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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Note: You may check out his previous repair articles in the below link:
https://www.jestineyong.com/the-ac-dc-ac-inverter-repaired/
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Albert van Bemmelen
December 23, 2015 at 5:17 pm
Thanks Beh for this article! I have seen a lot of defective SL lamps on the inside before but I believe it is my first view on the inside of a led lamp. I heard in the news recently that the manufacturers at least in Europe all Lie on the consumed current and value of given Lux. Being that they use more current and even give less Light. So it is not all bright technology (;-) . Cheers!
beh
December 24, 2015 at 11:02 am
Hi Albert
yes on the body of this lamp is written 3 watt consumption of energy but as you told who can prove this ? this needs special equipment and performing the tests .i wished i could give a correct answer to this question.
thanks for comment
beh
Parasuraman S
December 24, 2015 at 7:06 am
Good, descriptive article! Voltage will increase if two diodes are used on both sides of AC input (full wave rectifier). Then you might need more components to reduce it. Moreover, they would have designed the switching and pulse width taking into account the half wave rectified DC. So, probable reason is economy!
beh
December 24, 2015 at 11:11 am
Hi Parasuraman S
yes if they add the extra diode in the circuit the voltage is increasing
and a voltage regulator is required and the pcb getting bigger and this need more space and more components the size of this pcb is only 22x15mm the smallest one that i have ever seen yes could be the economical reasons forced the manufacturer to make this lamp in this way.
thanks for comment
beh
Gerald
December 24, 2015 at 8:21 am
Hi Beh,
Well done, thanks for sharing. Like Albert this is the first time I see the inside of those LED lamps. I have a number of them installed at home since a couple of years ago and none has failed so far (touching wood). I have taken apart a large number of CFL that failed after a couple of months and all of them failed because of the electronic components, none of them failed because of the CFL itself. Your interesting article shows that the history repeats itself. New technologies but the same old mistakes; cheap and poor quality components. Well, this keeps us on the job 😉
Cheers and Happy New Year to all the Electronic Repair members.
Gerald
beh
December 24, 2015 at 11:23 am
Hi Gerald
yes as you told the poor quality of electrolyte cap also could make this problem this cap is belong to a unknown manufacturer with name of XZ.
actually these kind of productions are not belong to big manufacturer in china just small work shops are assembling these lamps but in a huge amounts and then instant export to thirsty world of consuming the electronics.
GERALD happy new year and thanks for comment.....beh
Justin
December 24, 2015 at 2:14 pm
Ooh! Very nice!
Thanks
beh
December 24, 2015 at 4:02 pm
you are welcome
Yogesh Panchal
December 24, 2015 at 2:56 pm
Beh, good job! thanks for sharing.
beh
December 24, 2015 at 4:03 pm
you are welcome Yogesh
Robert Calk
December 24, 2015 at 2:58 pm
Thanks for the article, Beh. It's better to pay extra for quality devices when we can.
beh
December 24, 2015 at 4:03 pm
yes this is true and thanks
Royce
December 24, 2015 at 7:18 pm
Yes a very good article, thank you for info.
Royce
beh
December 26, 2015 at 1:51 am
ROYCE thanks for support
Dennis,
December 26, 2015 at 10:56 pm
Beh, well presented. Thank you
beh
January 4, 2016 at 12:57 pm
you are welcome DENNIS
reza
December 30, 2015 at 1:03 pm
Hi mr beh
thank u for sharing this good article.
beh
January 4, 2016 at 12:59 pm
thank you MR REZA
Humberto
January 8, 2016 at 11:27 pm
Hi beh, cheap devices China made cause a lot of troubles, they save electronis in the design.
Thanks for the article, I had never seen one of these devices inside
beh
January 13, 2016 at 10:36 pm
Hi Humberto
yes these cheap device are every where and are very problematical .
thanks for your comment and you are welcome
John Carston
July 26, 2022 at 9:17 am
I appreciate that you explained that two diodes are the minimun requirements to work a lamp. Last night, my uncle told me that he was looking for a lamp service that could repair his vintage lamp because of malfunctioning light, and he asked if I had any idea what would be the best option to consider. I'm grateful for this instructive article, I'll tell him that he can consult a lamp repair service for more information.