55 Inch Curved LED Samsung Television Model UA55MU7350K Came In Dead Now Repaired.
I received a phone call from a client who wanted his television checked by a technician, he requested for my ping location and I send him via whatsapp.
Within one hour he called me to say that he is around my area, I walked out and ushered him to the shop. I carried the 55-inch television into the shop and we had a small chat. I asked him how he came to know me and said he was referred to me by another client I repaired his television previously.
This info always put a smile on my face, a happy client will always come back and refer more client to your shop. After that little introduction, now it is time to do business and the business was to see his Television back to life.
I asked for a short history about the problem and he told me that they were just watching football and when his favorite team was about to score the television went down! He took it to the nearest technician and the technician told him the power board is faulty and beyond repair and hence needed a new power board.
He gave the technician the amount needed and the tech came back after two weeks with a board and installed it and nothing happens, still dead symptoms. The tech told him maybe the board is not compatible and left in hurry, the owner suspect the board was the same he took and even me I have no reason to doubt him since he was not given the other board, how sad?
Since the Television was brought in the evening I decided to check it out in the morning and therefore closed the shop.
Day two, I opened the television and went straight to main fuse and found it was open circuit. I replaced it with a jumper wire (this was done only for testing purposes) and applied the power via the series bulb current limiter and nothing happened. Noted no input at the AC connector and after testing the television power cable fuse (top plug) and was found open circuit also.
I replaced it and again applied the power and now I noted the series bulb current limiter was as bright as the sun.
Usually if you get this kind of scenario always expect a heavy short ahead. I checked the voltage across the main capacitor and got almost zero volts. I decided to dis-connect the power and do resistance testing looking for the shorted component(s).
I tested across the main capacitor and got a beep, this means there is a component shorted across the line. To isolate the problem, I decided to disconnect the transistors QP801 and QP802 guided by a circuit diagram I got from the net which was not exact but close to what I was looking for as you can below.
I did this by soldering out the two transistors(mosfets) as you can see below.
After soldering the two components out of the circuit, I applied the power again and the bulb went on briefly and off. With this I concluded no more shorted component and therefore I had to go to the shop to buy the two components which were both N-channel mosfet transistors, luckily they are readily in my market.
I came back with my parts and replaced them, applied the power again using the series bulb current limiter and power board was now powering on but power was pulsating. I decided to change the control I.C (ICM801S) which was driving these mosfets, the part number was 6C17106 which was an SMD I.C.
Getting an smd component is my local market is not easy and knew the road ahead will be bumpy. First I decided to check with my local technician to find out if they have the ic from their junk board, I got one and I bought it at 10 dollars (1000 kshs)
I went home happy and before replacing the I.C decided to confirm the part number only to find I was given the wrong part; the tech took advantage I did not have the magnifying lens to check the number. I decided not to go there again but import the part,I got it at aliexpress and within one month the item landed in Kenya.
I replaced the part and applied the power and was happy with the results. I put the power board back to the main television and after applying the power I noted the backlight were on from the back of the television since the television was placed upside down.
I checked the screen and noted it was indicating “no signal”. I re-assembled everything slowly and carefully and after connecting the antenna this is what I saw.
For more information on LCD/LED television troubleshooting and repair guide you can grab this eBook written from the technician workbench point of view.
Thank you friends
Stay safe.
Humphrey Kimathi is from Nairobi Kenya and he has just launched his new book “Foundations Electricity & Electronics”
You can also checkout his other ebooks below:
1) Lcd-Led television repair guide
3) CRT Television repair course and
4) Basic Electronics course.
He is also a blogger at Electronicsrepairmadeasy.com
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Note: You may check out his previous post in the below links:
https://jestineyong.com/led-tv-with-no-picture-but-audio-present-now-repaired/
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28 Comments
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Andrew F. Ali
November 13, 2020 at 7:08 pm
Good job!!
Humphrey Mndaka
November 16, 2020 at 3:51 pm
Thanks and welcome Andrew.
Regards Humphrey
Opheas
November 18, 2020 at 10:39 am
Hie Mr humphrey have you done dstv decoder repairs
Albert van Bemmelen
November 13, 2020 at 8:54 pm
Good explained repair with detailed circuit of these often harder to fix large 55 inch TV's! I'm sure that next time the customer safely can watch his favorite team score without his TV short circuiting again.
