LED Light Blinking in 40″ Samsung LCD TV
A customer brought in this Samsung 40″ LCD TV for repair with the complaint of front power LED was blinking. The LED blinking usually can be caused by several factors but the most common one is the power supply fault and the next cause was the data corrupted in either the MCU IC, EEprom or the Flash Rom (memory ICs). The LED signal is coming from the MCU IC thus if the DC supply to this IC is improper (faulty power supply) or the IC itself memory is corrupted, the power LED light will blink.
I opened the TV cover and saw four circuit boards. They were the power supply, inverter, Mainboard and T-con board-see the photos below:
One more symptom of this TV was the relay clicking on/off intermittently. Below is the photo of the relay:
Usually I will observe the symptom first then by using sight to do the visual inspection on all the circuit boards. It was very obvious the fault was at the power supply section because I saw quite number of filter capacitors were bulged. Their functions are to filter the AC ripple and to store current.
Obviously a bulged filter cap would not be able to store enough current but at the same time the current was still being drawn by the mainboard. A lack of current supplied to the mainboard can cause the DC volt to drop thus affecting the whole function of the mainboard. And this is why the power LED blinks (MCU IC did not get enough of DC supply voltage).
Replacement of 7 filter capacitors solved the power LED blinking problem-see the photos below:
Conclusion- Assuming if all the filter caps were good then I may have to suspect the memory ICs. If you wish to learn how to check components like a professional you can get Jestine’s ebook HERE. If you wish to have ideas about troubleshooting and repairing LCD/LED TVs, you can check out Kent’s ebook and also Damon’s ebook. Ok, will be seeing you again in the next article.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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https://jestineyong.com/blinking-stand-by-led-light-in-led-tv-repaired/
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Robert Calk Jr.
December 18, 2018 at 12:53 pm
Ahh, those pesky e-caps! Good job, Suranga.
Tito Kanshulu
December 18, 2018 at 5:23 pm
A job well done Suranga. that's interesting. Bulged capacitors are a real problem
Albert van Bemmelen
December 18, 2018 at 6:29 pm
If they would make power supplies that store energy in a magnetic way instead of in the capacitive way that would eliminate these bulge and leakage problems completely. Coils hardly ever deteriorate. But hélas it doesn't exist yet.
Robert Calk Jr.
December 19, 2018 at 6:36 am
Hi Albert,
Would you rather have the "weak link" to be a more expensive component? Luckily for us that most e-caps are not very expensive. Without e-caps we would have an even more throw-away society than we already have.
Albert van Bemmelen
December 20, 2018 at 5:42 am
HF coils do not make them more expensive than the often more expensive standard 50/60Hz transformer types in power supplies. The e-cap problem always causes much polution because in time they always will fail and even will destroy our expensive instruments like our Tektronix scopes. It should not mean that because better technical solutions do not yet exist the e-cap technology is perfect as it is. And if in future all cars use lithium-ion batteries as power source it probably will cause new environmental problems too. I mean polution has its price too.
Robert Calk Jr.
December 21, 2018 at 10:27 am
That is true. Well if we invent a cheap nontoxic dependable replacement for e-caps we will be very rich men!
Albert van Bemmelen
December 24, 2018 at 12:27 am
Maybe Robert, it is easier to invent new circuits that do not need e-caps anymore (LOL)? Have a great Xmas and a good New Year! (same wishes go to Jestine and all Readers/fellow contributors!)
Robert Calk Jr.
December 24, 2018 at 10:46 am
Yeah, but they will just insert their planned obsolescence somewhere else. Merry Christmas and Happy New Year!
Kigoma charles
December 18, 2018 at 11:51 pm
Waaaaaaaaaaaooooouuuu, fantastic job,God bless u.
Parasuraman S
December 19, 2018 at 8:54 am
Oh! My! Those leaky capacitors make a sticky job! Cleaning the board and handling it is a difficult job! Well done!
Joshua Oloo
December 19, 2018 at 3:39 pm
That is educative and it explains why we should put more emphasis on visual inspection first.
beh
December 20, 2018 at 12:16 am
SURANGA .this time your repair report is full of golden points .
& thanks
beh