RTRU5528 is the Canadian model and RTRU5527 is the US model.
This tv was reported as having no backlights. Opening up the panel, the backlights tested good with an LED tester. There was a standby light and the tv turned on but without backlight. I then noticed a blown up MOSFET on the power supply board. Some components on the back side were also damaged. Checking other components, D401 was shorted as well. I would recommend checking D401 – D404 and checking the main fuse F101. Power supply part number is HSL55D-2S9.
I have repaired dozens of LG LN series TVs with bad LED backlights. Symptom is the LG logo flashing on power up and the TV is on with sound but no video because the backlight has shut down. Though a LED tester will confirm the failure, it is possible to confirm bad LEDs without one but you need to remove the panel to watch the LEDs flash.
The flash is caused by protection circuitry shutting down the backlights because an error is detected in the LED driver circuitry. Driver circuits are current sources driving the leds wired in series like Christmas lights. LEDs can fail short (most common) which will cause an undervoltage situation. If LEDs fail open, there will be overvoltage that the driver can detect as well. If there is an open LED, the backlights may not flash at all. In non-smart LG models, there is no logo and there may just be a quick backlight flash.
The shutdown protects the rest of the LEDs and the power supply. It may also prevent the LEDs from burning up. I have seen LEDs burn up in LN series even with the protection shutdown.
There are a lot of youtube videos on panel removal and I will include one here from Shopjimmy. The panel is extremely fragile and you need to be extremely careful to not crack it. The boards flex connected to the panel can also be ripped off very easily. Damage to the panel or those boards is not repairable.
The TV will turn on with the panel disconnected so you can observe the flashing. By going frame by frame, I took a capture of the flash where you can see two LEDs not lighting up. If you have an LED tester, disconnect the strips from the power supply and probe each strip individually.
LEDs are likely to fail if the backlight level is set to maximum. They get hot and will burn out over time. Failure could occur between 2-5 yrs. On LGs, the default picture modes for Standard and Vivid modes are at 100% level. With the LN smart versions, apps may also default to 100% backlight and can only be changed in the Quick menu.
Full replacement of all strips with NEW ones. This option is preferred to minimize future problems with your backlights. Reputable sellers include Shopjimmy and ebay seller meihua361000 based in China. I have had failures with Rzconne branded strips so best to avoid those.
Replace bad strips with used ones. This option is cheaper if you have used strips but if you are buying strips, its only a bit more for new ones. Because there is wear on the existing LEDs, they may fail in the future.
It is preferred to have your replacement strips in hand before doing the repair. If your tv has been disassembled for weeks waiting for parts, you may forget how it goes together. You also risk damaging the LCD panel if you haven’t stored it safely and prevented it from gathering dust. However, some models use different panels so may have different strips even for the exact same model number.
To ensure your repair lasts, you need to turn down the backlight level. This setting is in the picture menu. For LGs, 50 to 70% is recommended. With apps, you need to access the Q.Menu to adjust the backlight level. You need to do check on ALL inputs and ALL apps. I would also recommend turning Energy Saving OFF since this could increase the backlight level in a bright room.
Samsung TVs also have LED failure but they don’t have shutdown protection. LEDs will fail until there is damage to the power supply or the screen will get very dim. With Samsung TVs, you can disconnect the cable from the main board to the power supply and this will force the backlights on for testing.
You can also set the backlight level on Samsung TVs. Dynamic picture mode will crank the backlights to 100% (level 20/20). It is recommended to set the backlight level between 10-14 to make them last.
These models have a protection feature but there is no backlight setting in the menu. However you can turn it down in the service menu under Panel Settings. With the TV on, try Input-1-1-4-7 or Source-2-4-8-0 Be very careful with service menu settings since you can brick your tv. I would check every input and set the backlight to around 60.
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 FDP3FN50NZ (N-CH, 500V, 3A, TO-220F). Digikey part would be FDPF3N50NZOS-ND though you can substitute with a highter amp rating. 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.