LED Lamp Repaired
One of my friends sent me six blown made in China led lamps and asked me why the life span of these lamps were between a week up to few months? I had to open it up to troubleshoot so that I can give him an answer. After opening of the lamps I found in all of them the PCB and other components turned to charcoal due to explosion of electrolyte capacitor. Five LED lamps were badly blown and one was in better condition.
Below are the components found in the circuit board :
1- Smd diode M7
2-Electrolytic cap with 2.2 microfarad 450 volt
3- Transistor MJE 13003
4- Resistor with code of 123 SMD and another one with code 100
6- SMD transistor 3Y =S8050
7- Two 5 VOLTS ZENER DIODES AS VOLTAGE REGULATORS
8- Smps transformer
All above components were installed on the primary side. In secondary side there was just one Smd resistor plus one Schottky diode
As you can see in following picture the big cap was bulgy and exploded
After replacing the electrolytic cap the LED lamp start to work again.
Why these led lamps won’t last long enough?
The minimum requirement for rectification and converting the AC to DC needs at least two diodes (full wave rectifier). Using only one diode (half wave rectifier) will produce a dirty DC and in the long run the filter capacitor will blow. This is not the first time I’m seeing such design in a China made products. If the manufacturer added another diode for rectification (full wave rectifier), I believe the capacitor would have a longer life and will benefit the users and the manufacturer in the long run.
I fully recommend Mr Jestine Yong ebook about SMPS Power supplies repair to all manufacturers and students. If you would like to learn how to troubleshoot and repair of SMPS.
This article was prepared for you by Mr Beh from Iran.
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