Fixing U11 Board In Samsung LED TV LA32E420E2R & Restoring Backlight
This was brought to me by a customer stating that it became dead after a lightning strike and was lying in one place due to chain of unpleasant events in his house. He requested me to look into and revive it if possible. After opening and doing a thorough cleaning of the inside I carried out the usual troubleshooting methods one by one.
There was no visible damage to the mother board or power supply. I replaced the blown fuse and applied power through a series bulb. There was no output. There was a lot of dry solder and the electrolytic capacitors were all checked to be beyond its limits. Now let us have a look at these boards before proceeding further:
So, did a thorough patch of dry solder of the PS board, which had both through hole and SMD components and replaced all the electrolytic capacitors on the PS Board. Then when I applied power, the outputs were present. But backlight did not get on. Normally, in Samsung LED TVs, the power supply and backlight will get on even if we do not connect it to the mother board. Since this TV was using the old CCFL, I checked up whether the Driver IC was getting VCC and whether the output was coming. The IC was getting the VCC but the output was found going off immediately on switch on. So, the IC was going into protection mode, detecting some abnormal current drawn by the CCFL.
According to the suggestion by my techie friends, who are experts in handling several such cases in a day, I bypassed the protection of the IC by connecting an LED at the protection pin No.10, cutting its connection to the board. Then the outputs were present and the backlight got lit. Just see the pictures to follow these explanations. First picture is that of the inverter board:
Having the backlight restored, which is known to work for many more hours, I turned my attention to the mother board. After connecting the PS to the mother board, there was no standby indication. Checked all the voltages in the mother board and found these to be ok. Tried changing the crystal. Required input voltages for the main IC were ok. So, heated up the uController as a part of routine revival method. Nothing worked and the IC did not respond. My techie friends were of opinion that the IC was prone to become defective like this in this model and there was no use of replacing it as it would fail soon. The cost was also prohibitively high. So, after consulting with the customer, I proceeded to fit a new U11 Universal Mother board using the same Power supply.
I downloaded the panel details from the web and learnt that the panel was working on 12V supply. I set the jumper wire on the U11 board to 12V. There is option for 3.3V, 5V and 12V.
Then selected an LVDS cable that will fit in the scaler board. We need to check whether the connector is up or down, power supply to the panel is on the left or right. We can easily see that with observation and the Fuse connected on the panel, where the voltage input goes. It will be like an SMD cap, large and the rate will be marked on the side. (This need not be the case in all boards!) The red color wires on the LVDS cable indicate the power supply. Normally these will be on the sides. So, we need to ensure that same type of LVDS cable is selected for interconnecting the board to the panel. Any mistake might damage Mother Board, Scaler Board and/or even the panel. The board is housed in a case that is available for purchase separately. This case can be fixed appropriately in a place so as to ensure that the LVDS cable reach the panel comfortably without any twist or turn. This is very important. Following pictures would be more helpful:
The next step was to wire the power supply, original IR and Standby indicator board, speakers. I looked at the markings on the PS board to locate pins 1) 12V DC supply (In this case it was 13V and that can be connected to the board as it can withstand the extra volt) 2) Power on 3) Back light on 4) Power Dim 5) Ground. Wires were soldered and marked with label stickers. Then the IR and standby LED wires were joined to the one that come from the board. Speaker wires were also joined in the same way.
The next step was to locate a suitable place to fix the board. As this TV was not having the stand, the slot was perfect for housing the U11 Board case. Kindly see the snaps of each stage:
After rechecking all connections to be doubly sure, I applied power and was glad to see the backlight getting on and panel. In order to adjust the resolution as per panel specification, which was 1366×768, we need to input the service code numbers, upon which there will be a display, from which we have to select. The codes are normally written on the box of the Mother board. Following details that I downloaded might be of use:
(Sorry you may have to crane your neck to read! I use horizontal pictures to reduce number of pages.) I used 20081 and it worked. In the service mode, there are options to select automatic on bypassing the standby mode and other settings. We can even select the brand name to be displayed.
The set was put on for testing for two days full and found to be working very well, upon which the customer was called to come and collect.
Mission accomplished with a lot of satisfaction getting gathered.
This article was prepared for you by Parasuraman Subramanian from India. He is 72 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.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous article on Panel Found Cracked On Restoring LG 47” 3D LED TV Model 47LM7610-TB