LG LN series TVs are very prone to LED backlight failure. See this post here. To reduce the chances of future failures, it is recommended to keep the backlight level between 50-60 (max 100). This step needs to be done for every input you are using. If you run a smart app, the backlight could be set back to 100 by default and it is a bit tricky to lower the backlight level.
Under Settings and Picture, picture modes Standard and Vivid both set the backlight level to 100. Eco mode is at default 70. For any of these modes, you can manually turn the backlight down. If a default is changed, the picture mode has a (User) suffix added indicating it has been changed from the default.
The Energy Savings feature will turn down the backlight level in in a dark room but will increase it in a bright room. It is better just to keep this setting OFF.
While we are in this menu option, motion smoothing is a feature which adds frames to make video smoother. While good for sports and other fast action scenes, it can make movies look like soap operas losing the cinematic effect. You can turn it off under Picture Options. Turn both Motion Eye Care and Trumotion OFF.
You need to perform the above steps for ALL inputs you are using since the settings are only applied to the currently selected input.
With apps, the settings option may not work. If it doesn’t, look for a button marked Q.Menu on the remote. Press this when a video is playing and it will bring up a different menu. Choose, Set Video. You can then turn the backlight down and turn off motion smoothing. You need to do this for every app you are using including the media player.
My SRS light came on which is a warning about the airbag system. Found this post on how to reset it but it wouldn’t reset. I had made a jig with wires soldered to a toggle switch to make it easier to perform the procedure.
I plugged in my OBD sensor and it didn’t display any fault codes. I found this post which allowed me to read the fault code of 9-3 by jumpering two OBD connections. The fault code indicated a faulty driver’s side belt buckle switch.
This video shows the complete procedure to fix it on a civic. My torx screws are the style that have a pin in the middle and I didn’t have the correct bit to remove it. My switch appeared to be working observing the seat belt indicator on the dash so I sprayed some air inside the buckle to help clear it. I then repeated the original procedure to clear the error and it finally cleared.
This TV turned on but with no backlight. Samsungs generally don’t shut off the backlight with failures so it was assumed there were open LEDs. Unplugging the cable between the main and power supply boards still had no backlight. With my LED tester on each of the 7 strips, I found open circuits in two of them. Moving good strips to the top rows, I was able to get half the backlight to light up and I reconnected the panel to confirm it was not damaged. This also confirmed the TV could start up and display video.
The LEDs have a footprint with a bump out and I had these in my inventory. I hadn’t noticed the orientation and heat damaged one strip with too many attempts since I had installed it upside down. The LEDs were a bit brown and showed signs of lots of heat and wear so I decided to do a full replacement with new strips. The power supply was also brown from heat in the LED controller section. Part number for replacement strips is 2013SVS40F or D2GE-400SCA-R3. The whole TV was also covered in brown dust which is a sign it was in a smoking environment.
This TV turned on with no backlight. Since there was no backlight flash, there was possibly an open LED in the string. Westinghouse uses the same white label Chinese TVs as RCA, Proscan, Haier and many other brands. The firmware in these sets do not give the user the ability to adjust the backlight level.
This TV was difficult to open up. The outer bezel was held in place by screws and metal tabs that had to be released by sliding a black plastic tab. It was also double sided taped to the panel. In this scenario, I leave the bezel attached to the panel when removing it.
Once open, I found one open LED which I replaced with a Samsung-compatible 3V module. All the LEDs were a bit brown showing signs of both heat and wear. The backlights were wired as one long string with 4 rows of LEDs. Once assembled, I tried the usual combination for RCA TVs to get into the service menu to turn down the backlight level but was unsuccessful. Googling found a working code. With the TV on, press menu-0-0-0-0 on the remote. To get to the backlight setting, go to Other -> Panel Settings. The default value setting for Energy Savings was very high at 90. I reduced to 55 which saved it under User picture mode. This step needs to be done on all inputs.
This TV would turn on with no backlight and no video. I could heard sound effects when I moved the toggle button which confirmed the main board was working and the TV was on.
I first suspected bad backlights which is the case for 90% of Samsungs with no backlight. Unplugging the main board cable at the power supply end forces the backlights on and they came on. This test confirmed both the power supply and backlights were good.
I checked the BL_ON signal from the main board and it was high as well indicating the main board is likely working. On this model, there is an extra cable from the power supply to the tcon board which appears to control the backlight on signal.
