Replacement Of PS Board And Mother Board Necessitated In Samsung Model UA46ES6200
An interesting story is being unveiled in repairing this heavy 46” metal body 3D, 4K LED TV brought by a new customer, referred to me by a techie friend of mine staying far away. The request made by the customer was that a replacement mother board bought by his friend online be fixed in this TV, as it got defective due to lightning. On further enquiry with the customer, I learnt that this was lying with an unknown technician near my town, who gave up as he could not manage to fix it due to problems of software incompatibility envisaged. The customer gave me the number of that technician and I called him in front of him to ascertain what the issue was technically, as I smelled something fishy and felt that I was in for some trouble. He told me that the TV was brought to him in dead condition due to lightning and with a lot of futile struggles; he sent the PS board to a faraway place where they undertook service of PS boards. He got back the PS Board but the backlight was not working and he used an external LED backlight driver and connected the replacement mother board but it did not work at all. He thought then it could be due to some software issue and gave up. Well, I never suspected that this was a cock and bull story until much later. I accepted the work as the customer was a very decent person and I felt confident to deal with him and to proceed with the repair work. Anyhow I did mention as a part of the conversation to the unknown techie that my job was not going to be simple, as the PS Board had to be set right first before any attempt to try the new mother board. As I had a lot of work pending on my table, I allowed the customer to leave the TV and mother board with me for taking up later.
I took up the work after finishing what was on the anvil and after making enough space on my table for keeping the TV for opening the back cover. I was surprised to see a lot of cobweb and dust inside the TV and my suspicion and intuition was aroused that this was not going to be an easy task that was presented to me. After using a vacuum cleaner to clean the inside since carrying this heavy TV outside was not easy, I applied power. In Samsung TVs, the backlight would get automatically on if the mother board is not connected. But in this case nothing happened. I checked the Voltages and found 12V, 5V and some 108V. I removed the PS Board and studied carefully what was wrong with it and carried out further deep investigations. I noticed that the PFC was not working as voltage buildup of around 390V across the tank capacitor was missing and it was just around 318V. Then I probed the area of PFC IC and its surrounding circuits in the primary. I saw a lot of rusted jumper wires and rusty legs of a few components. I replaced them and cleaned the board thoroughly with IPA. I was updating the customer with short videos of my work followed by voice messages through Whatsup. I even had telephone conversations with him which brought out the news that the TV was lying for around 10 months with the other techie and the Board was bought by them recently with a replacement (no refunds) warranty of 14 days, at the behest of that TV Technician! Now you can visualize what kind of trouble that I dragged myself into! My curiosity and craze to have some fun with new types of repair work overtook my sense and premonition when I took up the job! Anyhow, having got self-pushed into the water and got wet, I decided to pursue the work as I felt pity for the customer, who had spent a hell of a lot of money in fetching the mother board from a source known to all we, techies, as a money-monger, unreliable business firm. Though many of my techie friends prompted me to give up and return the set to the customer, it only pushed my interest in the case further up and up. After spending several hours and a few days in carrying out different methods like replacing the electrolytic capacitors including the tank capacitor, and retouching the entire board with fresh solder, I bumped upon a few more shocking findings! In fact, it was one of my techie friends who marked the parts and drew my attention. There were a few transistors and diodes removed and points shorted as a bypass and one SMD transistor was cracked. Let us have a look at the PS Board and the parts marked:
As the timer was on for return of the Mother Board, I was in panic and pressurized and tried everything possible with assistance of my techie friends. After setting right the man made defects on the board by replacing the defective and missing components as advised by expert friends, I could get the PFC built up, which showed a healthy reading:
