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).
Model UN46D6003 UN46D6003SF UN46D6003SFXZC
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.
Model 58L1350U – C suffix for Canadian model.
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.
Model: LN46D630 LN46D630M3F LN46D630M3FXZC
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.
Model LN46C630 L46C630K1F LN46C630K1FXZC
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.
Model UN55FH6030 UN55FH6030F UN55FH6030FXZC
I had previously encountered this model with failed backlights. This TV had different symptoms and the backlights were working but with no video. The usual suspect when there is backlight and sound but no video is the tcon board. The TV appeared previously repaired since the main board was from the 65″ version of the this TV. I still had the other TV so tested the 65″ main board on it and it was working fine. I couldn’t swap tcon boards since the panels were different even though it was the same model.
Searching the tcon part number BN96-27249A found repair kits indicating it had a common fault. Used boards were actually cheaper than the repair kit and only $12 USD from Electroparts online.
The replacement tcon worked and fixed the TV.
The backlights appeared good. I checked the backlight setting and it was in standard mode with a default level of 12/20 on all inputs. Though not the problem in this tv, It does appear running the backlights at 100% is what causes failure.
This TV responded to the power button and attempted to turn on but there was no backlight. Checking the signals at the power connector, I measured 19V at the 12V pins and 3.6V at the PS-ON pin but BL-ON wasn’t getting a signal so the main board was suspect.
Checking shopjimmy, they sell an eeprom for the main board with the symptom no backlights. They have a video showing the symptom on a similar model P502UI-B1
Ordered the eeprom but the problem was still there. Luckily, new main boards were available for $30 USD from Electroparts online through their ebay store. I have had a good experience from Electroparts since they had free returns and provided USPS labels.
After main board replacement, the TV turned on with backlight. There were also LEDs on the main board that lit up. A post on badcaps for P502UI-B1 indicates BGA failures on the main processor are the suspect and not the eeprom. Usually with eeprom failures, the tv doesn’t respond to the power button.
When plugged in, the TV squealed and wouldn’t turn on. Squealing is a sign of a shorted output on the transformer.
The service manual for this model can be found with a quick google search.
Checking the power supply board, the fuse was not blown and none of the output diodes on the AMP+13V and P-ON+21V lines were shorted. The squealing stopped when the cable from the power supply to the main board was disconnected. Measuring the resistance of the P-ON+21V line, it was 8 ohms indicating a short on the main board.
The schematic shows the P-ON+21V is input to five regulators on the main board that have decoupling capacitors for each one. The 4.7uF 0805 ones could potentially short. You will need to remove C3943, C3645, C3616, C3674 and C3625 to determine which one is shorted. It is advised to replace all of them. Digikey part would be 1276-6722-1-ND (4.7uF 35V X5R 0805)
The LG LN series is probably the most common model I perform LED backlight repair and replacement on. Symptom is typically the backlights flashing momentarily on power up or plug in before an error is detected causing the backlights to shut down.
In most cases, the panels use strips labelled L1 & R1 and L2 & R2 with 3 black dots and thin lenses and the LED themselves can be replaced with 3V 2835 ones.
I recently encountered a 50LN5310 with a slightly different panel and LED strips. Shopjimmy indicates there are 2 different strips that could be used on this model. On disassembly, the screws for the metal bezel holding the panel in place were different and the side tabs on the panel were taped to the plastic bezel holding the diffusers. The LED strips used the thick style lenses and measuring the LEDs themselves indicated they were the standard LG 3V 2835 type. If you try to remove a strip, you will likely pop off the lenses so it is recommended to replace the LED with the strip attached to the chassis.
On the TV I worked on, many of the lenses were loose and ready to fall off. It is recommended to keep the exact same orientation and have the lens perfectly centered on the LED when gluing it back on. I have been using 5 second fix glue recently since you can adjust the lens and check it before curing it with the UV light. The glue is fairly cheap on ebay shipped from China. If the lens is not perfectly centered, it could create bright spots on the screen. If the lens falls off, it will create another bright spot.