Disassemble LED Bulbs

LED bulbs are often quite easy to dismantle, but attention to the presence of the sector if you want to do some tests under tension. It often happens that a LED bulb failure is due to a power failure (the little electronic card housed in the base of the bulb) or a failure of a single LED in the case where the LEDs are all mounted in series. See an example of LED bulb down that was opened.
Dismantled LED bulb: mechanical components, power and card with LEDs.
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Stages of disassembly of the LED bulb
Each LED bulb has a particular Assembly. Here, an example is presented: all LED bulbs don’t take down that way, but it’s an example.
On this bulb, we need to start by dismantling the translucent dome (it is plastic and it is stuck) with a flat screwdriver.
We then see the map where are all LEDs. On this map, there are 2 wires emerging from the center of the bulb: it’s the power supply. Unsolder them! Then, we unscrewed the screws which fix the card with the LEDs. This Board is mounted on a metal stand that serves as a radiator. After removing the card with the LEDs, we see two screws: unscrew them and the nerve part separates from the rest of the bulb.
Rest of the bulb: this serves as a heater for the LED
The LED bulb 10W and LEDs are white hot (2700K)
The bulb Power Board is housed in the nerve and drowned in a kind of soft white dough.
The LED bulb failure
Here, the failure of the LED bulb is located on the power Board. The power supply is based on a small switching power supply compact, using no chemical filtering capacitor after the recovery of the sector 230V. Instead, there is a capacitor 100nF, 400V. It is this capacitor that is responsible for the failure. There are of course take it apart and replace it:
Responsible for the failure of the LED bulb exploded capacitor
It is replaced by another (here a 100nF 630V but 100nF, 400V would have agreed too):
The power of the LED bulb Board repair
Out of curiosity, we can observe the controller of the switching power supply integrated circuit. It is in a very small box (SOT23-6) with a dark marking “MMDCO”:
Controller of the power supply of the bulb
Test the repaired LED 10W bulb
It reconnects the area carefully (with a halogen bulb of 40W 80W in series to limit current in case of short circuit or error and do not blow out). The LED lights all:                                                  Repaired LED 10W bulb
Luckily, there was only this component that was to change. If the failure had occurred elsewhere, the repair of the bulb would have been much more difficult!
Light drunkenness: after repair, the LED bulb works again!
Measure the voltage and the LED current
When the bulb is powered, measure the voltage at the terminals of the son. Measure 34.8V. The map consists of 33 LED mounted in 3 branches of 11 LEDs in series. The 3 branches are in parallel. In each branch, there is a resistance of 1 Ohm in CMS, which ensures a better balancing of currents between the three branches.
When you measure the current consumption, measuring A 0.29.
The electric power consumed by the card led is therefore: 34.8V x 0.29 A = 10.1W
The manufacturer of light bulbs is very honest and does not artificially inflate the advertised power! The rated current of a single LED is 100mA (3 branches in parallel = 3 x 100 Ma = 300mA)
A variable voltage power
When we vary the supply voltage, there are the LED begin to glow from 25V about:
LED bulb: from 33 LED 10W
April 28, 2013: a precious day for this LED light bulb!
The life expectancy of this energy saving bulb was only 2 and a half years. It is a power supply problem which reduces the lifetime of the bulb. In reality, it is often the case
Final word
If you disassemble an LED bulb to fix it, he should know that sector is never far away. Mechanical Assembly of the bulb is based on screws and glue. Disassembly is often irreversible, but we understand how the LED bulb is assembled.