highly, we can replace the whole circuitry and led PCB with a MOB PCB that supports the onboard power supply, rectifier, current controlling IC, and LEDs. Commonly available in Market. 

If you don’t want to do or do not know about AC power, go to a nearby market and buy a new one. 

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1. Keep in mind all the small Led’s on Pcb are joined in series. If any one of them is damaged or blown up, the whole system stops working. In 75% of cases, this is the only problem that can be solved by placing the same value resistor or replacing the led with a new one.
2. The resistor of the driver stage is high wattage cement coated, in 170ohms. In 10% of cases, the resistor is faulty. This resistor saves the led from high voltage (it blew up if high voltage is given). Find the same new resistor and replace this. 
3. In 15% cases, there may be a fault in MOV (metal oxide varistor) or electrolytic capacitor. If found faulty, you can first check them, then replace them with a new one of the same value.

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