Humphrey Mndaka
November 16, 2020 at 3:52 pm
hahaha, nice one Albert, thanks.
Regards Humphrey
Yogesh Panchal
November 13, 2020 at 10:46 pm
Good Job! Sir
Humphrey Mndaka
November 16, 2020 at 3:54 pm
Thanks and welcome Yogesh.
Regards Humphrey
Tyrone Arendse
November 14, 2020 at 2:09 am
Good job and it look so easy the way you did the troubleshooting
Humphrey Mndaka
November 16, 2020 at 3:57 pm
Thanks for your feedback Tyrone.
Regards Humphrey
hongkong pom
November 14, 2020 at 3:33 am
Thank you Humphrey for the great description.
Nice to see you face as I have just bought your excellent ebook!
Humphrey Mndaka
November 16, 2020 at 4:00 pm
Thank you hongkong for your feedback and buying my product, be blessed and all the best from the desk of Humphrey.
Regards Humphrey
Imoudu Onwumah
November 14, 2020 at 4:29 am
My brother well done.I always gain from ur acticles. The last one helped me to repair t con board of a tv.Keep it up,and thanks.
Humphrey Mndaka
November 16, 2020 at 4:02 pm
Thank you my brother from Nigeria oh! hahaha.
Regards Humphrey
HECTOR DELATORRE
November 14, 2020 at 9:42 pm
Very good article, it was very detail and it teach us how to try and fix TV's. Continue with the good work
Humphrey Mndaka
November 16, 2020 at 4:04 pm
Thank you HECTOR for your feedback and glad to note you have learn something new in this article. all the best my friend.
Regards Humphrey
Parasuraman S
November 15, 2020 at 6:06 pm
Excellent work with a lot of experience shared! Well done! Many thanks for sharing!
Humphrey Mndaka
November 16, 2020 at 4:05 pm
Thank you sir!, I salute you.
Regards Humphrey
Joshua Oloo
November 16, 2020 at 9:00 pm
Your repair Articles are always precise and clear Hum.l noticed you're spreading your wings more so in Nairobi in matters Electronics.Congrats for that.Make an effort of opening such schools/workshops to cover major towns in Kenya.Thanks
Humphrey Mndaka
November 17, 2020 at 6:32 pm
Thanks Oloo for your feedback and nice advice.
Regards Humphrey
Egidio
November 17, 2020 at 12:31 am
Imam 32 inčni Samsung Led Tv Problem Napajanje Power suply BN4400664A
Dioda na sekundarnom djelu SB5150 zamjenio bez ošterećenja se dioda grije
drugih problema nisam nasao molim pomoč hvala
Egidio croaria.
============================================
I have a 32 inch Samsung Led Tv Problem Power Supply Power suply BN4400664A
The diode on the secondary part of the SB5150 is replaced without damage, the diode is heated
other problems i didn't find please help thanks
Egidio croaria.
Humphrey Mndaka
November 17, 2020 at 6:42 pm
Pozdrav Egidio, informacije koje su mi date nisu dovoljne za zaključivanje.
Pozdrav Humphrey
Humberto
November 17, 2020 at 11:56 am
Good repair and excellent explanations
Humphrey Mndaka
November 17, 2020 at 6:44 pm
Thank you my friend Humberto.
Regards Humphrey
Joven Urbano
November 17, 2020 at 11:38 pm
Great job! Just want to ask what made you suspect the two MOSFETs are shorted and not the other components? Thanks for sharing!
nader bahrami
November 20, 2020 at 3:53 pm
Good repair and excellent explanations
adirsom
November 20, 2020 at 9:48 pm
link ali Express vendedor
TIL
February 23, 2021 at 5:04 pm
Hi Humphrey, Good repair. I'm want to buy the same IC (6C17106) you used in this repair. Where can i find it? i tried aliexpress i could not find it. Did you perhaps use a different description/ part number to search for it? please assist.
hsko
October 16, 2022 at 10:05 pm
How many watts is your test lamp