Then I fixed an external LED driver board after trying a few others all bought exclusively for this TV. Then the backlight got on, arrangement of which can be seen in the second picture above. Then connected the mother board and found that the voltages were dropping and even the PFC dropped to 318V. Timer was running out and I had no alternative but to order for a replacement PS Board with the clearance from the customer and obtaining an advance to cover my expenses. I received the replacement PS board on the third day, in the meantime of which I wanted to check whether the Panel was working, which I should have done in the first stage itself when things looked dismal. As this was a Full HD TV and I was not having the LVDS cable for it, I ordered for it and got it next day. I connected a U11 Board to the TV with an external 12V DC adaptor and got encouraging results:
Having ensured that we are not heading for a total failure as the panel was in excellent working condition with a neat looking T-con Board, picture of which is given above; I carried out the work with new vigor and spirit. After fixing the replacement PS Board (used board in working condition), in which I had to do a couple of preventive steps like replacing rusty jumper wires and retouching dry joints, and removing the old PS Board and LED Driver board, I connected the mother board. The set got on with a standby indicator red LED light. It responded to the on command but the backlight did not get on and the Red LED blinked five times. I got the voltages for the mother board from my techie friends and checked all the vantage points. Everything was perfect. But the TV did not get on. The backlight was getting on in the PS Board, when the Mother Board was disconnected with a PFC voltage reading of around 390V indicating that it was healthy. After consultations with the techie friends, it was confirmed that the mother board was indeed faulty. My hands were tied as I could not carry out any repair work on the mother board because of the replacement warranty. Since the supplier wanted proof by video, I shared the videos of TV working very well with the U11 Board and another video covering the voltage readings of the PS Board and the behavior of the mother board on switch on.
The response from the supplier was that my methods of trouble shooting were obsolete and the TV should be handled by 3D qualified engineers! Well me and my expert techie friends had a good laugh as we were knowing about this supplier and his past records of wriggling out with flimsy excuses and reasoning. Then I sent a voice message to the supplier with the consent of the customer, admitting that I indeed was not a ‘3D qualified’ technician and would gladly accept any suggestions to carry out repair of the Mother Board, if they were willing instead of sending the board back for replacement. But they never responded to me and my customer’s friend, who was in touch with them, was also getting evasive time dragging responses. In the meantime, the techie friend who supplied the PS Board told me that he had the mother board and was ready to give it at a throw away price. With the consent of the customer, I ordered for it and got the Mother Board on the third day. The TV was found working very well with the replacement Mother Board. I forgot to mention that I requested my friend to send me the entire mother board with LVDS cable, Keyboard plus wireless Dongle and the WI-FI dongle, which he did at extra charges.
As the time limit for replacement of the board by the supplier was met like a last sixer scored to win a cricket match, the customer and his friend planned to insist upon a full refund because of the lukewarm and irresponsible and unreliable dealings of the supplier.
Anyhow, the curtain was finally drawn to this record breaking experience filled with tension, turmoil and testing times! I kept the TV ready for delivery after testing it for several hours with the old boards and parts replaced, adding utmost satisfaction filled with excitement and soaked with sweat!
The RC Unit of the old Mother Board did not work with the replaced board and I fetched a suitable one later, which also was found defective partially. But the customer himself got a replacement of the RC Unit from the shop on his way back after him and his wife (he brought his wife to help him carry the TV to the car) picked up the TV.
Anyhow what looked like a fool-hardy decision and poised to be a tragedy became a comedy bringing immense satisfaction to the customer, my techie friends and me! I need to mention that the customer was very, very decent, cooperative, understanding and encouraged me well, which culminated in the positive result. His attitude was also ‘come what may, let us get it to working condition again’ like a war hero! These are some fringe benefits we get sometimes!
This article was prepared for you by Parasuraman Subramanian from India. He is 74 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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Albert van Bemmelen
January 18, 2025 at 5:57 pm
After reading this repair that took the upmost sweat and had to be done in too limited time to finish successfully, it called for a message to that lukewarm, irresponsible and unreliable supplier by mentioning his name here to end his bad business for once and for all! Even after he has fully refunded the money paid for his crappy products!