The tcon board only had two out of three LEDs lit up and when disconnecting both ribbons to the panel, the third LED still did not light up. Powering up the TV with only one side connected at a time also did not produce backlight nor picture. This test indicates there is no panel fault and the tcon is suspect.
I ordered a tcon on Aliexpress and with the current shipping delays, it may be a few months until the part arrives.
Update: Tcon board finally arrived and TV powers up with backlight and video. The new tcon lights up with 3 LEDs.
This TV has a standby light but wouldn’t turn on or respond to the on/off button on the remote or side buttons. I was able to get it turn on randomly however.
Typically the suspect in these cases is the main board. I froze the EEPROM with an upside down can of duster and was able to get it turn on a few times. The part number for UF1 was W25Q16BSIG (16Mbit flash). I was able to read the contents with my CH341 programmer and I experimented by programming it into W25Q64BV (64Mbit) flashes I had. With new and larger flash installed, there was no standby light. I erased the original flash, reprogrammed it, and reinstalled it and it does appear fixed.
I have ordered the 16Mbit ICs in case the TV comes back with the same problem. I also turned down the backlight in the service menu to level 60. In this model, it needs to be done on all inputs and is saved under the User picture mode.
The owner indicated the flashlights were flashing which typically is a sign of failing backlights. I had asked them to turn down the backlight level and it was fine for a few weeks before the picture went dim. Testing the strip, 5 out of 68 LEDs were bad so I replaced the single strip. Powering up the TV, they would flash on power up before shutting off though they were all lighting up. The strips are wired as 4 banks of 17 LEDs and each bank tested good and measured 51V on my LED tester (3V LEDs). I have run into the issue of bad LEDs damaging the power supply so suspected the controller IC may have been damaged as well.
Searching online, there are a few reports of the OZ9998HDN IC overheating and needing replacement with symptoms of a flashing backlight.
I ordered the ICs from Aliexpress and the power supply did not turn on the backlights with both ICs that I installed. I ended up buying a new power supply board and this finally fixed the TV.
50L3400U is a similar model. I have run into this problem before with Toshibas where there is both LED and power supply damage.
The owner indicated he heard a pop and the TV died. He also found the main fuse blown. The power supply part number is BN44-00717A. Blown fuses typically are caused by shorted diodes and FETS and I found a short in one of the two PFC switching FETs 60R360 (NCH, 600V, 9A). I replaced both QP801C and QP802C with IPAN50R500 (NCH, 500V, 11A). The PFC circuit runs at 400V and the main filter caps are only rated to 450V so the lower voltage should be ok.
With the FET and fuse replaced, the TV powered up. I did recommend to the owner to not run in Dynamic mode since it could burn out the backlights.
With these symptoms, the backlights are suspect though I haven’t encountered this exact model before. The failures were intermittent so it was a bit tricky to find the source of the problem. With the TV apart, my LED tester got all strips to light though one strip measured a bit higher voltage than the others. With the TV powered up, I observed the suspected bad strip fail first before all the backlights shut down. Testing the strip, I found one bad LED (replaced with 6V) and the connector between the left and right strips was broken causing an intermittent connection.
With the TV together, I turned down the backlight level to 50 and also turned off the Dynalight feature.
This TV had no backlight but would turn on and off. Opening up the back, the power supply HTX-PI420402A had four pairs of wires going to the LED strips. I powered one pair with my LED tester and could observe the splash screen and confirmed that video was good.
I decided to open up the TV to check the strips and this edge lit TV used four sets – one at each side and two along an edge. All strips tested fine with my LED tester.
Shopjimmy sells a repair kit which includes two ICs and two FETs to repair the backlight circuit. I checked the FETs and diodes and none were shorted. Searching the power supply part number on badcaps, there was a suggestion to check the transformer for cold solder joints.
I found a cold joint and there were some clues if I had inspected the board more carefully. There was a scorch mark above the joint on the top of the PCB. The bottom of the PCB had an insulator sheet that had a hole at the cold joint location. And there was a crackling noise coming from the board occasionally, caused by the joint arcing.
Though 90% of no backlight cases are caused by bad LEDs, in this case it was the power supply.
Other models that may use this power supply – Haier LE42B1380 Haier LE55B1381 Viore LED42VF80 Seiki SE421TT Seiki LE-55GB2 Curtis LED4250A