There are a few posts on this model on badcaps and a youtube video pointing to Q9101 Q9101C as the culprit. Part is 50R380 (N-Channel, 500V, 14A) Digikey IPD50R380CEAUMA1CT-ND. This transistor fails due to shorted LED backlights. If you just replace the transistor without replacing the LED strips, the transistor will likely fail again. It is recommended to keep the backlight level between 10-14 and never run it at maximum 20.
This 4K TV turned on with backligth but no video. Usual suspect in this case is the tcon board. Searching the part on Shopjimmy gets the part number 55.55T12.C02 and I was able to find the board for $20 USD on Ebay from Electroparts online. From the shopjimmy website, this panel is used Sony model XBR-55X900A as well.
With the new tcon installed, the tv was repaired. I did a factory reset and noticed that the default picture mode was set to Energy Saving. In the service menu, source-2-5-8-0 with the tv on, the backlight is set to 34/100 in this mode. In standard mode, it is 58/100. Backlights shouldn’t be an issue in this model if you leave it in these two picture modes.
This tv had a standby light but wouldn’t respond to the power button. I tried freezing the eeprom but that didn’t help either. I ordered a new main board for the tv and the board fixed the problem though I still suspected the old board had an eeprom issue and could be repaired. Eeprom was marked 25Q64B and I ordered some replacements on ebay from China. I read the eeprom off the new board with my CH341 programmer. Once the new eeproms arrive, I will program them and test with the old board.
Update: I was successful in reading the suspect bad eeprom once I removed it from the board so it was unlikely an eeprom issue. With a new eeprom, tv did not turn on so I ended up using the replacement board.
This tv was reported as being dead with no front led and it wouldn’t power up. When I plugged it in, the front led was on but it wouldn’t respond to the power button. Badcaps posts indicated the usual suspects were D607 and C603 on the power supply board. These tested good on my power supply. All voltages appeared stable and present so the main board was getting power. There is an LED on the power supply board itself and it was flashing a 5 blink code. Searching online, I did find an eeprom for this model so I tried freezing it and it made it worse. The front LED was no longer lit after freezing. This test lead me to suspect bad bga connections on the processor.
LG LV series are known for bad BGA though I had read that the LS series had this problem as well. I heated the processor up and when I plugged in the TV, the front led came back and I could turn on the TV. With BGA failures, the lead-free solder balls crack over time and have poor connectivity. Heating up the processor will expand them enough to make contact.
The proper repair in this case is to get the processor reballed which is a bit expensive. I have found previously that baking the board is a temporary fix before the problem comes back. I did try to reflow the IC at 430 deg F with my hot air tool and flux but it didn’t work.
I was able to find a used board online but the problem may reoccur with a used board.
This TV turned on with no backlight. I found four intermittent LEDs on one strip and replaced them with 3V Samsung compatible ones. To turn down the backlight, you need to go into the service menu. For this model, with the tv on, push source-2-5-8-0 on the remote and the backlight level is under Panel Settings. I set it to around 55. This value needs to be set on EVERY input and may apply to only the current picture setting (Standard, Energy Saving, Dynamic, User).
This TV had a standby light but wouldn’t turn on. Unplugging the main board from the power supply would force the backlights on so both the backlight and power supply appeared good. I took a can of duster, inverted it, and sprayed it on the flash IC. With the flash frozen, the tv turned on.
The main board part number is BN94-06429C (BN94-05429C and BN94-05429D may be compatible. I was not able to find any of these used boards on ebay.
I considered replacing the flash module but didn’t have a programmer. It was also suggested the BGA nand module would also be replaced.
I suspected main boards from model UN46D6000SF would be compatible. Shopjimmy shows a large number of substitutable main boards for this model and also a few different panel numbers. None matched my number, LD460CGB-A2. Checking specs and pictures, UN46D6000 has 2 more HDMI ports, 2 more USB ports and VGA and ethernet connectors not available on UN46D6003.
I gambled on one board but had to return it because the connector to the front panel was different (larger black instead of white). The second board I ordered was a match and it worked.
After installation, I made sure the firmware was upgraded and performed a factory reset.
This TV wouldn’t turn on and didn’t seem to react to the power button. After awhile, a blink code of 3 slow blinks followed by 1 fast blink would display on the front LED.
A youtube video indicates this can be fixed by replacing the power supply board. A badcaps post indicates a bad Q7120 KIA378R12PI regulator by the power supply connector could cause this error code. I measured the regulator output (pin 2) and it was the expected 12V indicating it was ok. I also had a second power supply board and it measured the same.
Digging through a few other threads with the model, it was suggested to try disconnecting the four ribbon cables going from the tcon to the panel. When I disconnected all four, the backlight came on. I then tried two left and two right one at a time and I was able to get a picture with the two right ones connected and just lines from the two left side connected. This test indicates there was a panel fault on the left side. There is a workaround to this fault by removing the side tabs off the bad side. Removing the bevel from the left side, I was able to access the panel underneath and tore off the side tabs carefully. Reconnecting everything up, the tv turned on with a picture.
Update: The TV came back a few weeks later with a flickering image. It looks like a bad panel and the workaround didn’t last.
Got this TV in with report of no backlight. I tried probing the LED connector from the back but couldn’t figure out the wiring. Taking off the panel, all the backlights tested good so I put the panel back. The TV appeared dead and did not power on. A post on badcaps indicated to check Q301 for shorts. Q301 was shorted drain to source and measured about 400 ohm both gate to drain and gate to source. Part number was FQPF16N25C (N-CH, 250V, 16A, TO-220F). The main fuse was not blown. I replaced this part and the TV powered up. The standby light was not on but this may be set in the menu. I checked the backlight level after doing a reset and the default for standard mode is 5 out of max 50.
This TV would turn on and off with chimes but no backlight. Power supply is BN44-00463A. The PFC circuit generating 390VDC is suspect if the backlights don’t come on. I put alligator clips on the big capacitors and they were only reaching about 250VDC when the tv turned on before it shut down.
The usual suspects in this circuit are DP810, CI818, CP820, ICP801, CM809 and CM811. Electrolytic capacitors CM809 and CM811 were not bulged. I tested DP810 in circuit with my multimeter in diode mode. It measured open in one direction and 0.5V dropin the other so it was good. CI818 tested good in circuit with my multimeter in capacitance mode. CP820 didn’t test good and when I pulled it out, it tested as a resistor in my ESR meter. Value is 220pf/1KV and 2KV or 3KV can be substituted. With CP820 replaced, the backlights came on. If CP820 was not the fault, I would have replaced ICP801 which a FAN7930B IC.
This TV would turn on but without a backlight. Power supply part number is BN44-00341B. Posts on badcaps indicate film capacitor CI818 is suspect. I removed it and it tested bad. I ordered a replacement 0.47uF / 630V (PCF1574-ND Digikey) and the TV was fixed after replacement.